Android 屏幕截图

1.同时按下电源键+音量下键截屏

PhoneWindowManager.java

private void interceptScreenshotChord() {
        if (mScreenshotChordEnabled
                && mVolumeDownKeyTriggered && mPowerKeyTriggered && !mVolumeUpKeyTriggered) {
            final long now = SystemClock.uptimeMillis();
            if (now <= mVolumeDownKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS
                    && now <= mPowerKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) {
                mVolumeDownKeyConsumedByScreenshotChord = true;
                cancelPendingPowerKeyAction();

                mHandler.postDelayed(mScreenshotRunnable, getScreenshotChordLongPressDelay());②
            }
        }
    }

private final Runnable mScreenshotRunnable = new Runnable() {
        @Override
        public void run() {
            takeScreenshot();③
        }
    };

 @Override
    public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags, boolean isScreenOn) {
...
final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
...
        // Handle special keys.
        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_DOWN:
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_MUTE: {
                if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
                    if (down) {
                        if (isScreenOn && !mVolumeDownKeyTriggered
                                && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                            mVolumeDownKeyTriggered = true;
                            mVolumeDownKeyTime = event.getDownTime();
                            mVolumeDownKeyConsumedByScreenshotChord = false;
                            cancelPendingPowerKeyAction();
                            interceptScreenshotChord();①
                        }
                    } else {
                        mVolumeDownKeyTriggered = false;
                        cancelPendingScreenshotChordAction();
                    }
...
case KeyEvent.KEYCODE_POWER: {
                result &= ~ACTION_PASS_TO_USER;
                if (down) {
                    if (isScreenOn && !mPowerKeyTriggered
                            && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                        mPowerKeyTriggered = true;
                        mPowerKeyTime = event.getDownTime();
                        interceptScreenshotChord();①
                    }
...

// Assume this is called from the Handler thread.
    private void takeScreenshot() {
        synchronized (mScreenshotLock) {
            if (mScreenshotConnection != null) {
                return;
            }
            ComponentName cn = new ComponentName("com.android.systemui",
                    "com.android.systemui.screenshot.TakeScreenshotService");④
            Intent intent = new Intent();
            intent.setComponent(cn);
            ServiceConnection conn = new ServiceConnection() {
                @Override
                public void onServiceConnected(ComponentName name, IBinder service) {
                    synchronized (mScreenshotLock) {
                        if (mScreenshotConnection != this) {
                            return;
                        }
                        Messenger messenger = new Messenger(service);
                        Message msg = Message.obtain(null, 1);
                        final ServiceConnection myConn = this;
                        Handler h = new Handler(mHandler.getLooper()) {
                            @Override
                            public void handleMessage(Message msg) {
                                synchronized (mScreenshotLock) {
                                    if (mScreenshotConnection == myConn) {
                                        mContext.unbindService(mScreenshotConnection);
                                        mScreenshotConnection = null;
                                        mHandler.removeCallbacks(mScreenshotTimeout);
                                    }
                                }
                            }
                        };
                        msg.replyTo = new Messenger(h);
                        msg.arg1 = msg.arg2 = 0;
                        if (mStatusBar != null && mStatusBar.isVisibleLw())
                            msg.arg1 = 1;
                        if (mNavigationBar != null && mNavigationBar.isVisibleLw())
                            msg.arg2 = 1;
                        try {
                            messenger.send(msg);
                        } catch (RemoteException e) {
                        }
                    }
                }
                @Override
                public void onServiceDisconnected(ComponentName name) {}
            };
            if (mContext.bindServiceAsUser(
                    intent, conn, Context.BIND_AUTO_CREATE, UserHandle.CURRENT)) {
                mScreenshotConnection = conn;
                mHandler.postDelayed(mScreenshotTimeout, 10000);
            }
        }
    }

TakeScreenshotService.java

public class TakeScreenshotService extends Service {
    private static final String TAG = "TakeScreenshotService";

    private static GlobalScreenshot mScreenshot;

    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 1:
                    final Messenger callback = msg.replyTo;
                    if (mScreenshot == null) {
                        mScreenshot = new GlobalScreenshot(TakeScreenshotService.this);
                    }
                    mScreenshot.takeScreenshot(new Runnable() {
                        @Override public void run() {
                            Message reply = Message.obtain(null, 1);
                            try {
                                callback.send(reply);
                            } catch (RemoteException e) {
                            }
                        }
                    }, msg.arg1 > 0, msg.arg2 > 0);
            }
        }
    };

    @Override
    public IBinder onBind(Intent intent) {
        return new Messenger(mHandler).getBinder();
    }
}

GlobalScreenshot.java

SaveImageInBackgroundTask(Context context, SaveImageInBackgroundData data,
            NotificationManager nManager, int nId) {
        Resources r = context.getResources();

        // Prepare all the output metadata
        mImageTime = System.currentTimeMillis();
        String imageDate = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date(mImageTime));
        mImageFileName = String.format(SCREENSHOT_FILE_NAME_TEMPLATE, imageDate);

        mScreenshotDir = new File(Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_PICTURES), SCREENSHOTS_DIR_NAME);
        mImageFilePath = new File(mScreenshotDir, mImageFileName).getAbsolutePath();④

        // Create the large notification icon
        mImageWidth = data.image.getWidth();
        mImageHeight = data.image.getHeight();
        int iconSize = data.iconSize;

        final int shortSide = mImageWidth < mImageHeight ? mImageWidth : mImageHeight;
        Bitmap preview = Bitmap.createBitmap(shortSide, shortSide, data.image.getConfig());
        Canvas c = new Canvas(preview);
        Paint paint = new Paint();
        ColorMatrix desat = new ColorMatrix();
        desat.setSaturation(0.25f);
        paint.setColorFilter(new ColorMatrixColorFilter(desat));
        Matrix matrix = new Matrix();
        matrix.postTranslate((shortSide - mImageWidth) / 2,
                            (shortSide - mImageHeight) / 2);
        c.drawBitmap(data.image, matrix, paint);
        c.drawColor(0x40FFFFFF);
        c.setBitmap(null);

        Bitmap croppedIcon = Bitmap.createScaledBitmap(preview, iconSize, iconSize, true);

        // Show the intermediate notification
        mTickerAddSpace = !mTickerAddSpace;
        mNotificationId = nId;
        mNotificationManager = nManager;
        mNotificationBuilder = new Notification.Builder(context)
            .setTicker(r.getString(R.string.screenshot_saving_ticker)
                    + (mTickerAddSpace ? "" : ""))
            .setContentTitle(r.getString(R.string.screenshot_saving_title))
            .setContentText(r.getString(R.string.screenshot_saving_text))
            .setSmallIcon(R.drawable.stat_notify_image)
            .setWhen(System.currentTimeMillis());

        mNotificationStyle = new Notification.BigPictureStyle()
            .bigPicture(preview);
        mNotificationBuilder.setStyle(mNotificationStyle);

        Notification n = mNotificationBuilder.build();
        n.flags |= Notification.FLAG_NO_CLEAR;
        mNotificationManager.notify(nId, n);

        // On the tablet, the large icon makes the notification appear as if it is clickable (and
        // on small devices, the large icon is not shown) so defer showing the large icon until
        // we compose the final post-save notification below.
        mNotificationBuilder.setLargeIcon(croppedIcon);
        // But we still don't set it for the expanded view, allowing the smallIcon to show here.
        mNotificationStyle.bigLargeIcon(null);
    }

/**
     * Creates a new worker thread and saves the screenshot to the media store.
     */
    private void saveScreenshotInWorkerThread(Runnable finisher) {
        SaveImageInBackgroundData data = new SaveImageInBackgroundData();
        data.context = mContext;
        data.image = mScreenBitmap;
        data.iconSize = mNotificationIconSize;
        data.finisher = finisher;
        if (mSaveInBgTask != null) {
            mSaveInBgTask.cancel(false);
        }
        mSaveInBgTask = new SaveImageInBackgroundTask(mContext, data, mNotificationManager,
                SCREENSHOT_NOTIFICATION_ID).execute(data);③
    }

/**
     * Takes a screenshot of the current display and shows an animation.
     */
    void takeScreenshot(Runnable finisher, boolean statusBarVisible, boolean navBarVisible) {
        // We need to orient the screenshot correctly (and the Surface api seems to take screenshots
        // only in the natural orientation of the device :!)
        mDisplay.getRealMetrics(mDisplayMetrics);
        float[] dims = {mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels};
        float degrees = getDegreesForRotation(mDisplay.getRotation());
        boolean requiresRotation = (degrees > 0);
        if (requiresRotation) {
            // Get the dimensions of the device in its native orientation
            mDisplayMatrix.reset();
            mDisplayMatrix.preRotate(-degrees);
            mDisplayMatrix.mapPoints(dims);
            dims[0] = Math.abs(dims[0]);
            dims[1] = Math.abs(dims[1]);
        }

        // Take the screenshot
        mScreenBitmap = SurfaceControl.screenshot((int) dims[0], (int) dims[1]);①
        if (mScreenBitmap == null) {
            notifyScreenshotError(mContext, mNotificationManager);
            finisher.run();
            return;
        }

        if (requiresRotation) {
            // Rotate the screenshot to the current orientation
            Bitmap ss = Bitmap.createBitmap(mDisplayMetrics.widthPixels,
                    mDisplayMetrics.heightPixels, Bitmap.Config.ARGB_8888);
            Canvas c = new Canvas(ss);
            c.translate(ss.getWidth() / 2, ss.getHeight() / 2);
            c.rotate(degrees);
            c.translate(-dims[0] / 2, -dims[1] / 2);
            c.drawBitmap(mScreenBitmap, 0, 0, null);
            c.setBitmap(null);
            // Recycle the previous bitmap
            mScreenBitmap.recycle();
            mScreenBitmap = ss;
        }

        // Optimizations
        mScreenBitmap.setHasAlpha(false);
        mScreenBitmap.prepareToDraw();

        // Start the post-screenshot animation
        startAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels,
                statusBarVisible, navBarVisible);
    }

/**
     * Starts the animation after taking the screenshot
     */
    private void startAnimation(final Runnable finisher, int w, int h, boolean statusBarVisible,
            boolean navBarVisible) {
        // Add the view for the animation
        mScreenshotView.setImageBitmap(mScreenBitmap);
        mScreenshotLayout.requestFocus();

        // Setup the animation with the screenshot just taken
        if (mScreenshotAnimation != null) {
            mScreenshotAnimation.end();
            mScreenshotAnimation.removeAllListeners();
        }

        mWindowManager.addView(mScreenshotLayout, mWindowLayoutParams);
        ValueAnimator screenshotDropInAnim = createScreenshotDropInAnimation();
        ValueAnimator screenshotFadeOutAnim = createScreenshotDropOutAnimation(w, h,
                statusBarVisible, navBarVisible);
        mScreenshotAnimation = new AnimatorSet();
        mScreenshotAnimation.playSequentially(screenshotDropInAnim, screenshotFadeOutAnim);
        mScreenshotAnimation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // Save the screenshot once we have a bit of time now
                saveScreenshotInWorkerThread(finisher);②
                mWindowManager.removeView(mScreenshotLayout);

                // Clear any references to the bitmap
                mScreenBitmap = null;
                mScreenshotView.setImageBitmap(null);
            }
        });
        mScreenshotLayout.post(new Runnable() {
            @Override
            public void run() {
                // Play the shutter sound to notify that we've taken a screenshot
                mCameraSound.play(MediaActionSound.SHUTTER_CLICK);

                mScreenshotView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
                mScreenshotView.buildLayer();
                mScreenshotAnimation.start();
            }
        });
    }

SurfaceControl.java

/**
     * Like {@link SurfaceControl#screenshot(int, int, int, int)} but includes all
     * Surfaces in the screenshot.
     *
     * @param width The desired width of the returned bitmap; the raw
     * screen will be scaled down to this size.
     * @param height The desired height of the returned bitmap; the raw
     * screen will be scaled down to this size.
     * @return Returns a Bitmap containing the screen contents, or null
     * if an error occurs. Make sure to call Bitmap.recycle() as soon as
     * possible, once its content is not needed anymore.
     */
    public static Bitmap screenshot(int width, int height) {
        // TODO: should take the display as a parameter
        IBinder displayToken = SurfaceControl.getBuiltInDisplay(
                SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN);
        return nativeScreenshot(displayToken, width, height, 0, 0, true);
    }

android_view_SurfaceControl.cpp

static void nativeScreenshot(JNIEnv* env, jclass clazz,
        jobject displayTokenObj, jobject surfaceObj,
        jint width, jint height, jint minLayer, jint maxLayer, bool allLayers) {
    sp<IBinder> displayToken = ibinderForJavaObject(env, displayTokenObj);
    if (displayToken != NULL) {
        sp<Surface> consumer = android_view_Surface_getSurface(env, surfaceObj);
        if (consumer != NULL) {
            if (allLayers) {
                minLayer = 0;
                maxLayer = -1;
            }
            ScreenshotClient::capture(
                    displayToken, consumer->getIGraphicBufferProducer(),
                    width, height, uint32_t(minLayer), uint32_t(maxLayer));
        }
    }
}

static JNINativeMethod sSurfaceControlMethods[] = {
...
    {"nativeScreenshot", "(Landroid/os/IBinder;IIIIZ)Landroid/graphics/Bitmap;",
            (void*)nativeScreenshotBitmap },
    {"nativeScreenshot", "(Landroid/os/IBinder;Landroid/view/Surface;IIIIZ)V",
            (void*)nativeScreenshot },
...

SurfaceComposerClient.cpp

status_t ScreenshotClient::capture(
        const sp<IBinder>& display,
        const sp<IGraphicBufferProducer>& producer,
        uint32_t reqWidth, uint32_t reqHeight,
        uint32_t minLayerZ, uint32_t maxLayerZ) {
    sp<ISurfaceComposer> s(ComposerService::getComposerService());
    if (s == NULL) return NO_INIT;
    return s->captureScreen(display, producer,
            reqWidth, reqHeight, minLayerZ, maxLayerZ,
            false);
}

SurfaceFlinger.cpp

status_t SurfaceFlinger::captureScreen(const sp<IBinder>& display,
        const sp<IGraphicBufferProducer>& producer,
        uint32_t reqWidth, uint32_t reqHeight,
        uint32_t minLayerZ, uint32_t maxLayerZ,
        bool isCpuConsumer) {

    if (CC_UNLIKELY(display == 0))
        return BAD_VALUE;

    if (CC_UNLIKELY(producer == 0))
        return BAD_VALUE;

    class MessageCaptureScreen : public MessageBase {
        SurfaceFlinger* flinger;
        sp<IBinder> display;
        sp<IGraphicBufferProducer> producer;
        uint32_t reqWidth, reqHeight;
        uint32_t minLayerZ,maxLayerZ;
        bool useReadPixels;
        status_t result;
    public:
        MessageCaptureScreen(SurfaceFlinger* flinger,
                const sp<IBinder>& display,
                const sp<IGraphicBufferProducer>& producer,
                uint32_t reqWidth, uint32_t reqHeight,
                uint32_t minLayerZ, uint32_t maxLayerZ, bool useReadPixels)
            : flinger(flinger), display(display), producer(producer),
              reqWidth(reqWidth), reqHeight(reqHeight),
              minLayerZ(minLayerZ), maxLayerZ(maxLayerZ),
              useReadPixels(useReadPixels),
              result(PERMISSION_DENIED)
        {
        }
        status_t getResult() const {
            return result;
        }
        virtual bool handler() {
            Mutex::Autolock _l(flinger->mStateLock);
            sp<const DisplayDevice> hw(flinger->getDisplayDevice(display));
            if (!useReadPixels) {
                result = flinger->captureScreenImplLocked(hw,
                        producer, reqWidth, reqHeight, minLayerZ, maxLayerZ);
            } else {
                result = flinger->captureScreenImplCpuConsumerLocked(hw,
                        producer, reqWidth, reqHeight, minLayerZ, maxLayerZ);
            }
            static_cast<GraphicProducerWrapper*>(producer->asBinder().get())->exit(result);
            return true;
        }
    };

    // make sure to process transactions before screenshots -- a transaction
    // might already be pending but scheduled for VSYNC; this guarantees we
    // will handle it before the screenshot. When VSYNC finally arrives
    // the scheduled transaction will be a no-op. If no transactions are
    // scheduled at this time, this will end-up being a no-op as well.
    mEventQueue.invalidateTransactionNow();

    bool useReadPixels = false;
    if (isCpuConsumer) {
        bool formatSupportedBytBitmap =
                (mEGLNativeVisualId == HAL_PIXEL_FORMAT_RGBA_8888) ||
                (mEGLNativeVisualId == HAL_PIXEL_FORMAT_RGBX_8888);
        if (formatSupportedBytBitmap == false) {
            // the pixel format we have is not compatible with
            // Bitmap.java, which is the likely client of this API,
            // so we just revert to glReadPixels() in that case.
            useReadPixels = true;
        }
        if (mGpuToCpuSupported == false) {
            // When we know the GL->CPU path works, we can call
            // captureScreenImplLocked() directly, instead of using the
            // glReadPixels() workaround.
            useReadPixels = true;
        }
    }

    // this creates a "fake" BBinder which will serve as a "fake" remote
    // binder to receive the marshaled calls and forward them to the
    // real remote (a BpGraphicBufferProducer)
    sp<GraphicProducerWrapper> wrapper = new GraphicProducerWrapper(producer);

    // the asInterface() call below creates our "fake" BpGraphicBufferProducer
    // which does the marshaling work forwards to our "fake remote" above.
    sp<MessageBase> msg = new MessageCaptureScreen(this,
            display, IGraphicBufferProducer::asInterface( wrapper ),
            reqWidth, reqHeight, minLayerZ, maxLayerZ,
            useReadPixels);

    status_t res = postMessageAsync(msg);
    if (res == NO_ERROR) {
        res = wrapper->waitForResponse();
    }
    return res;
}

status_t SurfaceFlinger::captureScreenImplLocked(
        const sp<const DisplayDevice>& hw,
        const sp<IGraphicBufferProducer>& producer,
        uint32_t reqWidth, uint32_t reqHeight,
        uint32_t minLayerZ, uint32_t maxLayerZ)
{
    ATRACE_CALL();

    // get screen geometry
    const uint32_t hw_w = hw->getWidth();
    const uint32_t hw_h = hw->getHeight();

    // if we have secure windows on this display, never allow the screen capture
    if (hw->getSecureLayerVisible()) {
        ALOGW("FB is protected: PERMISSION_DENIED");
        return PERMISSION_DENIED;
    }

    if ((reqWidth > hw_w) || (reqHeight > hw_h)) {
        ALOGE("size mismatch (%d, %d) > (%d, %d)",
                reqWidth, reqHeight, hw_w, hw_h);
        return BAD_VALUE;
    }

    reqWidth = (!reqWidth) ? hw_w : reqWidth;
    reqHeight = (!reqHeight) ? hw_h : reqHeight;

    // Create a surface to render into
    sp<Surface> surface = new Surface(producer);
    ANativeWindow* const window = surface.get();

    // set the buffer size to what the user requested
    native_window_set_buffers_user_dimensions(window, reqWidth, reqHeight);

    // and create the corresponding EGLSurface
    EGLSurface eglSurface = eglCreateWindowSurface(
            mEGLDisplay, mEGLConfig, window, NULL);
    if (eglSurface == EGL_NO_SURFACE) {
        ALOGE("captureScreenImplLocked: eglCreateWindowSurface() failed 0x%4x",
                eglGetError());
        return BAD_VALUE;
    }

    if (!eglMakeCurrent(mEGLDisplay, eglSurface, eglSurface, mEGLContext)) {
        ALOGE("captureScreenImplLocked: eglMakeCurrent() failed 0x%4x",
                eglGetError());
        eglDestroySurface(mEGLDisplay, eglSurface);
        return BAD_VALUE;
    }

    renderScreenImplLocked(hw, reqWidth, reqHeight, minLayerZ, maxLayerZ, false);

    // and finishing things up...
    if (eglSwapBuffers(mEGLDisplay, eglSurface) != EGL_TRUE) {
        ALOGE("captureScreenImplLocked: eglSwapBuffers() failed 0x%4x",
                eglGetError());
        eglDestroySurface(mEGLDisplay, eglSurface);
        return BAD_VALUE;
    }

    eglDestroySurface(mEGLDisplay, eglSurface);

    return NO_ERROR;
}

status_t SurfaceFlinger::captureScreenImplCpuConsumerLocked(
        const sp<const DisplayDevice>& hw,
        const sp<IGraphicBufferProducer>& producer,
        uint32_t reqWidth, uint32_t reqHeight,
        uint32_t minLayerZ, uint32_t maxLayerZ)
{
    ATRACE_CALL();

    if (!GLExtensions::getInstance().haveFramebufferObject()) {
        return INVALID_OPERATION;
    }

    // get screen geometry
    const uint32_t hw_w = hw->getWidth();
    const uint32_t hw_h = hw->getHeight();

    // if we have secure windows on this display, never allow the screen capture
    if (hw->getSecureLayerVisible()) {
        ALOGW("FB is protected: PERMISSION_DENIED");
        return PERMISSION_DENIED;
    }

    if ((reqWidth > hw_w) || (reqHeight > hw_h)) {
        ALOGE("size mismatch (%d, %d) > (%d, %d)",
                reqWidth, reqHeight, hw_w, hw_h);
        return BAD_VALUE;
    }

    reqWidth  = (!reqWidth)  ? hw_w : reqWidth;
    reqHeight = (!reqHeight) ? hw_h : reqHeight;

    GLuint tname;
    glGenRenderbuffersOES(1, &tname);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, tname);
    glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_RGBA8_OES, reqWidth, reqHeight);

    // create a FBO
    GLuint name;
    glGenFramebuffersOES(1, &name);
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, name);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES,
            GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, tname);

    GLenum status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);

    status_t result = NO_ERROR;
    if (status == GL_FRAMEBUFFER_COMPLETE_OES) {

        renderScreenImplLocked(hw, reqWidth, reqHeight, minLayerZ, maxLayerZ, true);

        // Below we render the screenshot into the
        // CpuConsumer using glReadPixels from our FBO.
        // Some older drivers don't support the GL->CPU path so we
        // have to wrap it with a CPU->CPU path, which is what
        // glReadPixels essentially is.

        sp<Surface> sur = new Surface(producer);
        ANativeWindow* window = sur.get();

        if (native_window_api_connect(window, NATIVE_WINDOW_API_CPU) == NO_ERROR) {
            int err = 0;
            err = native_window_set_buffers_dimensions(window, reqWidth, reqHeight);
            err |= native_window_set_buffers_format(window, HAL_PIXEL_FORMAT_RGBA_8888);
            err |= native_window_set_usage(window,
                    GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN);

            if (err == NO_ERROR) {
                ANativeWindowBuffer* buffer;
                if (native_window_dequeue_buffer_and_wait(window,  &buffer) == NO_ERROR) {
                    sp<GraphicBuffer> buf = static_cast<GraphicBuffer*>(buffer);
                    void* vaddr;
                    if (buf->lock(GRALLOC_USAGE_SW_WRITE_OFTEN, &vaddr) == NO_ERROR) {
                        glReadPixels(0, 0, buffer->stride, reqHeight,
                                GL_RGBA, GL_UNSIGNED_BYTE, vaddr);
                        buf->unlock();
                    }
                    window->queueBuffer(window, buffer, -1);
                }
            }
            native_window_api_disconnect(window, NATIVE_WINDOW_API_CPU);
        }

    } else {
        ALOGE("got GL_FRAMEBUFFER_COMPLETE_OES while taking screenshot");
        result = INVALID_OPERATION;
    }

    // back to main framebuffer
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
    glDeleteRenderbuffersOES(1, &tname);
    glDeleteFramebuffersOES(1, &name);

    DisplayDevice::setViewportAndProjection(hw);

    return result;
}

2.基于framebuffer显存设备/dev/graphics/fb0截屏

a.自带工具screencap：screencap.cpp

int main(int argc, char** argv)
{
    ProcessState::self()->startThreadPool();

    const char* pname = argv[0];
    bool png = false;
    int32_t displayId = DEFAULT_DISPLAY_ID;
    int c;
    while ((c = getopt(argc, argv, "phd:")) != -1) {
        switch (c) {
            case 'p':
                png = true;
                break;
            case 'd':
                displayId = atoi(optarg);
                break;
            case '?':
            case 'h':
                usage(pname);
                return 1;
        }
    }
    argc -= optind;
    argv += optind;

    int fd = -1;
    if (argc == 0) {
        fd = dup(STDOUT_FILENO);
    } else if (argc == 1) {
        const char* fn = argv[0];
        fd = open(fn, O_WRONLY | O_CREAT | O_TRUNC, 0664);
        if (fd == -1) {
            fprintf(stderr, "Error opening file: %s (%s)\n", fn, strerror(errno));
            return 1;
        }
        const int len = strlen(fn);
        if (len >= 4 && 0 == strcmp(fn+len-4, ".png")) {
            png = true;
        }
    }

    if (fd == -1) {
        usage(pname);
        return 1;
    }

    void const* mapbase = MAP_FAILED;
    ssize_t mapsize = -1;

    void const* base = 0;
    uint32_t w, s, h, f;
    size_t size = 0;

    ScreenshotClient screenshot;
    sp<IBinder> display = SurfaceComposerClient::getBuiltInDisplay(displayId);
    if (display != NULL && screenshot.update(display) == NO_ERROR) {
        base = screenshot.getPixels();
        w = screenshot.getWidth();
        h = screenshot.getHeight();
        s = screenshot.getStride();
        f = screenshot.getFormat();
        size = screenshot.getSize();
    } else {
        const char* fbpath = "/dev/graphics/fb0";
        int fb = open(fbpath, O_RDONLY);
        if (fb >= 0) {
            struct fb_var_screeninfo vinfo;
            if (ioctl(fb, FBIOGET_VSCREENINFO, &vinfo) == 0) {
                uint32_t bytespp;
                if (vinfoToPixelFormat(vinfo, &bytespp, &f) == NO_ERROR) {
                    size_t offset = (vinfo.xoffset + vinfo.yoffset*vinfo.xres) * bytespp;
                    w = vinfo.xres;
                    h = vinfo.yres;
                    s = vinfo.xres;
                    size = w*h*bytespp;
                    mapsize = offset + size;
                    mapbase = mmap(0, mapsize, PROT_READ, MAP_PRIVATE, fb, 0);
                    if (mapbase != MAP_FAILED) {
                        base = (void const *)((char const *)mapbase + offset);
                    }
                }
            }
            close(fb);
        }
    }

    if (base) {
        if (png) {
            SkBitmap b;
            b.setConfig(flinger2skia(f), w, h, s*bytesPerPixel(f));
            b.setPixels((void*)base);
            SkDynamicMemoryWStream stream;
            SkImageEncoder::EncodeStream(&stream, b,
                    SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality);
            SkData* streamData = stream.copyToData();
            write(fd, streamData->data(), streamData->size());
            streamData->unref();
        } else {
            write(fd, &w, 4);
            write(fd, &h, 4);
            write(fd, &f, 4);
            size_t Bpp = bytesPerPixel(f);
            for (size_t y=0 ; y<h ; y++) {
                write(fd, base, w*Bpp);
                base = (void *)((char *)base + s*Bpp);
            }
        }
    }
    close(fd);
    if (mapbase != MAP_FAILED) {
        munmap((void *)mapbase, mapsize);
    }
    return 0;
}

b.DDMS

ScreenShotDialog.java

/**
     * Captures a new image from the device, and display it.
     */
    private void updateDeviceImage(Shell shell) {
        mBusyLabel.setText("Capturing...");     // no effect

        shell.setCursor(shell.getDisplay().getSystemCursor(SWT.CURSOR_WAIT));

        mRawImage = getDeviceImage();①

        updateImageDisplay(shell);
    }

    /**
     * Updates the display with {@link #mRawImage}.
     * @param shell
     */
    private void updateImageDisplay(Shell shell) {
        Image image;
        if (mRawImage == null) {
            Display display = shell.getDisplay();
            image = ImageLoader.createPlaceHolderArt(
                    display, 320, 240, display.getSystemColor(SWT.COLOR_BLUE));

            mSave.setEnabled(false);
            mBusyLabel.setText("Screen not available");
        } else {
            // convert raw data to an Image.
            PaletteData palette = new PaletteData(
                    mRawImage.getRedMask(),
                    mRawImage.getGreenMask(),
                    mRawImage.getBlueMask());

            ImageData imageData = new ImageData(mRawImage.width, mRawImage.height,
                    mRawImage.bpp, palette, 1, mRawImage.data);
            image = new Image(getParent().getDisplay(), imageData);

            mSave.setEnabled(true);
            mBusyLabel.setText("Captured image:");
        }

        mImageLabel.setImage(image);
        mImageLabel.pack();
        shell.pack();

        // there's no way to restore old cursor; assume it's ARROW
        shell.setCursor(shell.getDisplay().getSystemCursor(SWT.CURSOR_ARROW));
    }

/**
     * Grabs an image from an ADB-connected device and returns it as a {@link RawImage}.
     */
    private RawImage getDeviceImage() {
        try {
            return mDevice.getScreenshot();②
        }
        catch (IOException ioe) {
            Log.w("ddms", "Unable to get frame buffer: " + ioe.getMessage());
            return null;
        } catch (TimeoutException e) {
            Log.w("ddms", "Unable to get frame buffer: timeout ");
            return null;
        } catch (AdbCommandRejectedException e) {
            Log.w("ddms", "Unable to get frame buffer: " + e.getMessage());
            return null;
        }
    }

Device.java

@Override
    public RawImage getScreenshot()
            throws TimeoutException, AdbCommandRejectedException, IOException {
        return AdbHelper.getFrameBuffer(AndroidDebugBridge.getSocketAddress(), this);③
    }

AdbHelper.java

/**
     * Retrieve the frame buffer from the device.
     * @throws TimeoutException in case of timeout on the connection.
     * @throws AdbCommandRejectedException if adb rejects the command
     * @throws IOException in case of I/O error on the connection.
     */
    static RawImage getFrameBuffer(InetSocketAddress adbSockAddr, Device device)
            throws TimeoutException, AdbCommandRejectedException, IOException {

        RawImage imageParams = new RawImage();
        byte[] request = formAdbRequest("framebuffer:");④ //$NON-NLS-1$④
        byte[] nudge = {
            0
        };
        byte[] reply;

        SocketChannel adbChan = null;
        try {
            adbChan = SocketChannel.open(adbSockAddr);
            adbChan.configureBlocking(false);

            // if the device is not -1, then we first tell adb we're looking to talk
            // to a specific device
            setDevice(adbChan, device);

            write(adbChan, request);

            AdbResponse resp = readAdbResponse(adbChan, false /* readDiagString */);
            if (!resp.okay) {
                throw new AdbCommandRejectedException(resp.message);
            }

            // first the protocol version.
            reply = new byte[4];
            read(adbChan, reply);

            ByteBuffer buf = ByteBuffer.wrap(reply);
            buf.order(ByteOrder.LITTLE_ENDIAN);

            int version = buf.getInt();

            // get the header size (this is a count of int)
            int headerSize = RawImage.getHeaderSize(version);

            // read the header
            reply = new byte[headerSize * 4];
            read(adbChan, reply);

            buf = ByteBuffer.wrap(reply);
            buf.order(ByteOrder.LITTLE_ENDIAN);

            // fill the RawImage with the header
            if (!imageParams.readHeader(version, buf)) {
                Log.e("Screenshot", "Unsupported protocol: " + version);
                return null;
            }

            Log.d("ddms", "image params: bpp=" + imageParams.bpp + ", size="
                    + imageParams.size + ", width=" + imageParams.width
                    + ", height=" + imageParams.height);

            write(adbChan, nudge);

            reply = new byte[imageParams.size];
            read(adbChan, reply);

            imageParams.data = reply;
        } finally {
            if (adbChan != null) {
                adbChan.close();
            }
        }

        return imageParams;
    }

services.c

static int create_service_thread(void (*func)(int, void *), void *cookie)
{
    stinfo *sti;
    adb_thread_t t;
    int s[2];

    if(adb_socketpair(s)) {
        printf("cannot create service socket pair\n");
        return -1;
    }

    sti = malloc(sizeof(stinfo));
    if(sti == 0) fatal("cannot allocate stinfo");
    sti->func = func;
    sti->cookie = cookie;
    sti->fd = s[1];

    if(adb_thread_create( &t, service_bootstrap_func, sti)){
        free(sti);
        adb_close(s[0]);
        adb_close(s[1]);
        printf("cannot create service thread\n");
        return -1;
    }

    D("service thread started, %d:%d\n",s[0], s[1]);
    return s[0];
}

int service_to_fd(const char *name)
{
...
else if(!strncmp(name, "framebuffer:", 12)) {
        ret = create_service_thread(framebuffer_service, 0);⑤
...

sysdeps.h

static __inline__ int  adb_thread_create( adb_thread_t  *thread, adb_thread_func_t  func, void*  arg)
{
    thread->tid = _beginthread( (win_thread_func_t)func, 0, arg );
    if (thread->tid == (unsigned)-1L) {
        return -1;
    }
    return 0;
}

framebuffer_service.c

void framebuffer_service(int fd, void *cookie)
{
    struct fbinfo fbinfo;
    unsigned int i;
    char buf[640];
    int fd_screencap;
    int w, h, f;
    int fds[2];

    if (pipe(fds) < 0) goto done;

    pid_t pid = fork();
    if (pid < 0) goto done;

    if (pid == 0) {
        dup2(fds[1], STDOUT_FILENO);
        close(fds[0]);
        close(fds[1]);
        const char* command = "screencap";⑥
        const char *args[2] = {command, NULL};
        execvp(command, (char**)args);
        exit(1);
    }

    fd_screencap = fds[0];

    /* read w, h & format */
    if(readx(fd_screencap, &w, 4)) goto done;
    if(readx(fd_screencap, &h, 4)) goto done;
    if(readx(fd_screencap, &f, 4)) goto done;

    fbinfo.version = DDMS_RAWIMAGE_VERSION;
    /* see hardware/hardware.h */
    switch (f) {
        case 1: /* RGBA_8888 */
            fbinfo.bpp = 32;
            fbinfo.size = w * h * 4;
            fbinfo.width = w;
            fbinfo.height = h;
            fbinfo.red_offset = 0;
            fbinfo.red_length = 8;
            fbinfo.green_offset = 8;
            fbinfo.green_length = 8;
            fbinfo.blue_offset = 16;
            fbinfo.blue_length = 8;
            fbinfo.alpha_offset = 24;
            fbinfo.alpha_length = 8;
            break;
        case 2: /* RGBX_8888 */
            fbinfo.bpp = 32;
            fbinfo.size = w * h * 4;
            fbinfo.width = w;
            fbinfo.height = h;
            fbinfo.red_offset = 0;
            fbinfo.red_length = 8;
            fbinfo.green_offset = 8;
            fbinfo.green_length = 8;
            fbinfo.blue_offset = 16;
            fbinfo.blue_length = 8;
            fbinfo.alpha_offset = 24;
            fbinfo.alpha_length = 0;
            break;
        case 3: /* RGB_888 */
            fbinfo.bpp = 24;
            fbinfo.size = w * h * 3;
            fbinfo.width = w;
            fbinfo.height = h;
            fbinfo.red_offset = 0;
            fbinfo.red_length = 8;
            fbinfo.green_offset = 8;
            fbinfo.green_length = 8;
            fbinfo.blue_offset = 16;
            fbinfo.blue_length = 8;
            fbinfo.alpha_offset = 24;
            fbinfo.alpha_length = 0;
            break;
        case 4: /* RGB_565 */
            fbinfo.bpp = 16;
            fbinfo.size = w * h * 2;
            fbinfo.width = w;
            fbinfo.height = h;
            fbinfo.red_offset = 11;
            fbinfo.red_length = 5;
            fbinfo.green_offset = 5;
            fbinfo.green_length = 6;
            fbinfo.blue_offset = 0;
            fbinfo.blue_length = 5;
            fbinfo.alpha_offset = 0;
            fbinfo.alpha_length = 0;
            break;
        case 5: /* BGRA_8888 */
            fbinfo.bpp = 32;
            fbinfo.size = w * h * 4;
            fbinfo.width = w;
            fbinfo.height = h;
            fbinfo.red_offset = 16;
            fbinfo.red_length = 8;
            fbinfo.green_offset = 8;
            fbinfo.green_length = 8;
            fbinfo.blue_offset = 0;
            fbinfo.blue_length = 8;
            fbinfo.alpha_offset = 24;
            fbinfo.alpha_length = 8;
           break;
        default:
            goto done;
    }

    /* write header */
    if(writex(fd, &fbinfo, sizeof(fbinfo))) goto done;

    /* write data */
    for(i = 0; i < fbinfo.size; i += sizeof(buf)) {
      if(readx(fd_screencap, buf, sizeof(buf))) goto done;
      if(writex(fd, buf, sizeof(buf))) goto done;
    }
    if(readx(fd_screencap, buf, fbinfo.size % sizeof(buf))) goto done;
    if(writex(fd, buf, fbinfo.size % sizeof(buf))) goto done;

done:
    TEMP_FAILURE_RETRY(waitpid(pid, NULL, 0));

    close(fds[0]);
    close(fds[1]);
    close(fd);
}

c.screenshot2：Screenshot.java

/*
     * Grab an image from an ADB-connected device.
     */
    private static void getDeviceImage(IDevice device, String filepath, boolean landscape)
            throws IOException {
        RawImage rawImage;

        try {
            rawImage = device.getScreenshot();
        } catch (TimeoutException e) {
            printAndExit("Unable to get frame buffer: timeout", true /* terminate */);
            return;
        } catch (Exception ioe) {
            printAndExit("Unable to get frame buffer: " + ioe.getMessage(), true /* terminate */);
            return;
        }

        // device/adb not available?
        if (rawImage == null)
            return;

        if (landscape) {
            rawImage = rawImage.getRotated();
        }

        // convert raw data to an Image
        BufferedImage image = new BufferedImage(rawImage.width, rawImage.height,
                BufferedImage.TYPE_INT_ARGB);

        int index = 0;
        int IndexInc = rawImage.bpp >> 3;
        for (int y = 0 ; y < rawImage.height ; y++) {
            for (int x = 0 ; x < rawImage.width ; x++) {
                int value = rawImage.getARGB(index);
                index += IndexInc;
                image.setRGB(x, y, value);
            }
        }

        if (!ImageIO.write(image, "png", new File(filepath))) {
            throw new IOException("Failed to find png writer");
        }
    }

3.robotium：ScreenshotTaker.java

/**
	 * Takes a screenshot and saves it in "/sdcard/Robotium-Screenshots/".
	 * Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.
	 *
	 * @param view the view to take screenshot of
	 * @param name the name to give the screenshot image
	 * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
	 */
	public void takeScreenshot(final String name, final int quality) {
		View decorView = getScreenshotView();
		if(decorView == null)
			return;

		initScreenShotSaver();
		ScreenshotRunnable runnable = new ScreenshotRunnable(decorView, name, quality);
		activityUtils.getCurrentActivity(false).runOnUiThread(runnable);
	}

/**
	 * Gets the proper view to use for a screenshot.
	 */
	private View getScreenshotView() {
		View decorView = viewFetcher.getRecentDecorView(viewFetcher.getWindowDecorViews());
		final long endTime = SystemClock.uptimeMillis() + Timeout.getSmallTimeout();

		while (decorView == null) {	

			final boolean timedOut = SystemClock.uptimeMillis() > endTime;

			if (timedOut){
				return null;
			}
			sleeper.sleepMini();
			decorView = viewFetcher.getRecentDecorView(viewFetcher.getWindowDecorViews());
		}
		wrapAllGLViews(decorView);

		return decorView;
	}

	/**
	 * Extract and wrap the all OpenGL ES Renderer.
	 */
	private void wrapAllGLViews(View decorView) {
		ArrayList<GLSurfaceView> currentViews = viewFetcher.getCurrentViews(GLSurfaceView.class, decorView);
		final CountDownLatch latch = new CountDownLatch(currentViews.size());

		for (GLSurfaceView glView : currentViews) {
			Object renderContainer = new Reflect(glView).field("mGLThread")
					.type(GLSurfaceView.class).out(Object.class);

			Renderer renderer = new Reflect(renderContainer).field("mRenderer").out(Renderer.class);

			if (renderer == null) {
				renderer = new Reflect(glView).field("mRenderer").out(Renderer.class);
				renderContainer = glView;
			}
			if (renderer == null) {
				latch.countDown();
				continue;
			}
			if (renderer instanceof GLRenderWrapper) {
				GLRenderWrapper wrapper = (GLRenderWrapper) renderer;
				wrapper.setTakeScreenshot();
				wrapper.setLatch(latch);
			} else {
				GLRenderWrapper wrapper = new GLRenderWrapper(glView, renderer, latch);
				new Reflect(renderContainer).field("mRenderer").in(wrapper);
			}
		}

		try {
			latch.await();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}

	/**
	 * Returns a bitmap of a given WebView.
	 *
	 * @param webView the webView to save a bitmap from
	 * @return a bitmap of the given web view
	 *
	 */

	private Bitmap getBitmapOfWebView(final WebView webView){
		Picture picture = webView.capturePicture();
		Bitmap b = Bitmap.createBitmap( picture.getWidth(), picture.getHeight(), Bitmap.Config.ARGB_8888);
		Canvas c = new Canvas(b);
		picture.draw(c);
		return b;
	}

	/**
	 * Returns a bitmap of a given View.
	 *
	 * @param view the view to save a bitmap from
	 * @return a bitmap of the given view
	 *
	 */

	private Bitmap getBitmapOfView(final View view){
		view.destroyDrawingCache();
		view.buildDrawingCache(false);
		Bitmap orig = view.getDrawingCache();
		Bitmap.Config config = null;

		if(orig != null) {
			config = orig.getConfig();
		}

		if(config == null) {
			config = Bitmap.Config.ARGB_8888;
		}
		Bitmap b = orig.copy(config, false);
		view.destroyDrawingCache();
		return b;
	}

/**
	 * Here we have a Runnable which is responsible for taking the actual screenshot,
	 * and then posting the bitmap to a Handler which will save it.
	 *
	 * This Runnable is run on the UI thread.
	 */
	private class ScreenshotRunnable implements Runnable {

		private View view;
		private String name;
		private int quality;

		public ScreenshotRunnable(final View _view, final String _name, final int _quality) {
			view = _view;
			name = _name;
			quality = _quality;
		}

		public void run() {
			if(view !=null){
				Bitmap  b;

				if(view instanceof WebView){
					b = getBitmapOfWebView((WebView) view);
				}
				else{
					b = getBitmapOfView(view);
				}
				if(b != null)
					screenShotSaver.saveBitmap(b, name, quality);
				else
					Log.d(LOG_TAG, "NULL BITMAP!!");
			}
		}
	}

	/**
	 * This class is a Handler which deals with saving the screenshots on a separate thread.
	 *
	 * The screenshot logic by necessity has to run on the ui thread.  However, in practice
	 * it seems that saving a screenshot (with quality 100) takes approx twice as long
	 * as taking it in the first place.
	 *
	 * Saving the screenshots in a separate thread like this will thus make the screenshot
	 * process approx 3x faster as far as the main thread is concerned.
	 *
	 */
	private class ScreenShotSaver extends Handler {
		public ScreenShotSaver(HandlerThread thread) {
			super(thread.getLooper());
		}

		/**
		 * This method posts a Bitmap with meta-data to the Handler queue.
		 *
		 * @param bitmap the bitmap to save
		 * @param name the name of the file
		 * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
		 */
		public void saveBitmap(Bitmap bitmap, String name, int quality) {
			Message message = this.obtainMessage();
			message.arg1 = quality;
			message.obj = bitmap;
			message.getData().putString("name", name);
			this.sendMessage(message);
		}

		/**
		 * Here we process the Handler queue and save the bitmaps.
		 *
		 * @param message A Message containing the bitmap to save, and some metadata.
		 */
		public void handleMessage(Message message) {
			String name = message.getData().getString("name");
			int quality = message.arg1;
			Bitmap b = (Bitmap)message.obj;
			if(b != null) {
				saveFile(name, b, quality);
				b.recycle();
			}
			else {
				Log.d(LOG_TAG, "NULL BITMAP!!");
			}
		}

		/**
		 * Saves a file.
		 *
		 * @param name the name of the file
		 * @param b the bitmap to save
		 * @param quality the compression rate. From 0 (compress for lowest size) to 100 (compress for maximum quality).
		 *
		 */
		private void saveFile(String name, Bitmap b, int quality){
			FileOutputStream fos = null;
			String fileName = getFileName(name);

			File directory = new File(Environment.getExternalStorageDirectory() + "/Robotium-Screenshots/");
			directory.mkdir();

			File fileToSave = new File(directory,fileName);
			try {
				fos = new FileOutputStream(fileToSave);
				if (b.compress(Bitmap.CompressFormat.JPEG, quality, fos) == false)
					Log.d(LOG_TAG, "Compress/Write failed");
				fos.flush();
				fos.close();
			} catch (Exception e) {
				Log.d(LOG_TAG, "Can't save the screenshot! Requires write permission (android.permission.WRITE_EXTERNAL_STORAGE) in AndroidManifest.xml of the application under test.");
				e.printStackTrace();
			}
		}
	}

GLRenderWrapper.java

WebViewClassic.java

@Override
    public Picture capturePicture() {
        if (mNativeClass == 0) return null;
        Picture result = new Picture();
        nativeCopyBaseContentToPicture(result);
        return result;
    }

WebView.cpp

static void nativeCopyBaseContentToPicture(JNIEnv *env, jobject obj, jobject pict)
{
    SkPicture* picture = GraphicsJNI::getNativePicture(env, pict);
    GET_NATIVE_VIEW(env, obj)->copyBaseContentToPicture(picture);
}

void copyBaseContentToPicture(SkPicture* picture)
{
    if (!m_baseLayer || !m_baseLayer->content())
        return;
    LayerContent* content = m_baseLayer->content();
    SkCanvas* canvas = picture->beginRecording(content->width(), content->height(),
                                              SkPicture::kUsePathBoundsForClip_RecordingFlag);

    // clear the BaseLayerAndroid's previous matrix (set at each draw)
    SkMatrix baseMatrix;
    baseMatrix.reset();
    m_baseLayer->setMatrix(baseMatrix);

    m_baseLayer->draw(canvas, 0);

    picture->endRecording();
}

Graphics.cpp

SkPicture* GraphicsJNI::getNativePicture(JNIEnv* env, jobject picture)
{
    SkASSERT(env);
    SkASSERT(picture);
    SkASSERT(env->IsInstanceOf(picture, gPicture_class));
    SkPicture* p = (SkPicture*)env->GetIntField(picture, gPicture_nativeInstanceID);
    SkASSERT(p);
    return p;
}

Cafe：SnapshotHelper.java使用了除wrapper外相同的调用方法；

同样还有去除状态栏给Android设备屏幕截图。

4.UiDevice.takeScreenshot (File storePath)/takeScreenshot (File storePath, float scale, int quality)

UiDevice.java

/**
     * Take a screenshot of current window and store it as PNG
     *
     * Default scale of 1.0f (original size) and 90% quality is used
     * The screenshot is adjusted per screen rotation
     *
     * @param storePath where the PNG should be written to
     * @return true if screen shot is created successfully, false otherwise
     * @since API Level 17
     */
    public boolean takeScreenshot(File storePath) {
        Tracer.trace(storePath);
        return takeScreenshot(storePath, 1.0f, 90);①
    }

    /**
     * Take a screenshot of current window and store it as PNG
     *
     * The screenshot is adjusted per screen rotation
     *
     * @param storePath where the PNG should be written to
     * @param scale scale the screenshot down if needed; 1.0f for original size
     * @param quality quality of the PNG compression; range: 0-100
     * @return true if screen shot is created successfully, false otherwise
     * @since API Level 17
     */
    public boolean takeScreenshot(File storePath, float scale, int quality) {
        Tracer.trace(storePath, scale, quality);
        return getAutomatorBridge().takeScreenshot(storePath, quality);②
    }

UiAutomatorBridge.java

public boolean takeScreenshot(File storePath, int quality) {
        Bitmap screenshot = mUiAutomation.takeScreenshot();③
        if (screenshot == null) {
            return false;
        }
        BufferedOutputStream bos = null;
        try {
            bos = new BufferedOutputStream(new FileOutputStream(storePath));
            if (bos != null) {
                screenshot.compress(Bitmap.CompressFormat.PNG, quality, bos);
                bos.flush();
            }
        } catch (IOException ioe) {
            Log.e(LOG_TAG, "failed to save screen shot to file", ioe);
            return false;
        } finally {
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException ioe) {
                    /* ignore */
                }
            }
            screenshot.recycle();
        }
        return true;
    }

UiAutomation.java

/**
     * Takes a screenshot.
     *
     * @return The screenshot bitmap on success, null otherwise.
     */
    public Bitmap takeScreenshot() {
        synchronized (mLock) {
            throwIfNotConnectedLocked();
        }
        Display display = DisplayManagerGlobal.getInstance()
                .getRealDisplay(Display.DEFAULT_DISPLAY);
        Point displaySize = new Point();
        display.getRealSize(displaySize);
        final int displayWidth = displaySize.x;
        final int displayHeight = displaySize.y;

        final float screenshotWidth;
        final float screenshotHeight;

        final int rotation = display.getRotation();
        switch (rotation) {
            case ROTATION_FREEZE_0: {
                screenshotWidth = displayWidth;
                screenshotHeight = displayHeight;
            } break;
            case ROTATION_FREEZE_90: {
                screenshotWidth = displayHeight;
                screenshotHeight = displayWidth;
            } break;
            case ROTATION_FREEZE_180: {
                screenshotWidth = displayWidth;
                screenshotHeight = displayHeight;
            } break;
            case ROTATION_FREEZE_270: {
                screenshotWidth = displayHeight;
                screenshotHeight = displayWidth;
            } break;
            default: {
                throw new IllegalArgumentException("Invalid rotation: "
                        + rotation);
            }
        }

        // Take the screenshot
        Bitmap screenShot = null;
        try {
            // Calling out without a lock held.
            screenShot = mUiAutomationConnection.takeScreenshot((int) screenshotWidth,
                    (int) screenshotHeight);④
            if (screenShot == null) {
                return null;
            }
        } catch (RemoteException re) {
            Log.e(LOG_TAG, "Error while taking screnshot!", re);
            return null;
        }

        // Rotate the screenshot to the current orientation
        if (rotation != ROTATION_FREEZE_0) {
            Bitmap unrotatedScreenShot = Bitmap.createBitmap(displayWidth, displayHeight,
                    Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(unrotatedScreenShot);
            canvas.translate(unrotatedScreenShot.getWidth() / 2,
                    unrotatedScreenShot.getHeight() / 2);
            canvas.rotate(getDegreesForRotation(rotation));
            canvas.translate(- screenshotWidth / 2, - screenshotHeight / 2);
            canvas.drawBitmap(screenShot, 0, 0, null);
            canvas.setBitmap(null);
            screenShot = unrotatedScreenShot;
        }

        // Optimization
        screenShot.setHasAlpha(false);

        return screenShot;
    }

UiAutomationConnection.java

@Override
    public Bitmap takeScreenshot(int width, int height) {
        synchronized (mLock) {
            throwIfCalledByNotTrustedUidLocked();
            throwIfShutdownLocked();
            throwIfNotConnectedLocked();
        }
        final long identity = Binder.clearCallingIdentity();
        try {
            return SurfaceControl.screenshot(width, height);⑤
        } finally {
            Binder.restoreCallingIdentity(identity);
        }
    }

可以看到，绕来绕去又回到方法1了。