Show Toast in four different corners

<?xml version="1.0" encoding="utf-8"?>

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

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:onClick="upperLeft"
        android:text="show toast" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:onClick="upperRight"
        android:text="show toast" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:onClick="bottomLeft"
        android:text="show toast" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:onClick="bottomRight"
        android:text="show toast" />

</RelativeLayout>

import android.app.Activity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.widget.Toast;
/*from   w  w w .j a v a2s.  com*/
public class MainActivity extends Activity {

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

  public void upperLeft(View v) {
    Toast toast = Toast.makeText(this, "Upper Left!",
        Toast.LENGTH_SHORT);
    toast.setGravity(Gravity.TOP | Gravity.LEFT, 0, 0);
    toast.show();
  }

  public void upperRight(View v) {
    Toast toast = Toast.makeText(this, "Upper Right!",
        Toast.LENGTH_SHORT);
    toast.setGravity(Gravity.TOP | Gravity.RIGHT, 0, 0);
    toast.show();
  }

  public void bottomLeft(View v) {
    Toast toast = Toast.makeText(this, "Bottom Left!",
        Toast.LENGTH_SHORT);

    toast.setGravity(Gravity.BOTTOM | Gravity.LEFT, 0, 0);
    toast.show();
  }

  public void bottomRight(View v) {
    Toast toast = Toast.makeText(this, "Bottom Right!",
        Toast.LENGTH_SHORT);
    toast.setGravity(Gravity.BOTTOM | Gravity.RIGHT, 0, 0);
    toast.show();
  }
}