Starting with Android Marshmallow (Android 6), Google introduced Runtime permissions system where the user is asked to grant a permission in runtime rather than doing that during installation of the app. However, Unity for Android is not supporting it out of the box because:

• the corresponding Android API requires an Activity, when Unity can run without it. All non-Activity Unity applications are not supported for that reason
• the plugins may add a dangerous permission and not have the code to handle it correctly, thus causing the whole app to crash This is the reason why Unity prompts the user for all the permissions on startup. This behavior is the safest and most compatible.

NOTE: Unity 2018.3 introduces runtime permissions support and API, so starting with this version you don't need this plugin in most cases.

However, Google requires the runtime permission system to be implemented to get featured on Google Play. To let the user implement it (and take the responsibility), the Unity's dialog on startup can be suppressed by adding "unityplayer.SkipPermissionsDialog"="true" metadata tag to application or activity section of the Android Manifest.

This plugin is one of the Android runtime permissions for Unity implementations. It provides the API to check the status of a permission, request a set of permissions and get a callback with the result.

AndroidPermissionsManager is the class which provides you the following methods:

• bool IsPermissionGranted(string permissionName) to check the status of a permission
• void RequestPermission(string[] permissionNames, AndroidPermissionCallback callback) to query for an array of permissions. Pass AndroidPermissionCallback object with your own callback implementations defined in delegates (Action<string> onGrantedCallback is called when a permission is granted, Action<string> onDeniedCallback - when a permission is denied, Action<string> onPermissionDeniedAndDontAskAgainAction - when a permission is denied and the user marks "Don't ask again" checkbox, corresponding permission name is passed as a string param). NOTE: the callbacks are called from Java UI thread (which is different from Unity UI thread), so be careful about the APIs you call from the callback.

0. Should work with Unity 5.3+. Please report an issue if it does not for you
1. Add the plugin to your project. You need the AAR and the C# script (Assets/Plugins/Android/unityandroidpermissions.aar and Assets/Scripts/AndroidPermissionsManager.cs)
2. Use the C# API in your scripts to check the permission status and request it if necessary, right before you actually need this permission
3. Enjoy

For a script sample, please refer to Assets/Scripts/AndroidPermissionsUsageExample.cs.

Run gradlew assemble from src/UnityAndroidPermissions/

Please refer to Google documentation for more details: https://developer.android.com/training/permissions/requesting.html