Question

I need to toggle a specific amount of times between two (or maybe later on more) pictures after a button was pressed, and wait a second or two for the change. When a stop-button is pressed at any time, the toggling should stop. My code by now looks like this

IBOutlet UIImageView *exerciseView;

- (void) repetitionCycle {

    stopButtonPressed = NO;
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; 

    for (NSInteger counter = kRepetitions; counter >=0; counter--) {
        exerciseView.image = [UIImage imageNamed:@"blue.jpg"];  
        [NSThread sleepForTimeInterval:kSleepDuration];                                                                 
        if (stopButtonPressed) {break;}     

        image = [UIImage imageNamed:kExerciseEndingPosition];                                                           
        exerciseView.image = [UIImage imageNamed:@"image1.jpg"];
        [NSThread sleepForTimeInterval:kSleepDuration];     

        if (stopButtonPressed) {break;}     
    }

    self.stopRepetitionCycle;
    [pool release];

}

exerciseView is
Besides other things, in stopRepetitionCycle I just set stopButtonPressed to YES, so it stops after it finished the “for” for the first time.
It does count down, it does stop after one cycle, but it doesn’t change the picture.

While fiddling around, I set the initial picture via IB, so it finally displayed ANYTHING.. The fun part, when I hit the stop button in the right moment, the second picture is shown. So I guessed I need to set the view manually every time the image should toggle. But

        [self.exerciseView addSubview:image];

gives me the error

Incompatible Objective-C types "struct UIImage *", expected "struct UIView *" when passing argument 1 of "addSubview:" from distinct Objective-C type

Also

        [self.exerciseView.image addSubview:image];

doesn’t do the job and gives me a

UIImage may not respond to addSubview

Any idea what I have to do here?

Thank you very much!

Answer 1

Use UIImageView. It has built-in support for this.

imageView.animationImages = [NSArray arrayWithObjects:[UIImage imageNamed:@"blue.jpg"], [UIImage imageNamed:@"image1.jpg"], nil];
imageView.animationDuration = kSleepDuration * [imageView.animationImages count];

Wire this function to the start button

- (IBAction) startAnimation {
    [imageView startAnimating];
}

and this to the stop button

- (IBAction) stopAnimation {
    [imageView stopAnimating];
}