Android 应用程序在暂停时崩溃答案

【问题标题】：Android App Crashes when pausedAndroid 应用程序在暂停时崩溃
【发布时间】：2016-02-19 01:15:35
【问题描述】：

我有一个 android 活动，它使用表面视图显示实时相机预览。一切正常，但是当我按下手机上的锁定按钮然后解锁手机时，或者当来自另一个活动（例如蓝牙传输或来电）的对话框覆盖我的相机预览时，应用程序崩溃。我怀疑这是我的onResume() 或onPause() 活动的问题，因为我收到错误“释放（）之后调用的方法”。但是，我不确定如何解决这个问题。

相机活动：

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_camera_screen);
    setStatusBarColor();
    Display display = getWindowManager().getDefaultDisplay();
    final int height = display.getHeight();

    session = new SessionManager(getApplicationContext());
    try {
        mCamera = Camera.open();//you can use open(int) to use different cameras
    } catch (Exception e) {
        Log.d("ERROR", "Failed to get camera: " + e.getMessage());
    }


    if (mCamera != null) {
        mCameraView = new CameraPreview(this, mCamera);//create a SurfaceView to show camera data
        FrameLayout camera_view = (FrameLayout) findViewById(R.id.camera_view);
        camera_view.addView(mCameraView);//add the SurfaceView to the layout
        //rotate preview
        mCamera.setDisplayOrientation(90);
  //rotate camera
        Camera.Parameters p = mCamera.getParameters();
        p.setRotation(90);
        mCamera.setParameters(p);
    }
    @Override
protected void onPause() {
    super.onPause();
    if (mCamera != null) {
        mCamera.setPreviewCallback(null);
        mCameraView.getHolder().removeCallback(mCameraView);
        mCamera.release();
    }
}
@Override
public void onResume() {
    super.onResume();

    // Get the Camera instance as the activity achieves full user focus
    if (mCamera == null) {
        initializeCamera(); // Local method to handle camera initialization
    }
}



protected void initializeCamera(){
    // Get an instance of Camera Object
    try{
        mCamera = Camera.open();//you can use open(int) to use different cameras
    } catch (Exception e){
        Log.d("ERROR", "Failed to get camera: " + e.getMessage());
    }


    if(mCamera != null) {
        mCameraView = new CameraPreview(this, mCamera);//create a SurfaceView to show camera data
        FrameLayout camera_view = (FrameLayout)findViewById(R.id.camera_view);
        camera_view.addView(mCameraView);//add the SurfaceView to the layout
    }

}

【问题讨论】：

mCamera.release() 不会使 mCamera 为空。发布后将null分配给mCamera。

标签： java android android-camera onresume onpause

【解决方案1】：

尝试将此行添加到您的 onPause()：

camera_view.removeView(mCameraView);

【讨论】：

【解决方案2】：

onPause(){
...
mCamera.release(); // close mCamera, but not set it to null
//mCamera = null; // you need reset mCamera to trigger init method;
}
onResume(){
...
initializeCamera();// need mCamera == null
}

//If you find other problems.
//Add some codes in the initializeCamera().
{
//mCamera.setPreviewCallback("something");
//mCameraView.getHolder().addCallback(mCameraView);
}
//as onPause do.

【讨论】：