检查android中可用的网络

public void onClickTwitt() {    if (isNetworkAvailable(this)) {        Twitt twitt = new Twitt(getActivity(), consumer_key, secret_key);        twitt.shareToTwitter(_Title);    } else {        showToast("No Network Connection Available !!!");    }}public boolean isNetworkAvailable(Context context) {    ConnectivityManager connectivity =(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);    if (connectivity == null) {        return false;    } else {        NetworkInfo[] info = connectivity.getAllNetworkInfo();        for (NetworkInfo networkInfo : info) { if (networkInfo.getState() == NetworkInfo.State.CONNECTED) {     return true; }        }    }    return false;}