好的，我想添加一个 UIImageView 作为 subview ，然后在几秒钟后以启动画面的方式将其删除。我找到了三种不同的方法来做到这一点，但根据 Objective-C 和 Apple，我无法理解哪一种是最好的方法。

以下是三种不同的方法:

1) 在我的 MyAppDelegate.h 中

@interface MyAppDelegate : NSObject <UIApplicationDelegate> {

    MyViewController *myViewController;
    UIImageView *myImageView;
}


@property (nonatomic, retain) IBOutlet MyViewController *myViewController;
@property (nonatomic, retain) IBOutlet UIWindow *window;

@end

在 MyAppDelegate.m 中

   - (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) 在第二种方法中:

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

在 MyAppDelegate.m 中

@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)在第三种方法中:

In my MyAppDelegate.h


@interface MyAppDelegate : NSObject <UIApplicationDelegate> {

    MyViewController *myViewController;

}

@property (nonatomic, retain) IBOutlet MyViewController *myViewController;
@property (nonatomic, retain) IBOutlet UIWindow *window;

@end

在 MyAppDelegate.m 中

   - (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];

 }

所以总结一下.. 第一种方法不使用 UIImage 的属性，只使用一个变量，第二种方法使用属性，第三种方法只是创建 UIImage 并将其添加为 subview ，然后根据它的标签..

哪种方法是正确的。我相信这三个选项听起来都是正确的。但是有什么特定的方法是我应该遵循的吗？这些选项中的任何一个在内存和性能方面是否更好？

提前致谢

安德烈亚斯

最佳答案

您可以使用附加到 View 层的动画。下面的代码淡出 View - 但还有许多其他方法可以删除它。 (需要附上QuartzCore框架)

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"]; 

关于iphone - iOS - 以编程方式添加/删除 subview ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7373544/