Android获得屏幕宽高的三种方式

package com.km.screeninfo;
  import android.os.Bundle;
  import android.support.v.app.Fragment;
  import android.support.v.app.FragmentActivity;
  import android.util.DisplayMetrics;
  import android.view.LayoutInflater;
  import android.view.Menu;
  import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 public class MainActivity extends FragmentActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_main);
     if (savedInstanceState == null) {
       getSupportFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
     }
   }
   /**
    * A placeholder fragment containing a simple view.
    */
   public static class PlaceholderFragment extends Fragment {
     private TextView tvModel;
     private TextView tvScreenHeight;
     private TextView tvScreenHeight;
     private TextView tvScreenHeight;
     private TextView tvScreenWidth;
     private TextView tvScreenWidth;
     private TextView tvScreenWidth;
     private TextView tvScreenDensity;
     private TextView tvScreenDensityDPI;
     private TextView tvScreenDensity;
     private TextView tvScreenDensityDPI;
     private TextView tvScreenWidth;
     private TextView tvScreenHeight;
     public PlaceholderFragment() {
     }
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
       View rootView = inflater.inflate(R.layout.fragment_main, container, false);
       tvModel = (TextView) rootView.findViewById(R.id.tv_model);
       tvScreenHeight = (TextView) rootView.findViewById(R.id.tv_screen_height);
       tvScreenHeight = (TextView) rootView.findViewById(R.id.tv_screen_height);
       tvScreenHeight = (TextView) rootView.findViewById(R.id.tv_screen_height);
       tvScreenHeight = (TextView) rootView.findViewById(R.id.tv_screen_height);
       tvScreenWidth = (TextView) rootView.findViewById(R.id.tv_screen_width);
       tvScreenWidth = (TextView) rootView.findViewById(R.id.tv_screen_width);
       tvScreenWidth = (TextView) rootView.findViewById(R.id.tv_screen_width);
       tvScreenWidth = (TextView) rootView.findViewById(R.id.tv_screen_width);
       tvScreenDensity = (TextView) rootView.findViewById(R.id.tv_screen_density);
       tvScreenDensityDPI = (TextView) rootView.findViewById(R.id.tv_screen_densityDPI);
       tvScreenDensity = (TextView) rootView.findViewById(R.id.tv_screen_density);
       tvScreenDensityDPI = (TextView) rootView.findViewById(R.id.tv_screen_densityDPI);
       tvModel.setText(android.os.Build.MODEL);
       // 获取屏幕密度（方法）
       int screenWidth = getActivity().getWindowManager().getDefaultDisplay().getWidth(); // 屏幕宽（像素，如：px）
       int screenHeight = getActivity().getWindowManager().getDefaultDisplay().getHeight(); // 屏幕高（像素，如：p）
       tvScreenHeight.setText(screenHeight + " px");
       tvScreenWidth.setText(screenWidth + " px");
       // 获取屏幕密度（方法）
       DisplayMetrics dm = getResources().getDisplayMetrics();
       float density = dm.density; // 屏幕密度（像素比例：./././.）
       int densityDPI = dm.densityDpi; // 屏幕密度（每寸像素：///）
       float xdpi = dm.xdpi;
       float ydpi = dm.ydpi;
       int screenWidth = dm.widthPixels; // 屏幕宽（像素，如：px）
       int screenHeight = dm.heightPixels; // 屏幕高（像素，如：px）
       tvScreenHeight.setText(screenHeight + " px");
       tvScreenWidth.setText(screenWidth + " px");
       tvScreenDensity.setText(density + "");
       tvScreenDensityDPI.setText(densityDPI + "");
       // 获取屏幕密度（方法）
       DisplayMetrics dm = new DisplayMetrics();
       getActivity().getWindowManager().getDefaultDisplay().getMetrics(dm);
       density = dm.density; // 屏幕密度（像素比例：./././.）
       densityDPI = dm.densityDpi; // 屏幕密度（每寸像素：///）
       xdpi = dm.xdpi;
       ydpi = dm.ydpi;
       tvScreenDensity.setText(density + "");
       tvScreenDensityDPI.setText(densityDPI + "");
       int screenWidth = dm.widthPixels; // 屏幕宽（px，如：px）
       int screenHeight = dm.heightPixels; // 屏幕高（px，如：px）
       tvScreenHeight.setText(screenHeight + " px");
       tvScreenWidth.setText(screenWidth + " px");
       float screenWidthDip = (dm.widthPixels / density); // 屏幕宽（dip，如：dip）
       float screenHeightDip = (dm.heightPixels / density); // 屏幕宽（dip，如：dip）
       tvScreenHeight.setText(screenHeightDip + " dip");
       tvScreenWidth.setText(screenWidthDip + " dip");
       return rootView;
     }
   }
 } 

 int srceenW = this.getWindowManager().getDefaultDisplay().getWidth(); 
 int screenH = this.getWindowManager().getDefaultDisplay().getHeight();