android 获得屏幕宽度和高度

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

    <!-- 显示网络状态的标签控件 -->
    <TextView
        android:id="@+id/myyl"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp" />

</RelativeLayout>

package com.example.yanlei.yl;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.Gravity;
import android.view.View;
import android.view.WindowManager;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private TextView pTextView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WindowManager wm = this.getWindowManager();
        int width = wm.getDefaultDisplay().getWidth();

        int height = wm.getDefaultDisplay().getHeight();
        pTextView=(TextView)findViewById(R.id.myyl);
        pTextView.setText("屏幕宽度:"+width+",屏幕高度:"+height);

    }

}