简单的BlueTooth通信案例

记录一下自己的作业案例，这次作业感觉没运行出来，一开始在虚拟机调试，发现运行闪退。然后在真机上运行，安装上程序后也是有闪退的现象，也不知道哪出问题了真是没办法了。下面是一个在编译器显示的结果：
1、在AndroidManifest.xml文件中添加权限

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

2、在文件res/values/strings.xml里，添加程序运行过程中的状态描述文本及配色代码等

<resources>
<!--    <string name="app_name">BlueTooth</string>-->
    <string name="app_name">蓝牙Demo</string>
    <string name="send">发送</string>
    <string name="not_connected">你没有链接一个设备</string>
    <string name="bt_not_enabled_leaving">蓝牙不可用，离开聊天室</string>
    <string name="title_connecting">链接中...</string>
    <string name="title_connected_to">连接到：</string>
    <string name="title_not_connected">无链接</string>
    <string name="scanning">蓝牙设备搜索中...</string>
    <string name="select_device">选择一个好友链接</string>
    <string name="none_paired">没有配对好友</string>
    <string name="none_found">附近没有发现好友</string>
    <string name="title_paired_devices">已配对好友</string>
    <string name="title_other_devices">其它可连接好友</string>
    <string name="button_scan">搜索好友</string>
    <string name="connect">我的好友</string>
    <string name="discoverable">设置在线</string>
    <string name="back">退出</string>
    <string name="startVideo">开始聊天</string>
    <string name="stopVideo">结束聊天</string>
</resources>

3、编写activity_main.xml，添加Toolbar控件，Toolbar可能会出现版本的问题导致错误 。包含2个水平的TextView控件，在Toolbar控件的下方添加1个ListView控件，显示聊天内容。在ListView控件的下方添加水平放置的1个EditText控件和一个Button控件。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/bg01">

    <!--新版Android支持的Toolbar，对标题栏布局-->
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal">
            <TextView
                android:id="@+id/title_left_text"
                style="?android:attr/windowTitleStyle"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_alignParentLeft="true"
                android:layout_weight="1"
                android:gravity="left"
                android:ellipsize="end"
                android:singleLine="true" />
            <TextView
                android:id="@+id/title_right_text"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_alignParentRight="true"
                android:layout_weight="1"
                android:ellipsize="end"
                android:gravity="right"
                android:singleLine="true"
                android:textColor="#fff" />
        </LinearLayout>
    </android.support.v7.widget.Toolbar>

    <ListView android:id="@+id/in"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:stackFromBottom="true"
        android:transcriptMode="alwaysScroll"
        android:layout_weight="1" />
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
        <EditText android:id="@+id/edit_text_out"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="bottom" />
        <Button android:id="@+id/button_send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/send"/>
    </LinearLayout>
</LinearLayout>

4、创建组件ChatService

public class ChatService {
    //本应用的主Activity组件名称
    private static final String NAME = "BluetoothChat";
    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;

    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(MainActivity.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);
    }
    
    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(MainActivity.MESSAGE_DEVICE_NAME);
        Bundle bundle = new Bundle();
        bundle.putString(MainActivity.DEVICE_NAME, device.getName());
        msg.setData(bundle);
        mHandler.sendMessage(msg);
        setState(STATE_CONNECTED);
    }

    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);
    }

    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(MainActivity.MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(MainActivity.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(MainActivity.MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(MainActivity.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();
            }
        }
    }

    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();
            }
        }
    }
    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(MainActivity.MESSAGE_READ, bytes, -1, buffer).sendToTarget();
                } catch (IOException e) {
                    connectionLost();
                    break;
                }
            }
        }

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

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

5、创建组件DeviceList，实现选取相关的蓝牙设备

public class DeviceList extends AppCompatActivity {
    private BluetoothAdapter mBtAdapter;
    private ArrayAdapter<String> mPairedDevicesArrayAdapter;
    private ArrayAdapter<String> mNewDevicesArrayAdapter;
    public static String EXTRA_DEVICE_ADDRESS = "device_address";  //Mac地址
    //定义广播接收者，用于处理扫描蓝牙设备后的结果
    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
                    mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
                }
            } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                if (mNewDevicesArrayAdapter.getCount() == 0) {
                    String noDevices = getResources().getText(R.string.none_found).toString();
                    mNewDevicesArrayAdapter.add(noDevices);
                }
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.device_list);
        //在被调用活动里，设置返回结果码
        setResult(Activity.RESULT_CANCELED);
        init();  //活动界面
    }
    private void init() {
        Button scanButton = findViewById(R.id.button_scan);
        scanButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Toast.makeText(DeviceList.this, R.string.scanning, Toast.LENGTH_LONG).show();
                doDiscovery();  //搜索蓝牙设备
            }
        });
        mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
        mNewDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
        //已配对蓝牙设备列表
        ListView pairedListView =findViewById(R.id.paired_devices);
        pairedListView.setAdapter(mPairedDevicesArrayAdapter);
        pairedListView.setOnItemClickListener(mPaireDeviceClickListener);
        //未配对蓝牙设备列表
        ListView newDevicesListView = findViewById(R.id.new_devices);
        newDevicesListView.setAdapter(mNewDevicesArrayAdapter);
        newDevicesListView.setOnItemClickListener(mNewDeviceClickListener);
        //动态注册广播接收者
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(mReceiver, filter);
        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        registerReceiver(mReceiver, filter);
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();
        Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();
        if (pairedDevices.size() > 0) {
            findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
            for (BluetoothDevice device : pairedDevices) {
                mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            }
        } else {
            String noDevices = getResources().getText(R.string.none_paired).toString();
            mPairedDevicesArrayAdapter.add(noDevices);
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (mBtAdapter != null) {
            mBtAdapter.cancelDiscovery();
        }
        this.unregisterReceiver(mReceiver);
    }
    private void doDiscovery() {
        findViewById(R.id.title_new_devices).setVisibility(View.VISIBLE);
        if (mBtAdapter.isDiscovering()) {
            mBtAdapter.cancelDiscovery();
        }
        mBtAdapter.startDiscovery();  //开始搜索蓝牙设备并产生广
    }
    private AdapterView.OnItemClickListener mPaireDeviceClickListener = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
            mBtAdapter.cancelDiscovery();
            String info = ((TextView) v).getText().toString();
            String address = info.substring(info.length() - 17);
            Intent intent = new Intent();
            intent.putExtra(EXTRA_DEVICE_ADDRESS, address);  //Mac地址
            setResult(Activity.RESULT_OK, intent);
            finish();
        }
    };
    private AdapterView.OnItemClickListener mNewDeviceClickListener = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
            mBtAdapter.cancelDiscovery();
            Toast.makeText(DeviceList.this, "请在蓝牙设置界面手动连接设备",Toast.LENGTH_SHORT).show();
            Intent intent = new Intent(Settings.ACTION_BLUETOOTH_SETTINGS);
            startActivityForResult(intent,1);
        }
    };
    //回调方法：进入蓝牙配对设置界面返回后执行
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        init();  //刷新好友列表
    }
}

7、创建组件BluetoothChat，这个是通过BlueTooth进行通信的主要activity程序

public class MainActivity 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 EditText mOutEditText;
    private Button mSendButton;
    private String mConnectedDeviceName = null;
    private ArrayAdapter<String> mConversationArrayAdapter;
    private StringBuffer mOutStringBuffer;
    private BluetoothAdapter mBluetoothAdapter = null;
    private ChatService mChatService = null;
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @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);
        ListView 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) {
        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
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    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(MainActivity.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;
        }
    }
}

代码中有一些简要的注释，稍微解释了下每个模块的功能。
最后需要源码的可以点击此链接下载：源码