如何以编程方式判断是否已连接蓝牙设备？

Question 1

我了解如何获取已配对设备的列表，但是如何知道它们是否已连接？

由于我在手机的蓝牙设备列表中看到了它们，并指出了它们的连接状态，因此这是必须的。

Question 2

向您的AndroidManifest添加蓝牙权限，

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

然后使用意图过滤器来听ACTION_ACL_CONNECTED，ACTION_ACL_DISCONNECT_REQUESTED和ACTION_ACL_DISCONNECTED广播：

public void onCreate() {
    ...
    IntentFilter filter = new IntentFilter();
    filter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
    filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECT_REQUESTED);
    filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
    this.registerReceiver(mReceiver, filter);
}

//The BroadcastReceiver that listens for bluetooth broadcasts
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
           ... //Device found
        }
        else if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
           ... //Device is now connected
        }
        else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
           ... //Done searching
        }
        else if (BluetoothDevice.ACTION_ACL_DISCONNECT_REQUESTED.equals(action)) {
           ... //Device is about to disconnect
        }
        else if (BluetoothDevice.ACTION_ACL_DISCONNECTED.equals(action)) {
           ... //Device has disconnected
        }           
    }
};

一些注意事项：

在应用程序启动时无法检索已连接设备的列表。蓝牙API不允许您查询，而是允许您收听更改。
解决上述问题的一项繁琐工作是检索所有已知/已配对设备的列表……然后尝试连接到每个设备（以确定是否已连接）。
或者，您可以让后台服务监视Bluetooth API并将设备状态写入磁盘，以供您的应用程序以后使用。

Question 3

在我的用例中，我只想查看是否为VoIP应用程序连接了蓝牙耳机。以下解决方案为我工作：

public static boolean isBluetoothHeadsetConnected() {
    BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    return mBluetoothAdapter != null && mBluetoothAdapter.isEnabled()
            && mBluetoothAdapter.getProfileConnectionState(BluetoothHeadset.HEADSET) == BluetoothHeadset.STATE_CONNECTED;
}

当然，您需要蓝牙许可：

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

Question 4

非常感谢Skylarsutton的回答。我将其发布为对他的回应，但由于我正在发布代码，因此无法作为评论回复。我已经赞成他的回答，所以我不在寻找任何要点。只是支付它。

由于某些原因，Android Studio无法解析BluetoothAdapter.ACTION_ACL_CONNECTED。也许在Android 4.2.2中已弃用？这是他的代码的修改。注册码是一样的；接收方代码略有不同。我在一项服务中使用了此服务，该服务会更新该应用程序其他部分引用的蓝牙连接标志。

    public void onCreate() {
        //...
        IntentFilter filter = new IntentFilter();
        filter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
        filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECT_REQUESTED);
        filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
        this.registerReceiver(BTReceiver, filter);
    }

    //The BroadcastReceiver that listens for bluetooth broadcasts
    private final BroadcastReceiver BTReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
            //Do something if connected
            Toast.makeText(getApplicationContext(), "BT Connected", Toast.LENGTH_SHORT).show();
        }
        else if (BluetoothDevice.ACTION_ACL_DISCONNECTED.equals(action)) {
            //Do something if disconnected
            Toast.makeText(getApplicationContext(), "BT Disconnected", Toast.LENGTH_SHORT).show();
        }
        //else if...
    }
};

Question 5

https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/bluetooth/BluetoothDevice.java中的BluetoothDevice系统API中有一个isConnected函数。

如果您想知道有界（配对）设备当前是否已连接，以下功能对我来说很好：

public static boolean isConnected(BluetoothDevice device) {
    try {
        Method m = device.getClass().getMethod("isConnected", (Class[]) null);
        boolean connected = (boolean) m.invoke(device, (Object[]) null);
        return connected;
    } catch (Exception e) {
        throw new IllegalStateException(e);
    }
}

Question 6

该代码用于耳机配置文件，可能也适用于其他配置文件。首先，您需要提供配置文件侦听器（科特琳代码）：

private val mProfileListener = object : BluetoothProfile.ServiceListener {
    override fun onServiceConnected(profile: Int, proxy: BluetoothProfile) {
        if (profile == BluetoothProfile.HEADSET) 
            mBluetoothHeadset = proxy as BluetoothHeadset            
    }

    override fun onServiceDisconnected(profile: Int) {
        if (profile == BluetoothProfile.HEADSET) {
            mBluetoothHeadset = null
        }
    }
}

然后在检查蓝牙时：

mBluetoothAdapter.getProfileProxy(context, mProfileListener, BluetoothProfile.HEADSET)
if (!mBluetoothAdapter.isEnabled) {
    return Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
}

在调用onSeviceConnected之前需要花费一些时间。之后，您可以从以下位置获取已连接的耳机设备的列表：

mBluetoothHeadset!!.connectedDevices

Question 7

BluetoothAdapter.getDefaultAdapter().isEnabled ->蓝牙打开时返回true

val audioManager = this.getSystemService(Context.AUDIO_SERVICE) as AudioManager

audioManager.isBluetoothScoOn ->连接设备时返回true

Question 8

我确实在寻找一种方法来获取设备的连接状态，而不是监听连接事件。这对我有用：

BluetoothManager bm = (BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
List<BluetoothDevice> devices = bm.getConnectedDevices(BluetoothGatt.GATT);
int status = -1;

for (BluetoothDevice device : devices) {
  status = bm.getConnectionState(device, BLuetoothGatt.GATT);
  // compare status to:
  //   BluetoothProfile.STATE_CONNECTED
  //   BluetoothProfile.STATE_CONNECTING
  //   BluetoothProfile.STATE_DISCONNECTED
  //   BluetoothProfile.STATE_DISCONNECTING
}