Optimization

Use GridLayout

app/src/main/res/layout/activity_main.xml

 <?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     tools:context="fr.utc.simde.payutc.MainActivity"
-    android:layout_width="fill_parent"
-    android:layout_height="fill_parent" >
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:rowCount="2">
 
     <LinearLayout
-        android:layout_width="fill_parent"
-        android:layout_height="fill_parent"
+        android:layout_width="match_parent"
+        android:layout_rowWeight="1"
         android:gravity="center"
-        android:orientation="vertical"
-        android:layout_alignParentTop="true"
-        android:layout_alignParentStart="true">
+        android:orientation="vertical">
 
         <ImageView
             android:id="@+id/img_payutc"
             android:layout_width="100dp"
             android:layout_height="100dp"
-            android:layout_marginBottom="25dp"
-            android:src="@mipmap/ic_launcher_round" />
+            android:layout_margin="25dp"
+            android:src="@mipmap/ic_launcher_round"
+            android:contentDescription="@string/app_name" />
 
         <TextView
             android:id="@+id/text_app_config"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
-            android:layout_marginBottom="50dp"
+            android:layout_marginBottom="25dp"
             android:textStyle="bold"
             android:gravity="center"
             android:text="@string/app_not_configured" />
@@ -42,24 +43,17 @@
             android:id="@+id/button_username"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_marginBottom="100dp"
             android:text="@string/connexion" />
 
     </LinearLayout>
 
-    <RelativeLayout
-        android:layout_width="fill_parent"
-        android:layout_height="wrap_content"
-        android:layout_alignParentBottom="true" >
-
-        <TextView
-        android:id="@+id/text_app_registered"
-        android:layout_width="fill_parent"
-        android:layout_height="wrap_content"
-        android:gravity="center"
-        android:textStyle="italic"
-        android:layout_margin="10dp"
-        android:text="@string/app_not_registred" />
-    </RelativeLayout>
-
-</RelativeLayout>
+    <TextView
+    android:id="@+id/text_app_registered"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+        android:layout_rowWeight="1"
+    android:gravity="center"
+    android:textStyle="italic"
+    android:layout_margin="10dp"
+    android:text="@string/app_not_registred" />
+</GridLayout>