Android学习-网络技术HttpURLConnection和OKHttp

HttpURLConnection的用法

1.获取一个HttpURLConnection的实例，并传入目标地址，然后调用openConnection方法：

URL url=new URl("www.baidu.com");
HttpURLConnection connection=(HttpURLConnection) url.openConnection();

2.设置HTTP请求所使用的方法分为:GET和POST

GET表示从服务器那里获取，POST表示希望提交数据给服务器

connection.setRequestMethod("GET");

如果使用POST的方式提交，需要在获取输入流之前把提交的数据写出，注意每条数据要以键值对的形式存在，中间用&，例如提交用户名和密码：

connection.setRequestMethod("POST");
DataOutputStream out=new DataOutputStream(connection.getOutputStream());
out.writeByte("username=admin&password=123");

3.设置链接超时读取超时等

connection.setConnectionTimeout(8000);
connection.setReadTimeout(8000);

4.调用getInputStream()获取服务器返回的输入流，然后对输入流读取

InputStream in=connection.getInputStream();

5.关闭

connection.disconnect()

OkHttp

开源的OkHttp由Square公司开发，可以替代原生的HttpURLConnection。主页地址：https://github.com/square/okhttp

1.需要先添加依赖库，编辑app/build.gradle文件

compile “com.squareup.okhttp3:okhttp:3.4.1”

2.创建一个实例

OkHttpClient client=new OkHttpClient();

3.创建一个request对象

Request request=new Request.Builder.build();

可以在build（）方法之前丰富request对象。

Request request=new Request.Builder
.url(""www.baidu.com)
.build();

4.创建一个newCall()对象并调用他的execute()方法来发送请求并获取返回的数据

Response response=client.newCall(request).execute();

response对象就是服务器返回的数据

String responseData=response.body().string();

如果发起一个POST请求比GET复杂一点，需要构建出一个RequestBody对象来存放待提交的参数：

ResponseBody requestBody=new FormBody.Builder()
.add("username","admin")
.add("password","123")
.build();

然后在Request.Builder中调用一下post,把RequestBody传入：

Request request=new Request.Builder()
.url("")
.post(requestBody)
.build();

HttpURLConnection与OKhttp的实例代码：

package com.example.administrator.networktest;

import android.app.VoiceInteractor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

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

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
TextView responseText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button sendRequest=(Button) findViewById(R.id.send_request);
responseText=(TextView) findViewById(R.id.response_text);
sendRequest.setOnClickListener(this);
}
public void onClick(View v){
if(v.getId()==R.id.send_request){
// sendRequestWithHttpURLConnection();
sendRequestWithOkHttp();//用okhttp
}
}
private void sendRequestWithOkHttp(){
new Thread(new Runnable() {
@Override
public void run() {
try{
OkHttpClient okHttpClient=new OkHttpClient();
Request request=new Request.Builder()
.url("https://www.baidu.com")
.build();
Response response=okHttpClient.newCall(request).execute();
String responseData=response.body().string();

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

}
}

).start();

}
private  void sendRequestWithHttpURLConnection(){
//开启线程发起网络请求
new Thread(new Runnable() {
@Override
public void run() {
HttpURLConnection connection=null;
BufferedReader reader=null;
try{
URL url=new URL("https://www.baidu.com");
connection=(HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(8000);
connection.setReadTimeout(8000);
InputStream in=connection.getInputStream();
//下面对获取到的输入流进去读取
reader=new BufferedReader(new InputStreamReader(in));
StringBuilder response =new StringBuilder();
String line;
while((line=reader.readLine())!=null){
response.append(line);
}
showResponse(response.toString());
}catch (Exception e){
e.printStackTrace();
}finally {
if(reader!=null){
try{
reader.close();
}catch (Exception e){
e.printStackTrace();
}
}
if(connection!=null){
connection.disconnect();
}
}

}
}

).start();
}
private  void showResponse(final String response){
runOnUiThread(new Runnable() {
@Override
public void run() {
responseText.setText(response);
}
});
}
}

showResponse中调用了一个runOnUiThread()方法。因为android不允许在子线程中进行UI的操作，所以要通过这个方法切换到主线程去。