Question

See i have permissions for camera.打开前置摄像头返回null，即使我有使用摄像头的权限，搜索了很多答案但没有任何帮助这就是我试图打开前置摄像头的方法

Camera cam = null;
try{
cam = Camera.open(1);
}catch (Exception e){
Log.e("Manojjjj", "Camera failed to open: " + e.getMessage());       
e.printStackTrace();
}
return cam;

代码在android 5中工作正常，但在android 6中，它为前置摄像头返回null（后置摄像头工作正常），当我将id更改为0时（cam = Camera.open（0）），它没有任何问题打开相机。提前谢谢。

例外是：

09-01 16:52:29.228 24480-24480/com.magostech.dualcamera E/Manojjjj: Camera failed to open: Fail to connect to camera service

我搜索过的每个问题都说要添加运行时权限，但我已经给了运行时权限，所以我做得对，我认为我的问题不是添加运行时权限。

完整代码：

 private Camera mCamera = null;
private Camera mCamera1 = null;
private Handler mBackgroundHandler;
private CameraActivity mPreview;
private CameraPreview mPreview1;
FrameLayout preview;
FrameLayout preview1;
private static final int REQUEST_CAMERA_PERMISSION = 1;

public boolean safeToTakePicture = false;
String front,back;
Bitmap bitmap1;
Bitmap bitmap2;

private static final int PERMISSION_CALLBACK_CONSTANT = 100;
private static final int REQUEST_PERMISSION_SETTING = 101;
String[] permissionsRequired = new String[]{Manifest.permission.CAMERA,
        Manifest.permission.WRITE_EXTERNAL_STORAGE

        };
private SharedPreferences permissionStatus;
private boolean sentToSettings = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);
    permissionStatus = getSharedPreferences("permissionStatus",MODE_PRIVATE);
    checkForPermissions();
    // Create an instance of Camera


}

public void checkForPermissions(){
    if(ActivityCompat.checkSelfPermission(Main2Activity.this,permissionsRequired[0]) != PackageManager.PERMISSION_GRANTED
            ||ActivityCompat.checkSelfPermission(Main2Activity.this,permissionsRequired[1]) != PackageManager.PERMISSION_GRANTED){
        if(ActivityCompat.shouldShowRequestPermissionRationale(Main2Activity.this,permissionsRequired[0])
                ||ActivityCompat.shouldShowRequestPermissionRationale(Main2Activity.this,permissionsRequired[1])){
            AlertDialog.Builder builder = new AlertDialog.Builder(Main2Activity.this);
            builder.setTitle("Need Multiple Permissions");
            builder.setMessage("This app needs Camera and Location permissions.");
            builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                    ActivityCompat.requestPermissions(Main2Activity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
                }
            });
            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });
            builder.show();
        }
        else if (permissionStatus.getBoolean(permissionsRequired[0],false)) {
            //Previously Permission Request was cancelled with 'Dont Ask Again',
            // Redirect to Settings after showing Information about why you need the permission
            AlertDialog.Builder builder = new AlertDialog.Builder(Main2Activity.this);
            builder.setTitle("Need Multiple Permissions");
            builder.setMessage("This app needs Camera and Location permissions.");
            builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                    sentToSettings = true;
                    Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
                    Uri uri = Uri.fromParts("package", getPackageName(), null);
                    intent.setData(uri);
                    startActivityForResult(intent, REQUEST_PERMISSION_SETTING);
                    Toast.makeText(getBaseContext(), "Go to Permissions to Grant  Camera and Location", Toast.LENGTH_LONG).show();
                }
            });
            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });
            builder.show();
        }  else {
            //just request the permission
            ActivityCompat.requestPermissions(Main2Activity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
        }



        SharedPreferences.Editor editor = permissionStatus.edit();
        editor.putBoolean(permissionsRequired[0],true);
        editor.commit();
    } else {
        //You already have the permission, just go ahead.
        proceedAfterPermission();
    }


}


@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if(requestCode == PERMISSION_CALLBACK_CONSTANT){
        //check if all permissions are granted
        boolean allgranted = false;
        for(int i=0;i<grantResults.length;i++){
            if(grantResults[i]==PackageManager.PERMISSION_GRANTED){
                allgranted = true;
            } else {
                allgranted = false;
                break;
            }
        }

        if(allgranted){
            proceedAfterPermission();
        } else if(ActivityCompat.shouldShowRequestPermissionRationale(Main2Activity.this,permissionsRequired[0])
                || ActivityCompat.shouldShowRequestPermissionRationale(Main2Activity.this,permissionsRequired[1])
                || ActivityCompat.shouldShowRequestPermissionRationale(Main2Activity.this,permissionsRequired[2])){

            AlertDialog.Builder builder = new AlertDialog.Builder(Main2Activity.this);
            builder.setTitle("Need Multiple Permissions");
            builder.setMessage("This app needs Camera and Location permissions.");
            builder.setPositiveButton("Grant", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                    ActivityCompat.requestPermissions(Main2Activity.this,permissionsRequired,PERMISSION_CALLBACK_CONSTANT);
                }
            });
            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });
            builder.show();
        } else {
            Toast.makeText(getBaseContext(),"Unable to get Permission",Toast.LENGTH_LONG).show();
        }
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_PERMISSION_SETTING) {
        if (ActivityCompat.checkSelfPermission(Main2Activity.this, permissionsRequired[0]) == PackageManager.PERMISSION_GRANTED) {
            //Got Permission
            proceedAfterPermission();
        }
    }
}

private void proceedAfterPermission() {
    mCamera = getCameraInstance();
    mCamera1 = openFrontFacingCamera();
    // Create our Preview view and set it as the content of our activity.

        mPreview = new CameraActivity(this, mCamera);
        mPreview1 = new CameraPreview(this,mCamera1);
        preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview1 =(FrameLayout) findViewById(R.id.camera_preview1);
        preview.addView(mPreview);
        preview1.addView(mPreview1);

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

            if (safeToTakePicture) {
                mCamera.takePicture(null,null,backCamera);
                mCamera1.takePicture(null, null, frontCamera);
                safeToTakePicture = false;
            }
        }
    });

}


public static Camera getCameraInstance(){
    Camera c = null;

    try {
        c = Camera.open(0); // attempt to get a Camera instance

    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    return c; // returns null if camera is unavailable
}


private Camera openFrontFacingCamera(){
    int cameraCount = 0;

    Camera cam = null;

    Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
    cameraCount = Camera.getNumberOfCameras();
    for ( int camIdx = 0; camIdx < cameraCount; camIdx++ ) {
        Camera.getCameraInfo( camIdx, cameraInfo );
        if ( cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT  ) {
            try {
                Log.e("Cam Id",String.valueOf(camIdx));
                cam = Camera.open( camIdx );
            } catch (RuntimeException e) {
                e.printStackTrace();
                Log.e("Manoj", "Camera failed to open: " );
            }
        }
    }

    return cam;
}



@Override
protected void onPostResume() {
    super.onPostResume();
    if (sentToSettings) {
        if (ActivityCompat.checkSelfPermission(Main2Activity.this, permissionsRequired[0]) == PackageManager.PERMISSION_GRANTED) {
            //Got Permission
            proceedAfterPermission();
        }
    }
}


private Camera.PictureCallback frontCamera = new Camera.PictureCallback() {


    @Override
    public void onPictureTaken(final byte[] data, Camera camera) {

        camera.startPreview();
        String root = Environment.getExternalStorageDirectory().toString();
        File myDir = new File(root + "/Dual Camera");

        if (myDir.exists()) {
            myDir.delete();
        }
        myDir.mkdirs();

        String fname = "Image" + new Date().getTime() + ".jpg";

        File file = new File(myDir, fname);


        try{
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(data);
            fos.close();

            MediaScannerConnection.scanFile(Main2Activity.this, new String[]{file.getPath()}, new String[]{"image/jpeg"}, null);

            front = String.valueOf(file);
            bitmap1 = BitmapFactory.decodeFile(front);
            Log.e("Front",front);


            if(bitmap1!=null&&bitmap2!=null){
                mergeBitmap(bitmap1,bitmap2);
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        safeToTakePicture = true;
    }



};


public Bitmap mergeBitmap(Bitmap bitmap1, Bitmap bitmap2) {
    Bitmap mergedBitmap = null;

    int w, h = 0;

    h = bitmap1.getHeight() + bitmap2.getHeight();
    if (bitmap1.getWidth() > bitmap2.getWidth()) {
        w = bitmap1.getWidth();
    } else {
        w = bitmap2.getWidth();
    }

    mergedBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);

    Canvas canvas = new Canvas(mergedBitmap);

    canvas.drawBitmap(bitmap1, 0f, 0f, null);
    canvas.drawBitmap(bitmap2, 0f, bitmap1.getHeight(), null);

    saveBitmap(mergedBitmap);
    return mergedBitmap;
}

private Camera.PictureCallback backCamera = new Camera.PictureCallback() {


    @Override
    public void onPictureTaken(final byte[] data, Camera camera) {

        camera.startPreview();
        String root = Environment.getExternalStorageDirectory().toString();
        File myDir = new File(root + "/Dual Camera");

        if (myDir.exists()) {
            myDir.delete();
        }
        myDir.mkdirs();

        String fname = "Image" + new Date().getTime() + ".jpg";

        File file = new File(myDir, fname);



        try{
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(data);
            fos.close();

            MediaScannerConnection.scanFile(Main2Activity.this, new String[]{file.getPath()}, new String[]{"image/jpeg"}, null);

            back = String.valueOf(file);
            bitmap2 = BitmapFactory.decodeFile(String.valueOf(file));
            Log.e("Back",back);


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        safeToTakePicture = true;
    }



};

private void saveBitmap(Bitmap finalBitmap){
    String root = Environment.getExternalStorageDirectory().toString();
    File myDir = new File(root + "/Dual Camera");

    if (myDir.exists()) {
        myDir.delete();
    }
    myDir.mkdirs();

    String fname = "Merged" + new Date().getTime() + ".jpg";

    File file = new File(myDir, fname);

    try{
        FileOutputStream fos = new FileOutputStream(file);
        finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, fos);
        fos.flush();
        fos.close();

        MediaScannerConnection.scanFile(Main2Activity.this, new String[]{file.getPath()}, new String[]{"image/jpeg"}, null);
        Toast.makeText(getApplicationContext(),
                "Image Saved to:" + file, Toast.LENGTH_LONG).show();


    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

@Override
protected void onResume() {
    super.onResume();
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            == PackageManager.PERMISSION_GRANTED) {
        try {
            mCamera = Camera.open(0);
            mCamera.setPreviewCallback(null);
            mPreview = new CameraActivity(Main2Activity.this, mCamera);
            preview.addView(mPreview);
            mCamera.startPreview();

        }catch (Exception e) {
            Log.d("Manoj", "Error starting camera preview: " + e.getMessage());
        }try{
            if (mCamera1 == null){
                mCamera1 = openFrontFacingCamera();
                //mCamera1 = Camera.open(1);
                mCamera1.setPreviewCallback(null);
                mPreview1 = new CameraPreview(Main2Activity.this,mCamera1);
                preview1.addView(mPreview1);
                mCamera1.startPreview();
            }
        }catch (Exception e){
            Log.d("Manoj", "Error starting camera preview: " + e.getMessage());
        }
        safeToTakePicture = true;
    }
     else {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA},
                REQUEST_CAMERA_PERMISSION);
    }
}
@Override
protected void onPause() {

    try {
        // release the camera immediately on pause event
        // releaseCamera();
        mCamera1.stopPreview();
        mCamera1.setPreviewCallback(null);
        mPreview1.getHolder().removeCallback(mPreview1);
        mCamera1.release();
        mCamera1 = null;

    } catch (Exception e) {
        e.printStackTrace();
    }

    try{
        mCamera.stopPreview();
        mCamera.setPreviewCallback(null);
        mPreview.getHolder().removeCallback(mPreview);
        mCamera.release();
        mCamera = null;
    }catch (Exception e){
        e.printStackTrace();
    }
    super.onPause();
}
@Override
protected void onDestroy() {
    super.onDestroy();
    if (mBackgroundHandler != null) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            mBackgroundHandler.getLooper().quitSafely();
        } else {
            mBackgroundHandler.getLooper().quit();
        }
        mBackgroundHandler = null;
    }
}



@Override
public void onBackPressed(){
    super.onBackPressed();
}

Answer 1

试试这个：

 if( ContextCompat.checkSelfPermission(this, android.Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        requestPermissions(new String[]{android.Manifest.permission.CAMERA}, 5);
    }
}

使用 Ctrl + O 复制覆盖以下方法，粘贴可能会导致错误

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == 5) {
        if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // Now user should be able to use camera
        }
        else {
            // Your app will not have this permission. Turn off all functions
            // that require this permission or it will force close like your
            // original question
        }
    }
}

Answer 2

根据Android Doc，Android应用程序在流程沙箱中运行。对于Android 6.0或更高版本的操作系统，用户无法访问基本沙箱未提供的其他功能。您需要先申请 PERMISSION 。以下是那些重要的PERMISSIONS

如果设备运行Android 5.1（API级别22）或更低版本，或者应用程序的targetSdkVersion为22或更低，系统会要求用户在安装时授予权限，您可以访问任何敏感工具。

查看DOC了解更多详情。

在Android 6.0中打开前置摄像头遇到麻烦

2 个答案: