Can't receive data from URL in android

Question

I have a problem with connecting to internet. I want to show tbe first line in the source code of www.google.com. I coded in Java console and it run well. But when I did it in android, the textView can't not show any words. Original Java console program:

import java.io.BufferedInputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Scanner;

public class ReadUrl {
    static public String getRespond(String request) {

        try{
            URL url=new URL (request);
            URLConnection connection=url.openConnection();
            InputStream in=new BufferedInputStream(connection.getInputStream());

            Scanner scanner =new Scanner(in);
            String response=scanner.nextLine();
            scanner.close();
            return response;

        }
        catch (Exception e){
            return null;
        }
    }
    public static void main(String args[]){
       System.out.println (getRespond("http://www.google.com"));
    }
}

In android: File MainActivity.java:

package com.example.simpleinternet;

import java.io.BufferedInputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Scanner;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends Activity {

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

        TextView txtView=(TextView) findViewById(R.id.textView);
        txtView.setText(getRespond("www.google.com"));

    }
    public String getRespond(String request) {

        try{
            URL url=new URL (request);
            URLConnection connection=url.openConnection();
            InputStream in=new BufferedInputStream(connection.getInputStream());

            Scanner scanner =new Scanner(in);
            String response=scanner.nextLine();
            scanner.close();
            return response;

        }
        catch (IOException e){
            return null;
        }
    }
}

File AndroidManifest.xml:

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

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="19" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.simpleinternet.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>

File activity_main.xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World" />

</FrameLayout>

The error is :

> 07-07 14:44:55.760: E/AndroidRuntime(4449): 
> Java.lang.RuntimeException: Unable to start activity
> ComponentInfo{com.example.simpleinternet/com.example.simpleinternet.MainActivity}:
> android.os.NetworkOnMainThreadException

Sorry because I am a newbie in StackOverFlow. I will take it carefully. Can you check it for me ?

Evaluate exceptions instead of suppressing them. Then post your error message. — Gerald Schneider, Jul 07 '14 at 07:38
I think you can print out the exception message and post it rather than return a null value. — bixiaopeng, Jul 07 '14 at 07:44
Sorry, I added the problem's message to my post. Thank you for remind me — user251047, Jul 07 '14 at 07:54
Just what I thought. The exception should be self explanatory. — Gerald Schneider, Jul 07 '14 at 07:57
possible duplicate of [android.os.NetworkOnMainThreadException](http://stackoverflow.com/questions/6343166/android-os-networkonmainthreadexception) — Gerald Schneider, Jul 07 '14 at 07:58

score 0 · Answer 1 · answered Jul 07 '14 at 07:58

0

android.os.NetworkOnMainThreadException is thrown when an application attempts to perform a networking operation on its main thread.

You can run your code in AsyncTask to solve the issue.

answered Jul 07 '14 at 07:58

hungr

2,086
1
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score 0 · Answer 2 · edited May 23 '17 at 11:50

The exception that is thrown when an application attempts to perform a networking operation on its main thread.

Please refer to below links:

What is the problem:

http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html

Why is the problem: and Solution:

http://developer.android.com/training/articles/perf-anr.html

How to fix android.os.NetworkOnMainThreadException?

Can't receive data from URL in android

2 Answers2