Android Java Zoom边界

Question

我正在通过Android设备开发具有触摸屏控制功能的交互式视频装置。到目前为止，我想出了以下用于平移，缩放和平移限制的代码。但我无法弄清楚如何限制缩放（最小/最大）以及如何避免图像离开边界（它应该显示在整个屏幕上而没有任何偏移）。 谢谢你的帮助！

public boolean onTouchEvent(MotionEvent me) {
    switch (me.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
        savedMatrix.set(matrix);
        startPoint.set(me.getX(), me.getY());
        mode = DRAG;
        break;
    case MotionEvent.ACTION_POINTER_DOWN:
        oldDist = spacing(me);

        if (oldDist > 10f) {
            savedMatrix.set(matrix);
            midPoint(midPoint, me);
            mode = ZOOM;
        }

        break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
        mode = NONE;
        break;
    case MotionEvent.ACTION_MOVE:
        if (mode == DRAG) {
            float transX = me.getX() - startPoint.x;
            float transY = me.getY() - startPoint.y;

            matrix.set(savedMatrix);

            float[] f = new float[9];
            matrix.getValues(f);

            float viewWidth = 1317.0f + 1317.0f * ((f[Matrix.MSCALE_X] - 1) / 1.1365f );
            float viewWidth2 = 772.0f + 772.0f * ((f[Matrix.MSCALE_X] - 1) / 1.998f);
            float viewHeight = 1097.0f + 1097.0f * ((f[Matrix.MSCALE_X] - 1) / 1.463f);
            float viewHeight2 = 749.0f + 749.0f * ((f[Matrix.MSCALE_X] - 1) / 2.994f);

            if (f[Matrix.MTRANS_X] + transX < -viewWidth){
                Log.e("", "left bound");
                transX = -f[Matrix.MTRANS_X] -viewWidth;
            }

            if(f[Matrix.MTRANS_X] + transX > -viewWidth2 ){
                transX = -f[Matrix.MTRANS_X] -viewWidth2;
            }

            if (f[Matrix.MTRANS_Y] + transY > viewHeight){
                transY = -f[Matrix.MTRANS_Y] + viewHeight;
            }

            if(f[Matrix.MTRANS_Y] + transY < viewHeight2){
                transY = -f[Matrix.MTRANS_Y] + viewHeight2;
            }

            matrix.postTranslate(transX, transY);

        } else if (mode == ZOOM) {
            float newDist = spacing(me);
            if (newDist > 10f) {
                Log.e("MainActivity", "Correction: " + Float.toString(newDist / newDist));
                float transX = me.getX() - startPoint.x;
                float transY = me.getY() - startPoint.y;

                matrix.set(savedMatrix);
                float scale = newDist / oldDist;

                float[] f = new float[9];
                matrix.getValues(f);


                matrix.postScale(scale, scale, -startPoint.x+300.f, -startPoint.y+900.0f);

                if (f[Matrix.MSCALE_X] >= 270.0f) {
                    matrix.postScale((270.0f)/(f[Matrix.MSCALE_X]/scale), (270.0f)/(f[Matrix.MSCALE_Y]*scale), 0f ,0f);
                    mode = DRAG;
                    savedMatrix.set(matrix);
                    midPoint(midPoint, me);
                } else if (f[Matrix.MSCALE_X] < 0.29f) {
                    matrix.postScale((0.29f)/(f[Matrix.MSCALE_X]/scale), (0.29f)/(f[Matrix.MSCALE_Y]*scale), 0f ,0f);
                    mode = DRAG;
                    savedMatrix.set(matrix);
                    midPoint(midPoint, me);
                }
            }
        }
        break;
    }


    // Matrix
    try {
        socket = new DatagramSocket();
        // socket.setBroadcast(true);
    } catch (SocketException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    String dataString = matrix.toShortString();
    Log.e("Activity_Main", dataString);

    try {
        DatagramPacket packet = new DatagramPacket(dataString.getBytes(), dataString.length(), serverAddr, PORT);
        socket.send(packet);
        socket.close();
    } catch (Exception e) {

    }



    return true;
}

@SuppressLint("FloatMath")
private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
}

private void midPoint(PointF point, MotionEvent event) {
    float x = event.getX(0) + event.getX(1);
    float y = event.getY(0) + event.getY(1);
    point.set(x / 2, y / 2);
}