Android初级开发（九）——网络交互—HttpURLConnection

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一、使用HttpURLConnection的步骤
1、获取到HttpURLConnection的实例，并传入目标的网络地址，然后调用openConnection()方法

URL url = new URL("http://www.baidu.com");HttpURLConnection connection = (HttpURLConnection)url.openConnection();

2、设置HTTP请求所使用的方法GET和POST
GET:从服务器那里获取数据
之后再调用getInputStream()方法获取到服务器返回的输入流

connection.setRequestMethod("GET");InputStream in = connection.getInputStream();

POST:提交数据给服务器
每条数据都要以键值对的形式存在，数据与数据之间用“&”符号隔开

connection.setRequestMethod("POST");DataOutputStream out = new DataOutputStream(connection.getOutputStream());out.writeBytes("username=admin&password=123456");

3、调用disconnect()方法将HTTP连接关闭掉

connection.disconnect();

二、实例
需求：一个按钮用于发送HTTP请求，一个文本框用于将服务器返回的数据显示出来
1、效果图
这里写图片描述

2、布局文件

<?xml version="1.0" encoding="utf-8"?><LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">   <Button       android:id="@+id/send_request"       android:layout_width="match_parent"       android:layout_height="80dp"       android:text="发送请求"       android:textSize="25dp"/>    <ScrollView        android:layout_width="match_parent"        android:layout_height="match_parent">        <TextView            android:id="@+id/response_text"            android:layout_width="match_parent"            android:layout_height="wrap_content" />    </ScrollView></LinearLayout>

3、MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener {    TextView responseText;    Button sendRequset;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        sendRequset = (Button) findViewById(R.id.send_request);        responseText = (TextView) findViewById(R.id.response_text);        sendRequset.setOnClickListener(this);    }    @Override    public void onClick(View view) {        if (view.getId() == R.id.send_request){            sendRequsetWithHttpURLConnection();        }    }    private void sendRequsetWithHttpURLConnection() {        //开启线程来发起网络请求        new Thread(new Runnable() {            @Override            public void run() {                HttpURLConnection connection = null;                BufferedReader reader = null;                try {                    URL url = new URL("http://www.baidu.com");                    connection = (HttpURLConnection) url.openConnection();                    //提交数据给服务器的步骤                   // connection.setRequestMethod("POST");                   // DataOutputStream out = new DataOutputStream(connection.getOutputStream());                   // out.writeBytes("username=admin&password=123456");                    connection.setRequestMethod("GET");                    //设置链接超时的毫秒数                    connection.setConnectTimeout(8000);                    //设置读取超时的毫秒数                    connection.setReadTimeout(8000);                    InputStream in = connection.getInputStream();                    //下面对获取到的输入流进行读取                    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 (IOException e){                            e.printStackTrace();                        }                    }                    if (connection != null){                        connection.disconnect();                    }                }            }        }).start();    }    //结果传入showResponse方法中    private void showResponse(final String s) {        runOnUiThread(new Runnable() {            @Override            public void run() {                //在这里进行UI操作，将结果显示到界面上                responseText.setText(s);            }        });    }}

4、声明网络权限

<uses-permission android:name="android.permission.INTERNET"/>

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