Lecture 6: Thread Safe Event services and Coordinate System

CSS290: APPS ON MOBILE DEVICES

TODAY: CONCEPTS• Reading: Chapter 5

• Sensors and Services

• Thread invoking functions

• Delegates

• Logical Coordinate Control by Orientation vs. Hardware Coordinate from Accelerometer

DELEGATE KEYWORD: A FUNCTION POINTER• Define a data type that accepts a function!

• delegate returnType TypeName(parameter list)

• E.g. delegate void MyFuncType(double a, double b)

• New datatype is: MyFuncType!

• Convenient for passing function pointers around!

ADDING A NEW REFERENCE INTO IDE• The Reference Tab in the Solution Explorer

• Finding the right reference

• Using the reference in your code

• To work with Accelerometer we need

• Microsoft.Devices.Sensors

1. ACCTEST: ACCELEROMETER• Event service is called form an external thread

• SHOULD NOT change our variable from that service routine

• Called from external thread, danger of external thread and our own thread trying to change the same variable!

• Instead: BeginInvoke() called sometime later when it is safe.

• Accelerometer X/Y/Z

• Resting state for Z is -1 (gravitational pull)

• Notice: -Y is downwards.

• X/Y is associated with the hardware

• If you change the phone orientation, X/Y direciton DOES NOT change

2. ACC CONTROLS OBJ:• Accelerometer with Orientation

• Phone orientation changes the logical X/Y directions

• Accelerometer returns the same X/Y/Z readings regardless of phone orientation!

• We must translate the change!

• Switch on Orientation changing support

• Translate coordinate space depending on phone orientation

3. BOUND CHECK• Switch off orientation (annoying)

• mBall class

• Passed in ContentPanel for bound checking

• Random position inside the bound

• Bound intersection checking

• Test for X overlaps

• Test for Y overlaps

• Must satisfy all conditions for potential collision

EXERCISE 6:• Integrate Bound checking with Exercise 5

• Check for ball touch net in Timer service (nice central place)

• Integrate Music/Sound effect

• Integrate Accelerometer for moving the net

• No need for orientation support

• BECAREFUL!!

• mTheNet must be a Shape! (Rectangle)!!

• UIImage does _NOT_ work!!