Bitmap和Drawable相互转换方法

　 public Drawable bitmap2drawable(Bitmap bitmap){     
        BitmapDrawable bitmapDrawable = new BitmapDrawable(bitmap);
        return bitmapDrawable;                                    
    }                                                   
    public Bitmap drawable2bitmap(Drawable drawable){   
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;  
        Bitmap bitmap = bitmapDrawable.getBitmap();
        return bitmap;                                    
    }