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
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"];