Lecture 6 Slides October 13 2011

7/29/2019 Lecture 6 Slides October 13 2011

1/39

Developing Applications for iOSFall 2011

Stanford CS193p


2/39

TodayDemo continuationDelegating the Views data (its smileyness)

Adding a gesture recognizer to the View (and handled by the Controller) that mod

View ControllersMultiple MVCsSeguesUINavigationController

Demo

FridayGetting your application running on a device


3/39

View ControllerHopefully youve got a pretty good handle on the basicYour Controller in an MVC grouping is always a subclass ofUIViewController.

It manages a View (made up of subviews that you usually have some outlets/actioIt is the liaison between that View and the Model (which is UI-independent).

So how do we grow our application to use multiple MVWe need infrastructure to manage them all.Thats what storyboards and controllers of controllers are all about.


4/39

MVCs working togetherWhat happens when your application gets more features?

Now all of your UI cant fit in one MVCs view.


5/39

MVCs working togetherWhat happens when your application gets more features?

We never have an MVCs view span across screens

So well have to create a new MVC for these new fea


6/39

MVCs working together

So how do we switch the screen to show this other MVC?


7/39

UINavigationController


We use a controller of controllers to do that.For example, a UINavigationController.


8/39


MVCs working togetherThe UINavigationController is a

Controller whose View looks like this.


9/39



rootViewController

But its special because we can set itsrootViewController outlet to another MVC


10/39



... and it wiView ins


11/39



Then a UI element in this View (e.g. a UIButton) can to the otherMVC and its View will now appear in the UINavigationController.


12/39

UINavigationContr



13/39

UINavigationContr


Notice this Back buttonautomatically appears.


14/39

UINavigationContr


When we click it, wellgo back to the first MVC.


15/39




16/39

SeguesLets talk about how the segue gets set up firstThen well look at how we create a UINavigationController in our storyboard.


17/39

To create a segue, you hold down ctrl and dragfrom the button to the other View Controller.


18/39

To create a segue, you hold down ctrl and dragfrom the button to the other View Controller.


19/39

This segue will be created.


20/39

You can change the segue type by clicking on thesegue and looking in the attributes inspector.

This is the identifier for this segue (ShowOther in this case).You use it in prepareForSegue:sender: to figure out which segue is happening.

Or you can use it to programmatically force a segue with performSegueWithIdentifier:sender:.


21/39

Push is the kind of segue you use when the twoControllers are inside a UINavigationController.


22/39

But theres a problem here.These View Controllers are not inside a UINavigationController.

Push will do nothing.


23/39

This arrow means that this is where the application starts.You can pick it up and drag it to whichever VC you want.

This switch also controls that.


24/39

Weve double-clicked on the backgroundhere to make everything smaller.

These also control the zooming.


25/39

You can embed a View Controller in aUINavigationController from the Editor menu.


26/39

Notice that application startingpoint was preserved.


27/39

This is not a segue, its therootViewController outlet of the

UINavigationController.

i i ll


28/39

UINavigationControllerUIView obtained from the view property of UIViewController most recently pushed (or

UIN i i C ll


29/39


NSString obtained from the title property UIViewController most recently pushed (or

UIN i ti C t ll


30/39



An NSArray ofUIBarButtonItems obtained frtoolbarItems property of the UIViewControlrecently pushed (or root)

UIN i ti C t ll


31/39



An NSArray ofUIBarButtonItems obtained frtoolbarItems property of the UIViewControlrecently pushed (or root)

A UIBarButton item whose title is an NSStrithe title property of the previous UIViewCwas pushed. It is being displayed on a buttthe navigation controller which, when toucheprevious UIViewController to reappear. Thisbutton.

UIN i ti C t ll


32/39


When does a pushed MVC pop off?Usually because the user presses the back button (shown on the previous slide)

But it can happen programmatically as well with this UINavigationController in- (void)popViewControllerAnimated:(BOOL)animated;

This does the same thing as clicking the back button.Somewhat rare to call this method. Usually we want the user in control of navigBut you might do it if some action the user takes in a view makes it irrelevant to

ExampleLets say we push an MVC which displays a database record and has a delete butt

- (IBAction)deleteCurrentRecord:(UIButton *)sender{

// delete the record we are displaying // we just deleted the record we are displaying! // so it does not make sense to be on screen anymore, so pop

[self.navigationController popViewControllerAnimated:YES];}

Notice that all UIViewCUINavigationContr

This is nil if they

Vi C t ll


33/39

View ControllerOther kinds of segues besides PushReplace - Replaces the right-hand side of a UISplitViewController (iPad only)

Popover - Puts the view controller on the screen in a popover (iPad only)Modal - Puts the view controller up in a way that blocks the app until it is dismis

Custom - You can create your own subclasses ofUIStoryboardSegue

Well talk about iPad-related segues on TuesdayReplace & Popover

Well talk about Modal later in the quarterPeople often use Modal UIs as a crutch, so we dont want to go to that too early

Vi C t ll


34/39

View ControllerFiring off a segue from codeSometimes it makes sense to segue directly when a button is touched, but not alw

For example, what if you want to conditionally segue?You can programmatically invoke segues using this method in UIViewController:

- (void)performSegueWithIdentifier:(NSString *)segueId sender:(id)sende

The segueId is set in the attributes inspector in Xcode (seen on previous slide).The sender is the initiator of the segue (a UIButton or yourself (UIViewControl

- (IBAction)rentEquipment

{

if (self.snowTraversingTalent == Skiing) {[self performSegueWithIdentifier:@AskAboutSkis sender:self];

} else {

[self performSegueWithIdentifier:@AskAboutSnowboard sender:s

}

}

S s


35/39

SeguesWhen a segue happens, what goes on in my code?The segue offers the source VC the opportunity to prepare the new VC to come

This method is sent to the VC that contains the button that initiated the segue:- (void)prepareForSegue:(UIStoryboardSegue *)seguesender:(id)sender{

if ([segue.identifier isEqualToString:@DoAParticularThing]) {UIViewController *newController = segue.destinationViewControl

// send messages to newController to prepare it to appear on screen // the segue will do the work of putting the new controller on screen

}

}You should pass data the new VC needs here and let it run.Think of the new VC as part of the View of the Controller that initiates the seguIt must play by the same rules as a View.

For example, it should not talk back to you except through delegation.So, for complicated MVC relationships, you might well set the new VCs delegate to

View Controller


36/39

Instantiating a UIViewController by name from a storSometimes (very rarely) you might want to put a VC on screen yourself (i.e., not NSString *vcid = @something;

UIViewController *controller = [storyboard instantiateViewControllerWithId

Usually you get the storyboard above from self.storyboard in an existing UIViThe identifier vcid must match a string you set in Xcode to identify a UIViewCon

View Controller

This UIViewController in the storyboard can beinstantiated using the identifier hellothere.

View Controller


37/39

Instantiating a UIViewController by name from a storSometimes (very rarely) you might want to put a VC on screen yourself (i.e., not NSString *vcid = @something;

UIViewController *controller = [storyboard instantiateViewControllerWithId

Usually you get the storyboard above from self.storyboard in an existing UIViThe identifier vcid must match a string you set in Xcode to identify a UIViewCon

Example: creating a UIViewController in a target/actioLay out the View for a DoitViewController in your storyboard and name it doi- (IBAction)doit{

DoitViewController *doit =[self.storyboard instantiateViewControllerWithIdentifier:@doi

doit.infoDoitNeeds = self.info;[self.navigationController pushViewController:doit animated:YES];

}

View Controller

Note use ofself.navigation

Demo


38/39

DemoNew application: PsychologistOur psychologist will make a diagnosis and use the Happiness MVC to communicat

Psychologist really has no Model (perhaps its diagnosis, but it doesnt store it anSome MVCs are just for presenting user-interface (e.g. UINavigationController

Watch for ...Reusing the Happiness MVC.Creating a segue between our new MVC and a Happiness MVC.

Embedding our view controllers in a UINavigationController.

Coming Up


39/39

Coming UpNext LectureiPad

FridayGetting your application running on a device

Documents

Lecture 6 Slides October 13 2011