How to preform an action while the button is pressed? - ios

Question

I have a button and i need to change the label while the button is pressed to #"PRESSED" and if it's let go I need to change it to #"LET GO".
I've found many answers, but i have no idea how to implement them in Xcode 5.
That are the ones i tried:
You can start your action on the touchDownInside and stop it on the touchUpInside actions - you can hook them up in IB.
or
Add targets to your button for both control states, UIControlEventTouchDown and UIControlEventTouchUpInside or UIControlEventTouchUpOutside
or even
Add a dispatch source iVar to your controller...
dispatch_source_t _timer;
Then, in your touchDown action, create the timer that fires every so many seconds. You will do your repeating work in there.
If all your work happens in UI, then set queue to be
dispatch_queue_t queue = dispatch_get_main_queue();
and then the timer will run on the main thread.
- (IBAction)touchDown:(id)sender {
if (!_timer) {
dispatch_queue_t queue = dispatch_get_global_queue(
DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
// This is the number of seconds between each firing of the timer
float timeoutInSeconds = 0.25;
dispatch_source_set_timer(
_timer,
dispatch_time(DISPATCH_TIME_NOW, timeoutInSeconds * NSEC_PER_SEC),
timeoutInSeconds * NSEC_PER_SEC,
0.10 * NSEC_PER_SEC);
dispatch_source_set_event_handler(_timer, ^{
// ***** LOOK HERE *****
// This block will execute every time the timer fires.
// Do any non-UI related work here so as not to block the main thread
dispatch_async(dispatch_get_main_queue(), ^{
// Do UI work on main thread
NSLog(#"Look, Mom, I'm doing some work");
});
});
}
dispatch_resume(_timer);
}
Now, make sure to register for both touch-up-inside and touch-up-outside
- (IBAction)touchUp:(id)sender {
if (_timer) {
dispatch_suspend(_timer);
}
}
Make sure you destroy the timer
- (void)dealloc {
if (_timer) {
dispatch_source_cancel(_timer);
dispatch_release(_timer);
_timer = NULL;
}
}
I am new to iOS and have no idea whatsoever how to do any of that! Thanks a lot for any help in advance!

Answer 1

I would do this with a GestureRecognzier. Here is some code:
- (void)viewDidLoad
{
[super viewDidLoad];
UILongPressGestureRecognizer *gr = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(buttonIsPressed:)];
gr.minimumPressDuration = 0.1;
[self.button addGestureRecognizer:gr];
}
-(IBAction)buttonIsPressed:(UILongPressGestureRecognizer*)gesture {
if (gesture.state == UIGestureRecognizerStateBegan) {
self.label.text = #"Button is pressed!";
}
else if (gesture.state == UIGestureRecognizerStateEnded) {
self.label.text = #"Button is not pressed";
}
}
You need an IBOutlet for the label and the button.

Answer 2

The first method does what you want, here's an example implementation:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIButton *myButton = [[UIButton alloc] initWithFrame:CGRectMake(self.view.bounds.size.width / 2.0 - 50.0, self.view.bounds.size.height / 2.0 - 25.0, 100.0, 50.0)];
myButton.backgroundColor = [UIColor colorWithRed:0.2 green:0.3 blue:0.8 alpha:1.0];
[myButton setTitle:#"PRESS ME" forState:UIControlStateNormal];
[myButton addTarget:self action:#selector(setPressed:) forControlEvents:UIControlEventTouchDown];
[myButton addTarget:self action:#selector(setLetGo:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:myButton];
}
-(void)setPressed:(id)sender
{
UIButton *myButton = (UIButton *)sender;
[myButton setTitle:#"PRESSED" forState:UIControlStateNormal];
}
-(void)setLetGo:(id)sender
{
UIButton *myButton = (UIButton *)sender;
[myButton setTitle:#"LET GO" forState:UIControlStateNormal];
}

Answer 3

If you are new to xCode this can be difficult to understand. Follow this and you'll be allright.
Go to Storyboard and put a button in the view now go to the Inspector and change State config from Default to Highlighted
In placeholder 'highlighted title' put 'Pressed'
Now click on the Assistant Editor to open the .m file next to Storyboard
CNTRL + Click and drag from the Button to the .m file code to create a TouchUpInside event, mine called buttonPressed
Put this code in the method body and you are good to go!
This is what it will look like, pressed and released: