Android 传递片段时内存泄漏

Question

我有这个代码，我正在使用条形码 Google API 视觉。当我打开片段并将设备旋转 6 次或更多次时，我在转储堆中看到许多实例保留在内存中（参见图片）。即使在我执行强制垃圾收集之后，它们也保持不变。在我下面的代码中，我没有看到任何内存泄漏。

图片是GC后的

The weird part is that some devices only show 1 instance of the classes after GC which is normal.

Emulator API 27  : NO MEMORY LEAKS
Samsung j500FN   : NO MEMORY LEAKS
Xiaomi mi8       : Memory Leak
Galaxy Tablet E  : Memory Leak

MainActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            Fragment sf = getSupportFragmentManager().findFragmentByTag("Scanner");
                transaction.add(R.id.root, new Scanner(), "Scanner");
                transaction.addToBackStack(null);
                transaction.commit(); 

        }
    });
}

扫描仪

public class Scanner extends Fragment{

public SurfaceView cameraView;
public BarcodeDetector barcode;
public CameraSource cameraSource;
private SurfaceHolder.Callback cameraCallback;
private ActivityScanBinding mbinding;

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    Log.d("ActivityScan","onCreate");
}

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    Log.d("ActivityScan","onCreateView");

    mbinding = DataBindingUtil.inflate(inflater, R.layout.activity_scan, container, false);


    mbinding.getRoot().setOnTouchListener(new View.OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event) {
            return true;
        }

    });
    cameraView = mbinding.getRoot().findViewById(R.id.cameraView);

    return mbinding.getRoot();
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    Scan();
}

@Override
public void onDestroy() {

    Log.d("ActivityScan","Destroyed");
    if(barcode!=null) {
        barcode.release();
        Log.d("barcode","Released");
    }
    if(cameraSource!=null) {
        cameraSource.release();
        Log.d("cameraSource ","Released");
    }
    if(cameraView!=null) {
        removeCameraViewCallback();
    }

    super.onDestroy();
}

@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
    super.onSaveInstanceState(outState);
}



public void Scan(){

    cameraView.setZOrderMediaOverlay(true);

    barcode = new BarcodeDetector.Builder(getActivity())
            .setBarcodeFormats(Barcode.QR_CODE)
            .build();

        if(!barcode.isOperational()){
            return;
        }


    cameraSource = new CameraSource.Builder(getActivity(), barcode)
            .setFacing(CameraSource.CAMERA_FACING_FRONT)
            .setRequestedFps(24)
            .setAutoFocusEnabled(true)
            .setRequestedPreviewSize(1920,1080)
            .build();

    cameraCallback = new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {

                if(ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED){
                    cameraSource.start(cameraView.getHolder());
                }
            }
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            cameraSource.stop();
        }
    };

    cameraView.getHolder().addCallback(cameraCallback);

    barcode.setProcessor(new Detector.Processor<Barcode>() {

        @Override
        public void release() {}

        @Override
        public void receiveDetections(Detector.Detections<Barcode> detections) {
            final SparseArray<Barcode> barcodes =  detections.getDetectedItems();
            if(barcodes.size() > 0){

            }
        }
    });


}

public void removeCameraViewCallback(){
    cameraView.getHolder().removeCallback(cameraCallback);
}
}

请查看我的代码，如果有内存泄漏请告诉我。

Leak Canary 显示：

Answer 1

为什么要在 onDestroy 方法中释放 barcode 和 cameraSource？根据 this onDestroy() 方法可以跳过并且不被调用。也许 onStop() 是释放资源更合适的地方？并分别在onStart()获取。

@Override
public void onStop() {

    Log.d("ActivityScan","Destroyed");
    if(barcode!=null) {
        barcode.release();
        Log.d("barcode","Released");
    }
    if(cameraSource!=null) {
        cameraSource.release();
        Log.d("cameraSource ","Released");
    }
    if(cameraView!=null) {
        removeCameraViewCallback();
    }

    super.onStop();
}

另外，创建BarcodeDetector和CameraSource时不要传Activity，可以的话传ApplicationContext

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