释放Exception Camera预览后调用的方法

Question

我有一个使用我的CameraPreview类的活动类(CameraActivity).在"OnResume"中启动相机和预览.在"OnPause"中,我正在发布相机资源.当应用程序启动时,一切都在"OnResume"内工作正常,但是当我通过意图启动另一个活动时(例如在浏览器中打开URL)然后回到我的活动,然后在"OnResume"内发生异常,发起CamerPreview类.请在下面找到代码:

// CameraActivity类

public void onResume(){
    super.onResume();
    Log.d("inside onResume, camera==="+mCamera, "inside onResume");
    try {
        if(mCamera==null)
        {

    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);


        autoFocusHandler = new Handler();
        mCamera = getCameraInstance();
        int rotation = this.getWindowManager().getDefaultDisplay().getRotation();


        scanner = new ImageScanner();
        scanner.setConfig(0, Config.X_DENSITY, 3);
        scanner.setConfig(0, Config.Y_DENSITY, 3);

        mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB);

        FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
        preview.addView(mPreview);



    }





} catch (Exception e) {
    // TODO Auto-generated catch block
    Log.e("onResume",Log.getStackTraceString(e));
}



public void onPause{
    try {
        super.onPause();
        if (mCamera != null) {
            previewing = false;
            mCamera.stopPreview();
                mCamera.setPreviewCallback(null);
                mCamera.release();
                mCamera = null;
                mPreview=null;


    }
} catch (Exception e) {
    // TODO Auto-generated catch block
    Log.e("releaseCamera",Log.getStackTraceString(e));
}
}



 public static Camera getCameraInstance(){
        Camera c = null;
        try {
            c = Camera.open();
        } catch (Exception e){
            Log.e("getCameraInstance",Log.getStackTraceString(e));

    }
    return c;
}

//以下是CameraPreview类:

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    Camera mCamera;
    PreviewCallback previewCallback;
    AutoFocusCallback autoFocusCallback;
    private int rotation;
    public int getRotation() {
        return rotation;
    }

    public void setRotation(int rotation) {
        this.rotation = rotation;
    }

    public CameraPreview(Context context, Camera camera,
                         PreviewCallback previewCb,
                         AutoFocusCallback autoFocusCb) {
        super(context);
        mCamera = camera;
        previewCallback = previewCb;
        autoFocusCallback = autoFocusCb;

        /*
         * Set camera to continuous focus if supported, otherwise use
         * software auto-focus. Only works for API level >=9.
         */
        /*
        Camera.Parameters parameters = camera.getParameters();
        for (String f : parameters.getSupportedFocusModes()) {
            if (f == Parameters.FOCUS_MODE_CONTINUOUS_PICTURE) {
                mCamera.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
                autoFocusCallback = null;
                break;
            }
        }
        */

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);

        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }


    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            if(mCamera==null){
                mCamera=Camera.open();
            }
            mCamera.setPreviewDisplay(holder);
        } catch (IOException e) {
            Log.d("DBG", "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {

        // Camera preview released in activity
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        /*
         * If your preview can change or rotate, take care of those events here.
         * Make sure to stop the preview before resizing or reformatting it.
         */
        if (mHolder.getSurface() == null){
          // preview surface does not exist
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
        }

try{
            mCamera.setPreviewDisplay(mHolder);
            mCamera.setPreviewCallback(previewCallback);
            mCamera.startPreview();
            mCamera.autoFocus(autoFocusCallback);
        } catch (Exception e){
            Log.d("DBG", "Error starting camera preview: " + e.getMessage());
        }
    }

}

这是来自logCat:

11-05 10:14:34.585: E/AndroidRuntime(7864): FATAL EXCEPTION: main
11-05 10:14:34.585: E/AndroidRuntime(7864): java.lang.RuntimeException: Method called after release()
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.hardware.Camera.setPreviewDisplay(Native Method)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.hardware.Camera.setPreviewDisplay(Camera.java:393)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at com.intagleo.qraugmented.detection.camera.CameraPreview.surfaceCreated(CameraPreview.java:74)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.SurfaceView.updateWindow(SurfaceView.java:552)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:215)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.View.dispatchWindowVisibilityChanged(View.java:4027)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewRoot.performTraversals(ViewRoot.java:790)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1867)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.os.Looper.loop(Looper.java:130)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at android.app.ActivityThread.main(ActivityThread.java:3687)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at java.lang.reflect.Method.invokeNative(Native Method)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at java.lang.reflect.Method.invoke(Method.java:507)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
11-05 10:14:34.585: E/AndroidRuntime(7864):     at dalvik.system.NativeStart.main(Native Method)

编辑

我更新了"surfaceDestroyed"并按照建议添加了日志,但现在我在"onPause" - > onSurfaceDestroyed中遇到异常.最初onPause正在执行.

1-通过方法"getCameraInstance"在活动类的"onResume"中创建相机实例,并将mCamera实例传递给CameraPreview类.我尝试更改它,以便仅在"onSurfaceCreated"上创建相机实例,并将mCamera实例分配回活动类,但它不起作用.我还注意到,通过调试,"CameraPreview"类的previewCallBack成员第一次有效,但第二次"CameraPreview"类的"previewCallBack"成员为null.

请注意,第一次调用"onResume"时,一切正常,但是当它在onPause之后第二次运行时,最初会发生异常,尽管onResume中的代码相同.

11-06 01:25:28.375: I/onResume(4332): INITIATED
// Workinf fine till now. Now opening another intent activity
11-06 01:26:23.500: I/onPause(4332): INITIATED
11-06 01:26:23.804: "OnSurfaceDestroyed": "Initiated"
11-06 01:26:23.945: E/AndroidRuntime(4332): FATAL EXCEPTION: main
11-06 01:26:23.945: E/AndroidRuntime(4332): java.lang.RuntimeException: Method called after release()
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.hardware.Camera.stopPreview(Native Method)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at com.intagleo.qraugmented.detection.camera.CameraPreview.surfaceDestroyed(CameraPreview.java:85)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.SurfaceView.reportSurfaceDestroyed(SurfaceView.java:596)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.SurfaceView.updateWindow(SurfaceView.java:490)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:215)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.View.dispatchWindowVisibilityChanged(View.java:4027)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:720)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewRoot.performTraversals(ViewRoot.java:790)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1867)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.os.Looper.loop(Looper.java:130)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at android.app.ActivityThread.main(ActivityThread.java:3687)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at java.lang.reflect.Method.invokeNative(Native Method)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at java.lang.reflect.Method.invoke(Method.java:507)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
11-06 01:26:23.945: E/AndroidRuntime(4332):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

正如您已将相机添加到FrameLayout,如下所示:

FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
preview.addView(mPreview);

该surfaceCreated方法将被调用,因此mCamera.setPreviewDisplay(holder);将被调用.

当你创建/打开一个新的相机时,FrameLayout仍然有你以前的相机,所以surfaceCreated除了你的新相机之外,它还会被调用.

你应该做的是,从FrameLayout你释放你的相机(onPause()方法)时删除你以前的相机,如下所示:

preview.removeView(mPreview);

希望能帮助到你.

Answer 2

丹是对的.另见这里.

代码示例:

public class MainActivity extends Activity {
    private FrameLayout mFlCameraPreview;
    private Camera mCamera;
    private CameraPreview mCameraPreview;

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

        mFlCameraPreview = (FrameLayout) findViewById(R.id.main_fl_camera_preview);
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mCamera == null) {
            mCamera = getCameraInstance();
        }

        if (mCameraPreview == null) {
            mCameraPreview = new CameraPreview(this, mCamera);
            mFlCameraPreview.addView(mCameraPreview);
        }

    }

    @Override
    protected void onPause() {
        super.onPause();
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }

        if (mCameraPreview != null) {
            mFlCameraPreview.removeView(mCameraPreview);
            mCameraPreview = null;
        }
    }

    public static Camera getCameraInstance() {
        Camera camera = null;
        try {
            camera = Camera.open();
        } catch (Exception e) {

        }
        return camera;
    }
}