我想通过蓝牙在android应用程序中连续从ble硬件读取数据.
连接已完成,我可以将数据从应用程序发送到ble,但是无法从ble读取数据.

从ble获取一些数据时必须调用onCharactersticChanged方法,但此回调方法未调用.我想通知ble但

writeChar.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
BluetoothGattDescriptor descriptor = new BluetoothGattDescriptor(BLEUtils.CLIENT_CHARACTERISTIC_CONFIG_UUID, BluetoothGattDescriptor.PERMISSION_WRITE_SIGNED);

descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);

gatt.writeDescriptor(descriptor);

  // Enable local notifications
        gatt.setCharacteristicNotification(writeChar, true);

 boolean succes = gatt.writeDescriptor(descriptor);

其返回假

解决方法:

我建议您在订阅特性时应设置ENABLE_NOTIFICATION_VALUE.这是我执行此操作的代码：

public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            List<BluetoothGattService> services = getSupportedGattServices();
            for (BluetoothGattService service : services) {
                if (!service.getUuid().equals(UUID_TARGET_SERVICE))
                    continue;

                List<BluetoothGattCharacteristic> gattCharacteristics =
                        service.getCharacteristics();

                // Loops through available Characteristics.
                for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
                    if (!gattCharacteristic.getUuid().equals(UUID_TARGET_CHARACTERISTIC))
                        continue;

                    final int charaProp = gattCharacteristic.getProperties();

                    if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
                        setCharacteristicNotification(gattCharacteristic, true);
                    } else {
                        Log.w(TAG, "Characteristic does not support notify");
                    }
                }
            }
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }
    }

那么您可以通过NOTIFICATION订阅特征：

public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
                                          boolean enabled) {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w(TAG, "BluetoothAdapter not initialized");
        return;
    }
    mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);

    BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID_DESCRIPTOR);
    descriptor.setValue(enabled?BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
                                :BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
    mBluetoothGatt.writeDescriptor(descriptor);

}

之后,您可以开始写入设备：

    @Override
    public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            if (descriptor.getCharacteristic().getUuid().equals(UUID_TARGET_CHARACTERISTIC)) {
                Log.i(TAG, "Successfully subscribed");
            }

            byte[] data = <Your data here>;
            BluetoothGattService Service = mBluetoothGatt.getService(UUID_TARGET_SERVICE);

            BluetoothGattCharacteristic charac = Service
            .getCharacteristic(UUID_TARGET_CHARACTERISTIC);

            charac.setValue(data);
            mBluetoothGatt.writeCharacteristic(charac);
        } else {
            Log.e(TAG, "Error subscribing");
        }
    }

并且您将收到回调onCharactersticChanged以进行读取,而无需实际调用读取操作.

请记住,mBluetoohGatt一次只能处理1个操作,如果您在上一个未完成的情况下执行另一个操作,则不会放入队列中,但会返回false.