UIView animation 里面的center值变化了，但是KVO监听不到？

Question

animationuiviewimageviewKVO

Answer 1

在看了几篇讨论和文章后
1. http://stackoverflow.com/questions/1555690/key-value-observing-during-uiview-animations
2. http://stackoverflow.com/questions/1557739/observing-animated-property-changes-in-a-calayer
3.https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/CoreAnimation_guide/AnimatableProperties/AnimatableProperties.html#//apple_ref/doc/uid/TP40004514-CH11-SW1通过timer去选择性的获取属性变化是可靠的办法
动画可以做的属性见3，没有center， kvo观察它没有意义通过实验实现动画layer的delegate
观察postion靠谱，我自己实验了一个小程序，仅供参考,希望能对你有帮助～//
//  ViewController.m
//  ObsverveAnimationProperty
//
//  Created by xiaomanwang on 14-3-7.
//  Copyright (c) 2014年 xiaomanwang. All rights reserved.
//#import "ViewController.h"static const int duration = 2;@interface ViewController ()@property(nonatomic, strong)UIView*viewForAnimated;
@property(nonatomic, strong)NSTimer *timer;@end@implementation ViewController- (void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    _viewForAnimated = [UIView new];
    _viewForAnimated.backgroundColor = [UIColor redColor];
    _viewForAnimated.frame = CGRectMake(20, 20, 100,100);
    [self.view addSubview:_viewForAnimated];    _viewForAnimated.layer.delegate = self;
    
    UIButton*btn = [UIButton buttonWithType:UIButtonTypeCustom];
    [btn setTitle:@"do" forState:UIControlStateNormal];    [btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [self.view addSubview:btn];
    btn.frame = CGRectMake(200, 100, 40, 30);
    [btn addTarget:self action:@selector(doAnimation) forControlEvents:UIControlEventTouchUpInside];
    
//    [self addObserver:self forKeyPath:@"viewForAnimated.frame" options:NSKeyValueObservingOptionNew context:NULL];
    [self addObserver:self forKeyPath:@"viewForAnimated.layer.presentationLayer.position" options:NSKeyValueObservingOptionNew context:NULL];
    [self addObserver:self forKeyPath:@"viewForAnimated.layer.presentationLayer.bounds" options:NSKeyValueObservingOptionNew context:NULL];}- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    //这里观察的presentationlayer没有东西，观察不到,动画的时候的presentationlayer是临时创建的
    NSLog(@"change:%@",change);
}- (void)doAnimation
{
    self.timer = [NSTimer timerWithTimeInterval:0.01 target:self selector:@selector(getPos) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
    
    CGRect frame = _viewForAnimated.frame;
    if(_viewForAnimated.frame.origin.y >= 250.0)
    {
        frame.origin.y = 20;
    }
    else
    {
        frame.origin.y = 250;
    }
    [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
        
        _viewForAnimated.frame = frame;
        
    } completion:^(BOOL finished) {
        [self performSelector:@selector(stopTimer) withObject:nil afterDelay:duration];
    }];
}- (void)stopTimer
{
    if(self.timer)
    {
        [self.timer invalidate];
        self.timer = nil;
    }
}- (void)getPos
{
    NSLog(@"current pos%@",NSStringFromCGPoint([[_viewForAnimated.layer presentationLayer] position]));
}- (id<CAAction>)actionForLayer:(CALayer *)layer forKey:(NSString *)event
{
    NSLog(@"view.layer:%@",_viewForAnimated.layer);
    NSLog(@"view.layer.presentationLayer:%@",_viewForAnimated.layer.presentationLayer);
    //这里观察到的event是position
    NSLog(@"layer:%@:event:%@",layer, event);
    return nil;
}@end

Answer 2

一般UIView显式的去进行动画时，他的位置其实没有变，只不过在图层树中的显示图层在变化，让你有种在动画的效果。

Answer 3

太谢谢了！虽然问题我自己之前解决掉了，今天刚上CSDN才看到，但是还是太谢谢您了！