Android Studio Tutorial | Runtime Permissions in Android Studio

In This Video You Can See How To Give Runtime Permissions In Android
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Every Android app runs in a limited-access sandbox. If an app needs to use resources or information outside of its own sandbox, the app has to request the appropriate permission. You declare that your app needs a permission by listing the permission in the app manifest and then requesting that the user approve each permission at runtime (on Android 6.0 and higher).

This video describes how to use the Android Support Library to check for and request permissions. The Android framework provides similar methods as of Android 6.0 (API level 23), but using the support library makes it easier to provide compatibility with older versions of Android.
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The system's behavior after you declare a permission depends on how sensitive the permission is. Some permissions are considered "normal" so the system immediately grants them upon installation. Other permissions are considered "dangerous" so the user must explicitly grant your app access. For more information about the different kinds of permissions, see Protection levels.
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Check for permissions

If your app needs a dangerous permission, you must check whether you have that permission every time you perform an operation that requires that permission. Beginning with Android 6.0 (API level 23), users can revoke permissions from any app at any time, even if the app targets a lower API level. So even if the app used the camera yesterday, it can't assume it still has that permission today.
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Request permissions

When your app receives PERMISSION_DENIED from checkSelfPermission(), you need to prompt the user for that permission. Android provides several methods you can use to request a permission, such as requestPermissions(), as shown in the code snippet below. Calling these methods brings up a standard Android dialog, which you cannot customize.

How this is displayed to the user depends on the device Android version as well as the target version of your application, as described in the Permissions Overview.
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Explain why the app needs permissions

In some circumstances, you want to help the user understand why your app needs a permission. For example, if a user launches a photography app, the user probably won't be surprised that the app asks for permission to use the camera, but the user might not understand why the app wants access to the user's location or contacts. Before your app requests a permission, you should consider providing an explanation to the user. Keep in mind that you don't want to overwhelm the user with explanations; if you provide too many explanations, the user might find the app frustrating and remove it.

One approach you might use is to provide an explanation only if the user has already denied that permission request. Android provides a utility method, shouldShowRequestPermissionRationale(), that returns true if the user has previously denied the request, and returns false if a user has denied a permission and selected the Don't ask again option in the permission request dialog, or if a device policy prohibits the permission.

If a user keeps trying to use functionality that requires a permission, but keeps denying the permission request, that probably means the user doesn't understand why the app needs the permission to provide that functionality. In a situation like that, it's probably a good idea to show an explanation.

More advice about how to create a good user experience when asking for permission is provided in App Permissions Best Practices.
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Request the permissions you need

If your app doesn't already have the permission it needs, the app must call one of the requestPermissions() methods to request the appropriate permissions. Your app passes the permissions it wants and an integer request code that you specify to identify this permission request. This method functions asynchronously. It returns right away, and after the user responds to the prompt, the system calls the app's callback method with the results, passing the same request code that the app passed to requestPermissions().
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Handle the permissions request response

When the user responds to your app's permission request, the system invokes your app's onRequestPermissionsResult() method, passing it the user response. Your app has to override that method to find out whether the permission was granted. The callback is passed the same request code you passed to requestPermissions().