android - 将 gatt 特性写入 BLE 设备时出现问题
问题描述
我正在尝试使用Google 的示例项目将自定义特征写入 BLE 设备。
在DeviceControlActivity我循环遍历获取BluetoothGattService的 s 时，我尝试为其中一个设置特征。在这一点上，我只是随机挑选一个来测试。
private void displayGattServices(List<BluetoothGattService> gattServices) {
...
// Loops through available GATT Services.
for (BluetoothGattService gattService : gattServices) {
uuid = gattService.getUuid().toString();
if(uuid.equals("00001800-0000-1000-8000-00805f9b34fb") && !firstTime){
firstTime = true;
BluetoothGattCharacteristic customChar = new BluetoothGattCharacteristic(MY_CHARACTERISTIC,
BluetoothGattCharacteristic.PROPERTY_READ | BluetoothGattCharacteristic.PROPERTY_WRITE,
BluetoothGattCharacteristic.PERMISSION_READ |BluetoothGattCharacteristic.PERMISSION_WRITE);
byte[] val = new byte[20];
val[0] = 71;
val[1] = 97;
val[2] = 108;
val[3] = 97;
val[4] = 120;
val[5] = 121;
val[6] = 32;
val[7] = 70;
val[8] = 105;
val[9] = 116;
val[10] = -30;
val[11] = -109;
val[12] = -108;
val[13] = 32;
val[14] = 40;
val[15] = 70;
val[16] = 57;
val[17] = 66;
val[18] = 57;
val[19] = 41;
customChar.setValue(val);
boolean isAdded = gattService.addCharacteristic(customChar);
Log.d(TAG,"CARAC ADDED? "+isAdded);
}
...
}
此调用返回 true，根据文档，这意味着写入操作成功，但是当我重新扫描服务（不执行上面的代码）时，当我尝试读取所述特征的值时，我也addCharacteristic找不到状态 135 BluetoothGattCharacteristic. 根据这个帖子的意思是GATT_ILLEGAL_PARAMETER
请注意，字节数组实际上是从另一个特征复制的，因此通常它应该可以解决问题。
我尝试写入的设备是否可能不支持写入？还是服务本身？
编辑：
按照评论的建议，我尝试使用下面的代码修改现有特征但没有成功（我认为该特征是使用 READ only 标志创建的？）
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
...
uuid = gattCharacteristic.getUuid().toString();
// UUID for device name
if(uuid.equals("00002a00-0000-1000-8000-00805f9b34fb") && !firstTime){
firstTime = true;
gattCharacteristic.setValue("Hello");
boolean isAdded = mBluetoothLeService.writeCharacteristic(gattCharacteristic);
Log.d(TAG,"CARAC ADDED? "+isAdded); // returns false
}
我还尝试设置GattServer并创建具有新特性的新服务，但也没有任何成功。这是代码（这部分使用 Kotlin）：
mBluetoothGattServer = mBluetoothManager?.openGattServer(this@MainActivity,gattCallback)
mBluetoothGattServer?.connect(result.device,false)
val gattCallback = object: BluetoothGattServerCallback() {
override fun onConnectionStateChange(device: BluetoothDevice?, status: Int, newState: Int) {
super.onConnectionStateChange(device, status, newState)
if (newState == BluetoothProfile.STATE_CONNECTED) {
val service = BluetoothGattService(UUID.fromString("f000aa01-0451-4000-b000-000000000000"), BluetoothGattService.SERVICE_TYPE_PRIMARY)
val characteristic = BluetoothGattCharacteristic(UUID.fromString("00002a00-0000-1000-8000-00805f9b34fb"),
BluetoothGattCharacteristic.PROPERTY_READ or BluetoothGattCharacteristic.PROPERTY_WRITE or BluetoothGattCharacteristic.PROPERTY_NOTIFY,
BluetoothGattCharacteristic.PERMISSION_READ or BluetoothGattCharacteristic.PERMISSION_WRITE)
characteristic.addDescriptor(BluetoothGattDescriptor(UUID.fromString("00002902-0000-1000-8000-00805f9b34fb"), BluetoothGattCharacteristic.PERMISSION_WRITE))
service.addCharacteristic(characteristic)
mBluetoothGattServer?.addService(service)
}
}
// Not sure if this is needed but it never triggers.
override fun onCharacteristicWriteRequest(device: BluetoothDevice?, requestId: Int, characteristic: BluetoothGattCharacteristic?, preparedWrite: Boolean, responseNeeded: Boolean, offset: Int, value: ByteArray?) {
super.onCharacteristicWriteRequest(device, requestId, characteristic, preparedWrite, responseNeeded, offset, value)
mBluetoothGattServer?.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, "Hello".toByteArray())
}