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:
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2:
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3:
This is the complete code to implement multiple or single runtime permissions
Step 1
Add permission in
manifestfor camera and also other required permissions
like
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
Step 2
declare this variable
public static final int REQUEST_ID_MULTIPLE_PERMISSIONS= 7;
and 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();
}
回答4:
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5:
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.
来源：https://stackoverflow.com/questions/42275906/how-to-ask-runtime-permissions-for-camera