Android中如何判断是否联网

private Boolean isOnline()  {
ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo ni = cm.getActiveNetworkInfo();
if(ni != null && ni.isConnected())
{
//        Toast.makeText(this, "网络连接正常", 1000).show();
return true;
}
else{
Toast.makeText(this, "网络连接失败请点击菜单设置", 3000).show();
}
return false;
}

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