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I have a button that I am trying to make in the center of the screen:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="@color/black"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="0dp"
    android:paddingRight="0dp"
    android:paddingTop="0dp"
    android:paddingBottom="0dp"
    tools:context="com.vroy.trapper.MainMenuActivity">



    <Button
        android:id="@+id/playBtn"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/play_button_text"
        android:background="@drawable/round_button"
        />


</RelativeLayout>

(I set the width/height to 0dp because I programmatically change them.)

The problem is while while in the XML design tab the button appears to be in the center of the screen (if I set the width/height to 50dp for testing) when I actually run the program the button appears in the top left of the screen.

How do I make sure the button is actually in the center of the screen?

Here is the code where I set the width/height of the button:

 int screenWidth = getResources().getDisplayMetrics().widthPixels;
  //  int screenHeight = getResources().getDisplayMetrics().heightPixels;

    Button playBtn = (Button) findViewById(R.id.playBtn);
    int playBtnWidth = screenWidth/3;
    playBtn.setLayoutParams(new LayoutParams(playBtnWidth, playBtnWidth));
Foobar
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  • I'm not sure why you are having this problem but have you tried layout_centerinparent? That should center the button both vertically and horizontally. – Sammy Jaafar Feb 16 '16 at 20:56
  • @SammyJaafar This did not work either. – Foobar Feb 16 '16 at 21:03
  • You can try centering it programmatically. Maybe this post will be helpful: http://stackoverflow.com/questions/3985787/android-relativelayout-programmatically-set-centerinparent – Sammy Jaafar Feb 16 '16 at 21:09

1 Answers1

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By setting the LayoutParams programmatically you are resetting all the information within those parameters to the default (with the exception of the height and width, since you set those in the constructor). Try creating the LayoutParams as a variable, then set the layout location.

LayoutParams params = new LayoutParams(playBtnWidth, playBtnWidth);
params.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
playBtn.setLayoutParams(params);

Link to RelativeLayout

Helix
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