IPad cancel button (a-la Keynote and other apps)

Question

In Keynote (and other applications), I noticed that the “standard” interface for running Undo / Redo is to provide a Undo button on the toolbar.

Pressing a button (which is always on) Disables a recent operation. (If there was no last operation to cancel, it will display the Undo / Redo menu).

A long press of the Cancel button opens the Cancel / Redo menu.

I was looking for methods to implement this, and the best answer I have found so far is at the following link .

I wonder if anyone knows an easier way?

Thanks!

Answer 1

After looking through all the methods and discussing with friends below, the solution I used is used, since UIBarButtonItem answers both taps and takes a long time to press (TapOrLongPressBarButtonItem).

It is based on the following principles:

• Subclass UIBarButtonItem
• Use a custom view (so it’s really trivial to handle a long press - since our user view has no problems with a long click gesture handler ...)

... Until now, this approach has been in a different stream of SO - and I did not like this approach, since I could not find and easily enough create a custom view similar to the iPad navigation bar button ... Soooo ...

Use UIGlossyButton from Water Lou (thanks to the water!). This usage is encapsulated in a subclass ...

The resulting code is as follows:

@protocol TapOrPressButtonDelegate; @interface TapOrPressBarButtonItem : UIBarButtonItem { UIGlossyButton* _tapOrPressButton; __weak id<TapOrPressButtonDelegate> _delegate; } - (id)initWithTitle:(NSString*)title andDelegate:(id<TapOrPressButtonDelegate>)delegate; @end @protocol TapOrPressButtonDelegate<NSObject> - (void)buttonTapped:(UIButton*)button withBarButtonItem:(UIBarButtonItem*)barButtonItem; - (void)buttonLongPressed:(UIButton*)button withBarButtonItem:(UIBarButtonItem*)barButtonItem; @end @implementation TapOrPressBarButtonItem - (void)buttonLongPressed:(UILongPressGestureRecognizer*)gesture { if (gesture.state != UIGestureRecognizerStateBegan) return; if([_delegate respondsToSelector:@selector(buttonLongPressed:withBarButtonItem:)]) { [_delegate buttonLongPressed:_tapOrPressButton withBarButtonItem:self]; } } - (void)buttonTapped:(id)sender { if (sender != _tapOrPressButton) { return; } if([_delegate respondsToSelector:@selector(buttonTapped:withBarButtonItem:)]) { [_delegate buttonTapped:_tapOrPressButton withBarButtonItem:self]; } } - (id)initWithTitle:(NSString*)title andDelegate:(id<TapOrPressButtonDelegate>)delegate { if (self = [super init]) { // Store delegate reference _delegate = delegate; // Create the customm button that will have the iPad-nav-bar-default appearance _tapOrPressButton = [UIGlossyButton buttonWithType:UIButtonTypeCustom]; [_tapOrPressButton setTitle:title forState:UIControlStateNormal]; [_tapOrPressButton setNavigationButtonWithColor:[UIColor colorWithRed:123.0/255 green:130.0/255 blue:139.0/255 alpha:1.0]]; // Calculate width... CGSize labelSize = CGSizeMake(1000, 30); labelSize = [title sizeWithFont:_tapOrPressButton.titleLabel.font constrainedToSize:labelSize lineBreakMode:UILineBreakModeMiddleTruncation]; _tapOrPressButton.frame = CGRectMake(0, 0, labelSize.width+20, 30); // Add a handler for a tap [_tapOrPressButton addTarget:self action:@selector(buttonTapped:) forControlEvents:UIControlEventTouchUpInside]; // Add a handler for a long-press UILongPressGestureRecognizer* buttonLongPress_ = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(buttonLongPressed:)]; [_tapOrPressButton addGestureRecognizer:buttonLongPress_]; // Set this button as the custom view of the bar item... self.customView = _tapOrPressButton; } return self; } // Safe guards... - (id)initWithImage:(UIImage *)image style:(UIBarButtonItemStyle)style target:(id)target action:(SEL)action { NSLog(@"%s not supported!", __FUNCTION__); return nil; } - (id)initWithImage:(UIImage *)image landscapeImagePhone:(UIImage *)landscapeImagePhone style:(UIBarButtonItemStyle)style target:(id)target action:(SEL)action { NSLog(@"%s not supported!", __FUNCTION__); return nil; } - (id)initWithTitle:(NSString *)title style:(UIBarButtonItemStyle)style target:(id)target action:(SEL)action { NSLog(@"%s not supported!", __FUNCTION__); return nil; } - (id)initWithBarButtonSystemItem:(UIBarButtonSystemItem)systemItem target:(id)target action:(SEL)action { NSLog(@"%s not supported!", __FUNCTION__); return nil; } - (id)initWithCustomView:(UIView *)customView { NSLog(@"%s not supported!", __FUNCTION__); return nil; } @end 

And all you have to do is:

1. An instant is as follows:

 TapOrPressBarButtonItem* undoMenuButton = [[TapOrPressBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Undo", @"Undo Menu Title") andDelegate:self]; 

---

2. Connect the button to the navigation bar:

 [self.navigationItem setLeftBarButtonItem:undoMenuButton animated:NO]; 

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3. Enter the TapOrPressButtonDelegate protocol, and you're done ...

 -(void)buttonTapped:(UIButton*)button withBarButtonItem:(UIBarButtonItem*)barButtonItem { [self menuItemUndo:barButtonItem]; } -(void)buttonLongPressed:(UIButton*)button withBarButtonItem:(UIBarButtonItem*)barButtonItem { [self undoMenuClicked:barButtonItem]; } 

Hope this helps someone else ...

Answer 2

If you use IB (or in the Xcode4 constructor ... I assume that it is being called), then you can select "Cancel" from the first responder and drag this action onto the button. I can give you more specific instructions if this does not apply to him.

Here it looks like

It is on the left under the “Received Actions” column below.

Answer 3

I believe the key is in the UINavigationBar itself. Unlike UIButtons or other common touch tracking objects, I suspect that UIBarItems do not handle their own strokes. They do not inherit UIResponder or UIControl methods. However, the UINavigationBar is of course. And I personally added gestures directly to the UINavigationBar many times.

I suggest that you redefine touch processing in a subclass of UINavigationBar and check the bindings to its children. If the baby is your special cancel button, you can handle it accordingly.

Answer 4

 UIButton* undoButton = [UIButton buttonWithType:UIButtonTypeCustom]; [undoButton addTarget:self action:@selector(undoPressStart:) forControlEvents:UIControlEventTouchDown]; [undoButton addTarget:self action:@selector(undoPressFinish:) forControlEvents:UIControlEventTouchUpInside]; UIBarButtonItem* navButton = [[[UIBarButtonItem alloc] initWithCustomView:undoButton] autorelease]; self.navigationItem.rightBarButtonItem = navButton; 

You do not have to add the UIBarButtonItem as rightBarButtonItem, it is a simple and easy way to show you how to create your UIBarButtonItem with a custom view, which is the UIButton with which you want to handle events.

You will need to execute unodPressStart: and undoPressFinish: by saving state. I would say, at startup, save the current NSDate or some grainy representation of time. If you are done, check if the time has passed, and if it exceeds a certain threshold, show the menu - otherwise (and also, if the start date has never been recorded), cancel.

As an improvement, you will most likely want to also watch the UIControlEventTouchDragExit event to cancel a long press.