基于WiFi模块的Android WiFi通信

通过一段时间的学习和应用，理解了Android通信，通过这篇文章记录一下学习过程。

基于ESP8266的Android WiFi通信广泛应用于物联网领域，常用是通过局域网实现Android端和下位机的通信，达到控制目的。

此篇文章记录的内容，需要手机连接到WiFi模块，通过wifi让Android端和硬件部分处于同一个局域网内。Android网络通信通过socket编程实现网络的连接，通过IO流实现数据的发送与接收。

首先，创建一个Android项目，首先，需要给予APP网络权限：

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

第二步，创建一个类SendThead，内容为发送和接收的代码，首先定义IP，端口port，以及接收/发送’变量，打开套接字实现网络的连接，连接结束关闭套接字，采取多线程实现信息的发送与接收：

package com.example.a14942.smart_see;

/**
 * Created by 14942 on 2018/3/26.
 */

import android.os.Handler;
import android.os.Message;
import android.util.Log;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;

class SendThread implements Runnable {

    private String ip;
    private int port;
    BufferedReader in;
    PrintWriter out;      //打印流
    Handler mainHandler;
    Socket s;
    private String receiveMsg;

    ArrayList<String> list = new ArrayList<String>();

    public SendThread(String ip,int port, Handler mainHandler) {     //IP，端口，数据
        this.ip = ip;
        this.port=port;
        this.mainHandler = mainHandler;
    }

    /**
     * 套接字的打开
     */
    void open(){
        try {
            s = new Socket(ip, port);
            //in收单片机发的数据
            in = new BufferedReader(new InputStreamReader(s.getInputStream()));
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(
                    s.getOutputStream())), true);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 套接字的关闭
     */
    void close(){
        try {
            s.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {

        //创建套接字
        open();

        //BufferedReader
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(200);
                        close();
                        open();
                    } catch (InterruptedException e1) {
                        e1.printStackTrace();
                    }
                    if (!s.isClosed()) {
                        if (s.isConnected()) {
                            if (!s.isInputShutdown()) {
                                try {
                                    Log.i("mr", "等待接收信息");

                                    char[] chars = new char[1024];					//byte[] bys = new byte[1024];		
                                    int len = 0;							//int len = 0;
                                    while((len = in.read(chars)) != -1){				//while((len = in.read(bys)) != -1) {	
                                        System.out.println("收到的消息：  "+new String(chars, 0, len));      in.write(bys,0,len);
                                        receiveMsg = new String(chars, 0, len);				// }
													
                                        Message msg=mainHandler.obtainMessage();
                                        msg.what=0x00;
                                        msg.obj=receiveMsg;
                                        mainHandler.sendMessage(msg);
                                    }

                                } catch (IOException e) {
                                    Log.i("mr", e.getMessage());
                                    try {
                                        s.shutdownInput();
                                        s.shutdownOutput();
                                        s.close();
                                    } catch (IOException e1) {
                                        e1.printStackTrace();
                                    }
                                    e.printStackTrace();
                                }
                            }
                        }
                    }

                }
            }

        });
        thread.start();

        while (true) {

            //连接中
            if (!s.isClosed()&&s.isConnected()&&!s.isInputShutdown()) {

                // 如果消息集合有东西，并且发送线程在工作。
                if (list.size() > 0 && !s.isOutputShutdown()) {
                    out.println(list.get(0));
                    list.remove(0);
                }

                Message msg=mainHandler.obtainMessage();
                msg.what=0x01;
                mainHandler.sendMessage(msg);
            } else {
                //连接中断了
                Log.i("mr", "连接断开了");
                Message msg=mainHandler.obtainMessage();
                msg.what=0x02;
                mainHandler.sendMessage(msg);
            }
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                try {
                    out.close();
                    in.close();
                    s.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                e.printStackTrace();
            }
        }

    }

    public void send(String msg) {
        System.out.println("msg的值为：  " + msg);
        list.add(msg);
    }

}

第三步，创建主活动，编写布局（xml）文件，这里我创建了一个温度显示框，和两个开关控制按钮（switch控件）：

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/screen"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@drawable/bb"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:layout_x="30dp"
        android:layout_y="130dp"
        android:orientation="horizontal">


        <TextView
            android:id="@+id/textView2"
            android:layout_width="50sp"
            android:layout_height="wrap_content"
            android:layout_marginLeft="33px"
            android:text="湿度"
            android:textColor="#000000"
            android:textSize="18sp" />

        <TextView
            android:id="@+id/ttv2"
            android:layout_width="160sp"
            android:layout_height="wrap_content"
            android:background="#FFFFFF"
            android:text=""
            android:textSize="18sp" />

        <TextView
            android:layout_width="60sp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:paddingLeft="10px"
            android:text="%rh"
            android:textColor="#000000"
            android:textSize="18sp" />

    </LinearLayout>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="开         关"
        android:textColor="#000000"
        android:textSize="18sp"
        android:layout_x="50dp"
        android:layout_y="200dp"
        />

    <Switch
        android:id="@+id/Switch2"
        android:layout_width="50sp"
        android:layout_height="wrap_content"
        android:layout_weight="1.01"
        android:layout_x="210dp"
        android:layout_y="270dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="自动手动"
        android:textColor="#000000"
        android:textSize="18sp"
        android:layout_x="50dp"
        android:layout_y="270dp"
        />

    <Switch
        android:id="@+id/Switch1"
        android:layout_width="50sp"
        android:layout_height="wrap_content"
        android:layout_x="210dp"
        android:layout_y="200dp" />

</AbsoluteLayout>

 第四步，编写主活动，包括实现网络连接（SendThead），实现消息的发送和接收，对开关控件（switch）定义点击事件：

package com.example.a14942.smart_see;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity{

    /*接收发送定义的常量*/
    private String mIp = "192.168.4.1";
    private int mPort = 9000;
    private SendThread sendthread;
    String receive_Msg;
    String l;
    String total0,total1,total2,total3;
    private Button button0;
    private Button button1;
    static PrintWriter mPrintWriterClient = null;
    static BufferedReader mBufferedReaderClient	= null;
    Switch switch1,switch2;
    /*****************************/


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //getSupportActionBar().hide();
        setContentView(R.layout.activity_main);
//        button0= (Button)findViewById(R.id.Water_W_N);
//        button0.setOnClickListener(button0ClickListener);
//        button1= (Button)findViewById(R.id.Water_W_O);
//        button1.setOnClickListener(button1ClickListener);

        /***************连接*****************/
        sendthread = new SendThread(mIp, mPort, mHandler);
        Thread1();
        new Thread().start();
        /**********************************/

        switch1 = (Switch) findViewById(R.id.Switch1);
        switch1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView,
                                         boolean isChecked) {
                // TODO Auto-generated method stub
                if (isChecked) {
                    sendthread.send("A");
                } else {
                    sendthread.send("B");
                }
            }

        });

        switch2 = (Switch) findViewById(R.id.Switch2);
        switch2.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView,
                                         boolean isChecked) {
                // TODO Auto-generated method stub
                if (isChecked) {
                    sendthread.send("C");
                } else {
                    sendthread.send("D");
                }
            }

        });
    }
//    private View.OnClickListener button0ClickListener = new View.OnClickListener() {
//        public void onClick(View arg0) {
//            mPrintWriterClient.print("j");
//            mPrintWriterClient.flush();
//
//        }
//    };
//    private View.OnClickListener button1ClickListener = new View.OnClickListener() {
//        public void onClick(View arg0) {
//            mPrintWriterClient.print("m");
//            mPrintWriterClient.flush();
//        }
//    };


    private class FragmentAdapter extends FragmentPagerAdapter {
        List<Fragment> fragmentList = new ArrayList<Fragment>();

        public FragmentAdapter(FragmentManager fm, List<Fragment> fragmentList) {
            super(fm);
            this.fragmentList = fragmentList;
        }

        @Override
        public Fragment getItem(int position) {
            return fragmentList.get(position);
        }

        @Override
        public int getCount() {
            return fragmentList.size();
        }

    }


    /*接收线程*******************************************************************************/
    /**
     * 开启socket连接线程
     */
    void Thread1(){
//        sendthread = new SendThread(mIp, mPort, mHandler);
        new Thread(sendthread).start();//创建一个新线程
    }

    Handler mHandler = new Handler()
    {
        public void handleMessage(Message msg)
        {
            TextView text0 = (TextView)findViewById(R.id.ttv2);
            super.handleMessage(msg);
            if (msg.what == 0x00) {

                Log.i("mr_收到的数据： ", msg.obj.toString());
                receive_Msg = msg.obj.toString();
                l = receive_Msg;
                text0.setText(l);
            }
        }
    };
}

这样，一个简单的物联网通信就实现了。希望对大家有所帮助，如有疑问，欢迎留言。

本次文章一样的源码暂时找不到了，附上依托以上的代码开发的简单的demo示例

csdn：https://download.csdn.net/download/weixin_40042248/13456038

github：https://github.com/Yang-Jianlin/ESP8266-with-Android