Why is method getSize() not working in Android Studio?

Question

I am currently trying to run code to get the width and height of the screen I am using in Android Studio. (Code below) Everything works in my code besides the getSize(); Method. I am running Api level 22 with my lowest level being 15.

Edit: I have just realized it may be something relating to "extends ActionBarActivity". Instead of just extending "Activity". Could this have an affect?

Here is the snippet of code not working:

public Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size); //error here with getSize not being recognized.
screenWidth = size.x;
screenHeight = size.y;

Here is all of the code:

package com.example.e99900004533.candycollector;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.graphics.Point;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Display;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.RelativeLayout;
import android.widget.EditText;
import android.widget.ImageButton;
import java.util.Random;

public class MainActivity extends ActionBarActivity {

    public EditText collectedTextEdit;
    public ImageButton candyEdit;
    public int collected = 0;
    public int screenWidth = 300;
    public int screenHeight = 300;
    public final int candySize = 50;
    Random random = new Random();

    public Display display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);
    //screenWidth = size.x;
    //screenHeight = size.y;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        collectedTextEdit = (EditText) findViewById(R.id.collectedText);
        candyEdit = (ImageButton) findViewById(R.id.candy);
        collectedTextEdit.setText("Collected: " + collected);
        System.out.println(screenWidth + " : " + screenHeight);
        addListenerOnButton();
    }

    public void addListenerOnButton() {
        candyEdit.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                collected += 1;
                collectedTextEdit.setText("Collected: " + collected);

                MarginLayoutParams marginParams = new MarginLayoutParams(candyEdit.getLayoutParams());
                marginParams.setMargins(random.nextInt(screenWidth - candySize), random.nextInt(screenHeight - candySize), 0, 0);
                RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(marginParams);
                candyEdit.setLayoutParams(layoutParams);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

And here is my Api Level:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.e99900004533.candycollector" >

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="22" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

you need to do that on your onCreate not outside of it

@Override
protected void onCreate(Bundle savedInstanceState) {
    display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);