1、建立android项目MyApplication

2、修改布局文件activity_my.xml

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

android:paddingBottom="@dimen/activity_vertical_margin"

tools:context=".MyActivity">

android:id="@+id/button01"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="获取网页内容" />

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:layout_below="@+id/button01">

android:id="@+id/textview01"

android:text=""

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

ScrollView用于给Textview添加滚动条。

3、添加联网权限 在AndroidManifest.xml添加，文件最终内容是：

package="com.example.letian.myapplication" >

android:allowBackup="true"

android:icon="@drawable/ic_launcher"

android:label="@string/app_name"

android:theme="@style/AppTheme" >

android:name=".MyActivity"

android:label="@string/app_name" >

4、修改MyActivity.java

package com.example.letian.myapplication;

import android.app.Activity;

import android.os.Bundle;

import android.os.StrictMode;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import java.io.BufferedReader;

import java.io.InputStreamReader;

public class MyActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_my);

final Button btn01 = (Button) this.findViewById(R.id.button01);

final TextView tv01 = (TextView) this.findViewById(R.id.textview01);

btn01.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

tv01.setText(getUrlContent("http://www.oschina.net/"));

}

});

}

private String getUrlContent(String url) {

HttpGet getRequest = new HttpGet(url);

getRequest.addHeader("User-Agent", " Mozilla/5.0 (Windows NT 6.3; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0");

try {

HttpResponse response = new DefaultHttpClient().execute(getRequest);

if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {

BufferedReader in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));

StringBuffer sb = new StringBuffer("");

String line = ""; //存储读取的一行内容

String NL = System.getProperty("line.separator"); //换行符

while ((line = in.readLine()) != null) {

sb.append(line+NL);

}

in.close();

return sb.toString();

} else {

return "读取失败：\n"+response.getStatusLine().getStatusCode();

}

} catch (Exception e) {

return "读取失败:\n"+e.toString();

}

}

}

5、但是运行结果并不令人满意，出现异常

网页请求时一个阻塞的过程，如果时间过长会造成程序假死，所以产生了该异常。这个异常在较新版本的Android中才提出。

6、一个并不推荐的解决办法

该方法可能会造成程序假死，所以最好不要在app中使用该方法。

在onCreate()的适当位置添加如下内容：

if (android.os.Build.VERSION.SDK_INT > 9) {

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();

StrictMode.setThreadPolicy(policy);

} app运行结果如下：

7、使用线程的方法来解决(推荐)

将MyActivity.java修改如下：

package com.example.letian.myapplication;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import java.io.BufferedReader;

import java.io.InputStreamReader;

public class MyActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_my);

final Button btn01 = (Button) this.findViewById(R.id.button01);

final TextView tv01 = (TextView) this.findViewById(R.id.textview01);

final Handler handler = new Handler(){

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

Bundle data = msg.getData();

tv01.setText(data.getString("value"));

}

};

final Runnable runnable = new Runnable(){

@Override

public void run() {

String result = getUrlContent("http://www.oschina.net/");

Message msg = new Message();

Bundle data = new Bundle();

data.putString("value", result);

msg.setData(data);

handler.sendMessage(msg);

}

};

btn01.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

new Thread(runnable).start();

}

});

}

/**

* 获取url对应的网页内容

* @param url

* @return

*/

private String getUrlContent(String url) {

HttpGet getRequest = new HttpGet(url);

getRequest.addHeader("User-Agent", " Mozilla/5.0 (Windows NT 6.3; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0");

try {

HttpResponse response = new DefaultHttpClient().execute(getRequest);

if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {

BufferedReader in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));

StringBuffer sb = new StringBuffer("");

String line = ""; //存储读取的一行内容

String NL = System.getProperty("line.separator"); //换行符

while ((line = in.readLine()) != null) {

sb.append(line+NL);

}

in.close();

return sb.toString();

} else {

return "读取失败：\n"+response.getStatusLine().getStatusCode();

}

} catch (Exception e) {

return "读取失败:\n"+e.toString();

}

}

}

参考：

http://stackoverflow.com/questions/6343166/android-os-networkonmainthreadexception

Android编程典型实例与项目开发 吴亚峰等编