Android处理大图避免OOM的完整方案

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    final int width = options.outWidth;
    final int height = options.outHeight;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {
        final int halfWidth = width / 2;
        final int halfHeight = height / 2;
        while ((halfWidth / inSampleSize) >= reqWidth 
                && (halfHeight / inSampleSize) >= reqHeight) {
            inSampleSize *= 2;
        }
    }
    return inSampleSize;
}

BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.drawable.large_image, options);
int imageWidth = options.outWidth;
int imageHeight = options.outHeight;

options.inJustDecodeBounds = false;
options.inSampleSize = calculateInSampleSize(options, targetWidth, targetHeight);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.large_image, options);

options.inPreferredConfig = Bitmap.Config.RGB_565; // 每个像素占 2 字节（内存减半）

options.inScaled = false;

InputStream is = getAssets().open("large_image.jpg");
BitmapRegionDecoder decoder = BitmapRegionDecoder.newInstance(is, false);
Rect rect = new Rect(startX, startY, startX + width, startY + height);
Bitmap bitmap = decoder.decodeRegion(rect, options);

if (bitmap != null && !bitmap.isRecycled()) {
    bitmap.recycle();
    bitmap = null;
}

Glide.with(context)
     .load("path/to/image")
     .override(targetWidth, targetHeight)
     .into(imageView);

<application android:largeHeap="true">

<activity android:hardwareAccelerated="true" />

内存占用 = 图片宽度 * 图片高度 * 每像素字节数
例如：4000x3000 的 ARGB_8888 图片 = 4000 * 3000 * 4B ≈ 48MB