Android项目中如何优化Bitmap的加载

public Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) { // First decode with inJustDecodeBounds=true to check dimensions final BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeResource(res, resId, options); // Calculate inSampleSize options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); // Decode bitmap with inSampleSize set options.inJustDecodeBounds = false; return BitmapFactory.decodeResource(res, resId, options);}public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) { if (reqWidth == 0 || reqHeight == 0) {  return 1; } // Raw height and width of image final int height = options.outHeight; final int width = options.outWidth; Log.d(TAG, "origin, w= " + width + " h=" + height); int inSampleSize = 1; if (height > reqHeight || width > reqWidth) {  final int halfHeight = height / 2;  final int halfWidth = width / 2;  // Calculate the largest inSampleSize value that is a power of 2 and  // keeps both height and width larger than the requested height and width.  while ((halfHeight / inSampleSize) >= reqHeight && (halfWidth / inSampleSize) >= reqWidth) {   inSampleSize *= 2;  } } Log.d(TAG, "sampleSize:" + inSampleSize); return inSampleSize;}