什么是HTTP协议
1.超文本传输协议（HTTP，HyperText Transfer Protocol）是互联网上应用最为广泛的一种网络协议。
2.HTTP是一个客户端和服务器端请求和应答的标准，客户端是终端用户，服务器端是网站。
3.HTTP是客户端浏览器或其他程序与Web服务器之间的应用层通信协议。
HTTP工作原理
1.客户端与服务器建立连接；
2.建立连接后，客户端香服务器端发送一个请求；
3.服务器接受到请求之后，向客户端发送响应信息；
4.客户端与服务器端断开连接；
请求报文与响应报文
1.请求报文格式：
请求行-通用信息头-请求头-实体头-报文主体
2.响应报文格式
状态行-通用信息头-响应头-实体头-报文主体
小例子：
main.xml :
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="fill_parent"
 4     android:layout_height="fill_parent"
 5     android:orientation="vertical" >
 6 
 7     <Button
 8         android:id="@+id/requestButton"
 9         android:layout_width="fill_parent"
10         android:layout_height="wrap_content"
11         android:text="@string/hello" />
12 
13 </LinearLayout>
14 
strings.xml :1 <?xml version="1.0" encoding="utf-8"?>
2 <resources>
3 
4     <string name="hello">向百度发送一次请求</string>
5     <string name="app_name">04_08_HTTP01</string>
6 
7 </resources>

manifest.xml :
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="org.gaolei.http"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6 
 7     <uses-sdk android:minSdkVersion="8" />
 8 
 9     <uses-permission android:name="android.permission.INTERNET"/>
10     <application
11         android:icon="@drawable/ic_launcher"
12         android:label="@string/app_name" >
13         <activity
14             android:name=".MainActivity"
15             android:label="@string/app_name" >
16             <intent-filter>
17                 <action android:name="android.intent.action.MAIN" />
18 
19                 <category android:name="android.intent.category.LAUNCHER" />
20             </intent-filter>
21         </activity>
22     </application>
23 
24 </manifest>

MainActivity.java :
 1 package org.gaolei.http;
 2 
 3 import java.io.BufferedReader;
 4 import java.io.IOException;
 5 import java.io.InputStream;
 6 import java.io.InputStreamReader;
 7 
 8 import org.apache.http.HttpEntity;
 9 import org.apache.http.HttpResponse;
10 import org.apache.http.client.ClientProtocolException;
11 import org.apache.http.client.HttpClient;
12 import org.apache.http.client.methods.HttpGet;
13 import org.apache.http.impl.client.DefaultHttpClient;
14 
15 import android.app.Activity;
16 import android.os.Bundle;
17 import android.view.View;
18 import android.view.View.OnClickListener;
19 import android.widget.Button;
20 
21 public class MainActivity extends Activity {
22     private Button button;
23     private HttpResponse httpResponse;
24     private HttpEntity httpEntity;
25 
26     @Override
27     public void onCreate(Bundle savedInstanceState) {
28         super.onCreate(savedInstanceState);
29         setContentView(R.layout.main);
30 
31         button = (Button) findViewById(R.id.requestButton);
32         button.setOnClickListener(new OnClickListener() {
33 
34             @Override
35             public void onClick(View arg0) {
36                 // 生成一个请求对象
37                 HttpGet httpGet = new HttpGet("http://www.baidu.com");
38 
39                 // 生成一个Http客户端对象
40                 HttpClient httpClient = new DefaultHttpClient();
41                 // 使用Http客户端发送请求对象
42                 InputStream inputStream = null;
43                 try {
44                     httpResponse = httpClient.execute(httpGet);
45                     httpEntity = httpResponse.getEntity();
46                     inputStream = httpEntity.getContent();
47                     BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
48                     String result = "";
49                     String line = "";
50                     while((line = reader.readLine()) != null) {
51                         result = result + line;
52                     }
53                 } catch (ClientProtocolException e) {
54                     e.printStackTrace();
55                 } catch (IOException e) {
56                     e.printStackTrace();
57                 }finally {
58                     try {
59                         inputStream.close();
60                     } catch (IOException e) {
61                         e.printStackTrace();
62                     }
63                 }
64 
65             }
66 
67         });
68     }
69 }
70 

1.HTTP请求的方法
2.使用GET方法发送请求
3.使用POST方法发送请求

main.xml: 
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="fill_parent"
 4     android:layout_height="fill_parent"
 5     android:orientation="vertical" >
 6 
 7     <EditText
 8         android:id="@+id/nameView"
 9         android:layout_width="fill_parent"
10         android:layout_height="wrap_content" />
11 
12     <EditText
13         android:id="@+id/ageView"
14         android:layout_width="fill_parent"
15         android:layout_height="wrap_content" />
16 
17     <Button
18         android:id="@+id/getButton"
19         android:layout_width="fill_parent"
20         android:layout_height="wrap_content"
21         android:text="@string/getButton" />
22 
23     <Button
24         android:id="@+id/postButton"
25         android:layout_width="fill_parent"
26         android:layout_height="wrap_content"
27         android:text="@string/postButton" />
28 
29 </LinearLayout>
strings.xml: 
1 <?xml version="1.0" encoding="utf-8"?>
2 <resources>
3 
4     <string name="hello">Hello World, MainActivity!</string>
5     <string name="app_name">04_09_HTTP02</string>
6     <string name="getButton">使用GET方式发送请求</string>
7     <string name="postButton">使用POST方式发送请求</string>
8 
9 </resources>
manifest.xml: 
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="org.gaolei.http"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6 
 7     <uses-sdk android:minSdkVersion="8" />
 8 
 9     <uses-permission android:name="android.permission.INTERNET" />
10 
11     <application
12         android:icon="@drawable/ic_launcher"
13         android:label="@string/app_name" >
14         <activity
15             android:name=".MainActivity"
16             android:label="@string/app_name" >
17             <intent-filter>
18                 <action android:name="android.intent.action.MAIN" />
19 
20                 <category android:name="android.intent.category.LAUNCHER" />
21             </intent-filter>
22         </activity>
23     </application>
24 
25 </manifest>
MainActivity.java :
  1 package org.gaolei.http;
  2 
  3 import java.io.BufferedReader;
  4 import java.io.IOException;
  5 import java.io.InputStream;
  6 import java.io.InputStreamReader;
  7 import java.io.UnsupportedEncodingException;
  8 import java.util.ArrayList;
  9 import java.util.List;
 10 
 11 import org.apache.http.HttpEntity;
 12 import org.apache.http.HttpResponse;
 13 import org.apache.http.NameValuePair;
 14 import org.apache.http.client.ClientProtocolException;
 15 import org.apache.http.client.HttpClient;
 16 import org.apache.http.client.entity.UrlEncodedFormEntity;
 17 import org.apache.http.client.methods.HttpGet;
 18 import org.apache.http.client.methods.HttpPost;
 19 import org.apache.http.impl.client.DefaultHttpClient;
 20 import org.apache.http.message.BasicNameValuePair;
 21 
 22 import android.app.Activity;
 23 import android.os.Bundle;
 24 import android.view.View;
 25 import android.view.View.OnClickListener;
 26 import android.widget.Button;
 27 import android.widget.EditText;
 28 
 29 public class MainActivity extends Activity {
 30     private Button getButton;
 31     private Button postButton;
 32 
 33     private EditText nameView;
 34     private EditText ageView;
 35 
 36     private HttpResponse httpResponse;
 37     private HttpEntity httpEntity;
 38 
 39     private String baseUrl = "http://192.168.1.100:8081/serverside/name";
 40 
 41     @Override
 42     public void onCreate(Bundle savedInstanceState) {
 43         super.onCreate(savedInstanceState);
 44         setContentView(R.layout.main);
 45 
 46         getButton = (Button) findViewById(R.id.getButton);
 47         getButton.setOnClickListener(new OnGetListener());
 48 
 49         postButton = (Button) findViewById(R.id.postButton);
 50         postButton.setOnClickListener(new OnPostListener());
 51 
 52         nameView = (EditText) findViewById(R.id.nameView);
 53         ageView = (EditText) findViewById(R.id.ageView);
 54     }
 55 
 56     private class OnGetListener implements OnClickListener {
 57 
 58         @Override
 59         public void onClick(View v) {
 60             String name = nameView.getText().toString();
 61             String age = ageView.getText().toString();
 62             String url = baseUrl + "?name=" + name + "&age=" + age;
 63             // 生成一个请求对象
 64             HttpGet httpGet = new HttpGet(url);
 65             // 生成一个Http客户端对象
 66             HttpClient httpClient = new DefaultHttpClient();
 67             // 使用Http客户端发送请求对象
 68             InputStream inputStream = null;
 69             try {
 70                 httpResponse = httpClient.execute(httpGet);
 71                 httpEntity = httpResponse.getEntity();
 72                 inputStream = httpEntity.getContent();
 73                 BufferedReader reader = new BufferedReader(
 74                         new InputStreamReader(inputStream));
 75                 String result = "";
 76                 String line = "";
 77                 while ((line = reader.readLine()) != null) {
 78                     result = result + line;
 79                 }
 80             } catch (ClientProtocolException e) {
 81                 e.printStackTrace();
 82             } catch (IOException e) {
 83                 e.printStackTrace();
 84             } finally {
 85                 try {
 86                     inputStream.close();
 87                 } catch (IOException e) {
 88                     e.printStackTrace();
 89                 }
 90             }
 91 
 92         }
 93 
 94     }
 95 
 96     private class OnPostListener implements OnClickListener {
 97 
 98         @Override
 99         public void onClick(View v) {
100             String name = nameView.getText().toString();
101             String age = ageView.getText().toString();
102 
103             NameValuePair nameValuePair1 = new BasicNameValuePair("name", name);
104             NameValuePair nameValuePair2 = new BasicNameValuePair("age", age);
105 
106             List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
107             nameValuePairs.add(nameValuePair1);
108             nameValuePairs.add(nameValuePair2);
109 
110             HttpEntity httpEntity = null;
111             try {
112                 httpEntity = new UrlEncodedFormEntity(nameValuePairs);
113                 HttpPost httpPost = new HttpPost(baseUrl);
114                 httpPost.setEntity(httpEntity);
115                 HttpClient httpClient = new DefaultHttpClient();
116                 // 使用Http客户端发送请求对象
117                 InputStream inputStream = null;
118                 try {
119                     httpResponse = httpClient.execute(httpPost);
120                     httpEntity = httpResponse.getEntity();
121                     inputStream = httpEntity.getContent();
122                     BufferedReader reader = new BufferedReader(
123                             new InputStreamReader(inputStream));
124                     String result = "";
125                     String line = "";
126                     while ((line = reader.readLine()) != null) {
127                         result = result + line;
128                     }
129                 } catch (ClientProtocolException e) {
130                     e.printStackTrace();
131                 } catch (IOException e) {
132                     e.printStackTrace();
133                 } finally {
134                     try {
135                         inputStream.close();
136                     } catch (IOException e) {
137                         e.printStackTrace();
138                     }
139                 }
140             } catch (UnsupportedEncodingException e) {
141                 e.printStackTrace();
142             }
143         }
144 
145     }
146 }