What is the best way to center (in the screen) a image button programmatically?

debugcn Published at Dev

user236520

I am trying to generate a button programatically in the center of the current view (which is the whole screen in this case). I get the screen height and width then find the center of the screen. Then I try to use the LayoutParams to set the top and left margins, taking into account the button size - but the result is not centered. What am I doing wrong?

public class StartActivity extends Activity {

private int cScreenWidth;
private int cScreenHeight;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start);

    RelativeLayout ll = (RelativeLayout)findViewById(R.id.startLayout);

    Display display = getWindowManager().getDefaultDisplay(); 
    cScreenWidth = display.getWidth();  // deprecated but needed for API 10
    cScreenHeight = display.getHeight();  // deprecated but needed for API 10

    ImageButton myButton = new ImageButton(this);
    myButton.setId(100);
    myButton.setBackgroundResource(R.drawable.ic_launcher);

    int size = Math.min(cScreenWidth / 3, cScreenHeight / 3);
    LayoutParams lp = new LayoutParams( size, size );
    lp.leftMargin = (cScreenWidth / 2) - (size / 2);
    lp.topMargin = (cScreenHeight / 2) - (size / 2);
    ll.addView(myButton, lp);
}

Shobhit Puri

Try the following:

RelativeLayout.LayoutParams layoutParams = 
    (RelativeLayout.LayoutParams)myButton.getLayoutParams();
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
myButton.setLayoutParams(layoutParams);

This way you don't need to explicitly define the margins.

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