AsyncDrawable，异步图片。
源码：
/** * Author: wyouflf * Date: 13-11-17 * Time: 上午11:42 */ public final class AsyncDrawable extends Drawable { private final WeakReference<ImageLoader> imageLoaderReference; private Drawable baseDrawable;//对原图片的包装 public AsyncDrawable(ImageLoader imageLoader, Drawable drawable) { if (imageLoader == null) { throw new IllegalArgumentException("imageLoader may not be null"); } baseDrawable = drawable; while (baseDrawable instanceof AsyncDrawable) { baseDrawable = ((AsyncDrawable) baseDrawable).baseDrawable; } imageLoaderReference = new WeakReference<ImageLoader>(imageLoader); } public ImageLoader getImageLoader() { return imageLoaderReference.get(); } public void setBaseDrawable(Drawable baseDrawable) { this.baseDrawable = baseDrawable; } public Drawable getBaseDrawable() { return baseDrawable; } //以下几个函数作为对Drawable的包装，要调用被包装对象的方法实现 @Override public void draw(Canvas canvas) { if (baseDrawable != null) { baseDrawable.draw(canvas); } } @Override public void setAlpha(int i) { if (baseDrawable != null) { baseDrawable.setAlpha(i); } } @Override public void setColorFilter(ColorFilter colorFilter) { if (baseDrawable != null) { baseDrawable.setColorFilter(colorFilter); } } @Override public int getOpacity() { return baseDrawable == null ? PixelFormat.TRANSLUCENT : baseDrawable.getOpacity(); } @Override public void setBounds(int left, int top, int right, int bottom) { if (baseDrawable != null) { baseDrawable.setBounds(left, top, right, bottom); } } @Override public void setBounds(Rect bounds) { if (baseDrawable != null) { baseDrawable.setBounds(bounds); } } @Override public void setChangingConfigurations(int configs) { if (baseDrawable != null) { baseDrawable.setChangingConfigurations(configs); } } @Override public int getChangingConfigurations() { return baseDrawable == null ? 0 : baseDrawable.getChangingConfigurations(); } @Override public void setDither(boolean dither) { if (baseDrawable != null) { baseDrawable.setDither(dither); } } @Override public void setFilterBitmap(boolean filter) { if (baseDrawable != null) { baseDrawable.setFilterBitmap(filter); } } @Override public void invalidateSelf() { if (baseDrawable != null) { baseDrawable.invalidateSelf(); } } @Override public void scheduleSelf(Runnable what, long when) { if (baseDrawable != null) { baseDrawable.scheduleSelf(what, when); } } @Override public void unscheduleSelf(Runnable what) { if (baseDrawable != null) { baseDrawable.unscheduleSelf(what); } } @Override public void setColorFilter(int color, PorterDuff.Mode mode) { if (baseDrawable != null) { baseDrawable.setColorFilter(color, mode); } } @Override public void clearColorFilter() { if (baseDrawable != null) { baseDrawable.clearColorFilter(); } } @Override public boolean isStateful() { return baseDrawable != null && baseDrawable.isStateful(); } @Override public boolean setState(int[] stateSet) { return baseDrawable != null && baseDrawable.setState(stateSet); } @Override public int[] getState() { return baseDrawable == null ? null : baseDrawable.getState(); } @Override public Drawable getCurrent() { return baseDrawable == null ? null : baseDrawable.getCurrent(); } @Override public boolean setVisible(boolean visible, boolean restart) { return baseDrawable != null && baseDrawable.setVisible(visible, restart); } @Override public Region getTransparentRegion() { return baseDrawable == null ? null : baseDrawable.getTransparentRegion(); } @Override public int getIntrinsicWidth() { return baseDrawable == null ? 0 : baseDrawable.getIntrinsicWidth(); } @Override public int getIntrinsicHeight() { return baseDrawable == null ? 0 : baseDrawable.getIntrinsicHeight(); } @Override public int getMinimumWidth() { return baseDrawable == null ? 0 : baseDrawable.getMinimumWidth(); } @Override public int getMinimumHeight() { return baseDrawable == null ? 0 : baseDrawable.getMinimumHeight(); } @Override public boolean getPadding(Rect padding) { return baseDrawable != null && baseDrawable.getPadding(padding); } @Override public Drawable mutate() { return baseDrawable == null ? null : baseDrawable.mutate(); } @Override public ConstantState getConstantState() { return baseDrawable == null ? null : baseDrawable.getConstantState(); } @Override protected void finalize() throws Throwable {//因为是异步，所以还要停止对应的loader super.finalize(); ImageLoader imageLoader = this.getImageLoader(); if (imageLoader != null) { imageLoader.cancel(); } } }