在Android中设置相机对焦区域

在几个教程和示例之后，我提出了下一个算法来将相机焦点设置在特定点上，问题是相机完全忽略该点并执行正常的整体焦点，而不是我指定的矩形区域。算法中还有什么我遗漏的吗？这已经在多款 Android 4.0 及以上版本的手机上进行了测试，因此这些设备支持焦点区域 API。请注意，我正在编写的应用程序仅适用于横向模式。

@Override
public boolean onTouchEvent(final MotionEvent event)
{
    if (event.getAction() == MotionEvent.ACTION_UP)
    {
        float x = event.getX();
        float y = event.getY();
        float touchMajor = event.getTouchMajor();
        float touchMinor = event.getTouchMinor();

        Rect touchRect = new Rect((int)(x - touchMajor / 2), (int)(y - touchMinor / 2), (int)(x + touchMajor / 2), (int)(y + touchMinor / 2));

        this.submitFocusAreaRect(touchRect);
    }
}

private void submitFocusAreaRect(final Rect touchRect)
{
    Camera.Parameters cameraParameters = camera.getParameters();

    if (cameraParameters.getMaxNumFocusAreas() == 0)
    {
        return;
    }

    // Convert from View's width and height to +/- 1000

    Rect focusArea = new Rect();

    focusArea.set(touchRect.left * 2000 / cameraSurfaceView.getWidth() - 1000, 
                      touchRect.top * 2000 / cameraSurfaceView.getHeight() - 1000,
                      touchRect.right * 2000 / cameraSurfaceView.getWidth() - 1000,
                      touchRect.bottom * 2000 / cameraSurfaceView.getHeight() - 1000);

    // Submit focus area to camera

    ArrayList<Camera.Area> focusAreas = new ArrayList<Camera.Area>();
    focusAreas.add(new Camera.Area(focusArea, 1000));

    cameraParameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
    cameraParameters.setFocusAreas(focusAreas);
    camera.setParameters(cameraParameters);

    // Start the autofocus operation

    camera.autoFocus(this);
}

在cameraParameters.setFocusAreas(focusAreas);之前，您应该添加以下内容：

cameraParameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);