安卓BLE快速连接和断开以读取1个特征.一些BLE设备在快速连接断开连接后停止广播

Question

我正在尝试编写一个android应用程序，扫描BLE设备，当它找到具有命名方案的特定设备时，它会连接到它并读取一个特征（设备的用户定义名称），然后立即断开连接。然后，它会将该设备与找到的任何其他设备一起显示在列表中，并读取用户定义的名称。然后，用户可以选择一个要连接的设备（或多个设备）并连接到它并从中流式传输数据

不断发生的问题是，在它获得用户定义的名称并断开连接后，BLE设备停止广播，当我扫描时，或者如果我在读取用户定义的名字并断开与它的连接后尝试连接，我就再也找不到它了。

这是安卓BLE堆栈的问题吗？还是我需要添加更多延迟（我使用的蓝牙服务有100毫秒的延迟）

这是我在服务中使用的部分代码

 public boolean initialize() {
    Log.i(TAG, "Initializing");
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    if (mBluetoothManager == null) {
        mBluetoothManager = (BluetoothManager) getSystemService(BLUETOOTH_SERVICE);
        if (mBluetoothManager == null) {
            Log.e(TAG, "Unable to initialize BluetoothManager.");
            return false;
        }
    }
    mBluetoothAdapter = mBluetoothManager.getAdapter();
    if (mBluetoothAdapter == null) {
        Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
        return false;
    }

    mReadyToWrite = true;
    mReadyToRead = true;
    mReady = true;
    mCharacteristicWriteQueue   = new ArrayDeque<BluetoothGattCharacteristic>();
    mCharacteristicReadQueue    = new ArrayDeque<BluetoothGattCharacteristic>();
    mDescriptorWriteQueue       = new ArrayDeque<BluetoothGattDescriptor>();
    mDescriptorReadQueue        = new ArrayDeque<BluetoothGattDescriptor>();
    //mBluetoothGattMap = new HashMap<String, BluetoothGatt>();
    return true;
}
/**
 * Connects to the GATT server hosted on the Bluetooth LE device.
 *
 * @param address The device address of the device.
 *
 * @return Return true if the connection is initiated successfully. The connection result
 *         is reported asynchronously through the
 *         {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
 *         callback.
 */
public boolean connect(final String address) {
    if (mBluetoothAdapter == null || address == null) {
        Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
        return false;
    }

    if(mBluetoothGattMap.containsKey(address)) {
        Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
        if (mBluetoothGattMap.get(address).connect()) {
            mConnectionState = STATE_CONNECTING;
            return true;
        } else {
            return false;
        }
    }
    final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
    if (device == null) {
        Log.w(TAG, "Device not found.  Unable to connect.");
        return false;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    mBluetoothGattMap.put(address, device.connectGatt(this, false, mGattCallback));

    Log.d(TAG, "Trying to create a new connection to address " + address);
    //mBluetoothDeviceAddress = address;
    mConnectionState = STATE_CONNECTING;
    return true;
}
/**
 * Disconnects an existing connection or cancel a pending connection. The disconnection result
 * is reported asynchronously through the
 * {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
 * callback.
 */
public void disconnect(String address) {
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    Log.i(TAG, "Disconnecting from gatt");
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    mBluetoothGattMap.get(address).disconnect();
}

public void close(String address) {
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    mBluetoothGattMap.get(address).close();
    mBluetoothGattMap.remove(address);
    Log.w(TAG, "Succeeed removing it");
}
public int getConnectionState(String address) {
    Log.i(TAG, "getting connection state for " + address);
    BluetoothGatt gatt = mBluetoothGattMap.get(address);
    return mBluetoothManager.getConnectionState(gatt.getDevice(), BluetoothProfile.GATT);
}
/**
 * Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
 * asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
 * callback.
 *
 * @param characteristic The characteristic to read from.
 */
public void readCharacteristic(String address, BluetoothGattCharacteristic characteristic) {
    Log.i(TAG, "reading characteristic");
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    if(mReadyToRead && mReady) {
        boolean result = mBluetoothGattMap.get(address).readCharacteristic(characteristic);
        mReadyToRead = false;
        mReady = false;
        if(!result) {
            Log.i(TAG, "read failed");
        }
    }else {
        mCharacteristicReadQueue.push(characteristic);
    }
}
public void writeCharacteristic(String address, BluetoothGattCharacteristic characteristic) {
    Log.i(TAG, "writeCharacteristic - readyToWrite = " + mReadyToWrite + " queue size = " + mCharacteristicWriteQueue.size());
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    if(mReadyToWrite && mReady) {
        boolean result = mBluetoothGattMap.get(address).writeCharacteristic(characteristic);
        mReadyToWrite = false;
        mReady = false;
        if(!result) {
            Log.i(TAG, "characteristic write failed");
        }
    }else {
        mCharacteristicWriteQueue.push(characteristic);
    }
}
public void readDescriptor(String address, BluetoothGattDescriptor descriptor) {
    Log.i(TAG, "reading descriptor");
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    if(mReadyToRead && mReady) {
        boolean result = mBluetoothGattMap.get(address).readDescriptor(descriptor);
        mReadyToRead = false;
        mReady = false;
        if(!result) {
            Log.i(TAG, "descriptor read failed");
        }
    }else {
        mDescriptorReadQueue.push(descriptor);
    }
}
public void writeDescriptor(String address, BluetoothGattDescriptor descriptor) {
    Log.i(TAG, "writing descriptor for characteristic " + descriptor.getCharacteristic().getUuid().toString());
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    if(mReadyToWrite && mReady) {
        boolean result = mBluetoothGattMap.get(address).writeDescriptor(descriptor);
        mReadyToWrite = false;
        mReady = false;
        if(!result) {
            Log.i(TAG, "descriptor write failed");
        }
    }else {
        mDescriptorWriteQueue.push(descriptor);
    }
}
public BluetoothGattCharacteristic getCharacteristic(String address, UUID uuid) {
    if(!mBluetoothGattMap.containsKey(address)) {
        Log.i(TAG, "Device address " + address + " not found");
        return null;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    for(BluetoothGattService service : mBluetoothGattMap.get(address).getServices()) {
        Log.i(TAG, "Service: " + service.getUuid().toString());
        for (BluetoothGattCharacteristic characteristic : service.getCharacteristics()) {
            Log.i(TAG, "Characteristic: " + characteristic.getUuid().toString());
            if(characteristic.getUuid().equals(uuid)) {
                return characteristic;
            }
        }
    }
    Log.i(TAG, "Characteristic not found");
    return null;
}
public Set<String> getConnectedDevices(){
    return this.mBluetoothGattMap.keySet();
}
/**
 * Enables or disables notification on a give characteristic.
 *
 * @param characteristic Characteristic to act on.
 * @param enabled If true, enable notification.  False otherwise.
 */
public void setCharacteristicNotification(String address, BluetoothGattCharacteristic characteristic, boolean enabled) {
    if (mBluetoothAdapter == null || !mBluetoothGattMap.containsKey(address)) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    try {
        synchronized (Thread.currentThread()) {
            Thread.currentThread().wait(100);
        }
    }catch(InterruptedException e){
        //ignore
    }
    mBluetoothGattMap.get(address).setCharacteristicNotification(characteristic, enabled);
    BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(GattAttributes.CLIENT_CHAR_CONFIG));
    if(descriptor != null) {
        boolean status = descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
        Log.i(TAG, "descriptor " + descriptor.getUuid().toString() + " setValue() status: " + status);
        Log.i(TAG, "descriptor value: " + descriptor.getValue());
        writeDescriptor(address, descriptor);
    }
}
public void setPhoneEvents(byte priorities) {
    for(String address : mBluetoothGattMap.keySet()) {
        BluetoothGattCharacteristic characteristic = getCharacteristic(address, UUID.fromString(GattAttributes.ALERT_ATTRIBUTE));
        if (characteristic != null) {
            byte prioritiesBuf[] = new byte[1];
            prioritiesBuf[0] = priorities;
            characteristic.setValue(prioritiesBuf);
            writeCharacteristic(address, characteristic);
            Log.i(TAG, String.format("Forwarded phone alert priorities: 0x%X", priorities));
        } else {
            Log.e(TAG, "Failed to get the Alert ID characteristic from Gatt Server for device address " + address);
        }
    }
}
/**
 * Retrieves a list of supported GATT services on the connected device. This should be
 * invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
 *
 * @return A {@code List} of supported services.
 */
public List<BluetoothGattService> getSupportedGattServices(String address) {
    if (mBluetoothGattMap.get(address) == null) return null;
    return mBluetoothGattMap.get(address).getServices();
}

Answer 1

不断发生的问题是在它得到用户定义之后name并断开连接BLE设备停止广播，我可以扫描时或扫描后尝试连接时找不到它读取用户定义的名称并断开连接。

你的BLE设备不应该在连接断开后立即开始广告吗？我还建议你可以让你的BLE设备宣传你的定制服务，而不是你的应用程序来连接，然后读取特征；你只需使用"扫描过滤器"过滤掉你喜欢的设备。你只需要让低级别的代码来做这件事。

Answer 2

观察到的行为实际上是BLE外围设备的一个功能，而不是Android，或者更广泛地说，是中央设备程序的一个特性。

我最近一直在使用Laird BL600，它有一个"空中传送"、OTA编程模式，当该模式启用时，该模块在通电后会在长达10秒的时间内宣传OTA服务：仅此而已。在这种情况下，外设应用程序被设计为在任何连接断开后都不要返回广告。为了重新进入OTA模式，需要对设备进行电源循环。

正如郭所建议的，如果对外设程序有控制权，一个更简单的方案是BLE外设在其广告包中包含可读标识符（设备名称）和主要服务的GUID，这将使筛选向用户展示的设备变得更容易。

当用户希望连接到外围设备时，只有使用device.connectGatt(this, false, mGattCallback)才能成功如果设备仍在广告中并且在范围内。我认为这个调用中的第二个参数"autoconnect"的目的是将Android中的连接标记为挂起，并且当设备回到范围并发布广告时，连接应该自动发生，但我觉得这不是很可靠。