Let us see how to use motion and touch event in iOS by looking through a simple project that displays random number. This project displays random number on a label for a touch and motion event. Check out this link for more about events in iOS
After creating a single view application, add a new class that contains the method for generating random. If you do not want to add new class just for a single method then you can add the method as part of your ViewController class itself. arc4random_uniform accepts a seed value (90) and generated number will be below this seed value.
-(NSInteger)generateNumber {
return arc4random_uniform(90);
}
Now add a UILabel for displaying the generated random numbers. This includes both adding IBOutlet property and connecting it with UILabel on Interface Builder.
Motion Event
The are three motion-handling methods -(void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event, -(void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event and -(void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event
In this example, we can use the motionEnded method to call the displayNumber method
-(void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if (UIEventSubtypeMotionShake) {
[self displayNumber];
}
}
-(void)displayNumber {
RandomNumber *randomNumber = [[RandomNumber alloc] init];
self.displayRandomNumber.text = [NSString stringWithFormat:@”%d”,[randomNumber generateNumber]];
}
And to test this on Simulator, use the Shake Gesture menu under Hardware to simulate motion event.
Touch Event
There are four touch events corresponding to each touch phase.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
In this example, we will use the touchesEnded method for displaying the random numbers.
-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
[self displayNumber];
}
You can download the source code along with TDD classes for this beginner tutorial on touch and motion event from here.
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