public class BitmapUtil {

    //節省每次建立時產生的開銷，但要注意多執行緒操作synchronized
    private static final Canvas sCanvas = new Canvas();

    /**
     * 從一個view建立Bitmap:
     * 注意點：繪製之前要清掉 View 的焦點，因為焦點可能會改變一個 View 的 UI 狀態
     * 來源：https://github.com/tyrantgit/ExplosionField
     */
    public static Bitmap createBitmapFromView
 
(View view, float scale) {
        if (view instanceof ImageView) {
            Drawable drawable = ((ImageView) view).getDrawable();
            if (drawable != null && drawable instanceof BitmapDrawable) {
                return ((BitmapDrawable) drawable).getBitmap();
            }
        }
        view.clearFocus();
        Bitmap bitmap = createBitmapSafely((int
 
) (view.getWidth() * scale),
                (int) (view.getHeight() * scale), Bitmap.Config.ARGB_8888, 1);
        if (bitmap != null) {
            synchronized (sCanvas) {
                Canvas canvas = sCanvas;
                canvas.setBitmap(bitmap);
                canvas.save();
                // 防止 View 上面有些區域空白導致最終 Bitmap 上有些區域變黑
 

                canvas.drawColor(Color.WHITE); 
                canvas.scale(scale, scale);
                view.draw(canvas);
                canvas.restore();
                canvas.setBitmap(null);
            }
        }
        return bitmap;
    }

    //安全的建立bitmap;如果新建 Bitmap 時產生了 OOM，可以主動進行一次 GC - System.gc()，然後再次嘗試建立
    private static Bitmap createBitmapSafely(int width, int height, Bitmap.Config config, int retryCount) {
        try {
            return Bitmap.createBitmap(width, height, config);
        } catch (OutOfMemoryError e) {
            e.printStackTrace();
            if (retryCount > 0) {
                System.gc();
                return createBitmapSafely(width, height, config, retryCount - 1);
            }
            return null;
        }
    }
}