获取网络源码

package com.itheima.viewpagesource;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import com.itheima.viewpagesource.utils.StreamTool;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.text.TextUtils;
import android.view.View;
import android.webkit.URLUtil;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    protected static final int SUCCESS = 0;
    protected static final int ERROR = 1;
    protected static final int NETWORK_ERROR = 2;

    private EditText ed_path;
    private TextView tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ed_path = (EditText) findViewById(R.id.ed_path);
        tv = (TextView) findViewById(R.id.tv);
    }

    //定义一个秘书
    Handler handler = new Handler(){

        public void handleMessage(android.os.Message msg) {

            switch (msg.what) {
            case SUCCESS:

                String value = (String) msg.obj;
                tv.setText(value);
                break;
            case ERROR:
                System.out.println("ERROR ==============");
                Toast.makeText(MainActivity.this, "错误发生了  ..  ERROR", 0).show();

                break;
            case NETWORK_ERROR:
                System.out.println("NETWORK_ERROR  ==============");
                Toast.makeText(MainActivity.this, "错误发生了  ..  NETWORK_ERROR ", 0).show();

                break;

            default:
                break;
            }
        };
    };

    String path = null;
    public void viewPageSource(View v){

        path = ed_path.getText().toString().trim();

        if(TextUtils.isEmpty(path)){
            Toast.makeText(this, "路径有错误...", 0).show();
            return;
        }

        //连接网络  , 要启动一个新的线程去  干 耗时的事儿
        new Thread(){
            public void run() {

                try {
                    URL url = new URL(path);
                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();

                    //设置连接超时为 5 秒钟
                    conn.setConnectTimeout(5000);
                    conn.setRequestMethod("GET");

                    // User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)
                    //通过 设置 user-agent http的请求头 , 来骗  网站, 返回  pc机上 使用 浏览器 返回 数据的一个 页面 源代码

                    conn.setRequestProperty("User-Agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)");

                    String contentType = conn.getContentType();

                    int code = conn.getResponseCode();
                    if(code==200){

                        InputStream in = conn.getInputStream();

                        // BitFactory.decodeStream(in)
                        //如何一个将一个 流转换为 字符串 

                        //这里的data是从  服务器 返回的
                        String data = StreamTool.decodeStream(in);

                        // 展示的屏幕上
                        Message msg = Message.obtain();
                        msg.what =SUCCESS;
                        msg.obj = data;

                        handler.sendMessage(msg);
                    }else{

                        Message msg = Message.obtain();
                        msg.what =ERROR;

                        handler.sendMessage(msg);

                    }

                } catch (Exception e) {
                    e.printStackTrace();

                    Message msg = Message.obtain();
                    msg.what =NETWORK_ERROR;

                    handler.sendMessage(msg);
                }

            };
        }.start();

    }

}

StreamTool.decodeStream方法：

package com.itheima.viewpagesource.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class StreamTool {

    public static String decodeStream(InputStream in) throws IOException {

        // 底层流
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int len =0;
        byte[] buf = new byte[1024];

        while((len=in.read(buf))>0){
            baos.write(buf, 0, len);
        }

        String data = baos.toString();

        return data;
    }

}