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

11
votes

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.

1
bluetooth-lowenergyandroid-bluetoothandroid-4.3-jelly-bean

1 Answers

8
votes
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.