WifiManager wifi_service = (WifiManager)getSystemService(WIFI_SERVICE); 
WifiInfo wifiInfo = wifi_service.getConnectionInfo();

<level-list xmlns:android="http://schemas.android.com/apk/res/android">  
  <item android:maxLevel="50" android:drawable="@drawable/library_template_05" />  
  <item android:maxLevel="70" android:drawable="@drawable/library_template_05_2" />  
  <item android:maxLevel="100" android:drawable="@drawable/library_template_05_3" />  
</level-list> 

// wifi相关  
IntentFilter wifiIntentFilter;  // wifi监听器 

// wifi  
wifiIntentFilter = new IntentFilter();  
wifiIntentFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION); 

// 声明wifi消息处理过程  
private BroadcastReceiver wifiIntentReceiver = new BroadcastReceiver() {  
@Override  
public void onReceive(Context context, Intent intent) {  
    int wifi_state = intent.getIntExtra("wifi_state", 0);  
    int level = Math.abs(((WifiManager)getSystemService(WIFI_SERVICE)).getConnectionInfo().getRssi()); 
    Log.i(Global.TAG, "1111:" + level);  
    switch (wifi_state) {  
    case WifiManager.WIFI_STATE_DISABLING:  
      Log.i(Global.TAG, "1111:" + WifiManager.WIFI_STATE_DISABLING);  
      wifi_image.setImageResource(R.drawable.wifi_sel);  
      wifi_image.setImageLevel(level);  
      break;  
    case WifiManager.WIFI_STATE_DISABLED:  
      Log.i(Global.TAG, "2222:" + WifiManager.WIFI_STATE_DISABLED);  
      wifi_image.setImageResource(R.drawable.wifi_sel);  
      wifi_image.setImageLevel(level);  
      break;  
    case WifiManager.WIFI_STATE_ENABLING:  
      wifi_image.setImageResource(R.drawable.wifi_sel);  
      wifi_image.setImageLevel(level);  
      Log.i(Global.TAG, "33333:" + WifiManager.WIFI_STATE_ENABLING);  
      break;  
    case WifiManager.WIFI_STATE_ENABLED:  
      Log.i(Global.TAG, "4444:" + WifiManager.WIFI_STATE_ENABLED);  
      wifi_image.setImageResource(R.drawable.wifi_sel);  
      wifi_image.setImageLevel(level);  
      break;  
    case WifiManager.WIFI_STATE_UNKNOWN:  
      Log.i(Global.TAG, "5555:" + WifiManager.WIFI_STATE_UNKNOWN);  
      wifi_image.setImageResource(R.drawable.wifi_sel);  
      wifi_image.setImageLevel(level);  
      break;  
    }  
  }  
}; 

@Override  
protected void onResume() {  
  super.onResume();
  // 注册wifi消息处理器  
  registerReceiver(wifiIntentReceiver, wifiIntentFilter);  
} 
@Override  
protected void onPause() {  
  super.onPause();  
  unregisterReceiver(wifiIntentReceiver);  
} 

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>