如何将位图绘制到 SurfaceView？

Question

我正在尝试SurfaceView使用以下代码为我的实际绘制位图：（这将在另一个Thread和 a 中运行while，因为它需要刷新SurfaceView）。

        while (true)
        {
            try
            {
                // Enable drawing
                // ERROR LINE!
                Canvas ca = mPreview2.Holder.LockCanvas();

                // Get current frame
                Bitmap test = mediaPlayer.CurrentFrame;

                // Actual drawing
                Paint paint = new Paint();
                ca.DrawBitmap(test, 0, 0, paint);   

                // Stop drawing
                mPreview2.Holder.UnlockCanvasAndPost(ca);
            } catch (Exception ex)
            {
                throw ex;
            }
        }

但是我有以下错误：（这是在线发生的： Canvas ca = mPreview2.Holder.LockCanvas();

Java.Lang.NullPointerException: Attempt to invoke virtual method 'boolean android.graphics.Bitmap.isRecycled()' on a null object reference

Answer 1

现在我可以绘制位图，但我还有一个问题！

因为右屏幕的质量真的很差（见图）：

问题解决了：

我所做的使用是MemoryStream其压缩Bitmap为100，质量.JPG和解码byte array的Bitmap。现在效果很好！见下面的代码：

   private void DrawCanvas()
        {
            while (true)
            {
                Canvas canvas = holder2.LockCanvas();

                if (canvas != null)
                {
                    Bitmap currentBitmap = mediaPlayer.CurrentFrame;

                    if(currentBitmap != null)
                    {
                        Paint paint = new Paint();

                        MemoryStream ms = new MemoryStream();

                        currentBitmap.Compress(Bitmap.CompressFormat.Jpeg, 100, ms);

                        byte[] bitmapData = ms.ToArray();

                        Bitmap bitmap = BitmapFactory.DecodeByteArray(bitmapData, 0, bitmapData.Length);

                        Bitmap scaledBitmap = Bitmap.CreateScaledBitmap(bitmap, mPreview2.Width, mPreview2.Height, true);

                        canvas.DrawBitmap(scaledBitmap, 0, 0, paint);

                        bitmap.Recycle();
                        scaledBitmap.Recycle();
                        currentBitmap.Recycle();
                    }
                    holder2.UnlockCanvasAndPost(canvas);
                }
            }
        }