How do I align the right/left side of a button in android to the center of the screen?

Question

I was thinking it would be something like android:layout_startOf"centerHoriztonal" or something like that but I have searched and couldn't find anything. If it helps I am trying to make a soundboard app where all the buttons can be the same size across multiple device screens.

Answer 1

You can wrap the button(s) inside a horizontal LinearLayout and use layout_weight to divide the screen in half and then layout_alignParentLeft/layout_alignParentRight to align the buttons inside a RelativeLayout that takes up exactly half the screen width.

 <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

     <RelativeLayout
        android:layout_width="0px"
        android:layout_height="wrap_content"
        android:layout_weight="1">

         <Button 
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_alignParentRight="true"
             android:text="Button Text"
             /> 
     </RelativeLayout>

     <RelativeLayout
        android:layout_width="0px"
        android:layout_height="wrap_content"
        android:layout_weight="1">

     </RelativeLayout>

 </LinearLayout>

Another way to do it is to create a dummy view object that is centered horizontally in the parent view, and align your buttons to the left or right of it:

   <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

      <View
        android:id="@+id/dummyview"
        android:layout_width="0px"
        android:layout_height="0px"
        android:layout_centerHorizontal="true"/>

      <Button 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/dummyview"
        android:text="Button Text"/>

  </RelativeLayout>