如果未找到结果，请显示Toast

Question

Quickly about what I am trying to do. I am creating a script that scans looks for certain Wi-Fi connection. If it finds it, returns to StartingActivity with String.

But how do I make it display Toast if it scanned all connections and didn't found the right one. Because right now, it just sits there and does nothing. And I have to explain user that it found nothing.

Button btnHit;
TextView txtJson;
String urlfinal;
String fssid;
Intent intent;
private static final String  TAG = "My Activity";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_find_connection);

    btnHit = (Button) findViewById(R.id.request);
    txtJson = (TextView) findViewById(R.id.results);


    if (Build.VERSION.SDK_INT > 22) {

        final String CoarseLocation = Manifest.permission.ACCESS_COARSE_LOCATION;
        final String AccessWifi = Manifest.permission.ACCESS_WIFI_STATE;
        final String ChangeWifi = Manifest.permission.CHANGE_WIFI_STATE;

        if (checkSelfPermission(CoarseLocation) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 123);
        }

        if (checkSelfPermission(AccessWifi) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_WIFI_STATE, Manifest.permission.ACCESS_WIFI_STATE}, 123);
        }

        if (checkSelfPermission(ChangeWifi) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.CHANGE_WIFI_STATE, Manifest.permission.CHANGE_WIFI_STATE}, 123);
        }
    }



    LocationManager lman = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE);
    boolean network_enabled = false;

    try
    {
        network_enabled = lman.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
    } catch (Exception ex) {}


    if (!network_enabled)
    {
        startActivityForResult(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);
    }


    btnHit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            final WifiManager mWifiManager = (WifiManager) getSystemService(WIFI_SERVICE);

            mWifiManager.setWifiEnabled(true);

            IntentFilter filter = new IntentFilter();
            filter.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);

            registerReceiver(new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {

                    List<ScanResult> results = mWifiManager.getScanResults();
                    final int Amount = results.size();

                    int num = 0;

                    while (num < Amount)
                    {
                        Log.v(TAG, "SSID  =  " + results.get(num).SSID);

                        num = num+1;
                    }

                    int dis = 0;

                    String res = "Results:\n\n\n";

                    while (dis < Amount)
                    {
                        res = res + results.get(dis).SSID + "\n\n";

                        new JsonTask().execute(results.get(dis).SSID);

                        dis = dis+1;
                    }

                }
            }, filter);

            mWifiManager.startScan();

        }
    });

}



private class JsonTask extends AsyncTask<String, String, String> {

    ProgressDialog pd;

    protected void onPreExecute() {
        super.onPreExecute();

        pd = new ProgressDialog(FindConnection.this);
        pd.setMessage("Please wait...");
        pd.setCancelable(false);
        pd.show();
    }

    protected String doInBackground(String... params) {


        HttpURLConnection connection = null;
        BufferedReader reader = null;

        try {
            fssid = params[0];
            urlfinal = "http://myurl?ssid=" + fssid;
            URL url = new URL(urlfinal);
            connection = (HttpURLConnection) url.openConnection();
            connection.connect();


            InputStream stream = connection.getInputStream();

            reader = new BufferedReader(new InputStreamReader(stream));

            StringBuffer buffer = new StringBuffer();
            String line = "";

            while ((line = reader.readLine()) != null) {

                buffer.append(line+"\n");

                if (!line.equals("null"))
                {
                    String NetworkSSID = fssid;
                    String NetworkPass = line;

                    WifiConfiguration config = new WifiConfiguration();
                    config.SSID = "\"" + NetworkSSID +  "\"";

                    config.preSharedKey = "\"" + NetworkPass + "\"";

                    WifiManager wifiman = (WifiManager) getApplicationContext().getSystemService(WIFI_SERVICE);
                    wifiman.addNetwork(config);

                    List<WifiConfiguration> list = wifiman.getConfiguredNetworks();

                    for ( WifiConfiguration i : list )
                    {

                        if (i.SSID != null && i.SSID.equals("\"" + NetworkSSID + "\""))
                        {
                            wifiman.disconnect();
                            wifiman.enableNetwork(i.networkId, true);
                            wifiman.reconnect();

                            break;
                        }

                        Intent intent1 = new Intent(FindConnection.this, StartingPage.class);
                        intent1.putExtra("ssid_name", fssid);
                        startActivity(intent1);
                    }
                }

            }

            return buffer.toString();


        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        if (pd.isShowing()){
            pd.dismiss();
        }
    }
}

UPDATE:

My best guess how to do that is set a timer and if it sits there for 5 seconds then display a toast (that means it hasn't changed activity, so found no results). But it feel that it is not the best way to do it.

Answer 1

Show your toast after the following line, if results.size is zero (0).

final int Amount = results.size();

That is probably suffice. [I am not sure if you can throw toast from a broadcast receiver. I have barely worked with them.]

Cheers!