Android BLE中心设备的onCharacteristicChanged()方法没有回调

来源：互联网发布：mac大智慧交易软件编辑：程序博客网时间：2024/05/22 16:59

描述：当设备为 Indication 模式时，设备的值有变化时会主动返回给App，App在 onCharacteristicChanged() 方法中能收到返回的值。

Indication： 从机会先向主机发送一条通知，主机接收到通知后去读取从机数据
Notification：从机直接发送给主机数据

问题：在App中通过如下代码注册监听，注册成功后就能接收到设备主动反馈的值了。然而以下代码执行后依旧收不到反馈。但是对设备的读写都是可行的，并且iOS端可以接收到通知。

bluetoothGatt.setCharacteristicNotification(characteristic, true)

解决： 当上面的方法执行返回true后，还要执行如下的代码才能注册成功。

for(BluetoothGattDescriptor dp: characteristic.getDescriptors()){    if (dp != null) {        if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_NOTIFY) != 0) {            dp.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);        } else if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_INDICATE) != 0) {            dp.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);        }        gatt.writeDescriptor(dp);    }}

完整的代码如下：

public boolean enableNotification(BluetoothGatt gatt, UUID serviceUUID, UUID characteristicUUID) {    boolean success = false;    BluetoothGattService service = gatt.getService(serviceUUID);    if (service != null) {        BluetoothGattCharacteristic characteristic = findNotifyCharacteristic(service, characteristicUUID);        if (characteristic != null) {            success = gatt.setCharacteristicNotification(characteristic, true);            if (success) {                // 来源：http://stackoverflow.com/questions/38045294/oncharacteristicchanged-not-called-with-ble                for(BluetoothGattDescriptor dp: characteristic.getDescriptors()){                    if (dp != null) {                        if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_NOTIFY) != 0) {                            dp.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);                        } else if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_INDICATE) != 0) {                            dp.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);                        }                        gatt.writeDescriptor(dp);                    }                }            }        }    }    return success;}private BluetoothGattCharacteristic findNotifyCharacteristic(BluetoothGattService service, UUID characteristicUUID) {    BluetoothGattCharacteristic characteristic = null;    List<BluetoothGattCharacteristic> characteristics = service.getCharacteristics();    for (BluetoothGattCharacteristic c : characteristics) {        if ((c.getProperties() & BluetoothGattCharacteristic.PROPERTY_NOTIFY) != 0                && characteristicUUID.equals(c.getUuid())) {            characteristic = c;            break;        }    }    if (characteristic != null)        return characteristic;    for (BluetoothGattCharacteristic c : characteristics) {        if ((c.getProperties() & BluetoothGattCharacteristic.PROPERTY_INDICATE) != 0                && characteristicUUID.equals(c.getUuid())) {            characteristic = c;            break;        }    }    return characteristic;}

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