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我拍了一张照片，想通过用手指手势放置矩形来在上面画一个矩形。

在与屏幕交互时，一切正常并且显示正确。但是当我想用 sdcard 上的矩形保存图像时，我得到的图像具有正确的图像背景，但矩形有点破损。它们看起来像是有人剪掉了它们的某些部分。你可以感觉到它们曾经是矩形，但看起来像垃圾。

我的问题是为什么？

由于我的线程，我无法将所有内容保存在一个画布上并将其保存到 sdcard 中，我无法为画布设置位图。使用两个画布后，它就像我说的那样工作，但是矩形被破坏了。当我在画布上绘制没有底层图像位图的矩形时，矩形被正确保存。我真的不明白。我尝试了我能想象的一切，但没有得到错误。

我尝试发布我的整个代码的简短示例：

public class Mark extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mark);

        p = new Panel(this);
        frLayout = (FrameLayout)findViewById(R.id.preview);
        frLayout.addView(p);

        bitmap = BitmapFactory.decodeFile(image_path + "/img.jpg", options);
        img = (ImageView) findViewById(R.id.img_capturedImage);

        bitmapAll = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(),Bitmap.Config.ARGB_8888);

        save.setOnClickListener(new View.OnClickListener() {

                try {
                    out = new FileOutputStream(file);
                    bitmapAll.compress(Bitmap.CompressFormat.JPEG, 100, out);
                    out.flush();
                    out.close();

                    MediaStore.Images.Media.insertImage(getContentResolver(),
                            file.getAbsolutePath(), file.getName(),
                            file.getName());
                } catch (Exception e) {
                       e.printStackTrace();
                }
            }
        });
    }

    class Panel extends SurfaceView implements SurfaceHolder.Callback {
        private TutorialThread _thread;
        Canvas myCanvas;

        public Panel(Context context) {
            super(context);
            getHolder().addCallback(this);
            _thread = new TutorialThread(getHolder(), this);
            setFocusable(true);
        }


        @Override
        public boolean onTouchEvent(MotionEvent event) {
            synchronized (_thread.getSurfaceHolder()) {

                switch(event.getAction() & MotionEvent.ACTION_MASK){
                    ... save the coordinates for the rectangle ...
                }

                return true;
        }


        @Override
        public void onDraw(Canvas canvas) {

            myCanvas = new Canvas(bitmapAll);

            Paint paint = new Paint();

            myCanvas.drawBitmap(bitmap, 0, 0, paint);
            canvas.drawBitmap(bitmap, 0, 0, paint);

            paint.setXfermode(new PorterDuffXfermode(Mode.SRC_OVER));

            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(3);

            Rect rect;

            for (...go over every saved rectangle ...) {
                rect.set(...coordinates...);
                canvas.drawRect(rect, paint);
                myCanvas.drawRect(rect, paint);
            }
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            // TODO Auto-generated method stub
        }

        public void surfaceCreated(SurfaceHolder holder) {
            _thread.setRunning(true);
            _thread.start();
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            boolean retry = true;
            _thread.setRunning(false);
            while (retry) {
                try {
                    _thread.join();
                    retry = false;
                } catch (InterruptedException e) {
                }
            }
        }
    }

    class TutorialThread extends Thread {
        private SurfaceHolder _surfaceHolder;
        private Panel _panel;
        private boolean _run = false;

        public TutorialThread(SurfaceHolder surfaceHolder, Panel panel) {
            _surfaceHolder = surfaceHolder;
            _panel = panel;
        }

        public void setRunning(boolean run) {
            _run = run;
        }

        public SurfaceHolder getSurfaceHolder() {
            return _surfaceHolder;
        }

        @Override
        public void run() {
            Canvas c;
            while (_run) {
                c = null;
                try {
                    c = _surfaceHolder.lockCanvas(null);
                    synchronized (_surfaceHolder) {
                        _panel.onDraw(c);
                    } 
                } catch (Exception e) {
                    Log.e("Error", Log.getStackTraceString(e));
                } finally {
                    if (c != null) {
                        _surfaceHolder.unlockCanvasAndPost(c);
                    }
                }
            }
        }
    }
}
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