Force Close when button Clicked

I had a button that inside A layout, if the button clicked it was make Random Position method to button in every second button will move Randomly

So this is the view of my xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

     <RelativeLayout
         android:id="@+id/layout1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:layout_centerVertical="true"
         android:layout_margin="30dp"
         android:background="@drawable/backgroundblankred" >

         <Button
             android:id="@+id/button1"
             android:layout_width="100dp"
             android:layout_height="100dp"
             android:background="@drawable/eeclevelfirstblackbuton" />

     </RelativeLayout>

</RelativeLayout>

so this is the code to make the button move inside layout1 and not out from there

import android.app.Activity;
import android.graphics.Point;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends Activity {

Button buttonblack;
RelativeLayout layout1;

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

     layout1 = (RelativeLayout)findViewById(R.id.layout1);

     buttonblack = (Button)findViewById(R.id.button1);       
     buttonblack.setOnClickListener(new View.OnClickListener() {

                 @Override
                 public void onClick(View view) {
                     startRandomButton(buttonblack);    
                     }               
             });

     startRandomButton(buttonblack);    

}

public static Point getDisplaySize(@NonNull RelativeLayout layout12) {
    Point point = new Point();
    return point;       
}

private void setButtonRandomPosition(final Button button){

    //make the button not out from the layout1
    int randomX = new Random().nextInt(getDisplaySize(layout1).x);
    int randomY = new Random().nextInt(getDisplaySize(layout1).y);

    button.setX(randomX);
    button.setY(randomY);
}

private void startRandomButton(Button button) {
    Timer timer = new Timer();
    timer.schedule(new TimerTask() {
        @Override
        public void run() {
            setButtonRandomPosition(buttonblack);
        }
    }, 1000, 1000);//Update button position every second
}

but the app was force close when i open it, anyone can correct the problem with my code in there? Thank's.