Proper runtime permission implementation

app/src/main/java/com/topjohnwu/magisk/components/Activity.java

@@ -1,7 +1,9 @@
 package com.topjohnwu.magisk.components;
 
+import android.content.pm.PackageManager;
 import android.content.res.Configuration;
 import android.os.Bundle;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatActivity;
 import android.view.WindowManager;
@@ -13,6 +15,8 @@ import com.topjohnwu.magisk.utils.Topic;
 
 public class Activity extends AppCompatActivity {
 
+    private Runnable permissionGrantCallback;
+
     public Activity() {
         super();
         Configuration configuration = new Configuration();
@@ -36,6 +40,20 @@ public class Activity extends AppCompatActivity {
         super.onDestroy();
     }
 
+    @Override
+    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
+        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+            if (permissionGrantCallback != null) {
+                permissionGrantCallback.run();
+            }
+        }
+        permissionGrantCallback = null;
+    }
+
+    public void setPermissionGrantCallback(Runnable callback) {
+        permissionGrantCallback = callback;
+    }
+
     @Override
     public MagiskManager getApplicationContext() {
         return (MagiskManager) super.getApplicationContext();