功能说明

该程序主要实现蓝牙通信。具体功能有：
1、搜索附近蓝牙设备，并且能手动与周围设备发起蓝牙通信请求。
2、通信请求建立后，双方可以通过蓝牙进行文字的聊天。
3、用户可自定义自己的蓝牙设备是否能被周围的人发现。

项目结构

核心代码

/*MainActivity*/

public class BluetoothChat extends AppCompatActivity {

    public static final int MESSAGE_STATE_CHANGE = 1;
    public static final int MESSAGE_READ = 2;
    public static final int MESSAGE_WRITE = 3;
    public static final int MESSAGE_DEVICE_NAME = 4;
    public static final int MESSAGE_TOAST = 5;
    public static final String DEVICE_NAME = "device_name";
    public static final String TOAST = "toast";
    private static final int REQUEST_CONNECT_DEVICE = 1;  //请求连接设备
    private static final int REQUEST_ENABLE_BT = 2;
    private TextView mTitle;
    private ListView mConversationView;
    private EditText mOutEditText;
    private Button mSendButton;
    private String mConnectedDeviceName = null;
    private ArrayAdapter<String> mConversationArrayAdapter;
    private StringBuffer mOutStringBuffer;
    private BluetoothAdapter mBluetoothAdapter = null;
    private ChatService mChatService = null;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportActionBar().hide();  //隐藏标题栏
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1);
            }
        }
        Toolbar toolbar = findViewById(R.id.toolbar);
        //创建选项菜单
        toolbar.inflateMenu(R.menu.option_menu);
        //选项菜单监听
        toolbar.setOnMenuItemClickListener(new MyMenuItemClickListener());
        mTitle = findViewById(R.id.title_left_text);
        mTitle.setText(R.string.app_name);
        mTitle = findViewById(R.id.title_right_text);
        // 得到本地蓝牙适配器
        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBluetoothAdapter == null) {
            Toast.makeText(this, "蓝牙不可用", Toast.LENGTH_LONG).show();
            finish();
            return;
        }
        if (!mBluetoothAdapter.isEnabled()) { //若当前设备蓝牙功能未开启
            Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT); //
        } else {
            if (mChatService == null) {
                setupChat();  //创建会话
            }
        }
    }
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(grantResults.length>0){
            if(grantResults[0]!=PackageManager.PERMISSION_GRANTED){
                Toast.makeText(this, "未授权，蓝牙搜索功能将不可用！", Toast.LENGTH_SHORT).show();
            }
        }
    }
    @Override
    public synchronized void onResume() {  //synchronized：同步方法实现排队调用
        super.onResume();
        if (mChatService != null) {
            if (mChatService.getState() == ChatService.STATE_NONE) {
                mChatService.start();
            }
        }
    }
    private void setupChat() {
        mConversationArrayAdapter = new ArrayAdapter<String>(this, R.layout.message);
        mConversationView = findViewById(R.id.in);
        mConversationView.setAdapter(mConversationArrayAdapter);
        mOutEditText = findViewById(R.id.edit_text_out);
        mOutEditText.setOnEditorActionListener(mWriteListener);
        mSendButton = findViewById(R.id.button_send);
        mSendButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                TextView view = findViewById(R.id.edit_text_out);
                String message = view.getText().toString();
                sendMessage(message);
            }
        });
        //创建服务对象
        mChatService = new ChatService(this,mHandler);
        mOutStringBuffer = new StringBuffer("");
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        if (mChatService != null)
            mChatService.stop();
    }
    private void ensureDiscoverable() { //修改本机蓝牙设备的可见性
        //打开手机蓝牙后，能被其它蓝牙设备扫描到的时间不是永久的
        if (mBluetoothAdapter.getScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
            Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
            //设置在300秒内可见（能被扫描）
            discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
            startActivity(discoverableIntent);
            Toast.makeText(this, "已经设置本机蓝牙设备的可见性，对方可搜索了。", Toast.LENGTH_SHORT).show();
        }
    }
    private void sendMessage(String message) {
        if (mChatService.getState() != ChatService.STATE_CONNECTED) {
            Toast.makeText(this, R.string.not_connected, Toast.LENGTH_SHORT).show();
            return;
        }
        if (message.length() > 0) {
            byte[] send = message.getBytes();
            mChatService.write(send);
            mOutStringBuffer.setLength(0);
            mOutEditText.setText(mOutStringBuffer);
        }
    }
    private TextView.OnEditorActionListener mWriteListener = new TextView.OnEditorActionListener() {
        @Override
        public boolean onEditorAction(TextView view, int actionId, KeyEvent event) {
            if (actionId == EditorInfo.IME_NULL && event.getAction() == KeyEvent.ACTION_UP) {
                //软键盘里的回车也能发送消息
                String message = view.getText().toString();
                sendMessage(message);
            }
            return true;
        }
    };
    //使用Handler对象在UI主线程与子线程之间传递消息
    private final Handler mHandler = new Handler() {   //消息处理
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MESSAGE_STATE_CHANGE:
                    switch (msg.arg1) {
                        case ChatService.STATE_CONNECTED:
                            mTitle.setText(R.string.title_connected_to);
                            mTitle.append(mConnectedDeviceName);
                            mConversationArrayAdapter.clear();
                            break;
                        case ChatService.STATE_CONNECTING:
                            mTitle.setText(R.string.title_connecting);
                            break;
                        case ChatService.STATE_LISTEN:
                        case ChatService.STATE_NONE:
                            mTitle.setText(R.string.title_not_connected);
                            break;
                    }
                    break;
                case MESSAGE_WRITE:
                    byte[] writeBuf = (byte[]) msg.obj;
                    String writeMessage = new String(writeBuf);
                    mConversationArrayAdapter.add("我:  " + writeMessage);
                    break;
                case MESSAGE_READ:
                    byte[] readBuf = (byte[]) msg.obj;
                    String readMessage = new String(readBuf, 0, msg.arg1);
                    mConversationArrayAdapter.add(mConnectedDeviceName + ":  "
                            + readMessage);
                    break;
                case MESSAGE_DEVICE_NAME:
                    mConnectedDeviceName = msg.getData().getString(DEVICE_NAME);
                    Toast.makeText(getApplicationContext(),"链接到 " + mConnectedDeviceName, Toast.LENGTH_SHORT).show();
                    break;
                case MESSAGE_TOAST:
                    Toast.makeText(getApplicationContext(),
                            msg.getData().getString(TOAST), Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    };
    //返回进入好友列表操作后的数回调方法
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case REQUEST_CONNECT_DEVICE:
                if (resultCode == Activity.RESULT_OK) {
                    String address = data.getExtras().getString(DeviceList.EXTRA_DEVICE_ADDRESS);
                    BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
                    mChatService.connect(device);
                } else if (resultCode == Activity.RESULT_CANCELED) {
                    Toast.makeText(this, "未选择任何好友！", Toast.LENGTH_SHORT).show();
                }
                break;
            case REQUEST_ENABLE_BT:
                if (resultCode == Activity.RESULT_OK) {
                    setupChat();
                } else {
                    Toast.makeText(this, R.string.bt_not_enabled_leaving, Toast.LENGTH_SHORT).show();
                    finish();
                }
        }
    }
    //内部类，选项菜单的单击事件处理
    private class MyMenuItemClickListener implements Toolbar.OnMenuItemClickListener {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            switch (item.getItemId()) {
                case R.id.scan:
                    //启动DeviceList这个Activity
                    Intent serverIntent = new Intent(BluetoothChat.this, DeviceList.class);
                    startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE);
                    return true;
                case R.id.discoverable:
                    ensureDiscoverable();
                    return true;
                case R.id.back:
                    finish();
                    System.exit(0);
                    return true;
            }
            return false;
        }
    }
}

/*聊天界面ChatService*/

public class ChatService {
    //本应用的主Activity组件名称
    private static final String NAME = "BluetoothChat";
    // UUID：通用唯一识别码,是一个128位长的数字，一般用十六进制表示
    //算法的核心思想是结合机器的网卡、当地时间、一个随机数来生成
    //在创建蓝牙连接
    private static final UUID MY_UUID = UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66");
    private final BluetoothAdapter mAdapter;
    private final Handler mHandler;
    private AcceptThread mAcceptThread;
    private ConnectThread mConnectThread;
    private ConnectedThread mConnectedThread;
    private int mState;
    public static final int STATE_NONE = 0;
    public static final int STATE_LISTEN = 1;
    public static final int STATE_CONNECTING = 2;
    public static final int STATE_CONNECTED = 3;

    //构造方法，接收UI主线程传递的对象
    public ChatService(Context context, Handler handler) {
        //构造方法完成蓝牙对象的创建
        mAdapter = BluetoothAdapter.getDefaultAdapter();
        mState = STATE_NONE;
        mHandler = handler;
    }

    private synchronized void setState(int state) {
        mState = state;
        mHandler.obtainMessage(BluetoothChat.MESSAGE_STATE_CHANGE, state, -1).sendToTarget();
    }

    public synchronized int getState() {
        return mState;
    }

    public synchronized void start() {
        if (mConnectThread != null) {
            mConnectThread.cancel();
            mConnectThread = null;
        }
        if (mConnectedThread != null) {
            mConnectedThread.cancel();
            mConnectedThread = null;
        }
        if (mAcceptThread == null) {
            mAcceptThread = new AcceptThread();
            mAcceptThread.start();
        }
        setState(STATE_LISTEN);
    }

    //取消 CONNECTING 和 CONNECTED 状态下的相关线程，然后运行新的 mConnectThread 线程
    public synchronized void connect(BluetoothDevice device) {
        if (mState == STATE_CONNECTING) {
            if (mConnectThread != null) {
                mConnectThread.cancel();
                mConnectThread = null;
            }
        }
        if (mConnectedThread != null) {
            mConnectedThread.cancel();
            mConnectedThread = null;
        }
        mConnectThread = new ConnectThread(device);
        mConnectThread.start();
        setState(STATE_CONNECTING);
    }

    /*
        开启一个 ConnectedThread 来管理对应的当前连接。之前先取消任意现存的 mConnectThread 、
        mConnectedThread 、 mAcceptThread 线程，然后开启新 mConnectedThread ，传入当前刚刚接受的
        socket 连接。最后通过 Handler来通知UI连接
     */
    public synchronized void connected(BluetoothSocket socket, BluetoothDevice device) {
        if (mConnectThread != null) {
            mConnectThread.cancel();
            mConnectThread = null;
        }
        if (mConnectedThread != null) {
            mConnectedThread.cancel();
            mConnectedThread = null;
        }
        if (mAcceptThread != null) {
            mAcceptThread.cancel();
            mAcceptThread = null;
        }
        mConnectedThread = new ConnectedThread(socket);
        mConnectedThread.start();
        Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_DEVICE_NAME);
        Bundle bundle = new Bundle();
        bundle.putString(BluetoothChat.DEVICE_NAME, device.getName());
        msg.setData(bundle);
        mHandler.sendMessage(msg);
        setState(STATE_CONNECTED);
    }

    // 停止所有相关线程，设当前状态为 NONE
    public synchronized void stop() {
        if (mConnectThread != null) {
            mConnectThread.cancel();
            mConnectThread = null;
        }
        if (mConnectedThread != null) {
            mConnectedThread.cancel();
            mConnectedThread = null;
        }
        if (mAcceptThread != null) {
            mAcceptThread.cancel();
            mAcceptThread = null;
        }
        setState(STATE_NONE);
    }

    // 在 STATE_CONNECTED 状态下，调用 mConnectedThread 里的 write 方法，写入 byte
    public void write(byte[] out) {
        ConnectedThread r;
        synchronized (this) {
            if (mState != STATE_CONNECTED)
                return;
            r = mConnectedThread;
        }
        r.write(out);
    }

    // 连接失败的时候处理，通知 ui ，并设为 STATE_LISTEN 状态
    private void connectionFailed() {
        setState(STATE_LISTEN);
        Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(BluetoothChat.TOAST, "链接不到设备");
        msg.setData(bundle);
        mHandler.sendMessage(msg);
    }

    // 当连接失去的时候，设为 STATE_LISTEN 状态并通知 ui
    private void connectionLost() {
        setState(STATE_LISTEN);
        Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(BluetoothChat.TOAST, "设备链接中断");
        msg.setData(bundle);
        mHandler.sendMessage(msg);
    }

    // 创建监听线程，准备接受新连接。使用阻塞方式，调用 BluetoothServerSocket.accept()
    private class AcceptThread extends Thread {
        private final BluetoothServerSocket mmServerSocket;

        public AcceptThread() {
            BluetoothServerSocket tmp = null;
            try {
                //使用射频端口（RF comm）监听
                tmp = mAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
            } catch (IOException e) {
            }
            mmServerSocket = tmp;
        }

        @Override
        public void run() {
            setName("AcceptThread");
            BluetoothSocket socket = null;
            while (mState != STATE_CONNECTED) {
                try {
                    socket = mmServerSocket.accept();
                } catch (IOException e) {
                    break;
                }
                if (socket != null) {
                    synchronized (ChatService.this) {
                        switch (mState) {
                            case STATE_LISTEN:
                            case STATE_CONNECTING:
                                connected(socket, socket.getRemoteDevice());
                                break;
                            case STATE_NONE:
                            case STATE_CONNECTED:
                                try {
                                    socket.close();
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }
                                break;
                        }
                    }
                }
            }
        }

        public void cancel() {
            try {
                mmServerSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /*
        连接线程，专门用来对外发出连接对方蓝牙的请求和处理流程。
        构造函数里通过 BluetoothDevice.createRfcommSocketToServiceRecord() ，
        从待连接的 device 产生 BluetoothSocket. 然后在 run 方法中 connect ，
        成功后调用 BluetoothChatSevice 的 connected() 方法。定义 cancel() 在关闭线程时能够关闭相关socket 。
     */
    private class ConnectThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final BluetoothDevice mmDevice;

        public ConnectThread(BluetoothDevice device) {
            mmDevice = device;
            BluetoothSocket tmp = null;
            try {
                tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
            } catch (IOException e) {
                e.printStackTrace();
            }
            mmSocket = tmp;
        }

        @Override
        public void run() {
            setName("ConnectThread");
            mAdapter.cancelDiscovery();
            try {
                mmSocket.connect();
            } catch (IOException e) {
                connectionFailed();
                try {
                    mmSocket.close();
                } catch (IOException e2) {
                    e.printStackTrace();
                }
                ChatService.this.start();
                return;
            }
            synchronized (ChatService.this) {
                mConnectThread = null;
            }
            connected(mmSocket, mmDevice);
        }

        public void cancel() {
            try {
                mmSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /*
        双方蓝牙连接后一直运行的线程；构造函数中设置输入输出流。
        run()方法中使用阻塞模式的 InputStream.read()循环读取输入流，然后发送到 UI 线程中更新聊天消息。
        本线程也提供了 write() 将聊天消息写入输出流传输至对方，传输成功后回写入 UI 线程。最后使用cancel()关闭连接的 socket
     */
    private class ConnectedThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket) {
            mmSocket = socket;
            InputStream tmpIn = null;
            OutputStream tmpOut = null;
            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
                e.printStackTrace();
            }
            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        @Override
        public void run() {
            byte[] buffer = new byte[1024];
            int bytes;
            while (true) {
                try {
                    bytes = mmInStream.read(buffer);
                    mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer).sendToTarget();
                } catch (IOException e) {
                    connectionLost();
                    break;
                }
            }
        }

        public void write(byte[] buffer) {
            try {
                mmOutStream.write(buffer);
                mHandler.obtainMessage(BluetoothChat.MESSAGE_WRITE, -1, -1, buffer).sendToTarget();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public void cancel() {
            try {
                mmSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

activity布局效果：

结果展示

这个程序在虚拟机上跑是看不出效果的，所以最好连接一下真机，具体安卓连接真机可以参考这一篇11111111111
连接上真机后，不用打开设备管理器查看手机，直接打开AS，会看到我的华为：

在真机上就是这么个效果：

这是本人的gitee
本人的gitee
参考链接：
http://www.wustwzx.com/as/sy/sy09.html#mk2