Question

I have in my Android app a fairly simple Activity that displays three buttons, each launching a different Activity. Currently, I use a RelativeLayout to center the middle button both horizontally and vertically, then place the top and bottom buttons 30dp off the middle one (and also horizontally centered).

What I’d like to do, however, is make the buttons stretch to be a certain percentage of the screen width. I can’t figure out how to do this and keep the buttons centered. Is there a good object I can use as a “filler” in a LinearLayout on either side of the buttons (so I could just set the weights)? Or is there a way to do this that doesn’t involve a LinearLayout?

The XML for the layout as it stands is:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/button2"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="30dp"
        android:onClick="button1Callback"
        android:text="@string/button1Label" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:onClick="button2Callback"
        android:text="@string/button2Label" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button2"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="30dp"
        android:text="@string/button3Label" />

</RelativeLayout>

Answer 1

Sure. View or Frame both work.

<LinearLayout android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <View android:layout_height="0dp"  
    android:layout_width="0dp"
    android:layout_weight="60" />
   <Button android:layout_height="wrap_content"  
    android:layout_width="0dp"
    android:layout_weight="20" />
   <View android:layout_height="0dp"  
    android:layout_width="0dp"
    android:layout_weight="20" />
 </LinearLayout>

works fine as a spacer and seems to be utterly harmless as far as I can tell. I use this quite a bit in my app (although honestly, most of my buttons are fixed-width).

At one point I actually wrote a custom view with proportional layout. But in the end I ended up not using it at all. In almost all cases you can get equivalent proportional layout with judiciously applied weights in a linear layout.