Question

我正在为我的应用编写自定义相机。使用后置或前置摄像头打开活动时，它工作正常。但我真的很难在活动中切换相机。

当我点按切换相机按钮时，预览冻结，没有任何反应。我已经尝试了与相机和预览相关的其他问题中提出的答案和提示，但没有任何效果。

这是我的活动：

public class CameraActivity extends Activity implements SurfaceHolder.Callback {

    //================================================================================
    // Properties
    //================================================================================

    // Tag
    private final String TAG = "CameraActivity";

    // Camera and CameraPreview objects
    private Camera mCamera;

    // SurfaceHolder object
    private SurfaceHolder mSurfaceHolder;
//    private CameraPreview mPreview;

    // ImageButtons
    private ImageButton captureButton;
    private ImageButton camSwitchButton;

    // Picture previewLayout
    FrameLayout previewLayout;
    SurfaceView preview;

    // Current camera is facing FRONT or BACK
    private int currentCameraId = Camera.CameraInfo.CAMERA_FACING_FRONT;

    // Picture taking callback
    private Camera.PictureCallback mPictureCallback;

    //================================================================================
    // Methods
    //================================================================================

    @Override
    public void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Activity with no notification bar
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        // Set content view
        setContentView(R.layout.activity_camera);

        // Initialize activity and previews
        InitActivity();
        InitPreview();

        // Set onClicks
    }

    /**
     * Initialize activity views
     */
    private void InitActivity() {

        // Create an instance of Camera
        mCamera = GetCameraInstance(currentCameraId);

        // Set the SurfaceView
        preview = (SurfaceView) findViewById(R.id.camera_preview);
        mSurfaceHolder = preview.getHolder();
        mSurfaceHolder.addCallback(this);

    }

    /**
     * Initialize the camera preview
     */
    private void InitPreview() {

        if (mCamera != null) {

            try {
                mCamera.setPreviewDisplay(mSurfaceHolder);
            } catch (IOException e) {
                // log
            }

            mCamera.startPreview();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release(); // release the camera for other applications
            // mCamera = null;
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        if (mCamera == null) {
            InitActivity();
            InitPreview();
        }
    }

    /**
     * Get camera instance
     * @return Camera instance (null if doesn't exist)
     */
    private Camera GetCameraInstance(int camid) {

        Camera c = null;

        try {

            c = Camera.open(camid); // attempt to get a Camera instance

            Camera.Parameters campar = c.getParameters();

            // Set auto-focus
            if (getPackageManager().hasSystemFeature("android.hardware.camera.autofocus")) {
                campar.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
            }

            c.setParameters(campar);

        }
        catch (Exception e){
            // log
        }

        return c; // returns null if camera is unavailable
    }

    /**
     * Switch the camera from front to back and vica verca
     */
    private void SwitchCamera() {

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

        //swap the id of the camera to be used
        if (currentCameraId == Camera.CameraInfo.CAMERA_FACING_BACK) {
            currentCameraId = Camera.CameraInfo.CAMERA_FACING_FRONT;
        }
        else currentCameraId = Camera.CameraInfo.CAMERA_FACING_FRONT;

        // Remove the view and re-add it
        ViewGroup rootView = (ViewGroup) preview.getParent();
        rootView.removeView(previewLayout);

        mCamera = GetCameraInstance(currentCameraId);

        InitActivity();

    }

    @Override
    public void surfaceCreated(SurfaceHolder surfaceHolder) {
        Logger.Log(TAG, "SurfaceCreated");
        InitPreview();
    }

    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) {    
        // Return if no surface found
        if (mSurfaceHolder.getSurface() == null) {
            return;
        }

        // Start preview with new settings
        Camera.Parameters params = mCamera.getParameters();
        boolean isPortrait = IsPortrait();

        // Configure the parameters (so the image is showing correctly)
        ConfigureCameraParameters(params, isPortrait);

        // Start preview
        InitPreview();

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {

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

    /**
     * Configure the camer parameters
     * @param cameraParams Camera parameters
     * @param isPortrait Is the camera in portrait mode?
     */
    protected void ConfigureCameraParameters(Camera.Parameters cameraParams, boolean isPortrait) {

        int angle;

        Display display = getWindowManager().getDefaultDisplay();

        // Correct the orientation
        switch (display.getRotation()) {

            case Surface.ROTATION_0: // This is display orientation
                angle = 90; // This is camera orientation
                break;
            case Surface.ROTATION_90:
                angle = 0;
                break;
            case Surface.ROTATION_180:
                angle = 270;
                break;
            case Surface.ROTATION_270:
                angle = 180;
                break;
            default:
                angle = 90;
                break;
        }

        mCamera.setDisplayOrientation(angle);
        mCamera.setParameters(cameraParams);
    }

    /**
     * Check whether the camera is in portrait mode
     * @return True|False
     */
    private boolean IsPortrait() {
        return (getResources().getConfiguration().orientation
                == Configuration.ORIENTATION_PORTRAIT);
    }
}

清单中的权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />

如果有人可以提供帮助，我真的很感激。

Answer 1

你非常接近，每次切换相机时都不需要破坏表面视图，只需要破坏相机会话，然后确保将相机连接回Surfaceview以便显示。我在Razr Max上面向后面的逻辑时遇到了一些问题所以我只是将其切换为1和0。

    private void SwitchCamera() {

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

    //swap the id of the camera to be used
    if (currentCameraId == Camera.CameraInfo.CAMERA_FACING_FRONT) {
        currentCameraId = 0;
    } else  {
        currentCameraId = 1;
    }

    mCamera = GetCameraInstance(currentCameraId);

    InitPreview();
}

切换相机时Android相机预览会冻结吗？

1 个答案: