1. CSC 581: Mobile App Development
Spring 2018
Examples & advanced topics
dice shaker
motion sensor
counter
swipe gestures
tap gestures
countdown timer
scheduledTimer
random quotations
reading from a local file
HTTP requests

2. Dice shaker suppose we wanted to simulate the roll of two dice
could utilize buttons that change images when clicked (similar to slot machine)
or, could have two images that are changed when a separate button is clicked

3. Motion sensor many apps use the motion sensor to initiate actions
e.g., shake the phone to clear the fields, restart the game, or roll the dice
Swift provides various UIResponders to handle
touch events
motion events
press events
shaking the phone is a motion event
want to process when the motion is done
double check to verify UIEventSubtype is .shakeMotion

4. App example

5. Counter app suppose we wanted to have a counter app
right swipe increments the count; left swipe decrements
double tap resets the counter to 0
touch gestures can similarly be handled with UIResponders in the code
but, can be more simply handled via the storyboard
drag a Swipe Gesture Recognizer onto the storyboard
this adds an icon to the View Controller Tab Bar
edit its attributes to make it left/right/up/down
add an IBAction from the icon to specify the action
drag a Tap Gesture Recognizer onto the storyboard
edit its attributes to specify number of taps

6. App example

7. Countdown timer suppose we wanted to simulate a countdown timer
the user enters a duration in minutes & seconds
at the click of a button, the time remaining counts down until 0:00
Swift provides a Timer class for such tasks
the scheduledTimer method can schedule a method to be executed in the future, and repeatedly (if desired)
Timer.scheduledTimer(timeInterval: DURATION_IN_SEC,
target: self,
                     selector: #selector(METHOD_TO_BE_EXECUTED),
                     userInfo: nil,
repeats: TRUE_IF_REPEATED)
this class still has ties to Objective-C, so the selector method must have the as part of its header

8. App example

9. App example (cont.) suppose we wanted to add color to the display
@objc func updateTime() {
var min = Int(minLabel.text!)!
var sec = Int(secLabel.text!)!
// CODE FOR UPDATING min & sec
if min == 0 {
if sec == 0 {
self.view.backgroundColor = .red }
else if sec <= 10 {
self.view.backgroundColor = .orange
else if sec <= 30 {
self.view.backgroundColor = .yellow
else {
self.view.backgroundColor = .green
// CODE FOR UPDATING THE LABELS
suppose we wanted to add color to the display
30<sec : green
10<sec<30 : yellow
0<sec<10 : orange
0=sec : red
add the code on the right

10. Random quotes
suppose we wanted to develop an app for displaying random quotes
we have already seen how to read from a file added to the project Bundle
could start with a file of quotes, one per line
add it to the project Bundle, then read it in when the app loads
will need to be able to split it into its components, separated by newLines
finally, select and display a random quote when the user clicks on a button

11. App example

12. Another approach maintaining & updating the list of quotes is work!
there exist Web sites that store and display thousands of quotes
better solution would be to have the app request a quote directly from a site
in order for the app to send requests to a Web server:
must be able to specify a URL
must be able to specify a request for data at that URL
that request may have additional header information
or, it may have queries attached to it
finally, must be able to dispatch the request, wait for the response, and return the data when received

13. App example Concepts HTTP Requests URLSession dataTask downloadTask
uploadTask
AlamoFire*
API
Really Web API
Different URLs in Swift
URL
URLRequest
URLComponents
Asynchronous Calls
DispatchGroup

14. App example (cont.)