android - 如何在没有黑屏的情况下处理android相机打开

Question

我正在开发一个 android 应用程序，在其中的 fragment 中打开相机。每当第一次打开相机时。它以大约 1 秒的小冲击加载。使屏幕变黑。如何完全防止屏幕在那一秒变黑。

详细解释:
当我们在 Facebook Messenger 中打开相机时，甚至尝试在您的手机中正常打开相机时。打开需要一秒钟，同时屏幕变黑。同样的事情正在发生。这可以预防吗？怎么办？伙计们，我们将不胜感激您的回复。

下面是与上述问题相同的工作代码。

public class scan extends Fragment implements ZXingScannerView.ResultHandler{
private ZXingScannerView zXingScannerView;
    private SurfaceView mySurfaceView;
    private QREader qrEader;
    private Camera mCamera;
    private CameraPreview mPreview;
    private String m_Text="";
    private  String number="";
  
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    public scan() {
    }
    @Override
    public void handleResult(Result rawResult) {
       

        Log.e("handler", rawResult.getText()); 
        Log.e("handler", rawResult.getBarcodeFormat().toString()); 

        AlertDialog.Builder builder = new AlertDialog.Builder(this.getActivity());
        builder.setTitle("Scan Result");
        builder.setMessage(rawResult.getText());
        number = rawResult.getText().substring(rawResult.getText().length() - 13);

        //
        final EditText input = new EditText(this.getActivity());
     input.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
        builder.setView(input);

        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                m_Text = input.getText().toString();

            }
        });
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });

        builder.setNegativeButton("NO",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });

        AlertDialog alert1 = builder.create();
        alert1.show();


        zXingScannerView.resumeCameraPreview(this);
    }

    public static scan newInstance(String param1, String param2) {
        scan fragment = new scan();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }

        if(checkCameraHardware(getActivity().getApplicationContext())) {
            zXingScannerView = new ZXingScannerView(this.getActivity().getApplicationContext());
            zXingScannerView.setResultHandler(this);
            zXingScannerView.startCamera();
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_scan, container, false);

        FrameLayout preview =(FrameLayout)view.findViewById(R.id.camera_preview);
        preview.addView(zXingScannerView);

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

    /** Check if this device has a camera */
    public boolean checkCameraHardware(Context context) {
        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
            // this device has a camera
            return true;
        } else {
            // no camera on this device
            return false;
        }
    }


    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {

        if (mCamera!= null) {
            mCamera.stopPreview();
           mCamera.release();
            mCamera = null;
        }
        super.onDetach();
        mListener = null;
    }

    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

Answer 1

我看到您使用的是已弃用 Camera API。如果您希望您的应用程序在 Lollipop 或更高版本的设备上表现最佳，您应该切换到新的 camera2 API。请在此处查看讨论:Android camera android.hardware.Camera deprecated .

新 API 可以显着提高性能，但如果您受困于旧 API，请不要绝望。如果您没有使用最新版本的 ZXingScannerView，请更新此类以在后台线程中打开相机。此更改improved显着启动。

如果您的 fragment 是 ViewPager 的一部分(如 camera preview within viewpager )，请确保在寻呼机将 scan fragment 带到屏幕之前启动相机预览。

在其他情况下，最好选择 启动画面 范例的变体，这有利也有弊。您可以在相机预览表面的顶部短暂显示另一个非黑色 View ，或者如果您使用 OpenGL 预览，则显示预定义的纹理。