Android SDK的一个bug------parameters.getFocusDistances无法使用（被拍摄物体和摄像头之间的距离无法测量）

      这是很早之前我发现的一个问题，当时想利用“焦距”来定位被拍摄物体和手机摄像头之间的距离，注意不是摄像头预览画面里两个点之间的距离，这是个平面距离。本文所说的距离是垂直距离。最终失败，原因是parameters.getFocusDistances返回的值永远是inifinte。手机型号是华为U9200.

下面是测试核心代码：

@Override
    public void onAutoFocus(boolean success, Camera camera) {
        //READ FOCUS DISTANCES HERE
        Camera.Parameters parameters = camera.getParameters();
        float[] distances = new float[3];
        if (success) {
            // Only available with Android 9 (2.3)
            // Focus Mode is always reported as auto but
            // distances do not appear to be updating
            // always: 0.1, 1.2, Infinity, (on my device it's 0,0,0)
            Log.d("Focus Mode: ", parameters.getFocusMode());
            parameters.getFocusDistances(distances);
            Log.d("focus distance near", Float.toString(distances[0]));
            Log.d("focus distance optimum", Float.toString(distances[1]));
            Log.d("focus distance far", Float.toString(distances[2]));
        }
    }

@Override
    public void surfaceCreated(SurfaceHolder holder) {
        Log.e(getClass().getSimpleName(), "surfaceCreated");
        camera = Camera.open();
        Camera.Parameters parameters = camera.getParameters();
        float[] distances = new float[3];
        Log.d("Focus Mode: ", parameters.getFocusMode());
        parameters.getFocusDistances(distances);
        Log.d("focus distance 0", Float.toString(distances[0]));
        Log.d("focus distance 1", Float.toString(distances[1]));
        Log.d("focus distance 2", Float.toString(distances[2]));
    }

后查资料，早期的手机带有红外，通过发射红外可以测出来被拍摄物体和手机之间的距离。以前的相机的聚焦算法用的是物理算法也就是指的这。现代的大多通过软件聚焦，比如计算出人脸核心区域以此聚焦。但这些算法都是相机厂家的机密哦！！！但android手机里既然提供这个api理论上是可以获得距离的，只能说是个bug了！

参考：http://stackoverflow.com/questions/6401370/camera-focus-distances

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