Android杩涢樁緇冧範 - 楂樻晥鏄劇ずBit地图錛堝湪UI涓葷嚎紼嬪?澶勭悊Bit地图錛?

//瀛樺偍鐫?竴涓?笌涔嬪?搴旂殑task錛?鍦ㄤ换鍔¤繕鍦ㄦ墽琛屾椂鍏呭綋涓?釜鍗犱綅絎︼紝褰撲换鍔″畬鎴愭椂錛岄殢涔嬭?鏇挎崲static class AsyncDrawable extends BitmapDrawable {    private final WeakReference bitmapWorkerTaskReference;    public AsyncDrawable(Resources res, Bitmap bitmap,            BitmapWorkerTask bitmapWorkerTask) {        super(res, bitmap);        bitmapWorkerTaskReference =            new WeakReference(bitmapWorkerTask);    }    public BitmapWorkerTask getBitmapWorkerTask() {        return bitmapWorkerTaskReference.get();    }}

public void loadBitmap(int resId, ImageView imageView) {    if (cancelPotentialWork(resId, imageView)) {        final BitmapWorkerTask task = new BitmapWorkerTask(imageView);        // mPlaceHolderBitmap 寮曠敤鐨勫氨鏄?粯璁よ?鏄劇ず鐨勫浘鐗囧?璞?        final AsyncDrawable asyncDrawable =                new AsyncDrawable(getResources(), mPlaceHolderBitmap, task);        imageView.setImageDrawable(asyncDrawable);        task.execute(resId);    }}

public static boolean cancelPotentialWork(int data, ImageView imageView) {    // 鍙栧緱褰撳墠涓嶪mageView鐩稿叧鑱旂殑浠誨姟    final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);         // 濡傛灉瀛樺湪鐨勮瘽錛屽垯鍙栨秷    if (bitmapWorkerTask != null) {        final int bitmapData = bitmapWorkerTask.data;        if (bitmapData != data) {            // Cancel previous task            bitmapWorkerTask.cancel(true);        } else {            // The same work is already in progress            return false;        }    }    // No task associated with the ImageView, or an existing task was cancelled    return true;}

private static BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {   // imageView鏈夊彲鑳藉?鍥炴敹   if (imageView != null) {       final Drawable drawable = imageView.getDrawable();       if (drawable instanceof AsyncDrawable) {           final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;           return asyncDrawable.getBitmapWorkerTask();       }    }    return null;}     

class BitmapWorkerTask extends AsyncTask {    ...    @Override    protected void onPostExecute(Bitmap bitmap) {        // if task cancelled , this method is never invoked        // why check here ?         if (isCancelled()) {            bitmap = null;        }        if (imageViewReference != null && bitmap != null) {            final ImageView imageView = imageViewReference.get();            final BitmapWorkerTask bitmapWorkerTask =                    getBitmapWorkerTask(imageView);            // 鍒ゆ柇褰撳墠task鏄?惁鏄?浉鍏寵仈鐨則ask            if (this == bitmapWorkerTask && imageView != null) {                imageView.setImageBitmap(bitmap);            }        }    }}