Android Studio创建网络连接工程试验

1 新建工程

File–》new–》project，然后一路next，最后finish即可。

2 Android Studio添加必要的代码和依赖

2.1 AndroidManifest文件

添加了两句网络访问权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hong.myapplication">
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

2.2 添加网络访问工具GetPostUtil.java

package com.hong.myapplication;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

/**
 * Created by FR on 2017/4/14.
 */
public class GetPostUtil {
    /**
     * 向指定URL发送GET方法的请求
     * @param url 发送请求的URL
     * @param params 请求参数，请求参数应该是name1=value1&name2=value2的形式。
     * @return URL所代表远程资源的响应
     */
    public static String sendGet(String url, String params)
    {
        String result = "";
        BufferedReader in = null;

        try
        {
            String urlName = url + "?" + params;
            URL realUrl = new URL(urlName);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();

            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
            /*
             * 建立实际的连接
             * 如果需要发送POST请求，则需要获取URLConnection的OutputStream
             * 然后再向网络中输出请求参数
             */
            conn.connect();

            // 获取所有响应头字段
            Map<String, List<String>> map = conn.getHeaderFields();
            // 遍历所有的响应头字段
            for (String key : map.keySet())
            {
                System.out.println(key + "--->" + map.get(key));
            }

            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null)
            {
                result += "
" + line;
            }
        }
        catch (Exception e)
        {
            System.out.println("发送GET请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输入流
        finally
        {
            try
            {
                if (in != null)
                {
                    in.close();
                }
            }
            catch (IOException ex)
            {
                ex.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 向指定URL发送POST方法的请求
     * @param url 发送请求的URL
     * @param params 请求参数，请求参数应该是name1=value1&name2=value2的形式。
     * @return URL所代表远程资源的响应
     */
    public static String sendPost(String url, String params)
    {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";

        try
        {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();

            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");

            // 向网络中输出请求参数
            conn.setDoOutput(true);
            conn.setDoInput(true);

            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());

            // 发送请求参数
            out.print(params);

            // flush输出流的缓冲
            out.flush();

            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                switch (result += "
" + line) {

                }
//                Log.i("main",line );
            }
        }
        catch (Exception e)
        {
            System.out.println("发送POST请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输出流、输入流
        finally
        {
            try
            {
                if (out != null)
                {
                    out.close();
                }
                if (in != null)
                {
                    in.close();
                }
            }
            catch (IOException ex)
            {
                ex.printStackTrace();
            }
        }
        return result;
    }
}

2.3 修改主活动布局

仅仅增加了一个id便于后续在主活动java中控制

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/hellotxt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

2.4 修改主活动MainActivity.java

package com.hong.myapplication;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private String mResponse3 ;
    private String massage; //用于接收服务器返回的信息
    private static String PATH = "http://172.20.10.12:8080/Test_Servlet/Login_Servlet";  // 需要改成服务器地址

    private TextView hellotxtt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        hellotxtt= findViewById(R.id.hellotxt);

        hellotxtt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //给服务器发一条信息：areyouok
                //向服务器发一条命令，并获得修改成功的标志，确认后给用户弹出提示
                new Thread() {
                    @Override
                    public void run() {
                        String mResponse = GetPostUtil.sendPost(PATH, "areyouok");
                        Log.i("main", mResponse);
                        String[] str = mResponse.split("@");
                        Log.i("main", "str[1]="+str[1]);
                        if(str[1].equals("yes")){
                            Log.i("main", "服务器说它ok");
                        }else{
                            Log.i("main", "服务器没有应答");
                        }
                    }
                }.start();
            }
        });
    }
}

3 服务器端代码

package com.dj.test;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.codehaus.jackson.map.ObjectMapper;

import java.util.ArrayList;
import java.util.List;

import com.dj.entity.EnvData;
import com.dj.entity.User;

/**
 * Servlet implementation class Login_Servlet
 */
@WebServlet("/Login_Servlet")
public class Login_Servlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
    private static final String PANDUAN = "areyouok";

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Login_Servlet() {
        super();
         
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
			
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		
		
		String panduan = request.getParameter(PANDUAN);
		if(panduan==null) {//如果panduan为空，直接退出
			System.out.println("panduan为空");
			return;
		}
		//如果不为空则继续下面的处理
		//用json格式发送 执行下列代码前要先把两个相关jar包放在该放的位置
		String yes = "@yes@";
		ObjectMapper om1 = new ObjectMapper();
		om1.writeValue(response.getOutputStream(),yes);
		System.out.println("yes".toString()); 
	}
}

4 测试结果

安卓端：

05-05 21:25:06.068 25571-25803/com.hong.myapplication I/main: "@yes@"
05-05 21:25:06.068 25571-25803/com.hong.myapplication I/main: str[1]=yes
05-05 21:25:06.068 25571-25803/com.hong.myapplication I/main: 服务器说它ok

服务器端：

五月 05, 2020 9:20:52 下午 org.apache.catalina.startup.Catalina start
信息: Server startup in 883 ms
yes