【Android Demo】加载.gif格式图片

Android系统为了节省内存，一般不支持直接显示gif图片，即使你强制设置了，也只会显示图片的第一帧。

这个 Demo 是在网上看到的，是个思路，还是有些局限性，还是记录下，以后研究吧。

1.效果图：

2.实现原理：

通过解码gif图片形成多张静态图，然后通过线程和imageView来实现循环播放

3.准备GIF图片

4.详细代码

<1>工具类：CommonUtil.java

package com.yanis.tools;

import java.io.InputStream;

import com.yanis.tools.GifHelper.GifFrame;

public class CommonUtil {
    /**
     * 解码GIF图片
     *
     * @param is
     * @return
     */
    public static GifFrame[] getGif(InputStream is) {
        GifHelper gifHelper = new GifHelper();
        if (GifHelper.STATUS_OK == gifHelper.read(is)) {
            return gifHelper.getFrames();
        }
        return null;
    }
    /**
     * 判断图片是否为GIF格式
     * @param is
     * @return
     */
    public static boolean isGif(InputStream is) {
        GifHelper gifHelper = new GifHelper();
        return gifHelper.isGif(is);
    }
}

<2>解码类：GifHelper.java

package com.yanis.tools;

import java.io.InputStream;
import java.util.Vector;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;

//Handler for read & extract Bitmap from *.gif
public class GifHelper {  

  // to store *.gif data, Bitmap & delay
  public static class GifFrame {
      // to access image & delay w/o interface
      public Bitmap image;
      public int delay;  

      public GifFrame(Bitmap im, int del) {
          image = im;
          delay = del;
      }  

  }  

  // to define some error type
  public static final int STATUS_OK = 0;
  public static final int STATUS_FORMAT_ERROR = 1;
  public static final int STATUS_OPEN_ERROR = 2;  

  protected int status;  

  protected InputStream in;  

  protected int width; // full image width
  protected int height; // full image height
  protected boolean gctFlag; // global color table used
  protected int gctSize; // size of global color table
  protected int loopCount = 1; // iterations; 0 = repeat forever  

  protected int[] gct; // global color table
  protected int[] lct; // local color table
  protected int[] act; // active color table  

  protected int bgIndex; // background color index
  protected int bgColor; // background color
  protected int lastBgColor; // previous bg color
  protected int pixelAspect; // pixel aspect ratio  

  protected boolean lctFlag; // local color table flag
  protected boolean interlace; // interlace flag
  protected int lctSize; // local color table size  

  protected int ix, iy, iw, ih; // current image rectangle
  protected int lrx, lry, lrw, lrh;
  protected Bitmap image; // current frame
  protected Bitmap lastImage; // previous frame
  protected int frameindex = 0;  

  public int getFrameindex() {
      return frameindex;
  }  

  public void setFrameindex(int frameindex) {
      this.frameindex = frameindex;
      if (frameindex > frames.size() - 1) {
          frameindex = 0;
      }
  }  

  protected byte[] block = new byte[256]; // current data block
  protected int blockSize = 0; // block size  

  // last graphic control extension info
  protected int dispose = 0;
  // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
  protected int lastDispose = 0;
  protected boolean transparency = false; // use transparent color
  protected int delay = 0; // delay in milliseconds
  protected int transIndex; // transparent color index  

  protected static final int MaxStackSize = 4096;
  // max decoder pixel stack size  

  // LZW decoder working arrays
  protected short[] prefix;
  protected byte[] suffix;
  protected byte[] pixelStack;
  protected byte[] pixels;  

  protected Vector<GifFrame> frames; // frames read from current file
  protected int frameCount;  

  // to get its Width / Height
  public int getWidth() {
      return width;
  }  

  public int getHeigh() {
      return height;
  }  

  /**
   * Gets display duration for specified frame.
   *
   * @param n
   *            int index of frame
   * @return delay in milliseconds
   */
  public int getDelay(int n) {
      delay = -1;
      if ((n >= 0) && (n < frameCount)) {
          delay = ((GifFrame) frames.elementAt(n)).delay;
      }
      return delay;
  }  

  public int getFrameCount() {
      return frameCount;
  }  

  public Bitmap getImage() {
      return getFrame(0);
  }  

  public int getLoopCount() {
      return loopCount;
  }  

  protected void setPixels() {
      int[] dest = new int[width * height];
      // fill in starting image contents based on last image's dispose code
      if (lastDispose > 0) {
          if (lastDispose == 3) {
              // use image before last
              int n = frameCount - 2;
              if (n > 0) {
                  lastImage = getFrame(n - 1);
              } else {
                  lastImage = null;
              }
          }
          if (lastImage != null) {
              lastImage.getPixels(dest, 0, width, 0, 0, width, height);
              // copy pixels
              if (lastDispose == 2) {
                  // fill last image rect area with background color
                  int c = 0;
                  if (!transparency) {
                      c = lastBgColor;
                  }
                  for (int i = 0; i < lrh; i++) {
                      int n1 = (lry + i) * width + lrx;
                      int n2 = n1 + lrw;
                      for (int k = n1; k < n2; k++) {
                          dest[k] = c;
                      }
                  }
              }
          }
      }  

      // copy each source line to the appropriate place in the destination
      int pass = 1;
      int inc = 8;
      int iline = 0;
      for (int i = 0; i < ih; i++) {
          int line = i;
          if (interlace) {
              if (iline >= ih) {
                  pass++;
                  switch (pass) {
                  case 2:
                      iline = 4;
                      break;
                  case 3:
                      iline = 2;
                      inc = 4;
                      break;
                  case 4:
                      iline = 1;
                      inc = 2;
                  }
              }
              line = iline;
              iline += inc;
          }
          line += iy;
          if (line < height) {
              int k = line * width;
              int dx = k + ix; // start of line in dest
              int dlim = dx + iw; // end of dest line
              if ((k + width) < dlim) {
                  dlim = k + width; // past dest edge
              }
              int sx = i * iw; // start of line in source
              while (dx < dlim) {
                  // map color and insert in destination
                  int index = ((int) pixels[sx++]) & 0xff;
                  int c = act[index];
                  if (c != 0) {
                      dest[dx] = c;
                  }
                  dx++;
              }
          }
      }
      image = Bitmap.createBitmap(dest, width, height, Config.RGB_565);
  }  

  public Bitmap getFrame(int n) {
      Bitmap im = null;
      if ((n >= 0) && (n < frameCount)) {
          im = ((GifFrame) frames.elementAt(n)).image;
      }
      return im;
  }  

  public GifFrame[] getFrames() {
      if(null != frames) return frames.toArray(new GifFrame[0]);
      return null;
  }  

  public Bitmap nextBitmap() {
      frameindex++;
      if (frameindex > frames.size() - 1) {
          frameindex = 0;
      }
      return ((GifFrame) frames.elementAt(frameindex)).image;
  }  

  public int nextDelay() {
      return ((GifFrame) frames.elementAt(frameindex)).delay;
  }  

  // to read & parse all *.gif stream
  public int read(InputStream is) {
      init();
      if (is != null) {
          in = is;
          readHeader();
          if (!err()) {
              readContents();
              if (frameCount < 0) {
                  status = STATUS_FORMAT_ERROR;
              }
          }
      } else {
          status = STATUS_OPEN_ERROR;
      }
      try {
          is.close();
      } catch (Exception e) {
          e.printStackTrace();
      }
      return status;
  }  

  public boolean isGif(InputStream is) {
      init();
      if (is != null) {
          in = is;
          String id = "";
          for (int i = 0; i < 6; i++) {
              id += (char) read();
          }
          if (!id.toUpperCase().startsWith("GIF")) {
              return false;
          }
      }
      try {
          is.close();
      } catch (Exception e) {
          e.printStackTrace();
      }
      return true;
  }  

  protected void decodeImageData() {
      int NullCode = -1;
      int npix = iw * ih;
      int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi;  

      if ((pixels == null) || (pixels.length < npix)) {
          pixels = new byte[npix]; // allocate new pixel array
      }
      if (prefix == null) {
          prefix = new short[MaxStackSize];
      }
      if (suffix == null) {
          suffix = new byte[MaxStackSize];
      }
      if (pixelStack == null) {
          pixelStack = new byte[MaxStackSize + 1];
      }
      // Initialize GIF data stream decoder.
      data_size = read();
      clear = 1 << data_size;
      end_of_information = clear + 1;
      available = clear + 2;
      old_code = NullCode;
      code_size = data_size + 1;
      code_mask = (1 << code_size) - 1;
      for (code = 0; code < clear; code++) {
          prefix[code] = 0;
          suffix[code] = (byte) code;
      }  

      // Decode GIF pixel stream.
      datum = bits = count = first = top = pi = bi = 0;
      for (i = 0; i < npix;) {
          if (top == 0) {
              if (bits < code_size) {
                  // Load bytes until there are enough bits for a code.
                  if (count == 0) {
                      // Read a new data block.
                      count = readBlock();
                      if (count <= 0) {
                          break;
                      }
                      bi = 0;
                  }
                  datum += (((int) block[bi]) & 0xff) << bits;
                  bits += 8;
                  bi++;
                  count--;
                  continue;
              }
              // Get the next code.
              code = datum & code_mask;
              datum >>= code_size;
              bits -= code_size;  

              // Interpret the code
              if ((code > available) || (code == end_of_information)) {
                  break;
              }
              if (code == clear) {
                  // Reset decoder.
                  code_size = data_size + 1;
                  code_mask = (1 << code_size) - 1;
                  available = clear + 2;
                  old_code = NullCode;
                  continue;
              }
              if (old_code == NullCode) {
                  pixelStack[top++] = suffix[code];
                  old_code = code;
                  first = code;
                  continue;
              }
              in_code = code;
              if (code == available) {
                  pixelStack[top++] = (byte) first;
                  code = old_code;
              }
              while (code > clear) {
                  pixelStack[top++] = suffix[code];
                  code = prefix[code];
              }
              first = ((int) suffix[code]) & 0xff;
              // Add a new string to the string table,
              if (available >= MaxStackSize) {
                  break;
              }
              pixelStack[top++] = (byte) first;
              prefix[available] = (short) old_code;
              suffix[available] = (byte) first;
              available++;
              if (((available & code_mask) == 0)
                      && (available < MaxStackSize)) {
                  code_size++;
                  code_mask += available;
              }
              old_code = in_code;
          }  

          // Pop a pixel off the pixel stack.
          top--;
          pixels[pi++] = pixelStack[top];
          i++;
      }
      for (i = pi; i < npix; i++) {
          pixels[i] = 0; // clear missing pixels
      }
  }  

  protected boolean err() {
      return status != STATUS_OK;
  }  

  // to initia variable
  protected void init() {
      status = STATUS_OK;
      frameCount = 0;
      frames = new Vector<GifFrame>();
      gct = null;
      lct = null;
  }  

  protected int read() {
      int curByte = 0;
      try {
          curByte = in.read();
      } catch (Exception e) {
          status = STATUS_FORMAT_ERROR;
      }
      return curByte;
  }  

  protected int readBlock() {
      blockSize = read();
      int n = 0;
      if (blockSize > 0) {
          try {
              int count = 0;
              while (n < blockSize) {
                  count = in.read(block, n, blockSize - n);
                  if (count == -1) {
                      break;
                  }
                  n += count;
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
          if (n < blockSize) {
              status = STATUS_FORMAT_ERROR;
          }
      }
      return n;
  }  

  // Global Color Table
  protected int[] readColorTable(int ncolors) {
      int nbytes = 3 * ncolors;
      int[] tab = null;
      byte[] c = new byte[nbytes];
      int n = 0;
      try {
          n = in.read(c);
      } catch (Exception e) {
          e.printStackTrace();
      }
      if (n < nbytes) {
          status = STATUS_FORMAT_ERROR;
      } else {
          tab = new int[256]; // max size to avoid bounds checks
          int i = 0;
          int j = 0;
          while (i < ncolors) {
              int r = ((int) c[j++]) & 0xff;
              int g = ((int) c[j++]) & 0xff;
              int b = ((int) c[j++]) & 0xff;
              tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b;
          }
      }
      return tab;
  }  

  // Image Descriptor
  protected void readContents() {
      // read GIF file content blocks
      boolean done = false;
      while (!(done || err())) {
          int code = read();
          switch (code) {
          case 0x2C: // image separator
              readImage();
              break;
          case 0x21: // extension
              code = read();
              switch (code) {
              case 0xf9: // graphics control extension
                  readGraphicControlExt();
                  break;  

              case 0xff: // application extension
                  readBlock();
                  String app = "";
                  for (int i = 0; i < 11; i++) {
                      app += (char) block[i];
                  }
                  if (app.equals("NETSCAPE2.0")) {
                      readNetscapeExt();
                  } else {
                      skip(); // don't care
                  }
                  break;
              default: // uninteresting extension
                  skip();
              }
              break;  

          case 0x3b: // terminator
              done = true;
              break;  

          case 0x00: // bad byte, but keep going and see what happens
              break;
          default:
              status = STATUS_FORMAT_ERROR;
          }
      }
  }  

  protected void readGraphicControlExt() {
      read(); // block size
      int packed = read(); // packed fields
      dispose = (packed & 0x1c) >> 2; // disposal method
      if (dispose == 0) {
          dispose = 1; // elect to keep old image if discretionary
      }
      transparency = (packed & 1) != 0;
      delay = readShort() * 10; // delay in milliseconds
      transIndex = read(); // transparent color index
      read(); // block terminator
  }  

  // to get Stream - Head
  protected void readHeader() {
      String id = "";
      for (int i = 0; i < 6; i++) {
          id += (char) read();
      }
      if (!id.toUpperCase().startsWith("GIF")) {
          status = STATUS_FORMAT_ERROR;
          return;
      }
      readLSD();
      if (gctFlag && !err()) {
          gct = readColorTable(gctSize);
          bgColor = gct[bgIndex];
      }
  }  

  protected void readImage() {
      // offset of X
      ix = readShort(); // (sub)image position & size
      // offset of Y
      iy = readShort();
      // width of bitmap
      iw = readShort();
      // height of bitmap
      ih = readShort();  

      // Local Color Table Flag
      int packed = read();
      lctFlag = (packed & 0x80) != 0; // 1 - local color table flag  

      // Interlace Flag, to array with interwoven if ENABLE, with order
      // otherwise
      interlace = (packed & 0x40) != 0; // 2 - interlace flag
      // 3 - sort flag
      // 4-5 - reserved
      lctSize = 2 << (packed & 7); // 6-8 - local color table size
      if (lctFlag) {
          lct = readColorTable(lctSize); // read table
          act = lct; // make local table active
      } else {
          act = gct; // make global table active
          if (bgIndex == transIndex) {
              bgColor = 0;
          }
      }
      int save = 0;
      if (transparency) {
          save = act[transIndex];
          act[transIndex] = 0; // set transparent color if specified
      }
      if (act == null) {
          status = STATUS_FORMAT_ERROR; // no color table defined
      }
      if (err()) {
          return;
      }
      decodeImageData(); // decode pixel data
      skip();
      if (err()) {
          return;
      }
      frameCount++;
      // create new image to receive frame data
      image = Bitmap.createBitmap(width, height, Config.RGB_565);
      // createImage(width, height);
      setPixels(); // transfer pixel data to image
      frames.addElement(new GifFrame(image, delay)); // add image to frame
      // list
      if (transparency) {
          act[transIndex] = save;
      }
      resetFrame();
  }  

  // Logical Screen Descriptor
  protected void readLSD() {
      // logical screen size
      width = readShort();
      height = readShort();
      // packed fields
      int packed = read();
      gctFlag = (packed & 0x80) != 0; // 1 : global color table flag
      // 2-4 : color resolution
      // 5 : gct sort flag
      gctSize = 2 << (packed & 7); // 6-8 : gct size
      bgIndex = read(); // background color index
      pixelAspect = read(); // pixel aspect ratio
  }  

  protected void readNetscapeExt() {
      do {
          readBlock();
          if (block[0] == 1) {
              // loop count sub-block
              int b1 = ((int) block[1]) & 0xff;
              int b2 = ((int) block[2]) & 0xff;
              loopCount = (b2 << 8) | b1;
          }
      } while ((blockSize > 0) && !err());
  }  

  // read 8 bit data
  protected int readShort() {
      // read 16-bit value, LSB first
      return read() | (read() << 8);
  }  

  protected void resetFrame() {
      lastDispose = dispose;
      lrx = ix;
      lry = iy;
      lrw = iw;
      lrh = ih;
      lastImage = image;
      lastBgColor = bgColor;
      dispose = 0;
      transparency = false;
      delay = 0;
      lct = null;
  }  

  /**
   * Skips variable length blocks up to and including next zero length block.
   */
  protected void skip() {
      do {
          readBlock();
      } while ((blockSize > 0) && !err());
  }
}  

<3>Activity显示:MainActivity.java

package com.yanis.gifphoto;

import java.io.FileInputStream;
import java.io.InputStream;

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;

import com.yanis.tools.CommonUtil;
import com.yanis.tools.GifHelper.GifFrame;

public class MainActivity extends Activity {
    private PlayGifTask mGifTask;
    ImageView iv;
    GifFrame[] frames;
    FileInputStream fis=null;  

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);  

        iv = new ImageView(this);
        iv.setScaleType(ScaleType.CENTER);
        setContentView(iv, new LayoutParams(LayoutParams.MATCH_PARENT,
                LayoutParams.MATCH_PARENT));
        //对Gif图片进行解码
        final InputStream fis = getResources().openRawResource(R.drawable.gidpic);  

        /*try {
            fis = new FileInputStream(new File(Environment.getExternalStorageDirectory()+File.separator+"/tmp/111.gif"));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }*/  

        frames = CommonUtil.getGif(fis);
         mGifTask = new PlayGifTask(iv, frames);
         mGifTask.startTask();
        Thread th=new Thread(mGifTask);
        th.start();  

    }  

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(null != mGifTask) mGifTask.stopTask();  

    }  

    //用来循环播放Gif每帧图片
    private class PlayGifTask implements Runnable {
        int i = 0;
        ImageView iv;
        GifFrame[] frames;
        int framelen,oncePlayTime=0;  

        public PlayGifTask(ImageView iv, GifFrame[] frames) {
            this.iv = iv;
            this.frames = frames;  

            int n=0;
            framelen=frames.length;
            while(n<framelen){
                oncePlayTime+=frames[n].delay;
                n++;
            }
            Log.d("msg", "playTime= "+oncePlayTime);  //Gif图片单次播放时长

        }  

        Handler h2=new Handler(){
            public void handleMessage(Message msg) {
                switch(msg.what){
                 case 1:
                    iv.setImageBitmap((Bitmap)msg.obj);
                    break;
                }
            };
        };
        @Override
        public void run() {
            if (!frames[i].image.isRecycled()) {
          //      iv.setImageBitmap(frames[i].image);
                Message m=Message.obtain(h2, 1, frames[i].image);
                m.sendToTarget();
            }
            iv.postDelayed(this, frames[i++].delay);
            i %= framelen;
        }  

        public void startTask() {
            iv.post(this);
        }  

        public void stopTask() {
            if(null != iv) iv.removeCallbacks(this);
            iv = null;
            if(null != frames) {
                for(GifFrame frame : frames) {
                    if(frame.image != null && !frame.image.isRecycled()) {
                        frame.image.recycle();
                        frame.image = null;
                    }
                }
                frames = null;
          //      mGifTask=null;
            }
        }
    }
}

源代码地址：https://github.com/YeXiaoChao/Yc_demo_gifphoto

来源：http://blog.csdn.net/yudajun/article/details/7865653