Andriod中网络编程实例

package com.itheima.look;import java.io.ByteArrayOutputStream;import java.io.InputStream;public class StreamTools {//把一个inputStream 转换成一个String public static String readStream(InputStream in) throws Exception{//定义一个内存输出流ByteArrayOutputStream baos = new ByteArrayOutputStream();int len = -1;byte[] buffer = new byte[1024]; //1kbwhile((len=in.read(buffer))!=-1){baos.write(buffer, 0, len);}in.close();String content = new String(baos.toByteArray());return content;}}

package com.itheima.look;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import android.os.Bundle;import android.os.Handler;import android.os.Looper;import android.os.Message;import android.app.Activity;import android.view.Menu;import android.view.View;import android.widget.EditText;import android.widget.TextView;import android.widget.Toast;public class MainActivity extends Activity {protected  final int REQUESTSUCESS = 0;  //ctrl + shift + X  Yprotected  final int REQUESTNOTFOUND = 1;protected  final int REQUESTEXCEPTION = 2;private EditText et_path;private TextView tv_reuslt;//在主线程中定义一个handler private Handler handler = new Handler(){//这个方法是在主线程里面执行的 public void handleMessage(android.os.Message msg) {//所以就可以在主线程里面更新ui了 //[1]区分一下发送的是哪条消息 switch (msg.what) {case REQUESTSUCESS:   //代表请求成功String content =  (String) msg.obj;tv_reuslt.setText(content);break;case REQUESTNOTFOUND:   //代表请求成功Toast.makeText(getApplicationContext(), "请求资源不存在", 0).show();break;case REQUESTEXCEPTION:   //代表请求成功Toast.makeText(getApplicationContext(), "服务器忙 请稍后....", 1).show();break;default:break;}};};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);// [1]找到我们关心的控件et_path = (EditText) findViewById(R.id.et_path);tv_reuslt = (TextView) findViewById(R.id.tv_result);//[1.1]打印当前线程的名字 System.out.println("当前线程名字:"+Thread.currentThread().getName());}//[2]点击按钮进行查看 指定路径的源码 public void click(View v) {//[2.0]创建一个子线程 new Thread(){public void run() {try {//[2.1]获取源码路径 String path = et_path.getText().toString().trim();//[2.2]创建URL 对象指定我们要访问的 网址(路径)URL url = new URL(path);//[2.3]拿到httpurlconnection对象  用于发送或者接收数据 HttpURLConnection  conn = (HttpURLConnection) url.openConnection();//[2.4]设置发送get请求 conn.setRequestMethod("GET");//get要求大写  默认就是get请求//[2.5]设置请求超时时间conn.setConnectTimeout(5000);//[2.6]获取服务器返回的状态码 int code = conn.getResponseCode();//[2.7]如果code == 200 说明请求成功if (code == 200) {//[2.8]获取服务器返回的数据   是以流的形式返回的  由于把流转换成字符串是一个非常常见的操作  所以我抽出一个工具类(utils)InputStream in = conn.getInputStream(); //[2.9]使用我们定义的工具类 把in转换成StringString content = StreamTools.readStream(in);//2.9.0 创建message对象 Message msg = new Message();msg.what = REQUESTSUCESS;msg.obj = content;//2.9.1 拿着我们创建的handler(助手) 告诉系统 说我要更新uihandler.sendMessage(msg);  //发了一条消息  消息(msg)里把数据放到了msg里 handleMessage方法就会执行//[2.9.1]把流里面的数据展示到textview 上  这句话就属于更新ui的逻辑//tv_reuslt.setText(content);}else{//请求资源不存在  Toast是一个view 也不能在在线程更新uiMessage msg = new Message();msg.what = REQUESTNOTFOUND;//代表哪条消息handler.sendMessage(msg);}} catch (Exception e) {e.printStackTrace();Message msg = new Message();msg.what = REQUESTEXCEPTION;//代表哪条消息handler.sendMessage(msg);  //发送消息}};}.start();}}