How to Get the Default Light Sensor

public Sensor getDefaultSensor (int type) was added in API level 3
Use this method to get the default sensor for a given type. Note that the returned sensor could be a composite sensor, and its data could be averaged or filtered. If you need to access the raw sensors use getSensorList.
Parameters: type - of sensors requested
Returns: the default sensors matching the asked type.

1. Declare a Sensor object named mySensor.

2. Get a Reference to SensorManager named mySensorManager.

3. Save Sensor TYPE_LIGHT to integer named intMySensor.

4. Add the below line to the onCreate method. This will get the default light sensor and save it to mySensor.

mySensor = mySensorManager.getDefaultSensor(intMySensor);

5. Compile and run!

Resources:
http://developer.android.com/reference/android/hardware/SensorManager.html#getDefaultSensor(int)
http://android-coding.blogspot.com/2011/10/using-android-device-build-in-light.html