Android获取周围WIFI热点服务

public class MainActivity extends AppCompatActivity {  ArrayList<ScanResult> list;  //存放周围wifi热点对象的列表  WifiManager wifiManager;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    wifiManager = (WifiManager) getSystemService(WIFI_SERVICE);  //获得系统wifi服务    list = (ArrayList<ScanResult>)wifiManager.getScanResults();    sortByLevel(list);    init();  }  private void init(){    TextView tv1=(TextView)findViewById(R.id.tv1);    TextView tv2=(TextView)findViewById(R.id.tv2);    TextView tv3=(TextView)findViewById(R.id.tv3);    if (list.get(0).SSID != null && list.get(1).SSID != null){      tv1.setText("信号最强为"+list.get(0).SSID);      tv2.setText("信号第二位："+list.get(1).SSID);      tv3.setText("共有"+list.size()+"个wifi");    }  }  //将搜索到的wifi根据信号强度从强到弱进行排序  private void sortByLevel(ArrayList<ScanResult> list) {    for(int i=0;i<list.size();i++)      for(int j=1;j<list.size();j++)      {        if(list.get(i).level<list.get(j).level)  //level属性即为强度        {          ScanResult temp = null;          temp = list.get(i);          list.set(i, list.get(j));          list.set(j, temp);        }      }  }} 

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical">  <TextView    android:id="@+id/tv1"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="Hello World!" />  <TextView    android:id="@+id/tv2"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="Hello World!" />  <TextView    android:id="@+id/tv3"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="Hello World!" /></LinearLayout>