iOS - adding/removing a subview programmatically - iphone

Question

Ok I want to add a UIImageView as a subview and then remove it after a couple of seconds in the way a splash screen works. I found three different approaches to do it but I can not understand which one is the best approach according to Objective-C and Apple.
Below are the three different approaches:
1)
In my MyAppDelegate.h
#interface MyAppDelegate : NSObject <UIApplicationDelegate> {
MyViewController *myViewController;
UIImageView *myImageView;
}
#property (nonatomic, retain) IBOutlet MyViewController *myViewController;
#property (nonatomic, retain) IBOutlet UIWindow *window;
#end
and in MyAppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
myImageView =[[UIImageView alloc] initWithFrame:CGRectMake(0.0,0.0,self.window.frame.size.width,self.window.frame.size.height)];
myImageView.image=[UIImage imageNamed:#"Yoga.png"];
[self.window addSubview:myImageView ];
[self.window bringSubviewToFront:myImageView];
[self performSelector:#selector(removeImage) withObject:nil afterDelay:2.5];
return YES;
}
-(void) removeImage
{
[myImageView removeFromSuperview];
[myImageView release];
[self.window addSubview:myViewController.view];
[self.window makeKeyAndVisible];
}
2) in the second approach:
In my MyAppDelegate.h
#interface MyAppDelegate : NSObject <UIApplicationDelegate> {
MyViewController *myViewController;
UIImageView *myImageView;
}
#property (nonatomic, retain) IBOutlet UIImageView *myImageView;
#property (nonatomic, retain) IBOutlet MyViewController *myViewController;
#property (nonatomic, retain) IBOutlet UIWindow *window;
#end
and in MyAppDelegate.m
#synthesize myImageView;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
myImageView =[[UIImageView alloc] initWithFrame:CGRectMake(0.0,0.0,self.window.frame.size.width,self.window.frame.size.height)];
myImageView.image=[UIImage imageNamed:#"Yoga.png"];
[self.window addSubview:myImageView ];
[self.window bringSubviewToFront:myImageView];
[self performSelector:#selector(removeImage) withObject:nil afterDelay:2.5];
return YES;
}
-(void) removeImage
{
[myImageView removeFromSuperview];
[myImageView release];
[self.window addSubview:myViewController.view];
[self.window makeKeyAndVisible];
}
- (void)dealloc
{
[myViewController release];
[myImageView release];
}
3) in the third approach:
In my MyAppDelegate.h
#interface MyAppDelegate : NSObject <UIApplicationDelegate> {
MyViewController *myViewController;
}
#property (nonatomic, retain) IBOutlet MyViewController *myViewController;
#property (nonatomic, retain) IBOutlet UIWindow *window;
#end
and in MyAppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UIImageView *myImageView =[[UIImageView alloc] initWithFrame:CGRectMake(0.0,0.0,self.window.frame.size.width,self.window.frame.size.height)];
myImageView.image=[UIImage imageNamed:#"Yoga.png"];
myImageView.tag=22;
[self.window addSubview:myImageView ];
[myImageView release];
[self.window bringSubviewToFront:myImageView];
[self performSelector:#selector(removeImage) withObject:nil afterDelay:2.5];
return YES;
}
-(void) removeImage
{
for (UIView *subview in [self.view subviews]) {
if (subview.tag == 22){
[subview removeFromSuperview];
}
}
[self.window addSubview:myViewController.view];
[self.window makeKeyAndVisible];
}
- (void)dealloc
{
[myViewController release];
}
So to sum up.. The first approach does not use a property for the UIImage only a variable, the second one uses a property and the third one just creates the UIImage and adds it as a subview and then removes it based on its tag..
Which is the right approach to follow..I believe that all three options sound right.. But is there any certain way I should follow. Is any of these options better in terms of memory and performance?
Thanks in advance,
Andreas

Answer 1

You could use an animation attached to the view's layer. Code below fades the view out - but there are many other ways to remove it. (you need to attach the QuartzCore framework)
myImageView.layer.opacity = 0.0;
// this is the state the view will be in after the animation (e.g. invisible)
CABasicAnimation *theFade;
theFade = [CABasicAnimation animationwithKeyPath:#"opacity"];
theFade.duration = 10.0;
theFade.fromValue = [NSNumber numberWithFloat:1.0]; // i.e. visible
theFade.toValue = [NSNumber numberWithFloat:0.0]; // i.e. invisible
[myImageView.layer addAnimation:theFade forKey:#"animateOpacity"];

Answer 2

If you are not going to use the image again, there is no need to keep a pointer to it. Further, if you use IBOutlet, you need to add the view in IB as well. In this specific example I would say option 3 makes the most sence, especially considering that with this choice you can began with a standard "view based application" template and just add the bits about the image view and leave the rest alone. One last observation of choice 3 though; the 2 messages to window;
[self.window addSubview:myViewController.view];
[self.window makeKeyAndVisible];
Appear to be outside the scope of any method. This is likely just a copy and paste error, but make note that they should located within "didFinishLaunchingWithOptions:"