The temperature and pressure sensor on the Rainbow HAT uses the BMP280 chip. A similar component—BME280—has an extra humidity sensor and the driver is designed to work with both chips (hence, the X in the name Bmx280) since both have the same internal protocol. Again, remember that the one in the Rainbow HAT does not include a humidity sensor.
Android Things offers two ways to read data from sensors. The first one is to proactively read a value from the component itself, and the second one is to configure a SensorDriver that will deliver readings via a listener whenever the values change. This is meant to use the same framework as the sensors on a phone (namely gyroscope, magnetometer, and accelerometer).
Querying the component directly is simpler; it gives all the control and also all the responsibility to us. On the other...