Iphone 监视图像属性更改的UIImageView

如何检测

UIImageview

是否更改，以及图像更改时如何显示

NSLog

？这是我的密码：

-(void)changePhotoStatus
{
    NSArray *myArray = [NSArray arrayWithObjects:[NSString stringWithFormat:@"FasterText.png"],[NSString stringWithFormat:@"Don'tTouchText.png"],nil];

    fasttext.image = [UIImage imageNamed:[myArray objectAtIndex:arc4random() % [myArray count]]];

    if (fasttext.image == [UIImage imageNamed:@"Don'tToucText.png"]) {
        NSLog(@"cahn");
    }
}

---

我使用

NSTimer

调用图像的更改。但是

NSLog

不会出现。请提供帮助。

您可以使用键值编码，如下所示

- (void)registerSelfAsObserverForImageView
 {
    [imageView addObserver:self
                forKeyPath:@"image"
                   options:(NSKeyValueObservingOptionNew |
                            NSKeyValueObservingOptionOld)
                context:NULL];
}


- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context 
{
    // Put your code here to handle event of the imageview (object) changing value :)

    [super observeValueForKeyPath:keyPath
                         ofObject:object
                           change:change
                          context:context];
}

不要忘记在dealloc中注销，或者当您不再需要更新时

- (void)unregisterForChangeNotification
 {
     [imageView removeObserver:self forKeyPath:@"image"];
 }

---

这里有一个解决方案，假设您已正确设置视图文件

#import "JDemoViewController.h"

@interface JDemoViewController ()

@property (nonatomic, retain) NSArray *imageNameArray;

- (void) handleTimerEventFired;

@end

@implementation JDemoViewController

@synthesize imageView = _imageView;
@synthesize imageNameArray = _imageNameArray;

- (void) dealloc
{
    self.imageView = nil;
    self.imageNameArray = nil;
    [super dealloc];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    self.imageNameArray = [NSArray arrayWithObjects:@"img1",@"img2",@"img3",@"img4", nil];

    [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(handleTimerEventFired) userInfo:nil repeats:YES];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void) handleTimerEventFired
{    
    NSString *tempImageName = [self.imageNameArray objectAtIndex:(arc4random()%4)];

    UIImage* image = [UIImage imageNamed:tempImageName];

    self.imageView.image = image;

    if(tempImageName == @"img3")
    {
        NSLog(@"Image 3 was Loaded !");
    }

}

@end

---

更改完图像后，不要忘记使计时器失效。仔细检查nstimer代码。或者，如果计时器启动，则无需使其失效。只有在你想阻止它开火的时候才可以。@CameronLowellPalmer请检查这篇文章——这篇文章几乎完全是苹果定时器编程主题的副本。正如它所说的，如果它是重复的，你需要自己使它无效。然而，它是否无效取决于具体情况。

[NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(changePhotoStatus) userInfo:nil repeats:YES];