暂停 UIImageview 动画

Question

我想暂停UIImageView animation，根据我的研究发现，您可以停止图像的动画，但不能暂停序列。通过在UIImageView上调用语句 stop animating，它将停止动画并空白图像视图。

要暂停UIImages的动画，必须使用NSTimer。

我已经在应用程序中使用一种NSTimer以不同的时间间隔一个接一个地加载view controllers。我在每个view controller都有一个UIImages的幻灯片。

问题是当计时器暂停view controllers暂停进一步加载时，但当时显示的view controller仍会反复显示该view controller UIImages的幻灯片放映，直到暂停恢复。所以我也想暂停幻灯片。

这是我使用NSTimer的地方

-(void)playpauseAction:(id)sender {
if([audioPlayer isPlaying])
{
    [sender setImage:[UIImage imageNamed:@"Play Icon.png"] forState:UIControlStateSelected];
    [audioPlayer pause];
    [self pauseTimer];
}else{
    [sender setImage:[UIImage imageNamed:@"pause.png"] forState:UIControlStateNormal];
    [audioPlayer play];
    [self resumeTimer];
if(isFirstTime == YES)
    {
     self.timer = [NSTimer scheduledTimerWithTimeInterval:11.0
                                         target:self
                                         selector:@selector(displayviewsAction:)
                                         userInfo:nil
                                        repeats:NO];
        isFirstTime  = NO;
    }         
    } 
    }

这就是 displayviewsAction 以不同的时间间隔依次加载 11 个视图控制器的方式

- (void)displayviewsAction:(id)sender
 {  
 First *firstController = [[First alloc] init];
 firstController.view.frame = CGRectMake(0, 0, 320, 480);
 CATransition *transitionAnimation = [CATransition animation];
 [transitionAnimation setDuration:1];
 [transitionAnimation setType:kCATransitionFade];
 [transitionAnimation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
 [self.view.layer addAnimation:transitionAnimation forKey:kCATransitionFade];
 [self.view addSubview:firstController.view];
 [self.view addSubview:toolbar];
 [firstController release];   
 self.timer = [NSTimer scheduledTimerWithTimeInterval:23 target:self selector:@selector(Second) userInfo:nil repeats:NO];     
 }
 -(void)Second 
{
Second *secondController = [[Second alloc] init];
secondController.view.frame = CGRectMake(0, 0, 320, 480);
CATransition *transitionAnimation = [CATransition animation];
[transitionAnimation setDuration:1];
[transitionAnimation setType:kCATransitionReveal];
[transitionAnimation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
[self.view.layer addAnimation:transitionAnimation forKey:kCATransitionReveal];
[self.view addSubview:secondController.view]; 
[self.view addSubview:toolbar];
[secondController release];
self.timer = [NSTimer scheduledTimerWithTimeInterval:27 target:self selector:@selector(Third) userInfo:nil repeats:NO];
}

这就是在视图控制器中启动图像动画的方式

// Displays UIImageView
UIImageView* ImageView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 5, 300, 235)];
self.view.backgroundColor = [UIColor brownColor];
// load all the frames of our animation
ImageView.animationImages = [NSArray arrayWithObjects:    
                                [UIImage imageNamed:@"1a.png"],
                                [UIImage imageNamed:@"1b.png"],
                                nil];
 // all frames will execute in 25 seconds
 ImageView.animationDuration = 25;
// start animating
[ImageView startAnimating];
ImageView.layer.borderWidth = 2;
ImageView.layer.borderColor = [[UIColor whiteColor]CGColor];
[ImageView.layer setMasksToBounds:YES];
[ImageView.layer setCornerRadius:15.0f];
[baseView addSubview:ImageView]; 

现在，如果有人可以指导我如何在此NSTimer暂停时暂停此UIImage animation幻灯片。

感谢您的帮助。

Answer 1

您可以使用

Apple提供的代码来暂停和恢复动画。

-(void)pauseLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
layer.speed = 0.0;
layer.timeOffset = pausedTime;
}
-(void)resumeLayer:(CALayer*)layer
{
CFTimeInterval pausedTime = [layer timeOffset];
layer.speed = 1.0;
layer.timeOffset = 0.0;
layer.beginTime = 0.0;
CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
layer.beginTime = timeSincePause;
}

要让 CALayer 传递给 pauseLayer 函数，您可以使用以下代码。

CALayer *player = ImageView.layer;
[self pauseLayer:player];

希望对您有所帮助。