Android 制作一个网页源代码浏览器（HttpURLConnection）

package com.wuyou.htmlcodeviewer;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends ActionBarActivity {
    private static final int ERROR = 0;
    private static final int CHANGE_TEXT = 1;

    private EditText editText;
    private TextView textView;

    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            if (msg.what == CHANGE_TEXT) {
                textView.setText((String) msg.obj);
            } else if (msg.what == ERROR) {
                Toast.makeText(MainActivity.this, (String) msg.obj, Toast.LENGTH_LONG).show();
            }
        }
    };

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

        editText = (EditText) findViewById(R.id.et);
        textView = (TextView) findViewById(R.id.tv);
    }

    public void click(View view) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    String path = editText.getText().toString().trim();
                    if (TextUtils.isEmpty(path)) {
                        Message message = new Message();
                        message.what = ERROR;
                        message.obj = "地址不能为空！";
                        handler.sendMessage(message);
                    } else {
                        URL url = new URL(path);
                        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                        httpURLConnection.setRequestMethod("GET");
                        httpURLConnection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:22.0) Gecko/20100101 Firefox/22.0");
                        httpURLConnection.setConnectTimeout(5000);//设置连接服务器如果没有在5秒钟运行则抛出错误
                        if (httpURLConnection.getResponseCode() == 200) {
                            InputStream is = httpURLConnection.getInputStream();
                            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
                            String line = null;
                            StringBuilder sb = new StringBuilder();
                            while ((line = bufferedReader.readLine()) != null) {
                                sb.append(line);
                            }
                            Message message = new Message();
                            message.what = CHANGE_TEXT;
                            message.obj = sb.toString();
                            handler.sendMessage(message);
                        }
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                    Message message = new Message();
                    message.what = ERROR;
                    message.obj = "出错了！";
                    handler.sendMessage(message);
                }
            }
        }).start();
    }

}

<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity"
    tools:ignore="MergeRootFrame">

    <EditText
        android:id="@+id/et"
        android:text="http://www.baidu.com/"
        android:layout_height="wrap_content"
        android:layout_width="fill_parent" />

    <Button
        android:text="查看源代码"
        android:onClick="click"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content" />

    <ScrollView
        android:id="@+id/scroll"
        android:layout_height="fill_parent"
        android:layout_width="fill_parent">

        <TextView
            android:id="@+id/tv"
            android:layout_height="fill_parent"
            android:layout_width="fill_parent" />
    </ScrollView>

</LinearLayout>

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