What is the proper method for reading a GATT characteristic in Android?

Question

In attempting to read the value of a Bluetooth Low-Energy GATT characteristic in the Android API 18, I came across the following dilemma: What is the proper way to retrieve the value stored in a characteristic? And at which level of the stack should this action take place?

In conducting my own research, I stumbled upon what I understand are two possible methods:

• BluetoothGatt.readCharacteristic(BluetoothGattCharacteristic characteristic)

• BluetoothGattCharacteristic.getValue()

  public void onClick(View v){        
      byteValue = mBTValueCharacteristic.getValue();
      if ((byteValue[0] & 0x01) == 1)
          byteValue[0] = 0x00;
      else
          byteValue[0] = 0x01;
  
      mBTValueCharacteristic.setValue(byteValue);
      mBTGatt.writeCharacteristic(mBTValueCharacteristic);
  }
  

Above is the original code which led me to this issue. In it, I attempt to read the value of a characteristic, and simply toggle its state using a button.

Daye

Answer 1

BluetoothGatt.readCharacteristic(BluetoothGattCharacteristic characteristic)

This function is updating your BluetoothGattCharacteristic object (on your Android device) using characteristic value from the Bluetooth .

BluetoothGattCharacteristic.getValue()

This function is just a getter function of the BluetoothGattCharacteristic object. There is not any transaction between android and the bluetooth device.

Cordwood

Thank you for the clarification, but I have one more question then. Do you think I can both read the characteristic and obtain its value within the same click action? Will there be a timing issue due to the nature of the wireless connection? – Daye

Wait until onCharacteristicRead callback fires, or else you are just getting the old value. – Cordwood