Example of how to make httprequest an async task

Question

All,

I have a small functioning app that makes an httprequest to a server based on user input sent by a buttonclick. I'm looking for some help to make my small app compatible with SDK 11+, by making this httprequest an async task.

I've spent some days reading about async tasks, and understand the principle, and the reasons for making the httprequest away from the UI thread.

However I just can't get the code to work in my case. I can't even get it to compile. I've included below my functioning code (ie before trying to make the httprequest asyncronous)

I'd be very grateful for some specific help. I apologise for my rubbish code and that variations of this question have already been answered.

Thanks in advance Jamie

My MainActivity code is below:

package com.jrcdesign.ebookbeamer;
import java.io.IOException;
import org.apache.http.client.ClientProtocolException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.message.BasicNameValuePair;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.widget.Spinner;
import android.view.View.OnClickListener;


public class MainActivity extends Activity {

Button sendButton;
Button btnSubmit;
EditText msgTextField;
EditText msg2TextField;
Spinner spinner1;

/** Called when the activity is first created. */

@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    // load the layout
    setContentView(R.layout.main);        

    // make message text field object
    msgTextField = (EditText) findViewById(R.id.msgTextField);
    msg2TextField = (EditText) findViewById(R.id.msg2TextField);

    // make send button object
    sendButton = (Button) findViewById(R.id.sendButton);
    btnSubmit = (Button) findViewById(R.id.btnSubmit);    
    addListenerOnButton();
    addListenerOnSpinnerItemSelection(); 

}            

    public void addListenerOnSpinnerItemSelection() {
    spinner1 = (Spinner) findViewById(R.id.spinner1);
    spinner1.setOnItemSelectedListener(new CustomOnItemSelectedListener());
    }

    // get the selected dropdown list value
    public void addListenerOnButton() {

    spinner1 = (Spinner) findViewById(R.id.spinner1);
    btnSubmit = (Button) findViewById(R.id.btnSubmit);

    btnSubmit.setOnClickListener(new OnClickListener() {

      @Override
      public void onClick(View v) {

        Toast.makeText(MainActivity.this,
        "OnClickListener : " + 
                  "\nSpinner 1 : "+ String.valueOf(spinner1.getSelectedItem()),
            Toast.LENGTH_SHORT).show();

      msgTextField.setText("" + String.valueOf(spinner1.getSelectedItem()));

      }

    });
    }


    // Called when the SEND button is pressed
    // Need to make this an async task

    public void send(View v)
{
   // get the message from the message text box
    msgTextField.setText("" + String.valueOf(spinner1.getSelectedItem()));
    String msg = msgTextField.getText().toString();  
    String msg2 = msg2TextField.getText().toString();  

    if (msg.length()>0)
    {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost("http://54.235.198.96/test1.php");
     try {
       List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
       nameValuePairs.add(new BasicNameValuePair("id", msg2));
       nameValuePairs.add(new BasicNameValuePair("message", msg));
       httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

       httpclient.execute(httppost);
       msgTextField.setText(""); // clear text box
       msg2TextField.setText(""); // clear text box

       Toast.makeText(MainActivity.this,
                "Your request is being processed",
                    Toast.LENGTH_LONG).show();

     } catch (ClientProtocolException e) {
         // TODO Auto-generated catch block
     } catch (IOException e) {
         // TODO Auto-generated catch block
     }

    }
    else
    {
        // display message if text fields are empty
        Toast.makeText(getBaseContext(),"All fields are required",Toast.LENGTH_SHORT).show();
    }

}

}

Answer 1

Here is your Async Class:

private class AsyncTaskDownloadSomething extends
        AsyncTask<String[], String, String> {

    DataClassLentABook  mData;





    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        //Do some prepartations over here, before the task starts to execute
        //Like freeze the button and/or show a progress bar


    }





    @Override
    protected String doInBackground(String... urls) {
        // Task starts executing.
        String url = urls[0];

        // Execute HTTP requests here, with one url(urls[0]),
        // or many urls using the urls table
        // Save result in myresult

        return myresult;

    }





    protected void onPostExecute(String result) {
               //Do modifications you want after everything is finished
               //Like re-enable the button, and/or hide a progressbar
               //And of course do what you want with your result got from http-req



    }
}

To execute your async task, when your button is clicked, just write this:

new AsyncTaskDownloadSomething().execute(someURL);