#import "ViewController.h"
@interface ViewController (){
UIImageView *iv;
}
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
iv = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
iv.image = [UIImage imageNamed:@"haha"];
[self.view addSubview:iv];
[iv addObserver:self forKeyPath:@"center" options:NSKeyValueObservingOptionNew context:nil];
UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(200, 0, 100, 100)];
[myButton setTitle:@"ahahah" forState:UIControlStateNormal];
myButton.layer.borderColor = [[UIColor redColor]CGColor];
myButton.layer.borderWidth = 10;
[myButton addTarget:self action:@selector(click:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:myButton];
}
-(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
if ([keyPath isEqualToString:@"center"]) {
NSLog(@"changed");
}
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)click:(id)sender {
[UIView animateWithDuration:0.5 animations:^{
iv.frame = CGRectMake(0, 300, 100, 100);
}
completion:^(BOOL finished){
}];
}
@end
结果没有监听到。
但是如果不用UIView的animation ，直接设置点击button之后imageview的frame变化，则可以监听到。这是为什么？怎么解决？谢谢啦先
------解决方案--------------------
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];