1. EEC-492/693/793 iPhone Application Development
Lecture 9
Wenbing Zhao & Nigamanth Sridhar
9/21/2018
EEC492/693/793 - iPhone Application Development

2. Outline Administrative Objective-C
This Wed. 10/6: make-up session
Students who have completed all assignments can omit it
Oct 11 (next Monday), Columbus day, no class
Objective-C
@selector
Tab bar based multiview applications
Pickers
Assignments:
Build the Pickers app (chapter 7)
Continue building the calculator app
Objective-C part is shamelessly taken from Stanford CS193P winter 2010 lecture 3
9/21/2018
9/21/2018
EEC492/693/793 - iPhone Application Development
EEC492/693/793 - iPhone Application Development 2

3. EEC492/693/793 - iPhone Application Development
@selector
@selector is somewhat similar to the function pointer in C, or more accurately, the dlsym() call
It offers a mechanism for a developer to dynamically choose a method to invoke (or a message to send in OO language)
@selector takes the name of a method (with all arguments stripped off)
@selector returns a special type, SEL
SEL setWidthHeight;
setWidthHeight
// assuming we have a method:
-(void)setWidth: (int)w height: (int)h
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EEC492/693/793 - iPhone Application Development

4. EEC492/693/793 - iPhone Application Development
@selector
You can call a method (or send a message)
If you have a set of methods defined like these:
- (void) doSomething:
- (void) doSomething:(NSObject*)obj
- (void) doSomething:(NSObject*)obj1 withObject:(NSNumber*)obj2
The selectors will be declared like these, respectively:
@selector(doSomething:)
@selector(doSoemthing:) //same as before
@selector(doSomething:withObject:)
To perform a selector on an object, you can use:
[someObj
[someObj withObject: o];
[someObj withObject: o1, withObject: o2];
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EEC492/693/793 - iPhone Application Development

5. EEC492/693/793 - iPhone Application Development
@selector
Want to check if an object will respond to a message obtained via a selector?
-(BOOL)respondsToSelector:(SEL)aSelector
if ( [anObject )
[anObject setOrigin:0.0 :0.0];
else
fprintf(stderr, "%s can’t be placed\n",
[NSStringFromClass([anObject class]) UTF8String]);
Q: Why double colons in setOrigin:: ?
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EEC492/693/793 - iPhone Application Development

6. EEC492/693/793 - iPhone Application Development
@selector
@selector used in chapter 7
NSArray *sorted = [components
[self withObject:nil afterDelay:1.5];
[self withObject:nil afterDelay:.5];
9/21/2018
EEC492/693/793 - iPhone Application Development

7. Tab Bar Based Multiview Applications
Create needed individual view controllers and their nib files
Modify the app delegate:
Use UITabVarController as the root view controller
Add an outlet to the root controller
Add the root view as a subview to the main window
[window addSubview:rootController.view];
Connect the outlet to the root controller
Control-drag from the app delegate icon to the Tab Bar Controller icon, selecting the rootController outlet
Tab Bar
Controller
View Controller
9/21/2018
EEC492/693/793 - iPhone Application Development

8. Tab Bar Based Multiview Applications
In the IB, drag a Tab Bar Controller from the library to MainWindow.xib
Modify the number of views needed in the attribute inspector of the tab var controller (use the + or – sign)
Highlight each tab, link with nib file (⌘1), and specify to the proper controller class (⌘4)
Click on the tab again to change the selection to the tab bar item. In the inspector, link with the image file, and change to the desirable title
Implementing individual content views
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EEC492/693/793 - iPhone Application Development

9. EEC492/693/793 - iPhone Application Development
Pickers
A picker lets the user select an item from a list
For the picker to work, you must provide it with both a picker delegate and a picker datasource
The picker defers several jobs to its delegate
Determine what to draw for each of the rows in each of its components
The picker asks the delegate for either a string or a view that will be drawn at a given spot on a given component
The picker also gets its data from the delegate
The datasource tells the picker how many components it will be working with and how many rows make up each component
For a simple picker, its view controller is usually used as the datasource and delegate
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EEC492/693/793 - iPhone Application Development

10. Pickers: Datasource and Delegate
@interface SingleComponentPickerViewController : UIViewController
<UIPickerViewDelegate, UIPickerViewDataSource> {
UIPickerView *singlePicker;
NSArray *pickerData; }
#pragma mark -
#pragma mark Picker Data Source Methods
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { return 1;}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { return [pickerData count]; }
#pragma mark Picker Delegate Methods
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row
forComponent:(NSInteger)component {
return [pickerData objectAtIndex:row];
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EEC492/693/793 - iPhone Application Development

11. Pickers: More Delegate Methods
The content of one component might have to be updated if a row has been selected in a different component
(void)pickerView:(UIPickerView *)pickerView
didSelectRow:(NSInteger)row
inComponent:(NSInteger)component {
if (component == kStateComponent) {
NSString *selectedState = [self.states objectAtIndex:row];
NSArray *array = [stateZips objectForKey:selectedState];
self.zips = array; // swap zips array whenever the state changes
// set the right-hand component back to the 1st row
[picker selectRow:0 inComponent:kZipComponent animated:YES];
// tell it to reload itself
[picker reloadComponent:kZipComponent]; }
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EEC492/693/793 - iPhone Application Development

12. Pickers: More Delegate Methods
The width of each component in a picker can be adjusted by implementing a delegate method
- (CGFloat)pickerView:(UIPickerView *)pickerView
widthForComponent:(NSInteger)component {
if (component == kZipComponent)
return 90;
return 200; }
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EEC492/693/793 - iPhone Application Development

13. EEC492/693/793 - iPhone Application Development
NSBundle
A bundle is a special type of folder whose contents follow a specific structure
Applications and frameworks are both bundles
A primary use of NSBundle is to get to resources that added to the Resources folder of the project
If we want to get to those resources in our code, we usually have to use NSBundle
NSBundle *bundle = [NSBundle mainBundle];
// this will return a string containing the location of the statedictionary.plist file
NSString *plistPath = [bundle
// use the plist
NSDictionary *dictionary = [[NSDictionary alloc]
initWithContentsOfFile:plistPath];
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EEC492/693/793 - iPhone Application Development

14. UIImage and UIImageView
How to create a UIImageView
// by using a convenience method on the UIImage class, we don’t have to
// first determine the location of each image and then use that info to
// load the image
UIImage *seven = [UIImage
UIImageView *sevenView = [[UIImageView alloc] initWithImage:seven];
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EEC492/693/793 - iPhone Application Development

15. More Methods on Property
Set a property based on its name (mutator)
setValue:forKey:
[self setValue:imageViewArray forKey:fieldName];
// If fieldName is column1, and we have a property called
// column1, it is equivalent to:
[self setColumn1 imageViewArray)
Get the value of a property based on its name (accessor)
valueForKey:
NSArray *array = [self valueForKey:arrayName];
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EEC492/693/793 - iPhone Application Development

16. Adding Sounds to Your App
Import header file:
#import <AudioToolbox/AudioToolbox.h>
Getting the path to the sound file
NSString *path = [[NSBundle mainBundle]
Create sound ID
SystemSoundID soundID;
AudioServicesCreateSystemSoundID((CFURLRef)[NSURL fileURLWithPath:path], &soundID);
Play the sound
AudioServicesPlaySystemSound (soundID);
You must manually link with the AudioToolBox.framework
Make sure select a Reference Type of Relative to Current SDK
9/21/2018
EEC492/693/793 - iPhone Application Development