SkiaPooledImageRegionDecoder.java 文件源码

/**
 * Acquire a read lock to prevent decoding overlapping with recycling, then check the pool still
 * exists and acquire a decoder to load the requested region. There is no check whether the pool
 * currently has decoders, because it's guaranteed to have one decoder after {@link #init(Context, Uri)}
 * is called and be null once {@link #recycle()} is called. In practice the view can't call this
 * method until after {@link #init(Context, Uri)}, so there will be no blocking on an empty pool.
 */
@Override
public Bitmap decodeRegion(Rect sRect, int sampleSize) {
    debug("Decode region " + sRect + " on thread " + Thread.currentThread().getName());
    if (sRect.width() < imageDimensions.x || sRect.height() < imageDimensions.y) {
        lazyInit();
    }
    decoderLock.readLock().lock();
    try {
        if (decoderPool != null) {
            BitmapRegionDecoder decoder = decoderPool.acquire();
            try {
                // Decoder can't be null or recycled in practice
                if (decoder != null && !decoder.isRecycled()) {
                    BitmapFactory.Options options = new BitmapFactory.Options();
                    options.inSampleSize = sampleSize;
                    options.inPreferredConfig = bitmapConfig;
                    Bitmap bitmap = decoder.decodeRegion(sRect, options);
                    if (bitmap == null) {
                        throw new RuntimeException("Skia image decoder returned null bitmap - image format may not be supported");
                    }
                    return bitmap;
                }
            } finally {
                if (decoder != null) {
                    decoderPool.release(decoder);
                }
            }
        }
        throw new IllegalStateException("Cannot decode region after decoder has been recycled");
    } finally {
        decoderLock.readLock().unlock();
    }
}