如何处理没有黑屏的android相机打开

Question

我正在开发一个在片段中打开相机的 android 应用程序。每当相机第一次打开时。它以大约 1 秒的小抖动加载。使屏幕变黑。如何防止屏幕在那一秒完全变黑。

详细说明：
当我们在 Facebook Messenger 中打开相机，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。这可以防止吗？有什么办法吗？各位，我们将不胜感激。

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

我看到您使用了已弃用的相机 API。如果您希望您的应用在 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。

新的 API 可以显着提高性能，但如果您坚持使用旧 API，请不要绝望。如果您使用的不是最新版本的 ZXingScannerView，请更新该类以在后台线程中打开相机。此更改improved 启动显着。

如果您的片段是 ViewPager 的一部分（例如 camera preview within viewpager），请确保在分页器将 scan 片段带到屏幕之前启动相机预览。

在其他情况下，最好选择 splash screen 范式的变体，这有利有弊。您可以在相机预览表面上短暂显示另一个非黑色视图，或者如果您使用 OpenGL 预览，则显示预定义的纹理。

Answer 2

试试下面的代码打开相机并点击图片，因为它对我有用。

public class CameraImage extends Fragment {

private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE = 1888;
Button button;
ImageView imageView;

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

    final View rootView = inflater.inflate(R.layout.camera_image,
            container, false);

    button = (Button) rootView.findViewById(R.id.button);
    imageView = (ImageView) rootView.findViewById(R.id.imageview);

    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view) {

            Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            startActivityForResult(intent,
                    CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);

        }
    });

    return rootView;

}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
        if (resultCode == Activity.RESULT_OK) {

            Bitmap bmp = (Bitmap) data.getExtras().get("data");
            ByteArrayOutputStream stream = new ByteArrayOutputStream();

            bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
            byte[] byteArray = stream.toByteArray();

            // convert byte array to Bitmap

            Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray, 0,
                    byteArray.length);

            imageView.setImageBitmap(bitmap);

        }
    }        
 }    
}

希望它对你有用。