How to pass parameters from inside handler to an Asynctask?

[AhFai Chan]

Hi, my Java fails me again

I need to pass some parameters from my MainActivity to an asynctask using a handler, so I can start and stop the process anytime.

The parameters (this, loginstatus, result) in the asynctask are used to display the results in the UI ( the TextViews in the XML).

Problem: ( see pic)




Following is my MainActivity that calls the asynctask:

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {
    private boolean running;

    private EditText projectnameField,  licenseplateField;
    private TextView loginstatus, result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        projectnameField = (EditText)findViewById(R.id.editText1);
        licenseplateField = (EditText)findViewById(R.id.editText3);

        loginstatus = (TextView)findViewById(R.id.textView5);
        result = (TextView)findViewById(R.id.textView7);

         loginInsert();
    }
    /*****     get an HttpURLConnection and start uploading latitude and longitude  *****/
    public void onClickLogin(View view) {

        running = true;
    }

    /*****  stop the upload process                 *****/
    public void onClickLogout(View view) {

        running = false;
    }

    /***** Listener to continuously refresh latitude and longitude, do not rely on user's own setup       *****/
    public void refreshLocation(){
        // TODO
    }

    /***** method to start uplink and post latitude and longitude to MySQL     *****/
    public  void loginInsert() {

        final Handler handler = new Handler();
        final String projectname = projectnameField.getText().toString();
        final String licenseplate = licenseplateField.getText().toString();

        handler.post(new Runnable() {
            @Override
            public void run() {

                    if (running) {
                       // latitude = String.valueOf(loc.getLongitude());
                       // longitude = String.valueOf(loc.getLatitude());
                        new ConnectToServer(this, loginstatus, result).execute(projectname, licenseplate);    // ERROR here. problem with (this, loginstatus, result)
                      }
                /***** Repeat runnable every 60 seconds  *****/
                handler.postDelayed(this, 60000);
            }
         });
     }

And this is the Asynctask:

import android.content.Context;
import android.location.Location;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

public class ConnectToServer extends AsyncTask<String, Void, String> {

    private Context context;
    private TextView loginstatusField, resultField;
    final String link = "http://www.testhttpurllink.com/access_mysql/LoginInsert.php";

    public ConnectToServer(Context context, TextView loginstatusField, TextView resultField){

        this.context = context;
        this.loginstatusField = loginstatusField;
        this.resultField = resultField;

    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    protected String doInBackground(String... arg0) {

        String projectname = (String) arg0[0];
        String licenseplate = (String) arg0[1];
        String latitude = null;
        String longitude = null;

        try{
            LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
            Location loc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
            latitude = String.valueOf(loc.getLongitude());
            longitude = String.valueOf(loc.getLatitude());

            String data = URLEncoder.encode("projectname", "UTF-8") + "=" + URLEncoder.encode(projectname, "UTF-8");
            data += "&" + URLEncoder.encode("licenseplate", "UTF-8") + "=" + URLEncoder.encode(licenseplate, "UTF-8");
            data += "&" + URLEncoder.encode("latitude","UTF-8") + "=" + URLEncoder.encode(latitude, "UTF-8");
            data += "&" + URLEncoder.encode("longitude","UTF-8") + "=" + URLEncoder.encode(longitude, "UTF-8");

            URL url = new URL(link);
            URLConnection conn = url.openConnection();
            conn.setDoOutput(true);
            OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
            writer.write(data);
            writer.flush();

            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));

            StringBuilder stringbuilder = new StringBuilder();
            String line = null;

            // Read Server Response
            while ((line = reader.readLine()) != null) {
                stringbuilder.append(line);
                break;
            }
            reader.close();
            return stringbuilder.toString();
        } catch (Exception ex) {
            return new String ("Exception: "+ ex.getMessage());
        }
    }


    @Override
    protected void onPostExecute(String result) {
        this.loginstatusField.setText("You are logged in");
        this.resultField.setText(result);
    }
}

[Darryl A. J. Staflund]

Hi there,

I haven't really used Android handler's before, but from what I have read handlers can be used to send messages to other objects and messages can hold data bundles. So maybe you could add your data to a bundle, add the bundle to the message, and then use the handler to send the message to the AsyncTask. It should work in theory, but having never used handlers I am not sure.

Darryl

[Giovanni Montano]

Darryl A. J. Staflund wrote:Hi there,

I haven't really used Android handler's before, but from what I have read handlers can be used to send messages to other objects and messages can hold data bundles.  So maybe you could add your data to a bundle, add the bundle to the message, and then use the handler to send the message to the AsyncTask.  It should work in theory, but having never used handlers I am not sure.

Darryl

this is a great documentation, for the curious http://codetheory.in/android-handlers-runnables-loopers-messagequeue-handlerthread/