这与权限相关.由于API级别为27，因此您需要ACCESS_FINE_LOCATION或ACCESS_COARSE_LOCATION权限.您可能还需要Android 9的CHANGE_WIFI_STATE(无论如何，按照Google

This is related to permissions....since API level 27 you need either ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION permission. You may also need CHANGE_WIFI_STATE for Android 9 (that's the case for wifi scan anyway as per google permisson model

然后尝试此代码

   ConnectivityManager connManager = (ConnectivityManager) activity.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        if (networkInfo.isConnected()) {
            WifiManager wifiManager = (WifiManager) activity.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
            WifiInfo wifiInfo = wifiManager.getConnectionInfo();
            wifiInfo.getSSID();
            String name = networkInfo.getExtraInfo();
            String ssid = "\"" + wifiInfo.getSSID() + "\"";
}