11

我有一个使用我的 CameraPreview 类的活动类（CameraActivity）。在“OnResume”中，相机和预览被启动。在“OnPause”中，我正在释放相机资源。当应用程序启动时，“OnResume”内一切正常，但是当我通过意图启动另一个活动（例如在浏览器中打开 url）然后回到我的活动时，在“OnResume”发起的 CamerPreview 类中发生异常。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”并按照建议放置日志，但现在我在“onPause”-> onSurfaceDestroyed 中遇到异常。最初 onPause 执行良好。

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”内部创建相机实例并将 mCamera 实例分配回活动类，但它不起作用。我还通过调试注意到“CameraPreview”类的previewCallBack 成员第一次有效，但第二次“CameraPreview”类的“previewCallBack”成员为空。

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)
4

7 回答 7

42

当您将相机添加到 FrameLayout 时，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。

当您创建/打开一个新相机时，FrameLayout仍然有您以前的相机，因此surfaceCreated除了您的新相机外，它还将被调用。

你应该做的是，FrameLayout当你释放你的相机（在onPause()方法上）时移除你以前的相机，如下所示：

preview.removeView(mPreview);

希望能帮助到你。

于 2013-05-10T17:02:13.420 回答
5

丹是对的。也见这里。

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;
    }
}
于 2013-12-30T07:29:01.000 回答
1

编辑

这是一个很难回答的问题，我现在不能 100% 确定是什么导致了你的异常。我在下面包含了我的相机代码，希望这会有所帮助，我使用startCamera()和stopCamera()调用的方法onPause和onResume. 我也只CameraPreview在我的类中创建一个新实例onCreate，onResume除非我的cameraView == null. 我们做一些不同的事情。希望下面的代码会有所帮助，也许您可​​以使用它来使您的代码正常工作：

PS：一切都对我有用。即进入其他活动等。我没有测试的生命周期的唯一部分是onDestroy，但那是因为我的应用程序被设计为在这个周期的开头开始。

主要活动：

boolean cameraReleased = false;

@Override
protected void onPause() {
    Log.i("onPause", "CALLED:: cameraReleased = " + cameraReleased);
    Log.i("onResume", "CALLED:: cameraView = " + cameraView.toString());
    if (cameraReleased == false) {
        image = null;
        imageResult.setImageBitmap(null);
        imageResult.setImageResource(0);
        cameraView.stopCamera();
        cameraReleased = true;
    }

    if (cameraView == null) {
        Log.i("onPause", "cameraView == null");
        cameraView = new JJCameraSurfaceView(getApplicationContext());
        imageResult = new ImageView(getApplicationContext());
    }
    super.onPause();
}

@Override
protected void onDestroy() {
    Log.e("onDestroy", "INITIATED");
    super.onDestroy();
}

@Override
protected void onResume() {
    Log.i("onResume", "CALLED:: cameraReleased = " + cameraReleased);
    Log.i("onResume", "CALLED:: cameraView = " + cameraView.toString());
    if (cameraReleased == true) {
        image = null;
        imageResult.setImageBitmap(null);
        imageResult.setImageResource(0);
        cameraView.startCamera();
    }

    if (cameraView == null) {
        Log.i("onResume", "cameraView == null");
        cameraView = new JJCameraPreview(getApplicationContext());
        imageResult = new ImageView(getApplicationContext());
    }

    super.onResume();
}

@Override
public void onBackPressed() {
    // If Statement used to get out of my camera view and back to my MainActivity - Same Class
    if (“Camera Preview or Image Result is displayed”) {
        cameraView.stopCamera();
        image = null;
        imageResult.setImageBitmap(null);
        imageResult.setImageResource(0);
        cameraView.startCamera();
        return;
    }

    Log.i("onBackPressed", "WAS PRESSED");
    super.onBackPressed();
}

相机预览：

public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    Log.w("surfaceChanged", "STARTED");
    if (camera != null) {
        Log.w("surfaceChanged", "camera = NOT NULL");
        Camera.Parameters cParams = camera.getParameters();
        cParams.setPreviewSize(width, height);
        cParams.setSceneMode(Parameters.SCENE_MODE_NIGHT);
        camera.setParameters(cParams);
        camera.startPreview();
    }
}

public void surfaceCreated(SurfaceHolder holder) {
    Log.w("surfaceCreated", "STARTED");
    if (camera == null) {
        camera = Camera.open(); 
    }
    try {
        camera.setPreviewDisplay(mHolder);
    } catch (Exception e) {
        Log.e("setPreviewDisplay", "FAILED: " + e.getMessage());
    }
}

public void surfaceDestroyed(SurfaceHolder holder) {
    Log.w("CameraSurfaceDestroyed", "INITIATED");
    camera.stopPreview();
    camera.release();
    camera = null;
}

public void startCamera() {
    Log.w("startCamera", "CALLED");
    mHolder = getHolder();
    surfaceCreated(mHolder);
    camera.startPreview();
    mHolder.addCallback(this);
}

public void stopCamera() {
    mHolder = getHolder();
    mHolder.removeCallback(this);
    camera.stopPreview();
}
于 2012-11-05T16:57:34.383 回答
1

我的代码遇到了类似的问题，该问题因Method called after release()错误而强制关闭。

我正在调用一个SetupCamera()方法，在OnResume()该方法中检查一个空camera对象，然后调用camera.Open().

解决我的问题是摆脱空检查，并在阅读 Camera Docs 后调用它是否为camera.Open()空（我已经设置好） 。camera = nullonPause

我知道这对于追查我的问题并不确定，但它绝对对我有用！

于 2013-02-28T04:19:35.227 回答
1

我的工作解决方案：首先：在CameraActivity类中声明mCamera为数组：

Camera mCamera[] = new Camera[1];

第二：构造函数的声明CameraPreview必须是这样的：

public CameraPreview(Context context, Camera[] camera,
                     PreviewCallback previewCb,
                     AutoFocusCallback autoFocusCb) {
      mCamera = camera;
      ...
}

但mCamera在CameraPreview类中必须声明如下：

Camera[] mCamera; // without instantiating of the array!

最后：在所有方法中的两个类中，您应该将所有引用替换mCamera为mCamera[0]

PS：对不起我的英语

于 2015-09-09T20:42:34.850 回答
0

试试下面的代码，而不是重写 onPause() 和 onResume()，重写 onStop() 和 onRestart()。在活动生命周期中，当活动不可见时调用 onStop()，下一个生命周期方法调用将调用 onRestart()。看看下面的代码。

@Override
    protected void onStop() {
        super.onStop();
        try {
            m_camera.stopPreview();
            m_camera.release();
            preview.removeView(m_CameraPreview);
/*
m_CameraPreview is the object of the class that looks like this :                                public class CameraSurfaceView extends SurfaceView implements Callback
*/
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
    @Override
    protected void onRestart() {
        super.onRestart();
        m_camera=getCameraInstance();//Initialize the camera in your own way
        m_CameraPreview = new CameraSurfaceView(this, m_camera);
       preview = (FrameLayout)findViewById(R.id.camera_preview);   
        preview.addView(this.m_CameraPreview);
/* 
*camera_preview is the id of the framelayout defined in xml file and preview is *the instance of FrameLayout. 
*/
    }

正如 Dan 所说，框架布局将保留先前的相机实例，并且除了创建竞争条件的新对象之外，还将创建其表面视图回调。因此，您需要在 onStop() 中释放它并在 onRestart() 中重新初始化。希望这可以帮助。

于 2016-01-21T12:07:49.930 回答
0

我遇到了同样的错误。下面的序列解决了我的问题。

呼入 getHolder().removeCallback(this);_surfaceDestroyed()

称呼

 private void releaseCameraAndPreview() {

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

        if(mPreview != null){
            mPreview.destroyDrawingCache();
            mPreview.mCamera = null;
        }

    }

在onPause

称呼

  private boolean safeCameraOpenInView(View view) {
        boolean qOpened = false;
        releaseCameraAndPreview();
        mCamera = getCameraInstance();
        mCameraView = view;
        qOpened = (mCamera != null);

        if(qOpened == true){
            mPreview = new CameraPreview(getActivity().getBaseContext(), mCamera,view);
            preview = (FrameLayout) view.findViewById(R.id.camera_preview);
            preview.addView(mPreview);
            mPreview.startCameraPreview();
        }
        return qOpened;
    }

在onCreateView().

于 2017-04-03T06:12:24.887 回答