Tapping button to go through each frame of animation - iphone

Question

I am trying to create an app where when you tap a button it will go to the next frame in an animation.
I have 8 image files, and when I press the button I want the 1st image to display, and when i press the button again, I want the 2nd image to replace the 1st image and so on.
I was thinking something like:
-(IBAction)buttonPressDoStuff:(id)sender {
imageThing.image = [UIImage imageNamed:#"image1.png"];
imageThing.image = [UIImage imageNamed:#"image2.png"];
imageThing.image = [UIImage imageNamed:#"image3.png"];
imageThing.image = [UIImage imageNamed:#"image4.png"];
}
and somehow making this all work consecutively with each press.
I am fairly new at objective c, so any help would be much appreciated.
Can anyone throw up some sample code to do this?

Answer 1

Let's think about this. If you want to do something sequentially, that sounds like the job of an array. So what do you think about this:
In your .h file, add these instance variables:
NSMutableArray* picturesArray;
NSInteger counter;
And now in your .m file, in your class' init method:
//this loop will fill your array with the pictures
for(int idx = 0; idx < NUMBER_OF_PICTURES; idx++) {
//IMPORTANT: this assumes that your pictures' names start with
//'image0.png` for the first image, then 'image1.png`, and so on
//if your images' names start with 'image1.png' and then go up, then you
//should change the 'int idx = 0' declaration in the for loop to 'int idx = 1'
//so the loop will start at 0. You will then need to change the condition
//to 'idx < (NUMBER_OF_PICTURES + 1)' to accomodate the last image
NSString* temp = [NSString stringWithFormat:#"image%i.png", idx];
UIImage* tempImage = [UIImage imageNamed:temp];
[picturesArray addObject:tempImage];
}
and in your buttonPressDoStuff: method:
//this method will move to the next picture in the array each time it is pressed
-(IBAction)buttonPressDoStuff:(id)sender {
if(counter < [pictureArray count]) {
imageThing.image = [picturesArray objectAtIndex:counter];
counter++;
}
}
Your init method should look something like this:
- (id)initWithNibName:(NSString*)nibNameOrNil bundle:(NSBundle*)nibBundleOrNil {
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if(self) {
//do setup here
for(int idx = 0; idx < NUMBER_OF_PICTURES; idx++) {
NSString* temp = [NSString stringWithFormat:#"image%i.png", idx];
UIImage* tempImage = [UIImage imageNamed:temp];
[picturesArray addObject:tempImage];
}
}
//it is important that you return 'self' no matter what- if you don't,
//you will get the 'control reached end of non-void method' warning
return self;
}