UITapGestureRecognizer initWithTarget:action: method to take arguments? - ios

I'm using UITapGestureRecognizer because I'm using a UIScrollView that acts as a container for my UILabels. Basically I'm trying to use an action method with arguments so I can e.g. send myLabel.tag value to the action method to know what action to take depending on what UILabel has has been triggered by a tap.
One way of doing it is having as many action methods as UILabels but that isn't very "pretty" codewise. What I would like to achieve is just having one action method with switch statements.
Is this possible or will I have to do it like this (sigh):
UITapGestureRecognizer *myLabel1Tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(myLabel1Tap)];
[myLabel1Tap addGestureRecognizer:myLabel1Tap];
UITapGestureRecognizer *myLabel2Tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(myLabel2Tap)];
[myLabel1Tap addGestureRecognizer:myLabel2Tap];
UITapGestureRecognizer *myLabelNTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(myLabelNTap)];
[myLabel1Tap addGestureRecognizer:myLabelNTap];
- (void)myLabel1Tap {
// Perform action
}
- (void)myLabel2Tap {
// Perform action
}
- (void)myLabelNTap {
// Perform action
}

Add a single gesture recognizer to the view that is the superview of your various labels:
UITapGestureRecognizer *myLabelTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(myLabelTapHandler:)];
[myLabelParent addGestureRecognizer:myLabelTap];
Then when you handle the gesture, determine which label was tapped:
-(void)myLabelTapHandler:(UIGestureRecognizer *)gestureRecognizer {
UIView *tappedView = [gestureRecognizer.view hitTest:[gestureRecognizer locationInView:gestureRecognizer.view] withEvent:nil];
// do something with it
}

You can use just one UITapGestureRecognizer and in your gesture handler (your myLaberXTap), which has the syntax:
- (void)handleGesture:(UITapGestureRecognizer*)gestureRecognizer {
...
}
use gesture.view to know which view you are working on.

Related

How can I tell a custom UIView with UITextField receive touch events

What I'm working with is I have a custom UIView that combines a UILabel with a UITextField as part of some user input. I have several of these throughout the view that is being displayed in the app. What would be good is to be able to have the user touch either the UILabel or the UITextField and then have the UITextField allow for input of the field.
Is there an easy way to do this?
Add a tap gesture recognizer to your label, and when tapped tell the corresponding textfield to become first responder (which brings up the keyboard).
// In your init or awakeFromNib:
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(labelTapped:)];
self.label.userInteractionEnabled = YES;
[self.label addGestureRecognizer:tap];
...
- (void)labelTapped:(id)sender
{
[self.textField becomeFirstResponder];
}
Yes, there is and I actually tested it. You can add a tap gesture recognizer to your view (the one that contains the label and the text view) like so:
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(viewTapped:)];
[self addGestureRecognizer:[tap autorelease]];
and then, inside viewTapped:
-(void)viewTapped:(id)sender {
[self.yourTextField becomeFirstResponder];
}
Hope this helps!
You can define UIGestureRecognizer delegate method and check that is the the required tap gesture area . If it is then return TRUE else return FALSE .
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
// Disallow recognition of tap gestures in the segmented control.
if ((touch.view == yourButton)) {//change it to your condition
return NO;
}
return YES;
}

Adding a tap Gesture that calls a method in another class

Simply I want to add a tap gesture for a UIImageView that when the user touches, calls a method that is implemented in another class (not the same class that contains the UIImageView).
Can I do this and if so how can i do it ?
You can do that. But you need the instance of the target class (class in which method is going to execute) as delegate or something in the gesture adding class.
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self.delegate action:#selector(doSomething)];
Here delegate will be the instance of the target class that you have to set before going to that class.
Edit
I will explain a little more. Suppose you have two view controller classes VCA and VCB. you want to call a method in VCA from VCB through a tap gesture.
in VCB.h
#property (nonatomic,assign)VCA *delegate;
in VCB.m
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self.delegate action:#selector(doSomething)];
in VCA.m
You will present/ push VCB
VCB * viewController = [[VCB alloc]init];
viewController.delegate = self;
// push or present viewController
Declare recognizer selector on init
UITapGestureRecognizer *recognizer =
[UITapGestureRecognizer
initWithTarget:objectOfAnotherClass
action:#selector(methodImplementedOnObjectOfAnotherClass:)];
dont forget about defining number of taps (numberOfTapsRequired) and optional gesture recognizer required to fail (requireGestureRecognizerToFail:)
Link to article about selector.
One straightforward approach is calling the method of another class from the selector method of tapGesture ie.
Add UITapGestureRecogniser to the imageview
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self action:#selector(tapRecognised)];
[imageView addGestureRecognizer:tapGesture];
Dont forget to enable the userInteraction of the UIImageView, because by default for imageview userInteraction is disabled.
you can do this like below.
imageView.userInteractionEnabled = YES;
Then in the selector of tapGestureRecogniser call the method of another class
- (void)tapRecognised
{
[next tappedOnImage];
}
Here next is the object of another class. You can use delegation also to call the method.
Hope this will help you.
here self.desired view is the view in which you want to add gesture and you should add gesture in following way
and "webViewTapped.delegate = self" means you want to call a function of the same class when user tap and you can change it to your desired function by using delegate like self.delegate
UITapGestureRecognizer *viewTapped = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(tapAction:)];
webViewTapped.numberOfTapsRequired = 1;
webViewTapped.delegate = self;
[self.desiredView addGestureRecognizer:viewTapped];
- (void)tapAction:(UITapGestureRecognizer *)sender;
{
// do your stuff here
}

Button calc stopped working

I have a simple program that does a calculation on a button press. The result is placed into a label using the following code:
//converts the float to 2 descimal places then converts it to a string
NSString *stringRectResult=[[NSString alloc]
initWithFormat:#"%1.2f",floatCalcResult];
//displays the string result in the label
resultLabel.text=stringRectResult;
It works perfectly, however, I added in code to hide the decimal keyboard when the user touches off the keyboard. That works, but when I added this code the button to update the label no longer worked. Can anyone help? The code to hide the keyboard is below. The app works when I comment it out but does not when it is active
In viewDidLoad:
UITapGestureRecognizer *tapRecognizer = [[UITapGestureRecognizer alloc]
initWithTarget:self action:#selector(tap:)];
[self.view addGestureRecognizer:tapRecognizer];
Tap selector...
-(void)tap:(UIGestureRecognizer *)gr
{
[self.view endEditing:YES];
}
Thanks for any and all help.
The problem is that by intercepting all of the user's taps (in order to hide the keyboard), you're preventing any other user interface elements from being tapped. I would urge you to rethink your design; it's not usually necessary to have an explicit facility to hide the keyboard.
If you do want to keep this design, you can implement the gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: method in your class:
- (void) viewDidLoad
{
// ...
UITapGestureRecognizer *tapRecognizer = [[UITapGestureRecognizer alloc]
initWithTarget:self action:#selector(tap:)];
tapRecognizer.delegate = self;
[self.view addGestureRecognizer:tapRecognizer];
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}
Two things to keep in mind:
You need to mark your view controller as conforming to the UIGestureRecognizerDelegate protocol.
If you later add a second gesture recognizer to the view, you'll need to add a check inside the second method to treat the second recognizer differently.

Gesture Recognizers and Blocks

Can we use blocks with Gesture Recognizers? It doesn't appear so. For example, this does not work:
UITapGestureRecognizer *tapped = [[UITapGestureRecognizer alloc] initWithTarget: self
action:^(id sender) {
}
];
Am I missing something, or are blocks just not supported by the UIGestureRecognizer class?
However, this should:
UITapGestureRecognizer *tapped = [[UITapGestureRecognizer alloc] initWithTarget:[^{
// do stuff
} copy] action:#selector(invoke)];
You shouldn't probably do this, however, since it's a private method.

Handle tap gesture with an argument iphone / ipad

My problem is similar to this one with the only exception - my ImageView appears at the same place inside the window with different content in it. Content has unique identifier which I want to use to call content-specific actions.
To quickly recap, the guy is looking for a way to pass a parameter into the selector section of the initWithTarget method.
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleTapGesture:itemSKU:)];
How can I pass an attribute to the handleTapGesture method or how do I read the unique value otherwise?
Any thoughts appreciated.
EDIT: The content is being pulled from a database and is different every time. The unique identifier is pretty much like an SSN - doesn't repeat.
You could set the UIImageView tag property with your content identifier, and then read that information form the selector.
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleTapGesture:)];
[imageView addGestureRecognizer:tapGesture];
imageView.tag = 0;
And then:
- (void)handleTapGesture:(UITapGestureRecognizer *)sender
{
if( ((UIImageView *) sender.view).tag == 0 ) // Check the identifier
{
// Your code here
}
}
Try extending the UIImageView and add whatever values (as properties) and methods you will need.
#interface UIImageViewWithId: UIImageView
#property int imageId;
#end
Then, if you want to be even MORE awesome you may want to encapsulate your behavior in this "widget"'s implementation. This will keep your ViewController nice and clean, and allow you to use this widget across multiple controllers.
#implementation UIImageViewWithId
#synthesize imageId;
- (void)handleTapGesture:(UIGestureRecognizer *)gesture {
NSLog("Hey look! It's Id #%d", imageId);
}
#end
Then just delegate the tap to the individual UIImageViewWithIds
UIImageViewWithId *imageView = [[UIImageViewWithId ... ]]
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget: imageView action:#selector(handleTapGesture:)];

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