Ios – How to set up an UIScreenEdgePanGestureRecognizer using Interface Builder

interface-builderiosobjective cxcode

I can't get UIScreenEdgePanGestureRecognizer to work when I create when I add it to my view controller using Interface Builder, so I'm asking here to establish whether I'm doing something wrong or if there is a bug in Xcode.

Here are the steps to reproduce:

Create a new Xcode project using the "Single View Application" template for iOS.
Add a UIView to the main view controller by dragging one from the Object Library in Interface Builder
Add a UIScreenEdgePanGestureRecognizer to the view by dragging one from the Object Library in Interface Builder
Ensure that the gesture recogniser is enabled and that an edge is selected:

enter image description here

Open the assistant editor for the ViewController class and ctrl-drag from the UIScreenEdgePanGestureRecognizer to the ViewController's implementation block to create a new IBAction
` Add a breakpoint in the action's method body to test if the edge pan gesture is being recognized

The resulting code is as follows:

Code example

If I run the application on my device (iPhone 6 running iOS 8.02) the breakpoint does not get hit when I do an edge swipe.

Is there something I'm missing?

UPDATE: this was filed as a bug with Apple (rdar://18582306) on 08-Oct-2014 and still isn't resolved in Xcode 6.4 (6E35b)

Best Answer

I set up a project to test your question and found the same issue you did. Here are the scenarios I set up to test:

I did exactly as you did, using Interface Builder, to build the screen edge gesture. The only difference in my code is that I put a line of code in the selector so the debugger would have something to stop on. The debugger failed to halt exactly as you found.
```
-(void)handlePan:(id)sender
{
    NSString *test = @"";
}
```
I then created an additional gesture using the pinch gesture on the same view using Interface Builder and I was able to get the debugger to halt within that selector. So Interface Builder seems to be able to build other gestures correctly.
I then created the screen edge gesture manually using the following code and it worked as expected.

In the ViewController.h file I included the UIGestureRecognizerDelegate.

@interface ViewController : UIViewController <UIGestureRecognizerDelegate>
@end

In the ViewController.m file I implemented the gesture manually.

#import "ViewController.h"

@interface ViewController ()

-(void)handlePan:(id)sender;

@end

@implementation ViewController

- (void)viewDidLoad 
{
    [super viewDidLoad];
    UIScreenEdgePanGestureRecognizer *pan = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self
                                                                                              action:@selector(handlePan:)];
    [pan setEdges:UIRectEdgeLeft];
    [pan setDelegate:self];
    [self.view addGestureRecognizer:pan];
}

-(void)handlePan:(id)sender
{
    NSString *test = @"";
}

@end

I ended up with the same conclusion you did - there seems to be something wrong with the Interface Builder's implementation of the UIScreenEdgePanGestureRecognizer.

Related Solutions

Ios – How to change the name of an iOS app

Go to Targets in Xcode.
Build Settings on your project's target (your current development name).
Search for Product Name under Packaging. Change its value to what you want your new project name to be.

Ios – How to make a UITextField move up when the keyboard is present – on starting to edit

You will only need a ScrollView if the contents you have now do not fit in the iPhone screen. (If you are adding the ScrollView as the superview of the components just to make the TextField scroll up when keyboard comes up, then it's not needed.)
The standard way to prevent the TextFields from being covered by the keyboard is to move the view up/down whenever the keyboard is shown.

Here is some sample code:

#define kOFFSET_FOR_KEYBOARD 80.0

-(void)keyboardWillShow {
    // Animate the current view out of the way
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}

-(void)keyboardWillHide {
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}

-(void)textFieldDidBeginEditing:(UITextField *)sender
{
    if ([sender isEqual:mailTf])
    {
        //move the main view, so that the keyboard does not hide it.
        if  (self.view.frame.origin.y >= 0)
        {
            [self setViewMovedUp:YES];
        }
    }
}

//method to move the view up/down whenever the keyboard is shown/dismissed
-(void)setViewMovedUp:(BOOL)movedUp
{
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3]; // if you want to slide up the view

    CGRect rect = self.view.frame;
    if (movedUp)
    {
        // 1. move the view's origin up so that the text field that will be hidden come above the keyboard 
        // 2. increase the size of the view so that the area behind the keyboard is covered up.
        rect.origin.y -= kOFFSET_FOR_KEYBOARD;
        rect.size.height += kOFFSET_FOR_KEYBOARD;
    }
    else
    {
        // revert back to the normal state.
        rect.origin.y += kOFFSET_FOR_KEYBOARD;
        rect.size.height -= kOFFSET_FOR_KEYBOARD;
    }
    self.view.frame = rect;

    [UIView commitAnimations];
}


- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillShow)
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillHide)
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    // unregister for keyboard notifications while not visible.
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

Best Answer

Related Solutions

Ios – How to change the name of an iOS app

Ios – How to make a UITextField move up when the keyboard is present – on starting to edit

Related Topic