判断蓝牙是否连接

Android对于蓝牙开发从2.0版本的sdk才开始支持，而且模拟器不支持，测试至少需要两部手机，所以制约了很多技术人员的开发。
      1.  首先，要操作蓝牙，先要在AndroidManifest.xml里加入权限
  // 管理蓝牙设备的权限  
<uses-permissionandroid:name="android.permission.BLUETOOTH_ADMIN" />
 // 使用蓝牙设备的权限  
<uses-permissionandroid:name="android.permission.BLUETOOTH" />
2.打开蓝牙
获得蓝牙适配器（android.bluetooth.BluetoothAdapter），检查该设备是否支持蓝牙，如果支持，就打开蓝牙。
[java]
// 检查设备是否支持蓝牙      
adapter = BluetoothAdapter.getDefaultAdapter();    
if (adapter == null)    
{    
    // 设备不支持蓝牙      
}    
// 打开蓝牙      
if (!adapter.isEnabled())    
{    
    Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);    
    // 设置蓝牙可见性，最多300秒      
    intent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);    
    context.startActivity(intent);    
}   
// 检查设备是否支持蓝牙   
adapter = BluetoothAdapter.getDefaultAdapter();  
if (adapter == null)  
{  
    // 设备不支持蓝牙   
}  
// 打开蓝牙   
if (!adapter.isEnabled())  
{  
    Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);  
    // 设置蓝牙可见性，最多300秒   
    intent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);  
    context.startActivity(intent);  
} 
3.获取已配对的蓝牙设备（android.bluetooth.BluetoothDevice）
首次连接某蓝牙设备需要先配对，一旦配对成功，该设备的信息会被保存，以后连接时无需再配对，所以已配对的设备不一定是能连接的。
[java]
BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();    
Set<BluetoothDevice> devices = adapter.getBondedDevices();    
for(int i=0; i<devices.size(); i++)    
{    
    BluetoothDevice device = (BluetoothDevice) devices.iterator().next();    
   System.out.println(device.getName());    
}   
BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();  
Set<BluetoothDevice> devices = adapter.getBondedDevices();  
for(int i=0; i<devices.size(); i++)  
{  
    BluetoothDevice device = (BluetoothDevice) devices.iterator().next();  
   System.out.println(device.getName());  
} 
4.搜索周围的蓝牙设备
适配器搜索蓝牙设备后将结果以广播形式传出去，所以需要自定义一个继承广播的类，在onReceive方法中获得并处理蓝牙设备的搜索结果。
[java]
// 设置广播信息过滤      
IntentFilter intentFilter = new IntentFilter();    
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);    
intentFilter.addAction(BluetoothDevice.ACTION_BOND_STATE_CHANGED);    
intentFilter.addAction(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED);    
intentFilter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);    
// 注册广播接收器，接收并处理搜索结果      
context.registerReceiver(receiver, intentFilter);    
// 寻找蓝牙设备，android会将查找到的设备以广播形式发出去      
adapter.startDiscovery();   
// 设置广播信息过滤   
IntentFilter intentFilter = new IntentFilter();  
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);  
intentFilter.addAction(BluetoothDevice.ACTION_BOND_STATE_CHANGED);  
intentFilter.addAction(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED);  
intentFilter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);  
// 注册广播接收器，接收并处理搜索结果   
context.registerReceiver(receiver, intentFilter);  
// 寻找蓝牙设备，android会将查找到的设备以广播形式发出去   
adapter.startDiscovery();  自定义广播类
[java]
private BroadcastReceiver receiver = 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);    
            System.out.println(device.getName());    
       }    
   }    
} 
private BroadcastReceiver receiver = 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);  
            System.out.println(device.getName());  
       }  
   }  
}
5.蓝牙设备的配对和状态监视
[java]
private BroadcastReceiver receiver = new BroadcastReceiver() {    
    @Override    
    public void onReceive(Context context, Intent intent) {    
        String action = intent.getAction();    
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {    
            // 获取查找到的蓝牙设备      
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);    
            System.out.println(device.getName());    
            // 如果查找到的设备符合要连接的设备，处理      
            if (device.getName().equalsIgnoreCase(name)) {    
                // 搜索蓝牙设备的过程占用资源比较多，一旦找到需要连接的设备后需要及时关闭搜索      
                adapter.cancelDiscovery();    
                // 获取蓝牙设备的连接状态      
                connectState = device.getBondState();    
                switch (connectState) {    
                    // 未配对      
                    case BluetoothDevice.BOND_NONE:    
                        // 配对      
                        try {    
                            Method createBondMethod = BluetoothDevice.class.getMethod("createBond");    
                            createBondMethod.invoke(device);    
                        } catch (Exception e) {     
                            e.printStackTrace();    
                        }    
                        break;    
                    // 已配对      
                    case BluetoothDevice.BOND_BONDED:    
                        try {    
                            // 连接      
                           connect(device);    
                        } catch (IOException e) {    
                            e.printStackTrace();    
                        }    
                        break;    
                }    
            }    
       } else if(BluetoothDevice.ACTION_BOND_STATE_CHANGED.equals(action)) {    
            // 状态改变的广播      
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);    
            if (device.getName().equalsIgnoreCase(name)) {     
                connectState = device.getBondState();    
                switch (connectState) {    
                    case BluetoothDevice.BOND_NONE:    
                        break;    
                    case BluetoothDevice.BOND_BONDING:    
                        break;    
                    case BluetoothDevice.BOND_BONDED:    
                        try {    
                            // 连接      
                            connect(device);    
                        } catch (IOException e) {    
                            e.printStackTrace();    
                        }    
                        break;    
                }    
            }    
        }    
    }    
}   
private BroadcastReceiver receiver = new BroadcastReceiver() {  
    @Override  
    public void onReceive(Context context, Intent intent) {  
        String action = intent.getAction();  
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {  
            // 获取查找到的蓝牙设备   
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);  
            System.out.println(device.getName());  
            // 如果查找到的设备符合要连接的设备，处理   
            if (device.getName().equalsIgnoreCase(name)) {  
                // 搜索蓝牙设备的过程占用资源比较多，一旦找到需要连接的设备后需要及时关闭搜索   
                adapter.cancelDiscovery();  
                // 获取蓝牙设备的连接状态   
                connectState = device.getBondState();  
                switch (connectState) {  
                    // 未配对   
                    case BluetoothDevice.BOND_NONE:  
                        // 配对   
                        try {  
                            Method createBondMethod = BluetoothDevice.class.getMethod("createBond");  
                            createBondMethod.invoke(device);  
                        } catch (Exception e) {   
                            e.printStackTrace();  
                        }  
                        break;  
                    // 已配对   
                    case BluetoothDevice.BOND_BONDED:  
                        try {  
                            // 连接   
                           connect(device);  
                        } catch (IOException e) {  
                            e.printStackTrace();  
                        }  
                        break;  
                }  
            }  
       } else if(BluetoothDevice.ACTION_BOND_STATE_CHANGED.equals(action)) {  
            // 状态改变的广播   
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);  
            if (device.getName().equalsIgnoreCase(name)) {   
                connectState = device.getBondState();  
                switch (connectState) {  
                    case BluetoothDevice.BOND_NONE:  
                        break;  
                    case BluetoothDevice.BOND_BONDING:  
                        break;  
                    case BluetoothDevice.BOND_BONDED:  
                        try {  
                            // 连接   
                            connect(device);  
                        } catch (IOException e) {  
                            e.printStackTrace();  
                        }  
                        break;  
                }  
            }  
        }  
    }  
}  6.蓝牙设备的连接
[java]
private void connect(BluetoothDevice device) throws IOException {    
    // 固定的UUID      
    final String SPP_UUID = "00001101-0000-1000-8000-00805F9B34FB";    
    UUID uuid = UUID.fromString(SPP_UUID);    
    BluetoothSocket socket = device.createRfcommSocketToServiceRecord(uuid);    
    socket.connect();    
}   
private void connect(BluetoothDevice device) throws IOException {  
    // 固定的UUID   
    final String SPP_UUID = "00001101-0000-1000-8000-00805F9B34FB";  
    UUID uuid = UUID.fromString(SPP_UUID);  
    BluetoothSocket socket = device.createRfcommSocketToServiceRecord(uuid);  
    socket.connect();  
}