记录一下，直接调用系统的方法，实际测试可以获取，
注意：需要申请wifi相关权限，同时还有定位权限，Android 10中必须具有 ACCESS_FINE_LOCATION 权限才能使用

public static String getConnectedWifiMacAddress(Context context) {
    String connectedWifiMacAddress = null;
    WifiManager wifiManager = (WifiManager) context.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    List<ScanResult> wifiList;

    if (wifiManager != null) {
        wifiList = wifiManager.getScanResults();
        WifiInfo info = wifiManager.getConnectionInfo();
        if (wifiList != null && info != null) {
            for (int i = 0; i < wifiList.size(); i++) {
                ScanResult result = wifiList.get(i);
                if (info.getBSSID().equals(result.BSSID)) {
                    connectedWifiMacAddress = result.BSSID;
                }
            }
        }
    }
    return connectedWifiMacAddress;
}