Iphone 如何在UIView';上进行键值观察并获取KVO回调;什么样的框架?
我想查看Iphone 如何在UIView';上进行键值观察并获取KVO回调;什么样的框架?,iphone,ios,objective-c,uiview,key-value-observing,Iphone,Ios,Objective C,Uiview,Key Value Observing,我想查看ui视图的帧、边界或中心属性中的更改。我如何使用键值观察来实现这一点?编辑:我认为这个解决方案不够彻底。这个答案是出于历史原因而保留的。请参见我的最新答案: 您必须对frame属性执行KVO。在这种情况下,“self”是UIViewController 添加观察者(通常在viewDidLoad中完成): 删除观察者(通常在dealloc或VIEWDIDGEARE:中完成): 获取有关更改的信息 - (void)observeValueForKeyPath:(NSString *)key
ui视图
的帧
、边界
或中心
属性中的更改。我如何使用键值观察来实现这一点?编辑:我认为这个解决方案不够彻底。这个答案是出于历史原因而保留的。请参见我的最新答案:
您必须对frame属性执行KVO。在这种情况下,“self”是UIViewController 添加观察者(通常在viewDidLoad中完成): 删除观察者(通常在dealloc或VIEWDIDGEARE:中完成): 获取有关更改的信息
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if([keyPath isEqualToString:@"view.frame"]) {
CGRect oldFrame = CGRectNull;
CGRect newFrame = CGRectNull;
if([change objectForKey:@"old"] != [NSNull null]) {
oldFrame = [[change objectForKey:@"old"] CGRectValue];
}
if([object valueForKeyPath:keyPath] != [NSNull null]) {
newFrame = [[object valueForKeyPath:keyPath] CGRectValue];
}
}
}
通常存在不支持KVO的通知或其他可观察事件。即使医生说“不”,观察支持UIView的CALayer表面上是安全的。由于广泛使用KVO和适当的访问器(而不是ivar操作),观察CALayer在实践中起作用。这并不能保证继续下去 无论如何,视图的框架只是其他属性的产物。因此,我们需要遵守以下规定:
[self.view addObserver:self forKeyPath:@"frame" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"bounds" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"transform" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"position" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"zPosition" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"anchorPoint" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"anchorPointZ" options:0 context:NULL];
[self.view.layer addObserver:self forKeyPath:@"frame" options:0 context:NULL];
请参见此处的完整示例
注意:文档中不支持这一点,但到目前为止,它适用于所有iOS版本(当前为iOS 2->iOS 11)
注意:请注意,在回调最终值稳定之前,您将收到多个回调。例如,更改视图或图层的帧将导致图层更改位置
和边界
(按该顺序)
使用ReactiveCocoa,您可以
RACSignal *signal = [RACSignal merge:@[
RACObserve(view, frame),
RACObserve(view, layer.bounds),
RACObserve(view, layer.transform),
RACObserve(view, layer.position),
RACObserve(view, layer.zPosition),
RACObserve(view, layer.anchorPoint),
RACObserve(view, layer.anchorPointZ),
RACObserve(view, layer.frame),
]];
[signal subscribeNext:^(id x) {
NSLog(@"View probably changed its geometry");
}];
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.frame)),
rx.observe(CGRect.self, #keyPath(UIView.layer.bounds)),
rx.observe(CGRect.self, #keyPath(UIView.layer.transform)),
rx.observe(CGRect.self, #keyPath(UIView.layer.position)),
rx.observe(CGRect.self, #keyPath(UIView.layer.zPosition)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPoint)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPointZ)),
rx.observe(CGRect.self, #keyPath(UIView.layer.frame))
).merge().subscribe(onNext: { _ in
print("View probably changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.bounds))).subscribe(onNext: { _ in
print("View bounds changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.frame)),
rx.observe(CGRect.self, #keyPath(UIView.frame))).merge().subscribe(onNext: { _ in
print("View frame changed its geometry")
}).disposed(by: rx.disposeBag)
如果你只想知道什么时候bounds
改变,你可以这样做
@weakify(view);
RACSignal *boundsChanged = [[signal map:^id(id value) {
@strongify(view);
return [NSValue valueWithCGRect:view.bounds];
}] distinctUntilChanged];
[boundsChanged subscribeNext:^(id ignore) {
NSLog(@"View bounds changed its geometry");
}];
@weakify(view);
RACSignal *frameChanged = [[signal map:^id(id value) {
@strongify(view);
return [NSValue valueWithCGRect:view.frame];
}] distinctUntilChanged];
[frameChanged subscribeNext:^(id ignore) {
NSLog(@"View frame changed its geometry");
}];
如果您只想知道何时frame
发生更改,您可以这样做
@weakify(view);
RACSignal *boundsChanged = [[signal map:^id(id value) {
@strongify(view);
return [NSValue valueWithCGRect:view.bounds];
}] distinctUntilChanged];
[boundsChanged subscribeNext:^(id ignore) {
NSLog(@"View bounds changed its geometry");
}];
@weakify(view);
RACSignal *frameChanged = [[signal map:^id(id value) {
@strongify(view);
return [NSValue valueWithCGRect:view.frame];
}] distinctUntilChanged];
[frameChanged subscribeNext:^(id ignore) {
NSLog(@"View frame changed its geometry");
}];
目前无法使用KVO观察视图的帧。属性必须符合KVO才能被观察到。遗憾的是,UIKit框架的属性通常是不可见的,就像其他任何系统框架一样 从: 注意:尽管UIKit框架的类通常不支持KVO,但您仍然可以在应用程序的自定义对象(包括自定义视图)中实现它 此规则有一些例外,如NSOperationQueue的
操作
属性,但它们必须明确记录
即使在视图的属性上使用KVO目前可能有效,我也不建议在发布代码中使用它。这是一种脆弱的方法,依赖于未记录的行为。如果我可以参与对话的话:正如其他人所指出的,
frame
本身不能保证是可观察的关键值,CALayer
属性也不能保证是可观察的,即使它们看起来是
相反,您可以创建一个自定义的UIView
子类,该子类重写setFrame:
,并向代理宣布该收据。设置autoresizingMask
,使视图具有灵活的所有内容。将其配置为完全透明且小(以节省CALayer
备份的成本,但这并不重要),并将其添加为要查看大小变化的视图的子视图
早在我们第一次将iOS 5指定为要编码的API时,在iOS 4下,这就成功了,因此需要临时模拟
viewDidLayoutSubviews
(尽管覆盖layoutSubviews
更合适,但你明白了).在某些UIKit属性(如frame
)中使用KVO是不安全的。至少苹果是这么说的
我建议使用,这将帮助您在不使用KVO的情况下监听任何属性中的更改,使用信号很容易观察到某些内容:
[RACObserve(self, frame) subscribeNext:^(CGRect frame) {
//do whatever you want with the new frame
}];
如前所述,如果KVO不起作用,而您只想观察自己可以控制的视图,则可以创建一个覆盖setFrame或setBounds的自定义视图。需要注意的是,最终的所需帧值在调用时可能不可用。因此,我向下一个主线程循环添加了一个GCD调用,以再次检查该值
-(void)setFrame:(CGRect)frame
{
NSLog(@"setFrame: %@", NSStringFromCGRect(frame));
[super setFrame:frame];
// final value is available in the next main thread cycle
__weak PositionLabel *ws = self;
dispatch_async(dispatch_get_main_queue(), ^(void) {
if (ws && ws.superview)
{
NSLog(@"setFrame2: %@", NSStringFromCGRect(ws.frame));
// do whatever you need to...
}
});
}
有一种方法可以在根本不使用KVO的情况下实现这一点,为了其他人找到这篇文章,我将在这里添加它
Nick Lockwood的这篇优秀教程介绍了如何使用核心动画计时功能来驱动任何东西。它远优于使用计时器或CADisplay层,因为您可以使用内置的计时功能,或者相当容易地创建自己的立方贝塞尔函数(请参阅随附文章()。要不依赖KVO,您可以执行如下方法滑动:
@interface UIView(SetFrameNotification)
extern NSString * const UIViewDidChangeFrameNotification;
@end
@implementation UIView(SetFrameNotification)
#pragma mark - Method swizzling setFrame
static IMP originalSetFrameImp = NULL;
NSString * const UIViewDidChangeFrameNotification = @"UIViewDidChangeFrameNotification";
static void __UIViewSetFrame(id self, SEL _cmd, CGRect frame) {
((void(*)(id,SEL, CGRect))originalSetFrameImp)(self, _cmd, frame);
[[NSNotificationCenter defaultCenter] postNotificationName:UIViewDidChangeFrameNotification object:self];
}
+ (void)load {
[self swizzleSetFrameMethod];
}
+ (void)swizzleSetFrameMethod {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
IMP swizzleImp = (IMP)__UIViewSetFrame;
Method method = class_getInstanceMethod([UIView class],
@selector(setFrame:));
originalSetFrameImp = method_setImplementation(method, swizzleImp);
});
}
@end
现在观察应用程序代码中UIView的帧更改:
- (void)observeFrameChangeForView:(UIView *)view {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(viewDidChangeFrameNotification:) name:UIViewDidChangeFrameNotification object:view];
}
- (void)viewDidChangeFrameNotification:(NSNotification *)notification {
UIView *v = (UIView *)notification.object;
NSLog(@"View '%@' did change frame to %@", v, NSStringFromCGRect(v.frame));
}
更新了@hfossli对RxSwift和Swift 5的回答 使用RxSwift,您可以
RACSignal *signal = [RACSignal merge:@[
RACObserve(view, frame),
RACObserve(view, layer.bounds),
RACObserve(view, layer.transform),
RACObserve(view, layer.position),
RACObserve(view, layer.zPosition),
RACObserve(view, layer.anchorPoint),
RACObserve(view, layer.anchorPointZ),
RACObserve(view, layer.frame),
]];
[signal subscribeNext:^(id x) {
NSLog(@"View probably changed its geometry");
}];
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.frame)),
rx.observe(CGRect.self, #keyPath(UIView.layer.bounds)),
rx.observe(CGRect.self, #keyPath(UIView.layer.transform)),
rx.observe(CGRect.self, #keyPath(UIView.layer.position)),
rx.observe(CGRect.self, #keyPath(UIView.layer.zPosition)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPoint)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPointZ)),
rx.observe(CGRect.self, #keyPath(UIView.layer.frame))
).merge().subscribe(onNext: { _ in
print("View probably changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.bounds))).subscribe(onNext: { _ in
print("View bounds changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.frame)),
rx.observe(CGRect.self, #keyPath(UIView.frame))).merge().subscribe(onNext: { _ in
print("View frame changed its geometry")
}).disposed(by: rx.disposeBag)
如果你只想知道什么时候bounds
改变,你可以这样做
RACSignal *signal = [RACSignal merge:@[
RACObserve(view, frame),
RACObserve(view, layer.bounds),
RACObserve(view, layer.transform),
RACObserve(view, layer.position),
RACObserve(view, layer.zPosition),
RACObserve(view, layer.anchorPoint),
RACObserve(view, layer.anchorPointZ),
RACObserve(view, layer.frame),
]];
[signal subscribeNext:^(id x) {
NSLog(@"View probably changed its geometry");
}];
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.frame)),
rx.observe(CGRect.self, #keyPath(UIView.layer.bounds)),
rx.observe(CGRect.self, #keyPath(UIView.layer.transform)),
rx.observe(CGRect.self, #keyPath(UIView.layer.position)),
rx.observe(CGRect.self, #keyPath(UIView.layer.zPosition)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPoint)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPointZ)),
rx.observe(CGRect.self, #keyPath(UIView.layer.frame))
).merge().subscribe(onNext: { _ in
print("View probably changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.bounds))).subscribe(onNext: { _ in
print("View bounds changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.frame)),
rx.observe(CGRect.self, #keyPath(UIView.frame))).merge().subscribe(onNext: { _ in
print("View frame changed its geometry")
}).disposed(by: rx.disposeBag)
如果您只想知道何时frame
发生更改,您可以这样做
RACSignal *signal = [RACSignal merge:@[
RACObserve(view, frame),
RACObserve(view, layer.bounds),
RACObserve(view, layer.transform),
RACObserve(view, layer.position),
RACObserve(view, layer.zPosition),
RACObserve(view, layer.anchorPoint),
RACObserve(view, layer.anchorPointZ),
RACObserve(view, layer.frame),
]];
[signal subscribeNext:^(id x) {
NSLog(@"View probably changed its geometry");
}];
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.frame)),
rx.observe(CGRect.self, #keyPath(UIView.layer.bounds)),
rx.observe(CGRect.self, #keyPath(UIView.layer.transform)),
rx.observe(CGRect.self, #keyPath(UIView.layer.position)),
rx.observe(CGRect.self, #keyPath(UIView.layer.zPosition)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPoint)),
rx.observe(CGRect.self, #keyPath(UIView.layer.anchorPointZ)),
rx.observe(CGRect.self, #keyPath(UIView.layer.frame))
).merge().subscribe(onNext: { _ in
print("View probably changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.bounds))).subscribe(onNext: { _ in
print("View bounds changed its geometry")
}).disposed(by: rx.disposeBag)
Observable.of(rx.observe(CGRect.self, #keyPath(UIView.layer.frame)),
rx.observe(CGRect.self, #keyPath(UIView.frame))).merge().subscribe(onNext: { _ in
print("View frame changed its geometry")
}).disposed(by: rx.disposeBag)
这实际上不是一个问题。我只是想发布我的答案,因为我无法通过谷歌搜索和StackOverflow找到解决方案:-)…叹气!。。。分享就这么多…问一些你觉得有趣的问题,并且你已经有了解决方案,这是非常好的。然而-在问题的措辞上投入更多的精力,让它听起来真的像一个人会问的问题。很棒的QA,谢谢hfossil!!!不起作用。可以为UIView中的大多数属性添加观察者,但不能为框架添加观察者。我收到一条关于“可能未定义的键路径‘frame’”的编译器警告。不管怎么做,忽略这个警告,observeValueForKeyPath方法永远不会被调用。我现在在这里发布了一个更晚、更健壮的版本。确认了,对我也适用。UIView.frame可以正确地观察到。有趣的是,UIView.bounds不是。@hfossli你是对的,你不能