1. EEC-492/693/793 iPhone Application Development
Lecture 16
Wenbing Zhao & Nigamanth Sridhar
2/22/2019
EEC492/693/793 - iPhone Application Development

2. Outline Taps, touches and gestures Assignment: Terminology UITouch
UIEvent
UIResponder
Apps in chapter 13
Assignment:
Build the set of apps in chapter 13
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EEC492/693/793 - iPhone Application Development
EEC492/693/793 - iPhone Application Development 2

3. Taps, Touches and Gestures
Gesture: any sequence of events that happens from the time you touch the screen with one or more fingers until you lift your figures off the screen
Touch: refers to a finger being placed on the screen
One finger, one touch
Tap: you touch the screen with a single finger and then immediately lift your finger off the screen without moving it around
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EEC492/693/793 - iPhone Application Development

4. EEC492/693/793 - iPhone Application Development
The Responder Chain
Events get passed through the responder chain
First responder: usually the object with which the user is currently interacting
If a responder in the chain doesn’t handle a particular event, it passes that event up the responder chain
Application
Window
UIApplication
View
View Controller
superview
View
View Controller
superview
View
View Controller
View hierarchy
Event
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EEC492/693/793 - iPhone Application Development

5. EEC492/693/793 - iPhone Application Development
UITouch
Represents a single finger
@property(nonatomic,readonly) NSTimeInterval timestamp;
// indicates whether the touch began, moved, ended, or was canceled
@property(nonatomic,readonly) UITouchPhase phase;
@property(nonatomic,readonly) NSUInteger tapCount;
@property(nonatomic,readonly,retain) UIWindow *window;
@property(nonatomic,readonly,retain) UIView *view;
// The view in which the touch initially occurred
- (CGPoint)locationInView:(UIView *)view;
- (CGPoint)previousLocationInView:(UIView *)view;
Timestamp: The value of this property is the time, in seconds, since system startup the touch either originated or was last changed. You can store and compare the initial value of this attribute to subsequent timestamp values of the UITouch instance to determine the duration of the touch and, if it is being swiped, the speed of movement.
Phase: The property value is a constant that indicates whether the touch began, moved, ended, or was canceled. For descriptions of possible UITouchPhase values, see “Touch Phase.”
tapCount: The value of this property is an integer indicating the number of times the user tapped their fingers on a certain point within a predefined period.
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EEC492/693/793 - iPhone Application Development

6. EEC492/693/793 - iPhone Application Development
UIEvent
A container for one or more touches
@property(nonatomic,readonly) NSTimeInterval timestamp;
- (NSSet *)allTouches;
- (NSSet *)touchesForWindow:(UIWindow *)window;
- (NSSet *)touchesForView:(UIView *)view;
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EEC492/693/793 - iPhone Application Development

7. EEC492/693/793 - iPhone Application Development
UIEvent
- (NSSet *)allTouches;
UIEvent
UITouch
Window A
Window B
View A
View B
View C
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EEC492/693/793 - iPhone Application Development

8. EEC492/693/793 - iPhone Application Development
UIEvent
- (NSSet *)touchesForWindow:(UIWindow *)window;
UIEvent
UITouch
Window A
Window B
View A
View B
View C
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EEC492/693/793 - iPhone Application Development

9. EEC492/693/793 - iPhone Application Development
UIEvent
- (NSSet *)touchesForView:(UIView *)view;
UIEvent
UITouch
Window A
Window B
View A
View B
View C
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EEC492/693/793 - iPhone Application Development

10. EEC492/693/793 - iPhone Application Development
Receiving Touches
UIResponder
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
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EEC492/693/793 - iPhone Application Development

11. EEC492/693/793 - iPhone Application Development
UIResponder
NSObject
UIResponder
UIApplication
UIView
UIViewController
UIImageView
UILabel
UIControl
UIControl
UIScrollView
UIButton
UISlider
UISwitch
UITextField
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EEC492/693/793 - iPhone Application Development

12. Single & Multiple Touch Sequence
Show Stanford Slides
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EEC492/693/793 - iPhone Application Development

13. EEC492/693/793 - iPhone Application Development
The Touch Explore App
- (void)updateLabelsFromTouches:(NSSet *)touches {
NSUInteger numTaps = [[touches anyObject] tapCount];
NSString *tapsMessage = [[NSString alloc]
taps detected", numTaps];
tapsLabel.text = tapsMessage;
[tapsMessage release];
NSUInteger numTouches = [touches count];
NSString *touchMsg = [[NSString alloc] initWithFormat:
@"%d touches detected", numTouches];
touchesLabel.text = touchMsg;
[touchMsg release]; }
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
messageLabel.text Began";
[self updateLabelsFromTouches:touches];
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {…}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {…}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event{…}
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EEC492/693/793 - iPhone Application Development

14. EEC492/693/793 - iPhone Application Development
The Swipes App
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
gestureStartPoint = [touch locationInView:self.view]; }
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint currentPosition = [touch locationInView:self.view];
CGFloat deltaX = fabsf(gestureStartPoint.x - currentPosition.x);
CGFloat deltaY = fabsf(gestureStartPoint.y - currentPosition.y);
if (deltaX >= kMinimumGestureLength && deltaY <= kMaximumVariance) {
label.text swipe detected";
[self
withObject:nil afterDelay:2];
else if (deltaY >= kMinimumGestureLength &&
deltaX <= kMaximumVariance){
label.text swipe detected";
[self withObject:nil
afterDelay:2];
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EEC492/693/793 - iPhone Application Development

15. The Swipes App: Detect Multiple Swipes
When touchesBegan:withEvent: gets notified that a gesture has begun, we save one finger’s position
When we check for swipes, we loop through all the touches provided to the touchesMoved:withEvent: method, comparing each one to the saved point
If the user did a multiple-finger swipe, when comparing to the saved point, at least one of the touches we get in that method will indicate a swipe
If we find either a horizontal or vertical swipe, we loop through the touches again and make sure that every finger is at least the minimum distance away from the first finger’s horizontal or vertical position, depending on the type of swipe
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EEC492/693/793 - iPhone Application Development

16. The TapTaps App: Detecting Multiple Taps
If the user did a triple tap, there will be three separate notifications:
Single tap
Double tap
Triple tap
How can we handle the triple tap properly?
[self withObject:nil afterDelay:.4];
[NSObject cancelPreviousPerformRequestsWithTarget:self object:nil];
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EEC492/693/793 - iPhone Application Development

17. EEC492/693/793 - iPhone Application Development
The PinchMe App
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
if ([touches count] == 2) {
NSArray *twoTouches = [touches allObjects];
UITouch *first = [twoTouches objectAtIndex:0];
UITouch *second = [twoTouches objectAtIndex:1];
CGFloat currentDistance = distanceBetweenPoints(
[first locationInView:self.view], [second locationInView:self.view]);
if (initialDistance == 0)
initialDistance = currentDistance;
else if (currentDistance - initialDistance > kMinimumPinchDelta) {
label.text Pinch";
[self withObject:nil afterDelay:1.6f]; }
else if (initialDistance - currentDistance > kMinimumPinchDelta) {
label.text Pinch";
You need CGPointUtils.h and CGPointUtils.c
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EEC492/693/793 - iPhone Application Development

18. EEC492/693/793 - iPhone Application Development
The CheckPlease App
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint previousPoint = [touch previousLocationInView:self.view];
CGPoint currentPoint = [touch locationInView:self.view];
CGFloat angle = angleBetweenLines(lastPreviousPoint,
lastCurrentPoint, previousPoint, currentPoint);
if (angle >= kMinimumCheckMarkAngle&& angle <= kMaximumCheckMarkAngle
&& lineLengthSoFar > kMinimumCheckMarkLength) {
label.text
[self
withObject:nil afterDelay:1.6]; }
lineLengthSoFar += distanceBetweenPoints(previousPoint, currentPoint);
lastPreviousPoint = previousPoint;
lastCurrentPoint = currentPoint;
You need CGPointUtils.h and CGPointUtils.c
2/22/2019
EEC492/693/793 - iPhone Application Development