Button is not responding after clicking even with clicklistener class enabled

Question

So i am following the lynda course on android development and after following the URL connection tutorial, for some reason the instructor's code produces results but mine does not. here are the files that i have

Main.java

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

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Main extends Activity {



protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

     final EditText et = (EditText) findViewById(R.id.editText1);
     Button pressMe= (Button) findViewById(R.id.button1);
     final TextView tv = (TextView) findViewById(R.id.textView1);

    pressMe.setOnClickListener(new OnClickListener(){


        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            try{

                URL url = null;
                url = new URL(et.getText().toString());
                URLConnection conn = url.openConnection();
                BufferedReader reader = new BufferedReader(new    InputStreamReader(conn.getInputStream()));
                String line = "";
                while((line = reader.readLine()) != null){
                    tv.append(line);

                    }
                }
                catch(Exception e){

                    }



        }







    });


}
}

i have checked my code and compared it with the instructors. i have also checked online to see if the URL connection method is still valid and after research it is still valid. I have dont another tutorial using HTTpClient and i have gotten results from that. However for learning purposes i would like to see if URL connection works. I do hae the internet permission enbaled in my Android_manifest file. Thank you for the help.

Answer 1

The best way is to read all the incoming messages and append it to a string. In the below example, in the while loop, the incoming message is read into a string variable temp and the appended with line varaible. Now the line contains the full message at the end of the while loop and is set to the textView

//String variable to hold the full message
String line ="";

//String variable to hold the incoming message part
String temp;

while((temp = reader.readLine()) != null){
      //message appended to the line varable
      line.append(temp);
}

//Set the value in line to the textView here
tv.setText(line);

If still you are getting an error, you a probably catching and ignoring an error. In that case you have to observe the exception. To do that you can do something like this

catch(Exception e) {
    e.printStackTrace();
}

Now you can observe the exceptions caused in your logcat.

Answer 2

Yep, this was an NetworkOnMainThreadException!

You cannot load URLs within the GUI thread. You need to do that stuff on a different thread. That's why AsyncTask was created.

Here is a working app based on your code which runs perfectly on my Nexus 5 (Android KitKat 4.4.4).

** EDIT ** I tried to modify the text of a TextEdit from the doInBackground() method which is not allowed. Simply commented the lines below.

package com.example.stackoverflow27773175;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity
{
    private EditText et;
    private Button pressMe;
    private TextView tv;


    private class MyAsyncTask extends AsyncTask<String, Void, String>
    {

        @Override
        protected String doInBackground(String... params)
        {
            StringBuilder sb    = new StringBuilder();
            URL url             = null;

            try
            {
                url                     = new URL(params[0]);
                URLConnection conn      = url.openConnection();
                BufferedReader reader   = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                String line             = "";

                while((line = reader.readLine()) != null)
                {
                    sb.append(line);
                }

            } catch (MalformedURLException e)
            {
                e.printStackTrace();

                // Not allowed! 
                //tv.setText("Exception caught: MalformedURLException");
            } catch (IOException e)
            {
                e.printStackTrace();

                // Not allowed! 
                //tv.setText("Exception caught: IOException");
            }

            return sb.toString();
        }

        @Override
        protected void onPostExecute(String result)
        {
            tv.setText(result);
        }
    }

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

         et         = (EditText) findViewById(R.id.editText1);
         pressMe    = (Button) findViewById(R.id.button1);
         tv         = (TextView) findViewById(R.id.textView1);

         pressMe.setOnClickListener(new OnClickListener()
         {
             @Override
             public void onClick(View v)
             {
                 MyAsyncTask myAsyncTask    = new MyAsyncTask();
                 myAsyncTask.execute(new String[] {et.getText().toString()});
             }
        });
    }
}

Also, make sure to specify the android.permission.INTERNET permission in your AndroidManifest.xml before the <application> tag:

<uses-permission android:name="android.permission.INTERNET" />