怎樣使用Http協(xié)議訪問網(wǎng)絡(luò)

public abstract class HttpURLConnection extends URLConnection
java.lang.Object ???? java.net.URLConnection ? ???? java.net.HttpURLConnection
1、獲取HttpURLConnection實(shí)例
HttpURLConnection(URL url)Constructs a new HttpURLConnection instance pointing to the resource specified by theurl.
HttpURLConnection是abstract的，不能new出實(shí)例。一般new出一個(gè)URL對象并傳入目標(biāo)網(wǎng)絡(luò)地址，然后調(diào)用openConnection()方法。

URL?url?=?new?URL("http://www.baidu.com");
//public?URLConnection?openConnection?()?
//Returns?a?new?connection?to?the?resource?referred?to?by?this?URL.
//向url發(fā)出HTTP請求的HttpURLConnection實(shí)例
//Obtain?a?new?HttpURLConnection?by?calling?URL.openConnection()?and?casting?the?result?to?HttpURLConnection
connection?=??(HttpURLConnection)url.openConnection();

2、對HttpURLConnection實(shí)例設(shè)置HTTP請求所使用的方法，連接超時(shí)等

connection.setRequestMethod("GET");
connection.setConnectTimeout(8000);
connection.setReadTimeout(8000);

3、調(diào)用connection.getInputStream()獲得到服務(wù)器返回的輸入流（連接發(fā)生），對輸入流讀取

//發(fā)生連接（在其之前設(shè)置好參數(shù)）
InputStream?in?=?connection.getInputStream();//同url.openStream()；可以不用connection
//java.io.BufferedReader.BufferedReader(Reader?in)
//Constructs?a?new?BufferedReader,?providing?in?with?a?buffer?of?8192?characters.
//public?class?BufferedReader?extends?Reader
BufferedReader?reader?=?new?BufferedReader(new?InputStreamReader(in));
StringBuilder?responseStringBuilder?=?new?StringBuilder();
String?lineStr?;
while((lineStr?=?reader.readLine())!=?null){
	responseStringBuilder.append(lineStr);
					}

Android4.0后，網(wǎng)絡(luò)操作要在子線程中進(jìn)行。 采用Handler、Message發(fā)送消息。 ?

private?Handler?handler?=?new?Handler(){
		public?void?handleMessage(Message?msg){
			switch(msg.what){
			case?SHOW_RESPONSE:
				String?response?=?(String)msg.obj;
				responseTextView.setText(response);
				break;
			default:
				break;
			
			}
		}
	};

Message?message?=?Message.obtain(mHandler,?SEND_REQUEST,?responseString);
mHandler.sendMessage(message);

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