Question

大家好，我正在努力使用位图和画布。我要做的是用相机拍照，然后让用户创建两个矩形（通过滑动手指）并在图像中标记它们（矩形应该被标记，直到按下按钮，照片没有保存，它始终在内存中）。因此，基于相机示例，我使用SurfaceView进行布局以包含相机预览，然后我添加了代码以在onPictureTaken方法中绘制矩形。我搜索了一些关于如何实现它的例子但当然不起作用。到目前为止，我有这个代码（在onPictureTaken中）：

        final Bitmap bitmapPicture = BitmapFactory.decodeByteArray(arg0, 0,
                arg0.length);
        surfaceView.setOnTouchListener(new OnTouchListener() {
            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                switch (arg1.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    if (source coordinates of rect1 are not set) {
                        setSourceCoordinatesForRect1FromArg1();
                    } else {
                        setSourceCoordinatesForRect2FromArg1();
                    }
                    break;
                case MotionEvent.ACTION_UP:
                    if (end coordinates of rect1 are not set) {
                        setEndCoordinatesForRect1FromArg1();
                    } else {
                        setEndCoordinatesForRect2FromArg1();
                    }
                    break;
                default:
                    break;
                }
                if (coordinates for rect1 are set) {
                    Paint paint = new Paint();
                    Bitmap bmOverlay = Bitmap.createBitmap(bitmapPicture.getWidth(), bitmapPicture.getHeight(), bitmapPicture.getConfig());
                    Canvas canvas = new Canvas(bmOverlay);
                    paint.setColor(Color.GREEN);
                    paint.setStrokeWidth(3);
                    canvas.drawRect(/*all of my source coordinates*/, paint);
                } else {
                    if (coordinates for rect2 are set) {
                        Paint paint = new Paint();
                        Bitmap bmOverlay = Bitmap.createBitmap(bitmapPicture.getWidth(), bitmapPicture.getHeight(), bitmapPicture.getConfig());
                        Canvas canvas = new Canvas(bmOverlay);
                        paint.setColor(Color.YELLOW);
                        paint.setStrokeWidth(3);
                        canvas.drawRect(/*all of my end coordinates*/, paint);
                    }
                }
                return true;
            }
        });

我没有任何异常，但是没有绘制矩形，所以如果有人能告诉我我做错了什么，我真的很感激。另外，对于我的特定场景，是否适合使用GestureDetector而不是创建自定义的OnTouchListener？提前谢谢。

Answer 1

您可以创建画布和位图，但不要将它们连接到您的视图：

Bitmap bmOverlay = Bitmap.createBitmap(bitmapPicture.getWidth(), bitmapPicture.getHeight(), bitmapPicture.getConfig());
Canvas canvas = new Canvas(bmOverlay);
paint.setColor(Color.YELLOW);
paint.setStrokeWidth(3);
canvas.drawRect(/*all of my end coordinates*/, paint);

你需要创建一个位图（你做到了这一点），然后在那里绘制两个rects，然后将该位图连接到你的视图：

if (coordinates for rect1 are set) {
    Paint paint = new Paint();
    Canvas canvas = new Canvas(bitmapPicture);
    paint.setColor(Color.GREEN);
    paint.setStrokeWidth(3);
    canvas.drawRect(/*all of my source coordinates*/, paint);
    } else {
        if (coordinates for rect2 are set) {
            Paint paint = new Paint();
            Canvas canvas = new Canvas(bitmapPicture);
            paint.setColor(Color.YELLOW);
            paint.setStrokeWidth(3);
            canvas.drawRect(/*all of my end coordinates*/, paint);
        }
    }
}
yourImageView.setImageDrawable(new BitmapDrawable(getResources(), bitmapPicture));

Answer 2

好吧，经过很长一段时间我可以画出一个位图。碰巧我有几个错误：首先，我试图在SurfaceView中绘制，这是不可能的，然后我添加了一个ImageView来包含位图和画布，所以，现在我的代码看起来像这样：

Bitmap tempBitmap = Bitmap.createScaledBitmap(bt, bt.getWidth(), bt.getHeight(), true);
Canvas canvas = new Canvas(tempBitmap);
Paint paint = new Paint();
paint.setColor(Color.GREEN);
canvas.drawLine(x1, y1, x2, y1, paint);//up
canvas.drawLine(x1, y1, x1, y2, paint);//left
canvas.drawLine(x1, y2, x2, y2, paint);//down
canvas.drawLine(x2, y1, x2, y2, paint);

ImageView iView = (ImageView)findViewById(R.id.imageViewPreview);
iView.setImageBitmap(tempBitmap);
iView.draw(canvas);

此代码位于单独的活动中，我在其中实现了OnTouchListener以读取绘制矩形的坐标。读完坐标后，执行代码作为参考，布局是一个包含ImageView的FrameLayout（看看this答案）。
这段代码终于绘制了一个矩形，但幸运的是图像越来越大了:(但这是另一个问题，所以如果你想跟随它here is the link。

可以将画布绘制到android位图中

2 个答案: