android 网络是否可用

检查wifi：

 参考网址

http:///questions/1811852/android-if-wifi-is-enabled-and-active-launch-an-intent

private static boolean isConnected(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager)
        context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = null;
    if (cm != null) {
        networkInfo = cm.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    }
    return networkInfo == null ? false : networkInfo.isConnected();
}

检查网络是否可用：

参考网址：

http://www./check-if-the-network-is-available

public boolean isNetworkAvailable() {
   Context context = getApplicationContext();
   ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
   if (connectivity == null) {
      boitealerte(this.getString(R.string.alert),"getSystemService rend null");
   } else {
      NetworkInfo[] info = connectivity.getAllNetworkInfo();
      if (info != null) {
         for (int i = 0; i < info.length; i++) {
            if (info[i].getState() == NetworkInfo.State.CONNECTED) {
               return true;
            }
         }
      }
   }
   return false;
}

注意两个都需要在manifest文件中添加权限<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />