Activity插件化解决方案

--摘自《android插件化开发指南》

1.宿主App加载插件中的类

2.最简单的插件化方案就是在宿主的androidmanifest.xml中申明插件中的四大组件

把插件dex合并到宿主dex中，那么宿主app对应的classloader就可以加载插件中的任意类

/**
 * 由于应用程序使用的ClassLoader为PathClassLoader
 * 最终继承自 BaseDexClassLoader
 * 查看源码得知,这个BaseDexClassLoader加载代码根据一个叫做
 * dexElements的数组进行, 因此我们把包含代码的dex文件插入这个数组
 * 系统的classLoader就能帮助我们找到这个类
 *
 * 这个类用来进行对于BaseDexClassLoader的Hook
 * 类名太长, 不要吐槽.
 * @author weishu
 * @date 16/3/28
 */
public final class BaseDexClassLoaderHookHelper {

    public static void patchClassLoader(ClassLoader cl, File apkFile, File optDexFile)
            throws IllegalAccessException, NoSuchMethodException, IOException, InvocationTargetException, InstantiationException, NoSuchFieldException {
        // 获取 BaseDexClassLoader : pathList
        Object pathListObj = RefInvoke.getFieldObject(DexClassLoader.class.getSuperclass(), cl, "pathList");

        // 获取 PathList: Element[] dexElements
        Object[] dexElements = (Object[]) RefInvoke.getFieldObject(pathListObj, "dexElements");

        // Element 类型
        Class<?> elementClass = dexElements.getClass().getComponentType();

        // 创建一个数组, 用来替换原始的数组
        Object[] newElements = (Object[]) Array.newInstance(elementClass, dexElements.length + 1);

        // 构造插件Element(File file, boolean isDirectory, File zip, DexFile dexFile) 这个构造函数
        Class[] p1 = {File.class, boolean.class, File.class, DexFile.class};
        Object[] v1 = {apkFile, false, apkFile, DexFile.loadDex(apkFile.getCanonicalPath(), optDexFile.getAbsolutePath(), 0)};
        Object o = RefInvoke.createObject(elementClass, p1, v1);

        Object[] toAddElementArray = new Object[] { o };
        // 把原始的elements复制进去
        System.arraycopy(dexElements, 0, newElements, 0, dexElements.length);
        // 插件的那个element复制进去
        System.arraycopy(toAddElementArray, 0, newElements, dexElements.length, toAddElementArray.length);

        // 替换
        RefInvoke.setFieldObject(pathListObj, "dexElements", newElements);
    }
}

加载插件中的资源

private static void reloadInstalledPluginResources(ArrayList<String> pluginPaths) {
    try {
        AssetManager assetManager = AssetManager.class.newInstance();
        Method addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);

        addAssetPath.invoke(assetManager, mBaseContext.getPackageResourcePath());

        for(String pluginPath: pluginPaths) {
            addAssetPath.invoke(assetManager, pluginPath);
        }

        Resources newResources = new Resources(assetManager,
                mBaseContext.getResources().getDisplayMetrics(),
                mBaseContext.getResources().getConfiguration());

        RefInvoke.setFieldObject(mBaseContext, "mResources", newResources);
        //这是最主要的需要替换的，如果不支持插件运行时更新，只留这一个就可以了
        RefInvoke.setFieldObject(mPackageInfo, "mResources", newResources);

        mNowResources = newResources;
        //需要清理mTheme对象，否则通过inflate方式加载资源会报错
        //如果是activity动态加载插件，则需要把activity的mTheme对象也设置为null
        RefInvoke.setFieldObject(mBaseContext, "mTheme", null);
    } catch (Throwable e) {
        e.printStackTrace();
    }
}

public class TestActivity1 extends ZeusBaseActivity {
    private final static String TAG = "TestActivity1";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test1);

        findViewById(R.id.button1).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    Intent intent = new Intent();

                    String activityName = "jianqiang.com.hostapp.ActivityA";
                    intent.setComponent(new ComponentName("jianqiang.com.hostapp", activityName));

                    startActivity(intent);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

以上方案有2个缺点，就是新增的Activity无法在宿主AndroidManifest文件中预先占位了；并且插件和宿主的资源都合并到了一起，资源id会有冲突

启动没有在AndroidManifest中声明的插件Activity(采用欺上瞒下的做法)

class MockClass1 implements InvocationHandler {

    private static final String TAG = "MockClass1";

    Object mBase;

    public MockClass1(Object base) {
        mBase = base;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

        Log.e("bao", method.getName());

        if ("startActivity".equals(method.getName())) {
            // 只拦截这个方法
            // 替换参数, 任你所为;甚至替换原始Activity启动别的Activity偷梁换柱

            // 找到参数里面的第一个Intent 对象
            Intent raw;
            int index = 0;

            for (int i = 0; i < args.length; i++) {
                if (args[i] instanceof Intent) {
                    index = i;
                    break;
                }
            }
            raw = (Intent) args[index];

            Intent newIntent = new Intent();

            // 替身Activity的包名, 也就是我们自己的包名
            String stubPackage = "jianqiang.com.activityhook1";

            // 这里我们把启动的Activity临时替换为 StubActivity
            ComponentName componentName = new ComponentName(stubPackage, StubActivity.class.getName());
            newIntent.setComponent(componentName);

            // 把我们原始要启动的TargetActivity先存起来
            newIntent.putExtra(AMSHookHelper.EXTRA_TARGET_INTENT, raw);

            // 替换掉Intent, 达到欺骗AMS的目的
            args[index] = newIntent;

            Log.d(TAG, "hook success");
            return method.invoke(mBase, args);
        }

        return method.invoke(mBase, args);
    }
}

class MockClass2 implements Handler.Callback {

    Handler mBase;

    public MockClass2(Handler base) {
        mBase = base;
    }

    @Override
    public boolean handleMessage(Message msg) {

        switch (msg.what) {
            // ActivityThread里面 "LAUNCH_ACTIVITY" 这个字段的值是100
            // 本来使用反射的方式获取最好, 这里为了简便直接使用硬编码
            case 100:
                handleLaunchActivity(msg);
                break;
        }

        mBase.handleMessage(msg);
        return true;
    }

    private void handleLaunchActivity(Message msg) {
        // 这里简单起见,直接取出TargetActivity;

        Object obj = msg.obj;

        // 把替身恢复成真身
        Intent raw = (Intent) RefInvoke.getFieldObject(obj, "intent");

        Intent target = raw.getParcelableExtra(AMSHookHelper.EXTRA_TARGET_INTENT);
        raw.setComponent(target.getComponent());

        //修改packageName，这样缓存才能命中
        ActivityInfo activityInfo = (ActivityInfo) RefInvoke.getFieldObject(obj, "activityInfo");
        activityInfo.applicationInfo.packageName = target.getPackage() == null ?
                target.getComponent().getPackageName() : target.getPackage();

        try {
            hookPackageManager();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void hookPackageManager() throws Exception {

        // 这一步是因为 initializeJavaContextClassLoader 这个方法内部无意中检查了这个包是否在系统安装
        // 如果没有安装, 直接抛出异常, 这里需要临时Hook掉 PMS, 绕过这个检查.
        Object currentActivityThread = RefInvoke.invokeStaticMethod("android.app.ActivityThread", "currentActivityThread");

        // 获取ActivityThread里面原始的 sPackageManager
        Object sPackageManager = RefInvoke.getFieldObject(currentActivityThread, "sPackageManager");

        // 准备好代理对象, 用来替换原始的对象
        Class<?> iPackageManagerInterface = Class.forName("android.content.pm.IPackageManager");
        Object proxy = Proxy.newProxyInstance(iPackageManagerInterface.getClassLoader(),
                new Class<?>[] { iPackageManagerInterface },
                new MockClass3(sPackageManager));

        // 1. 替换掉ActivityThread里面的 sPackageManager 字段
        RefInvoke.setFieldObject(currentActivityThread, "sPackageManager", proxy);
    }
}

public class AMSHookHelper {

    public static final String EXTRA_TARGET_INTENT = "extra_target_intent";

    /**
     * Hook AMS
     * 主要完成的操作是  "把真正要启动的Activity临时替换为在AndroidManifest.xml中声明的替身Activity",进而骗过AMS
     */
    public static void hookAMN() throws ClassNotFoundException,
            NoSuchMethodException, InvocationTargetException,
            IllegalAccessException, NoSuchFieldException {

        //获取AMN的gDefault单例gDefault，gDefault是final静态的
        Object gDefault = RefInvoke.getStaticFieldObject("android.app.ActivityManagerNative", "gDefault");

        // gDefault是一个 android.util.Singleton<T>对象; 我们取出这个单例里面的mInstance字段
        Object mInstance = RefInvoke.getFieldObject("android.util.Singleton", gDefault, "mInstance");

        // 创建一个这个对象的代理对象MockClass1, 然后替换这个字段, 让我们的代理对象帮忙干活
        Class<?> classB2Interface = Class.forName("android.app.IActivityManager");
        Object proxy = Proxy.newProxyInstance(
                Thread.currentThread().getContextClassLoader(),
                new Class<?>[] { classB2Interface },
                new MockClass1(mInstance));

        //把gDefault的mInstance字段，修改为proxy
        RefInvoke.setFieldObject("android.util.Singleton", gDefault, "mInstance", proxy);
    }

    /**
     * 由于之前我们用替身欺骗了AMS; 现在我们要换回我们真正需要启动的Activity
     * 不然就真的启动替身了, 狸猫换太子...
     * 到最终要启动Activity的时候,会交给ActivityThread 的一个内部类叫做 H 来完成
     * H 会完成这个消息转发; 最终调用它的callback
     */
    public static void hookActivityThread() throws Exception {

        // 先获取到当前的ActivityThread对象
        Object currentActivityThread = RefInvoke.getStaticFieldObject("android.app.ActivityThread", "sCurrentActivityThread");

        // 由于ActivityThread一个进程只有一个,我们获取这个对象的mH
        Handler mH = (Handler) RefInvoke.getFieldObject(currentActivityThread, "mH");

        //把Handler的mCallback字段，替换为new MockClass2(mH)
        RefInvoke.setFieldObject(Handler.class,
                mH, "mCallback", new MockClass2(mH));
    }
}

动态替换Activity的插件化方案

1）为插件创建一个LoadedApk对象，并把它事先放到mPackages缓存中。这样getPackageInfo方法就会直接返回这个插件的LoadedApk对象，也就是永远命中缓存，永远不会走下面创建LoadedApk对象的逻辑

2）反射得到插件的loadedApk对象的mClassLoader字段，设置为插件的ClassLoader。

public class LoadedApkClassLoaderHookHelper {

    public static Map<String, Object> sLoadedApk = new HashMap<String, Object>();

    public static void hookLoadedApkInActivityThread(File apkFile) throws ClassNotFoundException,
            NoSuchMethodException, InvocationTargetException, IllegalAccessException, NoSuchFieldException, InstantiationException {

        // 先获取到当前的ActivityThread对象
        Object currentActivityThread = RefInvoke.invokeStaticMethod("android.app.ActivityThread", "currentActivityThread");

        // 获取到 mPackages 这个静态成员变量, 这里缓存了dex包的信息
        Map mPackages = (Map) RefInvoke.getFieldObject(currentActivityThread, "mPackages");

        //准备两个参数
        // android.content.res.CompatibilityInfo
        Object defaultCompatibilityInfo = RefInvoke.getStaticFieldObject("android.content.res.CompatibilityInfo", "DEFAULT_COMPATIBILITY_INFO");
        //从apk中取得ApplicationInfo信息
        ApplicationInfo applicationInfo = generateApplicationInfo(apkFile);

        //调用ActivityThread的getPackageInfoNoCheck方法loadedApk，得到，上面两个数据都是用来做参数的
        Class[] p1 = {ApplicationInfo.class, Class.forName("android.content.res.CompatibilityInfo")};
        Object[] v1 = {applicationInfo, defaultCompatibilityInfo};
        Object loadedApk = RefInvoke.invokeInstanceMethod(currentActivityThread, "getPackageInfoNoCheck", p1, v1);

        //为插件造一个新的ClassLoader
        String odexPath = Utils.getPluginOptDexDir(applicationInfo.packageName).getPath();
        String libDir = Utils.getPluginLibDir(applicationInfo.packageName).getPath();
        ClassLoader classLoader = new CustomClassLoader(apkFile.getPath(), odexPath, libDir, ClassLoader.getSystemClassLoader());
        RefInvoke.setFieldObject(loadedApk, "mClassLoader", classLoader);

        //把插件LoadedApk对象放入缓存
        WeakReference weakReference = new WeakReference(loadedApk);
        mPackages.put(applicationInfo.packageName, weakReference);

        // 由于是弱引用, 因此我们必须在某个地方存一份, 不然容易被GC; 那么就前功尽弃了.
        sLoadedApk.put(applicationInfo.packageName, loadedApk);
    }

    /**
     * 这个方法的最终目的是调用
     * android.content.pm.PackageParser#generateActivityInfo(android.content.pm.PackageParser.Activity, int, android.content.pm.PackageUserState, int)
     */
    public static ApplicationInfo generateApplicationInfo(File apkFile)
            throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchFieldException {

        // 找出需要反射的核心类: android.content.pm.PackageParser
        Class<?> packageParserClass = Class.forName("android.content.pm.PackageParser");
        Class<?> packageParser$PackageClass = Class.forName("android.content.pm.PackageParser$Package");
        Class<?> packageUserStateClass = Class.forName("android.content.pm.PackageUserState");

        // 我们的终极目标: android.content.pm.PackageParser#generateApplicationInfo(android.content.pm.PackageParser.Package,
        // int, android.content.pm.PackageUserState)
        // 要调用这个方法, 需要做很多准备工作; 考验反射技术的时候到了 - -!
        // 下面, 我们开始这场Hack之旅吧!

        // 首先拿到我们得终极目标: generateApplicationInfo方法
        // API 23 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        // public static ApplicationInfo generateApplicationInfo(Package p, int flags,
        //    PackageUserState state) {
        // 其他Android版本不保证也是如此.

        // 首先, 我们得创建出一个Package对象出来供这个方法调用
        // 而这个需要得对象可以通过 android.content.pm.PackageParser#parsePackage 这个方法返回得 Package对象得字段获取得到
        // 创建出一个PackageParser对象供使用
        Object packageParser = packageParserClass.newInstance();

        // 调用 PackageParser.parsePackage 解析apk的信息
        // 实际上是一个 android.content.pm.PackageParser.Package 对象
        Class[] p1 = {File.class, int.class};
        Object[] v1 = {apkFile, 0};
        Object packageObj = RefInvoke.invokeInstanceMethod(packageParser, "parsePackage", p1, v1);

        // 第三个参数 mDefaultPackageUserState 我们直接使用默认构造函数构造一个出来即可
        Object defaultPackageUserState = packageUserStateClass.newInstance();

        // 万事具备!!!!!!!!!!!!!!
        Class[] p2 = {packageParser$PackageClass, int.class, packageUserStateClass};
        Object[] v2 = {packageObj, 0, defaultPackageUserState};
        ApplicationInfo applicationInfo = (ApplicationInfo)RefInvoke.invokeInstanceMethod(packageParser, "generateApplicationInfo", p2, v2);

        String apkPath = apkFile.getPath();
        applicationInfo.sourceDir = apkPath;
        applicationInfo.publicSourceDir = apkPath;

        return applicationInfo;
    }
}

上述代码的思想是，反射PackageParser的generateApplicationInfo方法，硬生生地创建出一个ApplicationInfo对象

加载插件中类的方案1：为每个插件创建一个ClassLoader

public class CustomClassLoader extends DexClassLoader {

    public CustomClassLoader(String dexPath, String optimizedDirectory, String libraryPath, ClassLoader parent) {
        super(dexPath, optimizedDirectory, libraryPath, parent);
    }
}

总结就是把插件apk对应的LoadedApk对象，直接放入了缓存里，然后把这个LoadedApk对象的ClassLoader改为插件的ClassLoader

加载插件中类的方案2：合并多个dex

1）根据宿主的ClassLoader，获取宿主的dexElements字段

　　首先反射出BaseDexClassLoader的pathList字段，它是DexPathList类型的

　　然后反射出DexPathList的dexElements字段，这是个数组

2）根据插件的apkFile，反射出一个Element类型的对象，这就是插件dex

3）把插件dex和宿主dexElements合并成一个新的dex数组，替换宿主之前的dexElements字段

public final class BaseDexClassLoaderHookHelper {

    public static void patchClassLoader(ClassLoader cl, File apkFile, File optDexFile)
            throws IllegalAccessException, NoSuchMethodException, IOException, InvocationTargetException, InstantiationException, NoSuchFieldException {
        // 获取 BaseDexClassLoader : pathList
        Object pathListObj = RefInvoke.getFieldObject(DexClassLoader.class.getSuperclass(), cl, "pathList");

        // 获取 PathList: Element[] dexElements
        Object[] dexElements = (Object[]) RefInvoke.getFieldObject(pathListObj, "dexElements");

        // Element 类型
        Class<?> elementClass = dexElements.getClass().getComponentType();

        // 创建一个数组, 用来替换原始的数组
        Object[] newElements = (Object[]) Array.newInstance(elementClass, dexElements.length + 1);

        // 构造插件Element(File file, boolean isDirectory, File zip, DexFile dexFile) 这个构造函数
        Class[] p1 = {File.class, boolean.class, File.class, DexFile.class};
        Object[] v1 = {apkFile, false, apkFile, DexFile.loadDex(apkFile.getCanonicalPath(), optDexFile.getAbsolutePath(), 0)};
        Object o = RefInvoke.createObject(elementClass, p1, v1);

        Object[] toAddElementArray = new Object[] { o };
        // 把原始的elements复制进去
        System.arraycopy(dexElements, 0, newElements, 0, dexElements.length);
        // 插件的那个element复制进去
        System.arraycopy(toAddElementArray, 0, newElements, dexElements.length, toAddElementArray.length);

        // 替换
        RefInvoke.setFieldObject(pathListObj, "dexElements", newElements);
    }
}

解决插件化Activity启动模式的问题，使用的是占位Activity的思想，即事先为这3中启动模式创建很多的StubActivity，占位activity是什么启动模式，对应的插件activity就是什么启动模式

加载插件中类的方案3：修改app原生的ClassLoader

class ZeusClassLoader extends PathClassLoader {
    private List<DexClassLoader> mClassLoaderList = null;

    public ZeusClassLoader(String dexPath, ClassLoader parent) {
        super(dexPath, parent);

        mClassLoaderList = new ArrayList<DexClassLoader>();
    }

    /**
     * 添加一个插件到当前的classLoader中
     */
    protected void addPluginClassLoader(DexClassLoader dexClassLoader) {
        mClassLoaderList.add(dexClassLoader);
    }

    @Override
    protected Class<?> loadClass(String className, boolean resolve) throws ClassNotFoundException {
        Class<?> clazz = null;
        try {
            //先查找parent classLoader，这里实际就是系统帮我们创建的classLoader，目标对应为宿主apk
            clazz = getParent().loadClass(className);
        } catch (ClassNotFoundException ignored) {

        }

        if (clazz != null) {
            return clazz;
        }

        //挨个的到插件里进行查找
        if (mClassLoaderList != null) {
            for (DexClassLoader classLoader : mClassLoaderList) {
                if (classLoader == null) continue;
                try {
                    //这里只查找插件它自己的apk，不需要查parent，避免多次无用查询，提高性能
                    clazz = classLoader.loadClass(className);
                    if (clazz != null) {
                        return clazz;
                    }
                } catch (ClassNotFoundException ignored) {

                }
            }
        }
        throw new ClassNotFoundException(className + " in loader " + this);
    }
}

public class PluginManager {
    public final static List<PluginItem> plugins = new ArrayList<PluginItem>();

    //正在使用的Resources
    public static volatile Resources mNowResources;

    //原始的application中的BaseContext，不能是其他的，否则会内存泄漏
    public static volatile Context mBaseContext;

    //ContextImpl中的LoadedAPK对象mPackageInfo
    private static Object mPackageInfo = null;

    public static volatile ClassLoader mNowClassLoader = null;          //系统原始的ClassLoader
    public static volatile ClassLoader mBaseClassLoader = null;         //系统原始的ClassLoader

    public static void init(Application application) {
        //初始化一些成员变量和加载已安装的插件
        mPackageInfo = RefInvoke.getFieldObject(application.getBaseContext(), "mPackageInfo");
        mBaseContext = application.getBaseContext();
        mNowResources = mBaseContext.getResources();

        mBaseClassLoader = mBaseContext.getClassLoader();
        mNowClassLoader = mBaseContext.getClassLoader();

        try {
            AssetManager assetManager = application.getAssets();
            String[] paths = assetManager.list("");

            ArrayList<String> pluginPaths = new ArrayList<String>();
            for(String path : paths) {
                if(path.endsWith(".apk")) {
                    String apkName = path;

                    Utils.extractAssets(mBaseContext, apkName);

                    PluginItem item = generatePluginItem(apkName);
                    plugins.add(item);

                    pluginPaths.add(item.pluginPath);
                }
            }

            reloadInstalledPluginResources(pluginPaths);

        } catch (Exception e) {
            e.printStackTrace();
        }

        ZeusClassLoader classLoader = new ZeusClassLoader(mBaseContext.getPackageCodePath(), mBaseContext.getClassLoader());

        File dexOutputDir = mBaseContext.getDir("dex", Context.MODE_PRIVATE);
        final String dexOutputPath = dexOutputDir.getAbsolutePath();
        for(PluginItem plugin: plugins) {
            DexClassLoader dexClassLoader = new DexClassLoader(plugin.pluginPath,
                    dexOutputPath, null, mBaseClassLoader);
            classLoader.addPluginClassLoader(dexClassLoader);
        }

        RefInvoke.setFieldObject(mPackageInfo, "mClassLoader", classLoader);
        Thread.currentThread().setContextClassLoader(classLoader);
        mNowClassLoader = classLoader;

    }

    private static PluginItem generatePluginItem(String apkName) {
        File file = mBaseContext.getFileStreamPath(apkName);
        PluginItem item = new PluginItem();
        item.pluginPath = file.getAbsolutePath();
        item.packageInfo = DLUtils.getPackageInfo(mBaseContext, item.pluginPath);

        return item;
    }

    private static void reloadInstalledPluginResources(ArrayList<String> pluginPaths) {
        try {
            AssetManager assetManager = AssetManager.class.newInstance();
            Method addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);

            addAssetPath.invoke(assetManager, mBaseContext.getPackageResourcePath());

            for(String pluginPath: pluginPaths) {
                addAssetPath.invoke(assetManager, pluginPath);
            }

            Resources newResources = new Resources(assetManager,
                    mBaseContext.getResources().getDisplayMetrics(),
                    mBaseContext.getResources().getConfiguration());

            RefInvoke.setFieldObject(mBaseContext, "mResources", newResources);
            //这是最主要的需要替换的，如果不支持插件运行时更新，只留这一个就可以了
            RefInvoke.setFieldObject(mPackageInfo, "mResources", newResources);

            //清除一下之前的resource的数据，释放一些内存
            //因为这个resource有可能还被系统持有着，内存都没被释放
            //clearResoucesDrawableCache(mNowResources);

            mNowResources = newResources;
            //需要清理mtheme对象，否则通过inflate方式加载资源会报错
            //如果是activity动态加载插件，则需要把activity的mTheme对象也设置为null
            RefInvoke.setFieldObject(mBaseContext, "mTheme", null);
        } catch (Throwable e) {
            e.printStackTrace();
        }
    }
}

调用

Intent intent = new Intent();
String serviceName = PluginManager.plugins.get(0).packageInfo.packageName + ".TestService1";
intent.setClass(this, getClassLoader().loadClass(serviceName));
startService(intent);

以上的方案对于四大组件都是适用的

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