创建Bitmap

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private static final Canvas sCanvas = new Canvas();
   /**
    * 从一个view创建Bitmap:
    * 注意点：绘制之前要清掉 View 的焦点，因为焦点可能会改变一个 View 的 UI 状态
    * 来源：https://github.com/tyrantgit/ExplosionField
    *
    * @param view
    * @return
    */
   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();
               canvas.drawColor(Color.WHITE); // 防止 View 上面有些区域空白导致最终 Bitmap 上有些区域变黑
               canvas.scale(scale, scale);
               view.draw(canvas);
               canvas.restore();
               canvas.setBitmap(null);
           }
       }
       return bitmap;
   }
   public static Bitmap createBitmapFromView(View view) {
       return createBitmapFromView(view, 1f);
   }

创建安全Bitmap

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/**
  * 安全的创建bitmap;如果新建 Bitmap 时产生了 OOM，可以主动进行一次 GC - System.gc()，然后再次尝试创建
  *
  * @param width
  * @param height
  * @param config
  * @param retryCount
  * @return
  */
 public 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;
     }
 }