1. 编写如下项目：

2 编写Android清单文件

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.itheima28.htmldemo"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        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.itheima28.htmldemo.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>

3 编写布局文件activity_main.xml

<LinearLayout 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:orientation="vertical"

    tools:context=".MainActivity" >

    <LinearLayout

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal">

        <EditText

            android:id="@+id/et_url"

            android:layout_width="0dip"

            android:text="http://www.baidu.com"

            android:layout_height="wrap_content"

            android:singleLine="true"

            android:layout_weight="1"/>

        <Button

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:onClick="getHtml"

            android:text="GO"/>

    </LinearLayout>

    <ScrollView

        android:layout_width="fill_parent"

        android:layout_height="fill_parent">

        <TextView

            android:id="@+id/tv_html"

            android:layout_width="fill_parent"

            android:layout_height="fill_parent"/>

    </ScrollView>

</LinearLayout>

4 编写Activity的类MainActivity如下：

package com.itheima28.htmldemo;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.URL;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.text.TextUtils;

import android.util.Log;

import android.view.View;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends Activity {

    private static final String TAG = "MainActivity";

    private static final int SUCCESS = 0;

    protected static final int ERROR = 1;

    private EditText etUrl;

    private TextView tvHtml;

    private Handler handler = new Handler() {

       @Override

       public void handleMessage(Message msg) {

           super.handleMessage(msg);

           switch (msg.what) {

           case SUCCESS:

               tvHtml.setText((String) msg.obj);

              break;

           case ERROR:

              Toast.makeText(MainActivity.this, "访问失败", 0).show();

              break;

           default:

              break;

           }

       }

    };

    @Override

    protected void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.activity_main);

       etUrl = (EditText) findViewById(R.id.et_url);

       tvHtml = (TextView) findViewById(R.id.tv_html);

    }

    public void getHtml(View v) {

       final String url = etUrl.getText().toString();

       new Thread(new Runnable() {

           @Override

           public void run() {

              // 请求网络

              String html = getHtmlFromInternet(url);

              if(!TextUtils.isEmpty(html)) {

                  // 更新textview的显示了

                  Message msg = new Message();

                  msg.what = SUCCESS;

                  msg.obj = html;

                  handler.sendMessage(msg);

              } else {

                  Message msg = new Message();

                  msg.what = ERROR;

                  handler.sendMessage(msg);

              }

           }

       }).start();

    }

    /**

     * 根据给定的url访问网络, 抓去html代码

     * @param url

     * @return

     */

    protected String getHtmlFromInternet(String url) {

       try {

           URL mURL = new URL(url);

           HttpURLConnection conn = (HttpURLConnection) mURL.openConnection();

           conn.setRequestMethod("GET");

           conn.setConnectTimeout(10000);

           conn.setReadTimeout(5000);

//         conn.connect();

           int responseCode = conn.getResponseCode();

           if(responseCode == 200) {

              InputStream is = conn.getInputStream();

              String html = getStringFromInputStream(is);

              return html;

           } else {

              Log.i(TAG, "访问失败: " + responseCode);

           }

       } catch (Exception e) {

           e.printStackTrace();

       }

       return null;

    }

    /**

     * 根据流返回一个字符串信息

     * @param is

     * @return

     * @throws IOException

     */

    private String getStringFromInputStream(InputStream is) throws IOException {

       ByteArrayOutputStream baos = new ByteArrayOutputStream();

       byte[] buffer = new byte[1024];

       int len = -1;

       while((len = is.read(buffer)) != -1) {

           baos.write(buffer, 0, len);

       }

       is.close();

       String html = baos.toString();  // 把流中的数据转换成字符串, 采用的编码是: utf-8

       String charset = "utf-8";

       if(html.contains("gbk") || html.contains("gb2312")

              || html.contains("GBK") || html.contains("GB2312")) {       // 如果包含gbk, gb2312编码, 就采用gbk编码进行对字符串编码

           charset = "gbk";

       }

       html = new String(baos.toByteArray(), charset);  // 对原有的字节数组进行使用处理后的编码名称进行编码

       baos.close();

       return html;

    }

}