android - 表面 View 相机预览

Question

在让我的 SurfaceView 显示我的相机预览时遇到一点问题。我在这里查看了一些问题并通过 Google 搜索了一些 tuts，但我认为这可能是我这边的一个小错误，我只是没有看到。

代码

public class RoofPitchActivity extends Activity implements SensorEventListener {
    ...
    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;
    private Camera mCamera;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_roof_pitch);
        initViews();
    }

    private void initViews() {
        ...         

        Preview preview = new Preview(this);
        mCamera = Camera.open();
        preview.setCamera(mCamera);
    }

    ...
    ...

    class Preview extends ViewGroup implements SurfaceHolder.Callback {

        public Preview(Context context) {
            super(context);
            mSurfaceView = (SurfaceView) findViewById(R.id.preview);
            mSurfaceView = new SurfaceView(context);
            addView(mSurfaceView);

            mSurfaceHolder = mSurfaceView.getHolder();
            mSurfaceHolder.addCallback(this);
        }

        public void setCamera(Camera camera) {
            if (mCamera == camera) {
                return;
            }

            stopPreviewAndFreeCamera();

            mCamera = camera;

            if (mCamera != null) {
                requestLayout();

                try {
                    mCamera.setPreviewDisplay(mSurfaceHolder);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                mCamera.startPreview();
            }
        }

        private void stopPreviewAndFreeCamera() {

            if (mCamera != null) {
                mCamera.stopPreview();
                mCamera.release();
                mCamera = null;
            }
        }

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            mCamera.startPreview();
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            Camera.Parameters parameters = mCamera.getParameters();
            parameters.setPreviewSize(mSurfaceView.getWidth(), mSurfaceView.getHeight());
            requestLayout();
            mCamera.setParameters(parameters);
            mCamera.startPreview();
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            if (mCamera != null) {
                mCamera.stopPreview();
            }
        }

        @Override
        protected void onLayout(boolean changed, int l, int t, int r, int b) {
        }    
    }
}

因此，当 Activity 启动时，SurfaceView 是黑色的。相机似乎没有将预览渲染到 SurfaceView 上。我确定我遗漏了一些小东西，或者这可能只是对它的工作原理的根本误解。非常感谢有一些新的眼睛和一些解释。谢谢

Answer 1

所以我的问题的答案最终是针对特定设备的。代码是可以接受的，但我用来调试的设备是 Nexus 7。这意味着摄像头是前置的，对摄像头的正常调用不起作用。可以找到关于此的有趣且有趣的读物 in this article

Camera.open();

不起作用。你必须使用

Camera.open(0);

所以我的代码以对相机的条件检查结束，现在它工作正常。

像这样

public void setCamera() {
        stopPreviewAndFreeCamera();

        PackageManager pm = getPackageManager();
        boolean backCamera = pm.hasSystemFeature(PackageManager.FEATURE_CAMERA);
        boolean frontCamera = pm.hasSystemFeature(PackageManager.FEATURE_CAMERA_FRONT);

        if (frontCamera) {
            mCamera = Camera.open(0);
        } else if (backCamera) {
            mCamera = Camera.open();
        }

        if (mCamera != null) {
            Camera.Parameters parameters = mCamera.getParameters();
            parameters.setPreviewSize(mSurfaceView.getWidth(), mSurfaceView.getHeight());
            requestLayout();

            try {
                mCamera.setParameters(parameters);
                mCamera.setPreviewDisplay(mSurfaceHolder);
            } catch (IOException e) {
                e.printStackTrace();
            }                   
            mCamera.startPreview();
        }
}