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

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



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"/>