android program that connects to internet doesn't work

[Adam Preston]

hi, just asking why this program doesn't work..

computer specs:
-using eclipse adt bundle

android phone specs
- using model number: Samsung galaxy ace GT-S5830
- using android version 2.3.3

error produced:
On startup the application shows a blank white screen and then closes. Immediatley after, the android device pops up with an error message saying "the application WEConnectingToWebPage (process con.example.weconnectingtowebpage) has stopped unexpectedly. Please try again.

code for MainActivity.java:

package com.example.weconnectingtowebpage;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {
    private static final String DEBUG_TAG = "HttpExample";
    private EditText urlText;
    private TextView textView;
    String[] urls = new String[0];
   private Button GetData;
    		
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);   
        urlText = (EditText) findViewById(R.id.myUrl);
        textView = (TextView) findViewById(R.id.myText);
        GetData = (Button) findViewById(R.id.Button1);
        urls[0] = "http://www.google.com";
        // Gets the URL from the UI's text field.
        GetData.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				 String stringUrl = urlText.getText().toString();
			        ConnectivityManager connMgr = (ConnectivityManager) 
			            getSystemService(Context.CONNECTIVITY_SERVICE);
			        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
			        if (networkInfo != null && networkInfo.isConnected()) {
			            new DownloadWebpageTask().onPostExecute(stringUrl);
			        } else {
			            textView.setText("No network connection available.");
			        }
				
			}
		});
       
    }

    
    
    // When user clicks button, calls AsyncTask.
    // Before attempting to fetch the URL, makes sure that there is a network connection.
    public void myClickHandler(View view) {
       
    }

     // Uses AsyncTask to create a task away from the main UI thread. This task takes a 
     // URL string and uses it to create an HttpUrlConnection. Once the connection
     // has been established, the AsyncTask downloads the contents of the webpage as
     // an InputStream. Finally, the InputStream is converted into a string, which is
     // displayed in the UI by the AsyncTask's onPostExecute method.
     private class DownloadWebpageTask extends AsyncTask<String, Void, String> {
    	 
        // onPostExecute displays the results of the AsyncTask.
        protected void onPostExecute(String result) {
            textView.setText(result);
       }

		@Override
		protected String doInBackground(String... params) {
			
			try {
	             return downloadUrl(urls[0]);
	         } catch (IOException e) {
	             return "Unable to retrieve web page. URL may be invalid.";
	         }// TODO Auto-generated method stub
			
		}
		
    }
     
     private String downloadUrl(String myurl) throws IOException {
    	    InputStream is = null;
    	    // Only display the first 500 characters of the retrieved
    	    // web page content.
    	    int len = 500;
    	        
    	    try {
    	        URL url = new URL(myurl);
    	        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    	        conn.setReadTimeout(10000 /* milliseconds */);
    	        conn.setConnectTimeout(15000 /* milliseconds */);
    	        conn.setRequestMethod("GET");
    	        conn.setDoInput(true);
    	        // Starts the query
    	        conn.connect();
    	        int response = conn.getResponseCode();
    	        Log.d(DEBUG_TAG, "The response is: " + response);
    	        is = conn.getInputStream();

    	        // Convert the InputStream into a string
    	        String contentAsString = readIt(is, len);
    	        return contentAsString;
    	        
    	    // Makes sure that the InputStream is closed after the app is
    	    // finished using it.
    	    } finally {
    	        if (is != null) {
    	            is.close();
    	        } 
    	    }
    	}
     
     public String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
    	    Reader reader = null;
    	    reader = new InputStreamReader(stream, "UTF-8");        
    	    char[] buffer = new char[len];
    	    reader.read(buffer);
    	    return new String(buffer);
    	}
 
}

code for activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/myText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <EditText
        android:id="@+id/myUrl"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="37dp"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/Button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/myUrl"
        android:layout_marginTop="96dp"
        android:layout_toRightOf="@+id/myText"
        android:text="Get data" />

</RelativeLayout>

and finally code for the android manifest file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.weconnectingtowebpage"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.INTERNET" /> 
    
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.weconnectingtowebpage.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

I will be checking this thread regularly and any suggestions will be much appreciated

[Ron McLeod]

What does LogCat tell you?

[Steve Luke]

You will have to dig deeper into the error. There is a DDMS perspective in Eclipse that will let you look at LogCat messages. Make sure your phone is connected, that USB Debugging is activated, and then run the application and see what errors occur in the LogCat output.

[Adam Preston]

here is the log:

01-24 16:02:34.479: I/ApplicationPackageManager(959): cscCountry is not German : H3G
01-24 16:02:34.579: D/AndroidRuntime(959): Shutting down VM
01-24 16:02:34.579: W/dalvikvm(959): threadid=1: thread exiting with uncaught exception (group=0x40018578)
01-24 16:02:34.579: E/AndroidRuntime(959): FATAL EXCEPTION: main
01-24 16:02:34.579: E/AndroidRuntime(959): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.weconnectingtowebpage/com.example.weconnectingtowebpage.MainActivity}: java.lang.ArrayIndexOutOfBoundsException
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.os.Handler.dispatchMessage(Handler.java:99)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.os.Looper.loop(Looper.java:123)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread.main(ActivityThread.java:3687)
01-24 16:02:34.579: E/AndroidRuntime(959): at java.lang.reflect.Method.invokeNative(Native Method)
01-24 16:02:34.579: E/AndroidRuntime(959): at java.lang.reflect.Method.invoke(Method.java:507)
01-24 16:02:34.579: E/AndroidRuntime(959): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
01-24 16:02:34.579: E/AndroidRuntime(959): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
01-24 16:02:34.579: E/AndroidRuntime(959): at dalvik.system.NativeStart.main(Native Method)
01-24 16:02:34.579: E/AndroidRuntime(959): Caused by: java.lang.ArrayIndexOutOfBoundsException
01-24 16:02:34.579: E/AndroidRuntime(959): at com.example.weconnectingtowebpage.MainActivity.onCreate(MainActivity.java:38)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-24 16:02:34.579: E/AndroidRuntime(959): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
01-24 16:02:34.579: E/AndroidRuntime(959): ... 11 more

[Adam Preston]

i'm assuming it has something to do with AsyncTask but i'm relatively new to android programming and don't know enough about it to understand why an error is occuring.

[Ron McLeod]

There are a couple of issues with AyncTask, but this problem is related to your array. It indicates you have gone out-of-bounds. What size is your array, and what element are you trying to access when the exception is raised?

E/AndroidRuntime(959): Caused by: java.lang.ArrayIndexOutOfBoundsException
E/AndroidRuntime(959): at com.example.weconnectingtowebpage.MainActivity.onCreate(MainActivity.java:38)

[Ulf Dittmer]

You're initializing the "urls" array to be of zero length - so when you try to access the element at the first position ("urls[0]") you get the exception. Try "String[] urls = new String[1];" instead.

[Adam Preston]

Ulf Dittmer wrote:You're initializing the "urls" array to be of zero length - so when you try to access the element at the first position ("urls[0]") you get the exception. Try "String[] urls = new String[1];" instead.

of course, i see it now i'll fix the array exception first then i'll deal with asynctask. I will have to do it tomorrow now though.

[Adam Preston]

okay i fixed the array issue but now there is a problem with connecting to the internet. it says there is a security exception although i have enabled both two permissions:

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

Anyway here is the new log message:

01-25 19:16:04.199: I/ApplicationPackageManager(2239): cscCountry is not German : H3G
01-25 19:16:36.969: D/AndroidRuntime(2239): Shutting down VM
01-25 19:16:36.969: W/dalvikvm(2239): threadid=1: thread exiting with uncaught exception (group=0x40018578)
01-25 19:16:36.979: E/AndroidRuntime(2239): FATAL EXCEPTION: main
01-25 19:16:36.979: E/AndroidRuntime(2239): java.lang.SecurityException: ConnectivityService: Neither user 10073 nor current process has android.permission.ACCESS_NETWORK_STATE.
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.os.Parcel.readException(Parcel.java:1322)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.os.Parcel.readException(Parcel.java:1276)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.net.IConnectivityManager$Stub$Proxy.getActiveNetworkInfo(IConnectivityManager.java:369)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.net.ConnectivityManager.getActiveNetworkInfo(ConnectivityManager.java:251)
01-25 19:16:36.979: E/AndroidRuntime(2239): at com.example.weconnectingtowebpage.MainActivity$1.onClick(MainActivity.java:47)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.view.View.performClick(View.java:2485)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.view.View$PerformClick.run(View.java:9080)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.os.Handler.handleCallback(Handler.java:587)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.os.Looper.loop(Looper.java:123)
01-25 19:16:36.979: E/AndroidRuntime(2239): at android.app.ActivityThread.main(ActivityThread.java:3687)
01-25 19:16:36.979: E/AndroidRuntime(2239): at java.lang.reflect.Method.invokeNative(Native Method)
01-25 19:16:36.979: E/AndroidRuntime(2239): at java.lang.reflect.Method.invoke(Method.java:507)
01-25 19:16:36.979: E/AndroidRuntime(2239): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
01-25 19:16:36.979: E/AndroidRuntime(2239): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
01-25 19:16:36.979: E/AndroidRuntime(2239): at dalvik.system.NativeStart.main(Native Method)
01-25 19:18:04.349: I/ApplicationPackageManager(2321): cscCountry is not German : H3G
01-25 19:18:46.739: W/IInputConnectionWrapper(2321): beginBatchEdit on inactive InputConnection
01-25 19:18:46.739: W/IInputConnectionWrapper(2321): endBatchEdit on inactive InputConnection
01-25 19:18:46.739: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:18:46.749: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:18:51.819: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:18:51.819: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:19:18.439: I/ApplicationPackageManager(2321): cscCountry is not German : H3G
01-25 19:19:56.999: W/IInputConnectionWrapper(2321): beginBatchEdit on inactive InputConnection
01-25 19:19:56.999: W/IInputConnectionWrapper(2321): endBatchEdit on inactive InputConnection
01-25 19:19:56.999: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:19:56.999: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:20:02.089: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:20:02.089: W/IInputConnectionWrapper(2321): getExtractedText on inactive InputConnection
01-25 19:20:02.159: I/ApplicationPackageManager(2321): cscCountry is not German : H3G

[Ron McLeod]

Adding the ACCESS_NETWORK_STATE permission should have fixed that issue.

Maybe try making a clean build.

[Adam Preston]

Ron McLeod wrote:Adding the ACCESS_NETWORK_STATE permission should have fixed that issue.

Maybe try making a clean build.

done clean build and errors have gone, but warnings are still showing up:

01-25 20:06:47.979: W/IInputConnectionWrapper(1075): getExtractedText on inactive InputConnection

Is this something to do with my phone not being able to connect to the internet?

[Ron McLeod]

Do you see the same behaviour when running on the emulator?

[Adam Preston]

ill try it tomorrow but i heard configuring an emulator properly can be quite complicated

EDIT: nvm I think i have figured the problem out, problems occurred on line 48 and 43

[aniket chaudhary]

this is happening because you are not running network retated stuff in a new thread...android does not allow the network operations in main thread...it will work if you start a new thread for network connections

[Ron McLeod]

aniket chaudhary wrote:this is happening because you are not running network retated stuff in a new thread...android does not allow the network operations in main thread...it will work if you start a new thread for network connections

That is the case here - I ran the code without restructuring it (just a few bug fixes) and it worked.