Android 如何将PicturedRavable转换为位图

如何将PicturedRavable对象转换为位图对象？我尝试了下面显示的代码，它给出了空指针

       //Convert PictureDrawable to Bitmap
            private Bitmap pictureDrawable2Bitmap(PictureDrawable pictureDrawable){
            Bitmap bitmap = Bitmap.createBitmap(pictureDrawable.getIntrinsicWidth(),pictureDrawable.getIntrinsicHeight(), Config.ARGB_8888);
            Toast.makeText(HTMLActivity.this, "bitmap " + bitmap.toString(), Toast.LENGTH_LONG).show();
            Canvas canvas = new Canvas(bitmap);
            canvas.drawPicture(pictureDrawable.getPicture());
            return bitmap;
        }

下面是一个示例，显示我在代码中所做的操作

    private Picture picture;
    private String url;
    private WebView webview;
    private Bitmap HTMLBitmap;
    private PictureDrawable HTMLPicDraw;

     // goal is to convert WebView --> Picture --> PictureDrawable --> Bitmap
        picture = webview.capturePicture();
        HTMLPicDraw = new PictureDrawable(picture);
      // HTMLPicDraw a PictureDrawable object is good, no null pointer exception here
      // what is left is to go from PictureDrawable to Bitmap

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使用下面的代码，它为我工作

//  get bitmap from view
public static Bitmap getBitmapFromView(View view) {
            Bitmap returnedBitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(),Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(returnedBitmap);
            Drawable bgDrawable =view.getBackground();
            if (bgDrawable!=null) 
                bgDrawable.draw(canvas);
          /*  else 
                canvas.drawColor(Color.WHITE);*/
            view.draw(canvas);
            return returnedBitmap;
        }