I want to make a custom keyboard for my app and want to use the send button to set a character.
If I name all my buttons e.g. *a, *b, *c, *d etc. will it work to have one IBAction which takes the sender, grabs the name e.g. *a > a ? If so, how is this done.
Also, can a button be named as follows *0, *1, *2 rather than *zero, *one, *two?
Thanks
No, variables don't really work that way. You are confusing the object itself with the name of the variable that points to it. When your IBaction is passed the UIButton object, it's not passing a variable name along with it, your method defines the variable that references it as sender. And no, variable names cannot start with a digit in Objective C.
A common approach to differentiating between buttons in this way is to set the tag and branch on that. Alternatively, you can access the title - it depends on exactly what you are doing.
If you mean you want to point multiple UIButtons at the same IBAction and then extract the textual label of the button, you can simply use the currentTitle property of the sender.
For example:
- (IBAction)padButtonClicked:(id)sender {
NSLog(#"Button pressed: %#", [sender currentTitle]);
}
You are better off using tags for your buttons.
- (IBAction)buttonTapped:(id)sender {
NSLog(#"Button pressed: %i", sender.tag);
switch (sender.tag) {
case 0:
/* Button A Pressed */
break;
case 1:
/* Button B Pressed */
break;
/* and so forth... */
}
}
You will need to set the tags either in Interface Builder, or programmatically.
Related
I have a huge crazy scene in my story board that has 36 different buttons, and each one means something different when clicked on. I really don't want to go about creating 36 different methods, so how could I reference a button title or button name in a method that is called when one of the 36 buttons is pushed.
This is probably a simple question, but I'm new to iOS and Objective C...
Thanks!
You can create a single method, like so:
- (IBAction)buttonTapped:(id)sender{
// The button that was tapped is called "sender"
// This will log out the title of the button
//NSLog(#"Button: %#", sender.titleLabel.text);
//Edit: You need a cast in the above line of code:
NSLog(#"Button: %#", ((UIButton *)sender).titleLabel.text);
}
Then, you can use Interface Builder to connect to all of the buttons. You can have some sort of if/else logic to test which button was tapped.
You can check the titleLabel property, or you can assign an IBOutlet to each button and check for that.
For example:
if([sender isEqual:buttonOutlet1]){
//If this button is attached to buttonOutlet1
//do something
}
Alternatively, you can simply use the label of each button, not worrying about outlets.
A third option would be to generate and lay out the buttons in code, and then access them as elements of an array of buttons.
A fourth option would be to add tags to the buttons and check for the button's tag in your function.
Give each button a unique tag value. in the IBAction, sender.tag tells you which button was tapped.
The IBAction routine you set up to handle the button presses has a sender parameter. Examine that to decide.
-(IBAction) buttonPress: (id) sender {
UIButton *pressedButton = (UIButton *)sender;
NSString *buttonTitle = [pressedButton currentTitle];
if ([buttonTitle isEqualToString: #"SomeTitle"]) {
//do work for that button.
}
}
You can use a variety of NSString methods to compare or filter which button was pressed and handle it through if's or switches.
That's quite simple, but since you're new, here's an answer.
(According to Stanford cs193p course, 2010-2011 fall (that's what they did with the calculator app)) make a method that receives an argument, which is the UIButton.
for example:
- (IBAction) someMethodThatDoesSomething:(UIButton *)sender;
Then make if statements according to the sender.titleLabel.text
I don't know if there are any other solutions. Hope this helps!
-(IBAction)myButtonAction:(id)sender {
if ([sender tag] == 0) {
// do something here
}
if ([sender tag] == 1) {
// Do some think here
}
}
// in Other words
-(IBAction)myButtonAction:(id)sender {
NSLog(#"Button Tag is : %i",[sender tag]);
switch ([sender tag]) {
case 0:
// Do some think here
break;
case 1:
// Do some think here
break;
default:
NSLog(#"Default Message here");
break;
}
I have a button named start and I want to know in the method that it calls what it's name is and I'm not really sure how to do it. This is the method the button calls.
-(IBAction) startMotion: (id)sender {
UIButton * buttonName = (UIButton *) sender;
NSLog(#"Button Name: %#", buttonName.currentTitle);
}
The NSLog prints
Button Name: (null)
You can set the title of the button through
[b setTitle:#"Start" forState:UIControlStateNormal];
and to get the title (currentTitle is read-only and may be nil):
[b currentTitle];
BTW, if you just want to differentiate multiple buttons, you can just set the tag property (an integer value) of the buttons.
Also, check if you have the button specified as an IBOutlet in your viewController class, and is it connected properly as an outlet in Interface Builder?
I would rather set a certain Tag and compare the tag value rather than reading the title of the button since you have possibility to localize your app where button titles will possibly be different.
I was using the wrong property in Interface Builder.I was using name property of button in Interface Builder instead of the title property from the button settings.
How can I make a button that says "Show Picture" and when it's clicked it changes to "Hide Picture". I'm new to objective C, I know how to make a button in interface builder but don't know how to switch the button's text and function. Can someone help me out?
Don't abuse the tag property. It is advise only to be used as a button identifier (for example when you have few buttons in your view you set their tags as 0, 1, 2... so can identify which button is a sender). You could set some global int i variable and change it's value accordingly.
abuse the .tag property of the button. Hook up the touch down action to this function:
-(IBAction)buttonClick:(UIButton*)sender
{
if ( sender.tag )
{
sender.tag = 0;
sender.text = #"Show Picture";
// do actions when "hide" is clicked
} else {
sender.tag = 1;
sender.text = #"Hide Picture";
// do actions when "show" is clicked
}
}
Instead of (ab)using the tag property, you could also simply toggle the button between selected and not selected, like so:
- (IBAction)myButtonAction:(id)sender
{
[sender setSelected:![sender isSelected]];
// or in Objective-C 2.0 if you're so inclined
sender.selected = !sender.selected;
}
In IB, you could then set the text for the normal and the selected state of the button directly in the inspector (or programmatically through the setTitle:forState: method).
The tricky thing with this one is that a UIButton doesn't have an "official" text properly - see the docs here:
http://developer.apple.com/iphone/library/documentation/uikit/reference/UIButton_Class/UIButton/UIButton.html
because it's designed to have multiple, separate sets of texts, displayed according to the button's current state; i.e., whether it's currently enabled or disabled, highlighted, etc. So there's not one, simple property you can set to make this work.
So, you want to declare your button like this, as both an action and an outlet:
from button.h:
// inside the class declaration
BOOL pictureShown ; // initializer not required, defaults to 0 (NO)
UIButton * sampleButton ;
// skip irrelevant lines here
#property (nonatomic, retain) IBOutlet UIButton * sampleButton ;
- (IBAction) doSampleButton ;
Hook both of those up in Interface Builder, and then change the text using the setTitle:forState: method (and in this case, I've specified all the states, so the title stays the same across all of them). For example:
from button.m:
#synthesize sampleButton ;
- (IBAction) doSampleButton {
if (pictureShown == YES) {
// hide the picture, and then...
[sampleButton setTitle: #"Show Picture" forState: (UIControlStateNormal | UIControlStateHighlighted | UIControlStateSelected | UIControlStateDisabled)] ;
pictureShown = NO ;
} else {
// show the picture, and then...
[sampleButton setTitle: #"Hide Picture" forState: (UIControlStateNormal | UIControlStateHighlighted | UIControlStateSelected | UIControlStateDisabled)] ;
pictureShown = YES ;
}
}
You'll also note that I've declared an instance variable, "pictureShown", in the view controller for the view with the button, to track the current "mode" of the button, and that I'm essentially using an if statement inside the button's action to determine which function is carried out according to the current mode of the button, and to toggle the button text accordingly.
(I'm using this to track the current mode of the button rather than, for example, examining the current title of the button directly, or other ways of storing state on the button, because MVC-wise, this sort of state belongs in the controller class.)
(If the function required a lot of code, I'd use messages to self, i.e.:
[self showPicture] ;
[self hidePicture] ;
to avoid having to cram it all inside doSampleButton, but that's purely stylistic, rather than technically required.
I have the Value Changed event of two UISliders (both of which have referencing outlets) wired up to the following method:
-(IBAction) sliderMoved:(id) sender {}
How can I determine which slider was moved so that I can get its value and update the corresponding label? Or would it be simpler to have two separate events, one for each slider? The second option seems like unnecessary replication to me.
Cheers,
Dan
It's going to be the sender variable. Just do all your work with it.
It's legal to strongly type it, by the way. So if you know you're only going to deal with UISlider objects, you can do -(IBAction)someAction:(UISlider*)slider {}.
You can use [sender tag] to get the tag of the slider if you have set that up. Assign the tag when you create the sliders or in interface builder.
-(IBAction) sliderMoved:(UISlider*)sender {
switch ( [sender tag] ) {
case kMyOneSlider: ... break;
case kMyOtherSlider: ... break;
}
}
You can use == with the outlet members for each slider:
-(IBAction) sliderMoved:(UISlider*)sender {
if ( sender == mOneSlider ) ...;
if ( sender == mOtherSlider ) ...;
}
Or you can set up different actions for each slider. I generally share one action method if there is some common code in the handlers.
How do you add a (id) sender to the following code?
- (IBAction) gobutton: (UIButton *) button5 {
Everything I try fails, any help would be appreciated. Thanks.
EDIT: I need to keep the (UIButton *) button 5 reference in the (IBAction)
If I recall correctly, and if you are using this in the way I think you are,
- (IBAction) gobutton: (id) sender {
if(sender == button5)
//do something...
else
//do something else...
}
Assuming that you specified button5 as a parameter to indicate that this executes in response to button5 being pressed.
Ok, first.... IBAction doesn't really mean anything special except to Interface Builder. Basically:
#define IBAction void
So whenever you see IBAction, think "void". The only reason it's there is as a flag to tell Interface Builder that a method is a valid method to connect control actions to. The Objective-C compiler doesn't need to know about it and so it's defined to void since all "action" methods return void.
Second, action methods also have one argument which could be an object of any number of types. Because of this, action methods are supposed to use type id as the type for their argument. That way they can be passed a pointer to any Objective-C object without causing the compiler to generate a type checking error.
So usually actions should work something like this:
- (IBAction)myAction:(id)sender {
if (sender == self.someButton) {
UIButton *button = (UIButton *)sender;
...
return;
} else if (sender == self.someControl) {
UIControl *control = (UIControl *)sender;
...
return;
}
}
In other words, an id is almost like an untyped pointer like a void * is routinely used in C when some function needs to take a pointer to something of unknown type. sender could be different types of control, so something generic like id is used then sender is cast to something more specific once the code knows what it is.
Anyway, there is absolutely no reason to define something as having a return type of IBAction unless you are going to use that method as a target action in Interface Builder. Having an IBAction in your app delegate seems kind of unusual....
It's not clear what you are trying to do but most actions look like:
- (IBAction) gobutton: (id)sender;
The first parameter to an action is always the sender (you can specify the type and name as appropriate).
If a method is the action for a button, then the first parameter will be the button. If that method is the action for several buttons, then the first parameter will allow you to determine which button was tapped (as Leper describes).
What problem are you actually trying to solve?
There are techniques for passing information to the action method. For example, if you have a button that appears on a table view cell and performs the same action for every cell, then in the action method, you would want to be able to determine which cell's button was tapped.
How can I get the id of the sender before the user touches the control?
Found it! Set a tag and the use viewWithTag.
Can you create a simple structure that contains both the UIButton and the sender and use that?
struct myObject
{
UIButton* button5;
id sender;
}
...or, you could create your own NSObject (probably more cocoa-y):
#instance myObject : NSObject
{
...
}