Android解码gif问题

Question

我想在启动画面上加载 gif 图像。我使用了 webview，但它有问题。然后我在谷歌代码中找到了一个类，它允许我解码 gif 图像并显示它。问题是，在模拟器上它的工作。这是模拟器上的图像:

http://i47.tinypic.com/2ds0gvs.jpg

这是我在真实设备上得到的结果。我尝试在 2.2.2 和 2.3.6 上运行，结果相同，第一次循环通过正确，然后我得到这个:

http://i45.tinypic.com/2u6d4df.jpg

这是启动 Activity

    public class InitActivity extends Activity {
    Application APP = new Application();
    private GifView gifView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        setFullScreen();
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_activity_init);
        gifView = (GifView) findViewById(R.id.app_init_preloaderHolder);
        gifView.setGif(R.drawable.p);
        gifView.play();


    }

    public void setFullScreen(){
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
    }




}

这是 GifView 类

公共(public)类 GifView 扩展 View {

public static final int IMAGE_TYPE_UNKNOWN = 0;
public static final int IMAGE_TYPE_STATIC = 1;
public static final int IMAGE_TYPE_DYNAMIC = 2;

public static final int DECODE_STATUS_UNDECODE = 0;
public static final int DECODE_STATUS_DECODING = 1;
public static final int DECODE_STATUS_DECODED = 2;

private GifDecoder decoder;
private Bitmap bitmap;

public int imageType = IMAGE_TYPE_UNKNOWN;
public int decodeStatus = DECODE_STATUS_UNDECODE;

private int width;
private int height;

private long time;
private int index;

private int resId;
private String filePath;

private boolean playFlag = false;

public GifView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

/**
 * Constructor
 */
public GifView(Context context) {
    super(context);
}

private InputStream getInputStream() {
    if (filePath != null)
        try {
            return new FileInputStream(filePath);
        } catch (FileNotFoundException e) {
        }
    if (resId > 0)
        return getContext().getResources().openRawResource(resId);
    return null;
}

/**
 * set gif file path
 * 
 * @param filePath
 */
public void setGif(String filePath) {
    Bitmap bitmap = BitmapFactory.decodeFile(filePath);
    setGif(filePath, bitmap);
}

/**
 * set gif file path and cache image
 * 
 * @param filePath
 * @param cacheImage
 */
public void setGif(String filePath, Bitmap cacheImage) {
    this.resId = 0;
    this.filePath = filePath;
    imageType = IMAGE_TYPE_UNKNOWN;
    decodeStatus = DECODE_STATUS_UNDECODE;
    playFlag = false;
    bitmap = cacheImage;
    width = bitmap.getWidth();
    height = bitmap.getHeight();
    setLayoutParams(new LayoutParams(width, height));
}

/**
 * set gif resource id
 * 
 * @param resId
 */
public void setGif(int resId) {
    Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId);
    setGif(resId, bitmap);
}

/**
 * set gif resource id and cache image
 * 
 * @param resId
 * @param cacheImage
 */
public void setGif(int resId, Bitmap cacheImage) {
    this.filePath = null;
    this.resId = resId;
    imageType = IMAGE_TYPE_UNKNOWN;
    decodeStatus = DECODE_STATUS_UNDECODE;
    playFlag = false;
    bitmap = cacheImage;
    width = bitmap.getWidth();
    height = bitmap.getHeight();
    setLayoutParams(new LayoutParams(width, height));
}

private void decode() {
    release();
    index = 0;

    decodeStatus = DECODE_STATUS_DECODING;

    new Thread() {
        @Override
        public void run() {
            decoder = new GifDecoder();
            decoder.read(getInputStream());
            if (decoder.width == 0 || decoder.height == 0) {
                imageType = IMAGE_TYPE_STATIC;
            } else {
                imageType = IMAGE_TYPE_DYNAMIC;
            }
            postInvalidate();
            time = System.currentTimeMillis();
            decodeStatus = DECODE_STATUS_DECODED;
        }
    }.start();
}

public void release() {
    decoder = null;
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    if (decodeStatus == DECODE_STATUS_UNDECODE) {
        canvas.drawBitmap(bitmap, 0, 0, null);
        if (playFlag) {
            decode();
            invalidate();
        }
    } else if (decodeStatus == DECODE_STATUS_DECODING) {
        canvas.drawBitmap(bitmap, 0, 0, null);
        invalidate();
    } else if (decodeStatus == DECODE_STATUS_DECODED) {
        if (imageType == IMAGE_TYPE_STATIC) {
            canvas.drawBitmap(bitmap, 0, 0, null);
        } else if (imageType == IMAGE_TYPE_DYNAMIC) {
            if (playFlag) {
                long now = System.currentTimeMillis();

                if (time + decoder.getDelay(index) < now) {
                    time += decoder.getDelay(index);
                    incrementFrameIndex();
                }
                Bitmap bitmap = decoder.getFrame(index);
                if (bitmap != null) {
                    canvas.drawBitmap(bitmap, 0, 0, null);
                }
                invalidate();
            } else {
                Bitmap bitmap = decoder.getFrame(index);
                canvas.drawBitmap(bitmap, 0, 0, null);
            }
        } else {
            canvas.drawBitmap(bitmap, 0, 0, null);
        }
    }
}

private void incrementFrameIndex() {
    index++;
    if (index >= decoder.getFrameCount()) {
        index = 0;
    }
}

private void decrementFrameIndex() {
    index--;
    if (index < 0) {
        index = decoder.getFrameCount() - 1;
    }
}

public void play() {
    time = System.currentTimeMillis();
    playFlag = true;
    invalidate();
}

public void pause() {
    playFlag = false;
    invalidate();
}

public void stop() {
    playFlag = false;
    index = 0;
    invalidate();
}

public void nextFrame() {
    if (decodeStatus == DECODE_STATUS_DECODED) {
        incrementFrameIndex();
        invalidate();
    }
}

public void prevFrame() {
    if (decodeStatus == DECODE_STATUS_DECODED) {
        decrementFrameIndex();
        invalidate();
    }
}

这是gif解码器类

public class GifDecoder {
    /**
     * File read status: No errors.
     */
    public static final int STATUS_OK = 0;
    /**
     * File read status: Error decoding file (may be partially decoded)
     */
    public static final int STATUS_FORMAT_ERROR = 1;
    /**
     * File read status: Unable to open source.
     */
    public static final int STATUS_OPEN_ERROR = 2;
    /** max decoder pixel stack size */
    protected static final int MAX_STACK_SIZE = 4096;
    protected InputStream in;
    protected int status;
    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 lastBitmap; // previous frame
    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
    // 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;

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

        public Bitmap image;
        public int delay;
    }

    /**
     * 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 = frames.elementAt(n).delay;
        }
        return delay;
    }

    /**
     * Gets the number of frames read from file.
     * 
     * @return frame count
     */
    public int getFrameCount() {
        return frameCount;
    }

    /**
     * Gets the first (or only) image read.
     * 
     * @return BufferedBitmap containing first frame, or null if none.
     */
    public Bitmap getBitmap() {
        return getFrame(0);
    }

    /**
     * Gets the "Netscape" iteration count, if any. A count of 0 means repeat indefinitiely.
     * 
     * @return iteration count if one was specified, else 1.
     */
    public int getLoopCount() {
        return loopCount;
    }

    /**
     * Creates new frame image from current data (and previous frames as specified by their disposition codes).
     */
    protected void setPixels() {
        // expose destination image's pixels as int array
        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) {
                    lastBitmap = getFrame(n - 1);
                } else {
                    lastBitmap = null;
                }
            }
            if (lastBitmap != null) {
                lastBitmap.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;
                        break;
                    default:
                        break;
                    }
                }
                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.ARGB_8888);
    }

    /**
     * Gets the image contents of frame n.
     * 
     * @return BufferedBitmap representation of frame, or null if n is invalid.
     */
    public Bitmap getFrame(int n) {
        if (frameCount <= 0)
            return null;
        n = n % frameCount;
        return ((GifFrame) frames.elementAt(n)).image;
    }

    /**
     * Reads GIF image from stream
     * 
     * @param is
     *          containing GIF file.
     * @return read status code (0 = no errors)
     */
    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) {
        }
        return status;
    }

    /**
     * Decodes LZW image data into pixel array. Adapted from John Cristy's BitmapMagick.
     */
    protected void decodeBitmapData() {
        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[MAX_STACK_SIZE];
        }
        if (suffix == null) {
            suffix = new byte[MAX_STACK_SIZE];
        }
        if (pixelStack == null) {
            pixelStack = new byte[MAX_STACK_SIZE + 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; // XXX ArrayIndexOutOfBoundsException
            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 >= MAX_STACK_SIZE) {
                    break;
                }
                pixelStack[top++] = (byte) first;
                prefix[available] = (short) old_code;
                suffix[available] = (byte) first;
                available++;
                if (((available & code_mask) == 0) && (available < MAX_STACK_SIZE)) {
                    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
        }
    }

    /**
     * Returns true if an error was encountered during reading/decoding
     */
    protected boolean err() {
        return status != STATUS_OK;
    }

    /**
     * Initializes or re-initializes reader
     */
    protected void init() {
        status = STATUS_OK;
        frameCount = 0;
        frames = new Vector<GifFrame>();
        gct = null;
        lct = null;
    }

    /**
     * Reads a single byte from the input stream.
     */
    protected int read() {
        int curByte = 0;
        try {
            curByte = in.read();
        } catch (Exception e) {
            status = STATUS_FORMAT_ERROR;
        }
        return curByte;
    }

    /**
     * Reads next variable length block from input.
     * 
     * @return number of bytes stored in "buffer"
     */
    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;
    }

    /**
     * Reads color table as 256 RGB integer values
     * 
     * @param ncolors
     *          int number of colors to read
     * @return int array containing 256 colors (packed ARGB with full alpha)
     */
    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;
    }

    /**
     * Main file parser. Reads GIF content blocks.
     */
    protected void readContents() {
        // read GIF file content blocks
        boolean done = false;
        while (!(done || err())) {
            int code = read();
            switch (code) {
            case 0x2C: // image separator
                readBitmap();
                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;
                case 0xfe:// comment extension
                    skip();
                    break;
                case 0x01:// plain text extension
                    skip();
                    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;
            }
        }
    }

    /**
     * Reads Graphics Control Extension values
     */
    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
    }

    /**
     * Reads GIF file header information.
     */
    protected void readHeader() {
        String id = "";
        for (int i = 0; i < 6; i++) {
            id += (char) read();
        }
        if (!id.startsWith("GIF")) {
            status = STATUS_FORMAT_ERROR;
            return;
        }
        readLSD();
        if (gctFlag && !err()) {
            gct = readColorTable(gctSize);
            bgColor = gct[bgIndex];
        }
    }

    /**
     * Reads next frame image
     */
    protected void readBitmap() {
        ix = readShort(); // (sub)image position & size
        iy = readShort();
        iw = readShort();
        ih = readShort();
        int packed = read();
        lctFlag = (packed & 0x80) != 0; // 1 - local color table flag interlace
        lctSize = (int) Math.pow(2, (packed & 0x07) + 1);
        // 3 - sort flag
        // 4-5 - reserved lctSize = 2 << (packed & 7); // 6-8 - local color
        // table size
        interlace = (packed & 0x40) != 0;
        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;
        }
        decodeBitmapData(); // decode pixel data
        skip();
        if (err()) {
            return;
        }
        frameCount++;
        // create new image to receive frame data
        image = Bitmap.createBitmap(width, height, Config.ARGB_8888);
        setPixels(); // transfer pixel data to image
        frames.addElement(new GifFrame(image, delay)); // add image to frame
        // list
        if (transparency) {
            act[transIndex] = save;
        }
        resetFrame();
    }

    /**
     * Reads 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
    }

    /**
     * Reads Netscape extenstion to obtain iteration count
     */
    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());
    }

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

    /**
     * Resets frame state for reading next image.
     */
    protected void resetFrame() {
        lastDispose = dispose;
        lrx = ix;
        lry = iy;
        lrw = iw;
        lrh = ih;
        lastBitmap = 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());
    }
}

Answer 1

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