在ZXingScannerView中恢复片段后，扫描仪不显示

Question

我在片段中使用扫描仪。首次尝试扫描仪工作正常，但当我移动到新的活动并返回时，则不会显示扫描仪。

public class SampleFragment extends Fragment implements ZXingScannerView.ResultHandler{

    private ZXingScannerView mScannerView;
    private LinearLayout qrCameraLayout;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View fragmentView =  inflater.inflate(R.layout.fragment_qr_code_reader, container, false);
        qrCameraLayout = (LinearLayout) fragmentView.findViewById(R.id.ll_qrcamera);
        mScannerView = new ZXingScannerView(getActivity());
        mScannerView.setLayoutParams(new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.MATCH_PARENT));
        mScannerView.setResultHandler(this);
        mScannerView.startCamera();
        qrCameraLayout.addView(mScannerView);
        return fragmentView;
    }
    @Override
    public void onResume`enter code here`()
    {
        super.onResume();
       if(mScannerView==null)
        mScannerView.resumeCameraPreview(this);
        //after I switch to new activity and reopen, then scanner is not shown
    }
    @Override
    public void onPause()
    {
        super.onPause();
        mScannerView.resumeCameraPreview(this);
        mScannerView=null;
    }



    @Override
    public void handleResult(Result result) {

        Toast.makeText(getActivity(),result.getText().toString(),Toast.LENGTH_LONG).show();

    }
}

Answer 1

尝试将onResume和onPause方法更改为此

@Override
public void onResume() {
    super.onResume();
    mScannerView.setResultHandler(this); // Register ourselves as a handler for scan results.
    mScannerView.startCamera();          // Start camera on resume
}

@Override
public void onPause() {
    super.onPause();
    mScannerView.stopCamera();           // Stop camera on pause
}