1. EEC-492/693/793 iPhone Application Development
Lecture 7
Wenbing Zhao & Nigamanth Sridhar
12/24/2018
EEC492/693/793 - iPhone Application Development

2. Outline More in-depth Objective-C A primer on coordinate system
Memory management (and property) revisited
The self keyword
A primer on coordinate system
Autorotation and autosizing
Assignments:
Build autosize 1, autosize 2, and swap apps
Build a calculator app
Objective-C part is shamelessly taken from Stanford CS193P winter 2010 lecture 3
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EEC492/693/793 - iPhone Application Development
EEC492/693/793 - iPhone Application Development 2

3. Memory Management Revisited
What is going to happy if you were to run the code below (assuming other parts are implemented perfectly?
// in foo.h
@interface FooViewController : UITableViewController {     NSArray *stuff; }
@property (nonatomic, retain) NSArray *stuff;
// in foo.m
@synthesize stuff; - (void)viewDidLoad {         NSArray *arr = [[NSArray 2",                                       nil];     stuff = arr;     [arr release]; }
Code example and explanation taken from:
12/24/2018
EEC492/693/793 - iPhone Application Development

4. Memory Management Revisited
How about this piece of code?
// in foo.h
@interface FooViewController : UITableViewController {     NSArray *stuff; }
@property (nonatomic, retain) NSArray *stuff;
// in foo.m
@synthesize stuff; - (void)viewDidLoad {         NSArray *arr = [[NSArray 2",                                       nil];     self.stuff = arr;     [arr release]; }
12/24/2018
EEC492/693/793 - iPhone Application Development

5. Memory Management Revisited
First version would crash as soon as the app is started, while the second version would work just fine
The difference? Whether or not “self” is used:
self.stuff = arr;
This is quite puzzling. Shouldn’t we be able to access the class instance variable directly?
Yes, we do. We can certainly manipulate instance variables within the class without having to use: self.
What is the problem then?
12/24/2018
EEC492/693/793 - iPhone Application Development

6. Memory Management Revisited
The problem is related to memory management
Why version 1 crashed?
stuff = arr; this assignment does not retain the array (arr) (aside from the implicit retain via alloc+init)
When the next statement is executed: [arr release]; the retain count of the array (arr) drops to 0, and therefore, it is deallocated => stuff would point to nothing, which caused the crash
Why version 2 works?
self.stuff = arr; in this assignment, we are actually calling the setter of the property, which would increase the retain count by 1 due to the property declaration
@property (nonatomic, retain) NSArray *stuff;
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EEC492/693/793 - iPhone Application Development

7. EEC492/693/793 - iPhone Application Development
Property Delaration
@property (nonatomic, retain) NSArray *stuff;
retain means that the retain count (for the property) will be increased after the assignment
self.stuff = arr; // stuff’s retain count will be increased by 1
Furthermore, the previous object (which stuff pointed to) is sent a release message
This is why we can do this in viewDidUnload:
self.nameField = nil;
However, the release message is sent to instance variables directly un dealloc: method
[nameField release];
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EEC492/693/793 - iPhone Application Development

8. EEC492/693/793 - iPhone Application Development
The self Keyword
self is to be used within a method definition to refer to the object that performs the method
You normally send a message to self
However, the dot notation for declared properties (introduced in Objective-C 2.0) added confusion, especially for C++/Java programmers
What does self.stuff mean?
self.stuff = arr; // equivalent to [self setStuff: arr];
arr = self.stuff; // equivalent to arr = [self stuff];
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EEC492/693/793 - iPhone Application Development

9. EEC492/693/793 - iPhone Application Development
Coordinates
CGFloat
Just a floating point number
CGPoint
C struct with two CGFloats in it: x and y
Create with CGPointMake(x, y)
CGSize
C struct with two CGFloats in it: width and height.
Create with CGSizeMake(width, height)
CGRect
C struct with a CGPoint origin and a CGSize size.
Create with CGRectMake(x, y, width, height)
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EEC492/693/793 - iPhone Application Development

10. EEC492/693/793 - iPhone Application Development
Coordinates
(0,0)
Increasing x
Origin of View’s coordinate system is upper left
Units are “pixels”. For iPhone/iPod touch prior to 4g:
A view that starts in portrait mode will be 320 pixels wide and 460 pixels tall or 480 pixels if there’s no status bar
A view in landscape mode: 480 pixels wide & 300 (or 320 if no status bar) pixels wide
View property bounds is the rectangle, expressed as a location (x,y) and size (width,height) relative to its own coordinate system (0,0)
View’s frame is the rectangle, expressed as a location (x,y) and size (width,height) relative to the superview it is contained within
(250,85)
So is frame.size always the same as bounds.size? No: rotation.
Use center and frame to position/size the view in its superview.
Increasing y
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EEC492/693/793 - iPhone Application Development

11. EEC492/693/793 - iPhone Application Development
Bounds and Frames
View B’s bounds is ((0,0),(200,250))
View B’s frame is ((140,65),(320,320))
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EEC492/693/793 - iPhone Application Development

12. EEC492/693/793 - iPhone Application Development
Creating a View in Code
Use - (id)initWithFrame:(CGRect)aRect as the designated initializer
Example:
CGRect buttonRect = CGRectMake(20, 20, 120, 37);
UIButton *button = [[UIButton alloc] initWithFrame:buttonRect];
button.titleLabel.text it!”;
[window addSubview:button];
[button release];
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EEC492/693/793 - iPhone Application Development

13. Autorotation and Autosizing
Autorotation: enables you to use the app in different orientations
Three approaches to implementing autorotation:
Autosizing: specify the correct autosize attribtes for all UIControl objects in your view
Manually reposition the objects when notified that your view is rotating
Design two different version of your view, one for portrait mode and another for landscape mode
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EEC492/693/793 - iPhone Application Development

14. Specifying Rotation Support
Autorotation might not be suitable for all apps
You can control what orientation is supported in the method AutorotateToInterfaceOrientation:
Return yes if all orientations are supported
Or you can choose to support one or more specific orientations
UIInterfaceOrientationPortrait
UIInterfaceOrientationPortraitUpsideDown
UIInterfaceOrientationLandscapeLeft
UIInterfaceOrientationLandscapeRight
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)
interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait); }
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EEC492/693/793 - iPhone Application Development

15. Approach#1: Handling Rotation Using Autosize Attributes
Single-click the UIControl in the view, then press ⌘3 to bring up the size inspector
The inner square represents the current object
Red arrows inside the inner square represent the horizontal and vertical space inside the selected object
Solid: height/width of the object is free to change as the window resizes
Dashed: keep the height/width of the object at its original value if possible
Click on the arrow: solid->dashed or vice versa
Four red “I” shapes outside the inner box represent the distance between the edge of the selected object and the edge of the view
Dashed: space is flexible
Solid: the amount space should be kept constant if possible
Where we set attributes
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EEC492/693/793 - iPhone Application Development

16. Manually Reposition the Objects
Autosizing doesn’t work in all circumstances
No Good!
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EEC492/693/793 - iPhone Application Development

17. Approach#2: Manually Reposition the Objects
Introduce an outlet for each UIControl object and connect it
In the implementation file, manually position each object depending on the new orientation
- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)
interfaceOrientation duration:(NSTimeInterval)duration {
if (interfaceOrientation == UIInterfaceOrientationPortrait
|| interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown) {
button1.frame = CGRectMake(20, 20, 125, 125);
button2.frame = CGRectMake(175, 20, 125, 125);
button3.frame = CGRectMake(20, 168, 125, 125); ……
} else {
button2.frame = CGRectMake(20, 155, 125, 125);
button3.frame = CGRectMake(177, 20, 125, 125); }
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EEC492/693/793 - iPhone Application Development

18. Approach#3: Swapping Views
Create different views for different orientations
Needed only for complex interfaces
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EEC492/693/793 - iPhone Application Development

19. Accommodating Two Views
In the app’s ViewController, add a UIView outlet for each view, and connect them
Delete the original view, design and add new views in IB, and connect them
Specify the right size of the view in the size inspector
For the view that should be displayed by default, connect to the view outlet
In the following method, set the right view and transformation
self.view.transform = CGAffineTransformIdentity; // should not be here
(void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation) interfaceOrientation duration:(NSTimeInterval)duration {
if (interfaceOrientation == UIInterfaceOrientationPortrait) {
self.view = self.portrait;
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(0));
self.view.bounds = CGRectMake(0.0, 0.0, 300.0, 480.0); } ….
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EEC492/693/793 - iPhone Application Development

20. EEC492/693/793 - iPhone Application Development
Transformation
The transformation statement is to make sure the view is displayed properly
self.view.transform = CGAffineTransformMakeRotation(degreesToRadians(90));
Try commenting the above statement and see what happens
The following statement is the book should have been deleted
self.view.transform = CGAffineTransformIdentity;
CGAffineTransformIdentity means you want to reset a view to its original, untransformed state
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EEC492/693/793 - iPhone Application Development

21. Assignment: build a calculator app
Do this after you have done autosize 1, autosize 2, and swap apps
12/24/2018
EEC492/693/793 - iPhone Application Development