iOS - 以编程方式添加/删除子视图 [英] iOS - adding/removing a subview programmatically
问题描述
好的我想添加一个UIImageView作为子视图，然后在启动画面工作的几秒钟后删除它。我找到了三种不同的方法，但根据Objective-C和Apple，我无法理解哪种方法是最好的方法。
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.
以下是三种不同的方法：
Below are the three different approaches:
1）
在我的MyAppDelegate.h中
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
和MyAppDelegate.m
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）第二种方法：
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
和MyAppDelegate.m
and in MyAppDelegate.m
@synthesize myImageView;
@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）第三种方法：
In my MyAppDelegate.h
@interface MyAppDelegate : NSObject <UIApplicationDelegate> {
MyViewController *myViewController;
}
@property (nonatomic, retain) IBOutlet MyViewController *myViewController;
@property (nonatomic, retain) IBOutlet UIWindow *window;
@end
和MyAppDelegate.m
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];
}
总结一下..第一种方法不使用UIImage的属性只是一个变量，第二个使用属性，第三个只创建UIImage并将其添加为子视图，然后根据其标记将其删除..
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..
这是正确的方法。我相信所有三个选项都是正确的......但是我有什么办法可以遵循。这些选项中的任何一个在内存和性能方面都更好吗？
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?
提前致谢，
Andreas
推荐答案
如果您不打算再次使用该图像，则无需保留指针。此外，如果您使用 IBOutlet ，您还需要在IB中添加视图。在这个具体的例子中，我会说选项3是最有意义的，特别是考虑到这个选择你可以从标准的基于视图的应用程序模板开始，只需添加关于图像视图的位并离开其余的人。最后一个观察选择3; 2个消息到窗口;
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];
似乎超出任何方法的范围。这可能只是一个复制和粘贴错误，但请注意它们应位于 didFinishLaunchingWithOptions ：
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:"
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