STM32单片机通过ESP8266WiFi模块与Android APP实现数据传输（二）---上位机搭建

事物的难度远远低于对事物的恐惧
完成对STM32单片机和ESP8266 WiFi模块的配置之后，接下来需要完成Android APP代码的编写以及实现。

1.添加网络权限

因为我们需要对WiFi进行操作，所以需要网络的权限，在AndroiManifest.xml文件中加入以下代码：

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

2.建立TCP连接

首先通过文本输入控件得到IP地址和端口号，然后建立Socket连接。

case R.id.btn_turn:
                if (mSocket == null || !mSocket.isConnected()) {
                    if(!TextUtils.isEmpty(mText_ip.getText()) && !TextUtils.isEmpty(mText_port.getText())){
                        mip = mText_ip.getText().toString();
                        mport = Integer.parseInt(mText_port.getText().toString());
                        Log.i(TAG, "onClick: "+mport);
                        mConnectThread = new ConnectThread(mip, mport);
                        mConnectThread.start();
                    }else if(TextUtils.isEmpty(mText_ip.getText())){
                        Toast.makeText(this,"请输入IP地址",Toast.LENGTH_SHORT).show();
                    }else if(TextUtils.isEmpty(mText_port.getText())){
                        Toast.makeText(this,"请输入端口号",Toast.LENGTH_SHORT).show();
                    }
                }
                if (mSocket != null && mSocket.isConnected()) {
                    try {
                        mSocket.close();
                        mSocket = null;
                        mBtn_turn.setText("连接");
                        Toast.makeText(this, "连接已断开", Toast.LENGTH_SHORT).show();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                break;

上述代码是通过按钮点击事件获得到IP地址和端口号，然后通过创建一个ConnectThread类对象并调用里面的run()方法实现TCP连接。该类的代码如下：

private class ConnectThread extends Thread {
        private String ip;
        private int port;
        public ConnectThread(String ip, int port) {
            this.ip = ip;
            this.port = port;
        }
        @Override
        public void run() {
            try {
                mSocket = new Socket(ip, port);
                out = new PrintStream(mSocket.getOutputStream());
                mBufferedReader = new BufferedReader(new InputStreamReader(mSocket.getInputStream()));
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        mBtn_turn.setText("断开");
                        Toast.makeText(MainActivity.this, "连接成功", Toast.LENGTH_SHORT).show();
                    }
                });
            } catch (IOException e) {
                e.printStackTrace();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(MainActivity.this, "连接失败", Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }
    }

在run()方法中不仅建立了连接，而且还获得了该连接的输出流对象 out （用于APP向单片机发送数据）和输入流对象 mBufferedReader （用于APP接收单片机发来的数据）。

3.APP发送数据

在上文中得到了输出流对象 out，利用它的print()和flush()方法完成数据的发送，代码如下：

case R.id.btn_send:
                final String str = mSend_text.getText().toString();
                if (str != null && out != null) {
                    new Thread(new Runnable() {
                        @Override
                        public void run() {
                            out.print(str);
                            out.flush();
                        }
                    }).start();

                }
                break;

4.APP接收数据

在这里本文使用了定时器，设置每隔一段时间就去判断数据输入流对象mBufferedReader的方法ready()，从而得知是否有数据到来了，如果有就存入到一个全局变量中，然后通过Handler对象发送消息，进而实现在UI线程中更新TextView控件，代码如下：

private class ReceiveDataTask extends TimerTask {
        @Override
        public void run() {
            try {
                if (mBufferedReader != null && (mBufferedReader.ready())) {
                    char[] readbuff = new char[30];
                    byte[] readByte = new byte[30];
                    mBufferedReader.read(readbuff, 0, readbuff.length);
                    tempStrng = String.valueOf(readbuff);
                    readByte = tempStrng.getBytes();
                    readStrng = new String(readByte, 0, readByte.length, "GB2312");
                    Message message = Message.obtain();
                    message.what = 1212;
                    mHandler.sendMessage(message);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }

    private void startTimer() {
        Log.i(TAG, "startTimer:");
        if (mTimer == null) {
            mTimer = new Timer();
        }
        if (mReceiveDataTask == null) {
            mReceiveDataTask = new ReceiveDataTask();
        }
        mTimer.schedule(mReceiveDataTask, 0, 10);
    }

    private void stopTimer() {
        Log.i(TAG, "stopTimer: ");
        if (mReceiveDataTask != null) {
            mReceiveDataTask.cancel();
            mReceiveDataTask = null;
        }
        if (mTimer != null) {
            mTimer.cancel();
            mTimer = null;
        }
    }

消息处理代码如下：

private class myHandler extends Handler {
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
                case 1212:
                    mSend_text_dis.setText(readStrng);
                    break;
            }
        }
    }

开启定时器和关闭定时器代码如下：

    @Override
    protected void onStart() {
        super.onStart();
        startTimer();
    }

    @Override
    protected void onStop() {
        super.onStop();
        stopTimer();
    }