添加蓝牙权限

 <!--下面2个是普通权限，只需要在清单文件里注册，不需要在程序里动态申请--><uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /><uses-permission android:name="android.permission.BLUETOOTH" />

在文件res/values/strings.xml里，添加程序运行过程中的状态描述文本

<?xml version="1.0" encoding="utf-8"?>
<resources><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>

编写布局文件添加一个

使用垂直线性布局并嵌套水平线性布局实现，添加，添加1个Toolbar控件，其内包含2个水平的TextView控件；在Toolbar控件的下方添加1个ListView控件，用于显示聊天内容；最后在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"><!--新版Android支持的Toolbar，对标题栏布局--><androidx.appcompat.widget.Toolbarandroid:id="@+id/toolbar"android:layout_width="match_parent"android:layout_height="wrap_content"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="horizontal"><TextViewandroid: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" /><TextViewandroid: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></androidx.appcompat.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" /><LinearLayoutandroid: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>

编写用于蓝牙会话的服务组件ChatService

定义了3个内部类：AcceptThread（接受新连接）、ConnectThread（发出连接）和ConnectedThread （已连接）

AcceptThread

 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;}@Overridepublic 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();}}}

ConnectThread

    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;}@Overridepublic 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();}}}

ConnectedThread

    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;}@Overridepublic 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();}}}

建立供BluetoothChat使用的菜单文件optionmenu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"><item android:id="@+id/scan"android:icon="@android:drawable/ic_menu_myplaces"android:title="@string/connect" /><item android:id="@+id/discoverable"android:icon="@android:drawable/ic_menu_view"android:title="@string/discoverable" /><item android:id="@+id/back"android:icon="@android:drawable/ic_menu_close_clear_cancel"android:title="@string/back" />
</menu>

新建组件DeviceList，实现选取与之会话的蓝牙设备

本程序供菜单项主界面的选项菜单“我的友好”调用，用于：
（1）显示已配对的好友列表；
（2）搜索可配对的好友进行配对
（3）新选择并配对的蓝牙设备将刷新好友列表
定义已配对和未配对的蓝牙设备列表

        //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);

关键技术：动态注册一个广播接收者，处理蓝牙设备扫描的结果

//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);}

其中两个监听事件mPaireDeviceClickListener，mNewDeviceClickListener为

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);}};

使用菜单File→Refactor→Rename，重命名模块的MainActivity为BluetoothChat

实验步骤：
（1）在两个手机分别安装、运行本应用。如果未打开手机蓝牙，则进入打开蓝牙设置界面；
（2）在OptionMenu（选项菜单）里，选择“我的好友”，即可直接连接，再进行会话；
（3）新建好友前，需要先使用选项菜单“设置在线”，即要求对方可见（能被扫描到）。
然后，单击“搜索好友”按钮。

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}}

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@Overridepublic 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();}}}

附加device_name和message两个xml文件

两个文件只需要添加一个TextView组件即可

<TextView xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="wrap_content"android:textSize="18sp"android:padding="5dp"/>

实验代码

BlueToothChat.