在开发相机应用时，我遇到了一个异常，该异常仅在我切换到其他应用时发生(onPause() 用于我的应用)。

01-15 17:22:15.017: E/AndroidRuntime(14336): FATAL EXCEPTION: main
01-15 17:22:15.017: E/AndroidRuntime(14336): java.lang.RuntimeException: Method called after release()
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.hardware.Camera.setPreviewDisplay(Native Method)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.hardware.Camera.setPreviewDisplay(Camera.java:357)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at com.sora.cbir.yuki.image.leaf.CameraPreview.surfaceCreated(CameraPreview.java:32)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.SurfaceView.updateWindow(SurfaceView.java:551)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:213)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.View.dispatchWindowVisibilityChanged(View.java:4075)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:742)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewRoot.performTraversals(ViewRoot.java:858)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1995)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.os.Looper.loop(Looper.java:150)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at android.app.ActivityThread.main(ActivityThread.java:4389)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at java.lang.reflect.Method.invokeNative(Native Method)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at java.lang.reflect.Method.invoke(Method.java:507)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
01-15 17:22:15.017: E/AndroidRuntime(14336):    at dalvik.system.NativeStart.main(Native Method)

我做了一些研究，发现我需要添加

mCamera.setPreviewCallback(null);

作为 Android 相机堆栈的解决方法

我的 onPause() 现在看起来像这样:

@Override
protected void onPause() {
    super.onPause();
    try
    {    
        // release the camera immediately on pause event   
        //releaseCamera();
         mCamera.stopPreview(); 
         mCamera.setPreviewCallback(null);
         mCamera.release();
         mCamera = null;

    }
    catch(Exception e)
    {
        e.printStackTrace();
    }
}

还有我的onResume():

@Override
protected void onResume()
{
    super.onResume();
    try
    {
        mCamera.setPreviewCallback(null);
        mCamera = getCameraInstance();
        //mCamera.setPreviewCallback(null);
        mPreview = new CameraPreview(Imageupload.this, mCamera);//set preview
        preview.addView(mPreview);
    } catch (Exception e){
        Log.d(TAG, "Error starting camera preview: " + e.getMessage());
    }
}   
}

最后是我的 getCameraInstance() 方法:

public Camera getCameraInstance(){
    Camera camera = null;
    try {
        camera = Camera.open(); // attempt to get a Camera instance
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    Camera.Parameters parameters = camera.getParameters();
    //mPreviewSize = getBestPreviewSize(parameters, wt, ht);
    //mPictureSize = getBestPictureSize(parameters, wt, ht);
    //Shift W & H => if camera rotates 90 deg

    mPreviewSize = getOptimalPreviewSize(parameters, wt, ht); //original => wt,ht
    mPictureSize = getOptimalPictureSize(parameters, wt, ht); //original => wt,ht

    Log.d("CAMERA", "SCREEN RESOLUTION H: "+ht);
    Log.d("CAMERA", "SCREEN RESOLUTION W: "+wt);

    Log.d("CAMERA", "PREVIEW RESOLUTION H: "+mPreviewSize.height);
    Log.d("CAMERA", "PREVIEW RESOLUTION W: "+mPreviewSize.width);

    Log.d("CAMERA", "PICTURE RESOLUTION H: "+mPictureSize.height);
    Log.d("CAMERA", "PICTURE RESOLUTION W: "+mPictureSize.width);
    //set preview size based on device screen
    parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
    //set picture size based on device screen
    parameters.setPictureSize(mPictureSize.width, mPictureSize.height);
    //set output camera mode
    parameters.setPictureFormat(PixelFormat.JPEG);
    //set focous mode
    parameters.setFocusMode(FOCUS_MODE_AUTO);
    //set flash mode
    parameters.setFlashMode("auto");
    List<int[]> fps = parameters.getSupportedPreviewFpsRange();
    //System.out.println("FPS size: " +fps.size());
    //System.out.println("MAX FPS:"+(fps.get(fps.size()-1)[1])/1000);
    //log min and max camera supported fps
    Log.d("CAMERA", "CAMERA MAX FPS: "+(fps.get(fps.size()-1)[1])/1000);
    Log.d("CAMERA", "CAMERA MIN FPS: "+(fps.get(fps.size()-1)[0])/1000);
    if(camera_fps)
    {
        parameters.setPreviewFpsRange(fps.get(fps.size()-1)[1], fps.get(fps.size()-1)[1]);
    }
    //set camera parameters
    camera.setParameters(parameters);

    Toast.makeText(getApplicationContext(), "Your device are capable of previewing @" + fps.get(fps.size()-1)[1]/1000+"fps!",Toast.LENGTH_SHORT).show();
    return camera; // returns null if camera is unavailable
}

关于如何解决这个问题的任何想法？

最佳答案

我也遇到了同样的问题。 mCamera.setPreviewCallback(null); 没有帮助。在我的 Activity 中，我已将此添加到 releaseCamera:

mPreview.getHolder().removeCallback(mPreview);

现在可以使用了。

关于java - 释放()异常后调用的方法无法使用android相机恢复，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8868732/