How do you move a UIImage when you hold a button? - ios

Question

I declared 2 IBActions "rightButtonPress" and "leftButtonPress" I linked them to 2 IBOutlets and ran a block of code in the IBactions:
-(void)leftButtonPress:(id)sender{
PlayerSprite.center = CGPointMake(PlayerSprite.center.x - 1, PlayerSprite.center.y);
}
-(void)rightButtonPress:(id)sender{
PlayerSprite.center = CGPointMake(PlayerSprite.center.x + 1, PlayerSprite.center.y);
}
and i also created 2 timers:
- (void)viewDidLoad
{
TouchLeftCheck = [NSTimer scheduledTimerWithTimeInterval:.01
target:self
selector:#selector(leftButtonPress:)
userInfo:nil
repeats:YES];
TouchRightCheck = [NSTimer scheduledTimerWithTimeInterval:.01
target:self
selector:#selector(rightButtonPress:)
userInfo:nil
repeats:YES];
BarrelEntrance = [NSTimer scheduledTimerWithTimeInterval:.01
target:self
selector:#selector(barrelStartDown)
userInfo:nil
repeats:YES];
[self frontBarrelAnimation];
[super viewDidLoad];
// Do any additional setup after loading the view.
}
it all works well but when i linked it up to two IBObject Buttons something didn't work, when i linked my IBActions to my Objects(buttons), with "Touch Down" it didn't work. When i was in the ios simulator it only moved my object i time when i held and then it stopped, if you touch it again then the object moves one more time. But is there a link option that will allow me to make it do a smooth animation across the screen when i hold it down, and then stop when i let go? Thanks.

Answer 1

There are three components here:
A timer for animation
The start-touch event
The end-touch event
I recommend using an NSTimer to animate the view while the button is being pressed. This timer will be initialized and started when the button is pressed (touchDown:) and invalidated/nullified when the button is released (touchUpInside: and touchUpOutside:).
So to start off, bind the touch events to the button. (I assume that you are creating these buttons in interface builder, which is fine. If so, you can skip the initialization and just go straight to the addTarget: methods):
UIButton* leftButton = [[UIButton alloc] initWithFrame:...];
[leftButton addTarget:self action:#selector(startLeftAnimation) forControlEvents:UIControlEventTouchDown];
[leftButton addTarget:self action:#selector(stopAnimation) forControlEvents:UIControlEventTouchUpInside];
[leftButton addTarget:self action:#selector(stopAnimation) forControlEvents:UIControlEventTouchUpOutside];
Next, declare an instance variable timer:
#interface MyViewController
{
NSTimer* animationTimer;
}
Create the methods for the button events:
- (void)startLeftAnimation
{
animationTimer = [NSTimer scheduledTimerWithInterval: 0.02 target:self selector:#selector(animateLeft) userInfo:nil repeats:YES];
}
- (void)stopAnimation
{
if(animationTimer != nil)
{
[animationTimer invalidate];
animationTimer = nil;
}
}
Finally, create the animation method
- (void)animateLeft
{
PlayerSprite.center = CGPointMake(PlayerSprite.center.x - 1, PlayerSprite.center.y);
}
Rinse and repeat for the right button animation.