httpUrlConnection连接网络的用法(用到了handle传递消息,在主线程中更新UI)

由于httpclient在Android5.0以后已经过时,所以官方推荐使用httpUrlConnection来连接网络,现将该连接的基本方法展示,如下

注意:记得加入<uses-permission android:name="android.permission.INTERNET" />

另外,本例用到了handle来处理消息,跟新UI在主线程中,访问网络在子线程中

客户端代码:

package imqsl.com.testhttp;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

public class MainActivity extends AppCompatActivity {
    Button button = null;
    EditText edit = null;
    TextView textView = null;
    String result="";
    Handler handler=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button= (Button) findViewById(R.id.button);
        edit= (EditText) findViewById(R.id.edit);
        textView= (TextView) findViewById(R.id.text_display);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if ("".equals(edit.getText().toString())){
                    Toast.makeText(MainActivity.this,"请输入要发送的内容",Toast.LENGTH_SHORT).show();
                    return;
                }
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        send();
                        Message msg=handler.obtainMessage();//子线程中的handle用来给主线程传递消息,虽然本例中的msg没有使用,
但是主线程中的handle也要等待该Message,否则不会继续,然后更新UI
                        handler.sendMessage(msg);
                    }
                }).start();
            }
        });
        handler=new Handler(){//主线程中的handle用来接收子线程中的Message以便更新UI
            @Override
            public void handleMessage(Message msg) {
                Toast.makeText(MainActivity.this,result,Toast.LENGTH_SHORT).show();
                if (result!=null){
                    textView.setText(result);
                    edit.setText("");
                }
                super.handleMessage(msg);
            }
        };

    }

    private void send() {
        URL url;
        String target = "http://192.168.1.152:8080/flightcheck/testservlet";
        try {
            url=new URL(target);
            HttpURLConnection urlConn= (HttpURLConnection) url.openConnection();//注意:httpURLconnetion的创建是这样自的
            urlConn.setRequestMethod("POST");//设置连接方式,post必须设置,get可以不用设置,因为默认的就是get
            urlConn.setUseCaches(false);//是指是否缓存
            urlConn.setDoInput(true);//设置是否输入
            urlConn.setDoOutput(true);//设置是否输出
            DataOutputStream out=new DataOutputStream(urlConn.getOutputStream());
            String param="content="+ URLEncoder.encode(edit.getText().toString(),"utf-8");//使用URLEncoder.encode转换为utf-8以防止中文乱码
            out.writeBytes(param);//writeBytes写字节到输出流中,服务器端也是接收的bytes
            out.flush();//记得刷一下
            out.close();
            System.out.println("responsecode:"+urlConn.getResponseCode());
            if (urlConn.getResponseCode()==HttpURLConnection.HTTP_OK){//连接成功,则相等,httpURLConnection.http_ok=200
                BufferedReader bufferedReader=new BufferedReader(new  //处理流,转换流,节点流
                        InputStreamReader(urlConn.getInputStream()));
                String line=null;
                System.out.println("bufferedReader.readLine():"+bufferedReader.readLine());
                while ((line=bufferedReader.readLine())!=null){
                    result+=line+"
";                              //加了个"
"相当于换到了下一行
                }
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
}

xml文件代码:

<?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="wrap_content"
    android:orientation="vertical"
    >
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/edit"
        />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="发表"
        android:id="@+id/button"
        />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/text_display"
        />

</LinearLayout>

服务器端代码:

package test;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class testservlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public testservlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String content = new String(request.getParameter("content").getBytes("ISO-8859-1"), "UTF-8");//客户端writeBytes,服务器端就getBytes并转码
        System.out.println(content);
        response.setContentType("text/plain");
        response.setCharacterEncoding("utf-8");//加入本步设置客户端就可以得到服务器端发来的正确的中文了
        
        PrintWriter out=response.getWriter();//打印流,输出流,向客户端输入的意思
        out.print(content);//输出流,向客户端输入的意思
        out.flush();//打印流记得刷一下,不然不行
        out.close();
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}