Android怎样检查当前是否联网

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();
}

在AndroidManifest.xml中添加下面权限:

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