How to ask runtime permissions for Camera

问题:

I am doing an application to scan barcodes on a button click and it was working fine up to Lollipop versions. When I came to Marshmallow it stopped working. This is the error:

camerabase an error occurred while connecting to camera 0

It forces me to turn on permission by:

Settings --> application --> my app --> camera.

My question is how to allow camera permission to my app automatically in Marshmallow or by asking the user to turn on camera at runtime. A screen shot:

回答1:

    if (ContextCompat.checkSelfPermission(getContext(),
            Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {

        if (ActivityCompat.shouldShowRequestPermissionRationale((Activity)
                getContext(), Manifest.permission.CAMERA)) {


        } else {
            ActivityCompat.requestPermissions((Activity) getContext(), 
                    new String[]{Manifest.permission.CAMERA},
                    MY_PERMISSIONS_REQUEST_CAMERA);
        }

    }

回答2:

Below I have written a code for granting a runtime permissions for Camera, There is an Array of String in which you can give multiple requests granting as which is needed at runtime.

public class MainActivity extends AppCompatActivity {
    private static final int PERMISSION_REQUEST_CODE = 200;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (checkPermission()) {
        //main logic or main code

       // . write your main code to execute, It will execute if the permission is already given.

        } else {
            requestPermission();
        }
    }

    private boolean checkPermission() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                != PackageManager.PERMISSION_GRANTED) {
            // Permission is not granted
            return false;
        }
        return true;
    }

    private void requestPermission() {

        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.CAMERA},
                PERMISSION_REQUEST_CODE);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_REQUEST_CODE:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(getApplicationContext(), "Permission Granted", Toast.LENGTH_SHORT).show();

                    // main logic
                } else {
                    Toast.makeText(getApplicationContext(), "Permission Denied", Toast.LENGTH_SHORT).show();
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                                != PackageManager.PERMISSION_GRANTED) {
                            showMessageOKCancel("You need to allow access permissions",
                                    new DialogInterface.OnClickListener() {
                                        @Override
                                        public void onClick(DialogInterface dialog, int which) {
                                            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                                                requestPermission();
                                            }
                                        }
                                    });
                        }
                    }
                }
                break;
        }
    }

    private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
        new AlertDialog.Builder(MainActivity.this)
                .setMessage(message)
                .setPositiveButton("OK", okListener)
                .setNegativeButton("Cancel", null)
                .create()
                .show();
    }
}

回答3:

RxPermission is best library for asking permissions from user.

For camera permission the workaround is like this.

1) First add these permissions (or one you need) in your manifest.xml.

<uses-permission android:name="android.permission.CAMERA" />

2) Then ask run time permission from user in your activity.

RxPermissions rxPermissions = new RxPermissions(this);
rxPermissions
.request(Manifest.permission.CAMERA) // ask single or multiple permission once
.subscribe(granted -> {
    if (granted) {
       // All requested permissions are granted
    } else {
       // At least one permission is denied
    }
});

add this library in your build.gradle

allprojects {
    repositories {
        ...
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    implementation 'com.github.tbruyelle:rxpermissions:0.10.1'
    implementation 'com.jakewharton.rxbinding2:rxbinding:2.1.1'
}

Isn't this easy?

回答4:

This might help:

if (ContextCompat.checkSelfPermission(context, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)
{
    if(ActivityCompat.shouldShowRequestPermissionRationale((Activity) context, Manifest.permission.CAMERA))
    {
        AlertDialog.Builder alertBuilder = new AlertDialog.Builder(context);
        alertBuilder.setCancelable(true);
        alertBuilder.setTitle("Permission necessary");
        alertBuilder.setMessage("CAMERA is necessary");
        alertBuilder.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
            @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
            public void onClick(DialogInterface dialog, int which) {
                ActivityCompat.requestPermissions((Activity) context, 
                new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUESTS);
            }
        });
        AlertDialog alert = alertBuilder.create();
        alert.show();
    } else {
        ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUESTS);
    }
    return false;
} else {
    return true;
}

Where MY_PERMISSIONS_REQUESTS is your final value of the request code.

It works just fine for me.

回答5:

This is the complete code to implement runtime permissions

Add permission in manifest for camera

declare this variable

  public static final int RequestPermissionCode = 7;

Call this method checkAndroidVersion() in oncreate()

private void checkAndroidVersion() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkAndRequestPermissions();

        } else {
            // code for lollipop and pre-lollipop devices
        }

    }


private boolean checkAndRequestPermissions() {
        int camera = ContextCompat.checkSelfPermission(getActivity(),
                Manifest.permission.CAMERA);
        int wtite = ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE);
        int read = ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.READ_EXTERNAL_STORAGE);
        List<String> listPermissionsNeeded = new ArrayList<>();
        if (wtite != PackageManager.PERMISSION_GRANTED) {
            listPermissionsNeeded.add(Manifest.permission.WRITE_EXTERNAL_STORAGE);
        }
        if (camera != PackageManager.PERMISSION_GRANTED) {
            listPermissionsNeeded.add(Manifest.permission.CAMERA);
        }
        if (read != PackageManager.PERMISSION_GRANTED) {
            listPermissionsNeeded.add(Manifest.permission.READ_EXTERNAL_STORAGE);
        }
        if (!listPermissionsNeeded.isEmpty()) {
            ActivityCompat.requestPermissions(getActivity(), listPermissionsNeeded.toArray(new String[listPermissionsNeeded.size()]), REQUEST_ID_MULTIPLE_PERMISSIONS);
            return false;
        }
        return true;
    }


@Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        Log.d("in fragment on request", "Permission callback called-------");
        switch (requestCode) {
            case REQUEST_ID_MULTIPLE_PERMISSIONS: {

                Map<String, Integer> perms = new HashMap<>();
                // Initialize the map with both permissions
                perms.put(Manifest.permission.WRITE_EXTERNAL_STORAGE, PackageManager.PERMISSION_GRANTED);
                perms.put(Manifest.permission.CAMERA, PackageManager.PERMISSION_GRANTED);
                perms.put(Manifest.permission.READ_EXTERNAL_STORAGE, PackageManager.PERMISSION_GRANTED);
                // Fill with actual results from user
                if (grantResults.length > 0) {
                    for (int i = 0; i < permissions.length; i++)
                        perms.put(permissions[i], grantResults[i]);
                    // Check for both permissions
                    if (perms.get(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED
                            && perms.get(Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED && perms.get(Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
                        Log.d("in fragment on request", "CAMERA & WRITE_EXTERNAL_STORAGE READ_EXTERNAL_STORAGE permission granted");
                        // process the normal flow
                        //else any one or both the permissions are not granted
                    } else {
                        Log.d("in fragment on request", "Some permissions are not granted ask again ");
                        //permission is denied (this is the first time, when "never ask again" is not checked) so ask again explaining the usage of permission
//                        // shouldShowRequestPermissionRationale will return true
                        //show the dialog or snackbar saying its necessary and try again otherwise proceed with setup.
                        if (ActivityCompat.shouldShowRequestPermissionRationale(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE) || ActivityCompat.shouldShowRequestPermissionRationale(getActivity(), Manifest.permission.CAMERA) || ActivityCompat.shouldShowRequestPermissionRationale(getActivity(), Manifest.permission.READ_EXTERNAL_STORAGE)) {
                            showDialogOK("Camera and Storage Permission required for this app",
                                    new DialogInterface.OnClickListener() {
                                        @Override
                                        public void onClick(DialogInterface dialog, int which) {
                                            switch (which) {
                                                case DialogInterface.BUTTON_POSITIVE:
                                                    checkAndRequestPermissions();
                                                    break;
                                                case DialogInterface.BUTTON_NEGATIVE:
                                                    // proceed with logic by disabling the related features or quit the app.
                                                    break;
                                            }
                                        }
                                    });
                        }
                        //permission is denied (and never ask again is  checked)
                        //shouldShowRequestPermissionRationale will return false
                        else {
                            Toast.makeText(getActivity(), "Go to settings and enable permissions", Toast.LENGTH_LONG)
                                    .show();
                            //                            //proceed with logic by disabling the related features or quit the app.
                        }
                    }
                }
            }
        }

    }

    private void showDialogOK(String message, DialogInterface.OnClickListener okListener) {
        new AlertDialog.Builder(getActivity())
                .setMessage(message)
                .setPositiveButton("OK", okListener)
                .setNegativeButton("Cancel", okListener)
                .create()
                .show();
    }