Explain permissions

app/src/main/AndroidManifest.xml

@@ -352,6 +352,24 @@
             android:icon="@mipmap/ic_launcher"
             android:launchMode="singleTask" />
 
+        <!-- https://developer.android.com/training/permissions/explaining-access -->
+        <activity
+            android:name=".ActivityRationale"
+            android:excludeFromRecents="true"
+            android:exported="true"
+            android:icon="@mipmap/ic_launcher"
+            android:label="@string/app_name"
+            android:launchMode="singleTask"
+            android:permission="android.permission.START_VIEW_PERMISSION_USAGE"
+            android:theme="@style/Theme.AppCompat.Translucent">
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW_PERMISSION_USAGE" />
+                <action android:name="android.intent.action.VIEW_PERMISSION_USAGE_FOR_PERIOD" />
+
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+        </activity>
+
         <activity
             android:name="net.openid.appauth.RedirectUriReceiverActivity"
             android:exported="true"

app/src/main/java/eu/faircode/email/ActivityRationale.java

@@ -0,0 +1,34 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2021 by Marcel Bokhorst (M66B)
+*/
+
+import android.os.Bundle;
+
+public class ActivityRationale extends ActivityBase {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // https://developer.android.com/training/permissions/explaining-access
+
+        Helper.viewFAQ(this, 1);
+        finish();
+    }
+}