Is there a way to get a notification, a callback or some other means to call a method whenever a UIView becomes visible for the user, i.e. when a UIScrollview is the superview of some UIViews, and the ViewController of such a UIView shall get notified when its view is now visible to the user?
I am aware of the possible, but not so elegant solution of checking to which position the ScrollView scrolled (via UIScrollViewDelegate-methods) and compute if either one of the subviews is visible...
But I'm looking for a more universal way of doing this.
I've managed to solve the problem this way:
First, add a category for UIView with the following method:
// retrieve an array containing all super views
-(NSArray *)getAllSuperviews
{
NSMutableArray *superviews = [[NSMutableArray alloc] init];
if(self.superview == nil) return nil;
[superviews addObject:self.superview];
[superviews addObjectsFromArray:[self.superview getAllSuperviews]];
return superviews;
}
Then, in your View, check if the window-property is set:
-(void)didMoveToWindow
{
if(self.window != nil)
[self observeSuperviewsOnOffsetChange];
else
[self removeAsSuperviewObserver];
}
If it is set, we'll observe the "contentOffset" of each superview on any change. If the window is nil, we'll stop observing. You can change the keyPath to any other property, maybe "frame" if there is no UIScrollView in your superviews:
-(void)observeSuperviewsOnOffsetChange
{
NSArray *superviews = [self getAllSuperviews];
for (UIView *superview in superviews)
{
if([superview respondsToSelector:#selector(contentOffset)])
[superview addObserver:self forKeyPath:#"contentOffset" options:NSKeyValueObservingOptionNew context:nil];
}
}
-(void)removeAsSuperviewObserver
{
NSArray *superviews = [self getAllSuperviews];
for (UIView *superview in superviews)
{
#try
{
[superview removeObserver:self forKeyPath:#"contentOffset"];
}
#catch(id exception) { }
}
}
Now implement the "observeValueForKeyPath"-method:
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if([keyPath isEqualToString:#"contentOffset"])
{
[self checkIfFrameIsVisible];
}
}
Finally, check if the view's frame is visible inside the window's frame:
-(void)checkIfFrameIsVisible
{
CGRect myFrameToWindow = [self.window convertRect:self.frame fromView:self];
if(myFrameToWindow.size.width == 0 || myFrameToWindow.size.height == 0) return;
if(CGRectContainsRect(self.window.frame, myFrameToWindow))
{
// We are visible, do stuff now
}
}
If your view is exhibiting behavior, it should be within a view controller. On a view controller, the viewDidAppear method will be called each time the view appears.
- (void)viewDidAppear:(BOOL)animated
I don't think there's a universal way to do this for views. Sounds like you're stuck with scrollViewDidEndScrolling and other ScrollViewDelegate methods. But I'm not sure why you say it's elegant, they're quite straightforward.
view's layer property should tell us if that view is visible or not
[view.layer visibleRect];
but this isnt working for me.
So work around could be to use UiScrollView contentOffset property to calculate if particular view is visible or not.
Related
What I want to do is put a UIView on top of another UIView, and both of them are screen size. The top UIView includes lots cocos nodes and will respond when I touch them. But when I touch a place that has no cocos node, the bottom UIView should respond.
I don't know how to do this. My imagine is check if top uiView is handled touch, do nothing. other wise let the bottom UIView start respond. But I don't know how to check that. I only know how to check touch but it seems the UIView will also be touched when I touch some place it can't handle.
I think you not requires 2 views.
Just take one view only and add all your node to that view.
in .h
IBOutlet UIView *bgView;//your view
UITapGestureRecognizer *viewTapRecognizer;// view tap recognizer
in .m
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
viewTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handelGesture:)];
[bgView addGestureRecognizer:viewTapRecognizer];
for (UIView *subView in [bgView subviews]) {
UITapGestureRecognizer *nodeTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handelGesture:)];
[subView addGestureRecognizer:nodeTapRecognizer];
}
}
- (void)handelGesture:(UITapGestureRecognizer*)sender {
if (sender == viewTapRecognizer) {
// your view is tapped
NSLog(#"........Tapped view..........");
}
else {
// your node is tapped
NSLog(#"........Tapped node..........");
}
}
Try this. it might work for you.
You can achieve it by 2 ways: using pointInside... method or hitTest... method.
If you will use pointInside... you can use only your views (the top view and the bottom view). You will subclass UIView with the top view and override pointInside... method. You will return YES if user's tapped a cocoa node else returns NO.
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
BOOL inside = [self didUserTapCocoaNode:point];
return inside;
}
If you want more complex logic, you should use third view, subclass of UIView (the container view), that will be contain the top view and the bottom view. Override method hitTest..., and return the bottom or the top view.
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
UIView* result = nil;
if ([self touchedCocoaNode:point])
{
result = self.topView;
}
else
{
result = self.bottomView;
}
return result;
}
UPD
Example implementation of didUserTapCocoaNode with pseudo code:
- (BOOL)didUserTapCocoaNode:(CGPoint)pointInSelf
{
__block BOOL tappedSomeNode = NO;
[self.nodes enumerateObjectsUsingBlock:^(NodeType* obj, NSInteger idx, BOOL* stop){
CGPoint pointInNode = [obj convertPoint:pointInSelf fromView:self];
tappedSomeNode = [obj pointInside:pointInNode withEvent:nil];
*stop = tappedSomeNode;
}]
return tappedSomeNode;
}
I have the following code:
-(void)textFieldDidBeginEditing:(UITextField *)textField
{
CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];
CGRect viewRect = [self.view.window convertRect:self.view.bounds fromView:self.view];
...
}
As you can see it passes in a UITextField. I also have this code duplicated in the same ViewController but passing in a UITextView.
I want to be able to refactor this into a single method which passes in either the UITextField or UITextView? How can I do this?
Also this code appears in other View Controllers, so ideally I'd like to place it in a helper class, very new to iOS so not sure where to go from here.
I've removed most of the code from the method for brevity, but what it does is it slides the UI controls into view when the iOS keyboard appears.
You can expect UIView, as it seems you don't use any special text properties from those views.
-(void)textFieldDidBeginEditing:(UIView *)textField
{
CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];
CGRect viewRect = [self.view.window convertRect:self.view.bounds fromView:self.view];
// ...
}
Call a helper methods, that expects a UIView, the common super class.
-(void)textFieldDidBeginEditing:(UITextField *)textField
{
return [self textBeginEditing:textField];
}
-(void)textViewDidBeginEditing:(UITextView *)textView
{
return [self textBeginEditing:textView];
}
-(void)textBeginEditing:(UIView *)view
{
//and if you need to do something, where you need to now, if it is a textView or a field, use
if([view isKindOfClass:[UITextField class]]){
//…
} else if([view isKindOfClass:[UITextView class]]){
//…
}
}
I have set up an NSCollectionView in a cocoa application. I have subclassed the collection view's NSCollectionViewItem to send me a custom NSNotification when one of its views it selected / deselected. I register to receive a notification within my controller object when this notification is posted. Within this method I tell the view that has just been selected that it is selected and tell it to redraw, which makes it shade itself grey.
The NSCollectionViewItem Subclass:
-(void)setSelected:(BOOL)flag {
[super setSelected:flag];
[[NSNotificationCenter defaultCenter] postNotificationName:#"ASCollectionViewItemSetSelected"
object:nil
userInfo:[NSDictionary dictionaryWithObjectsAndKeys:(ASListView *)self.view, #"view",
[NSNumber numberWithBool:flag], #"flag", nil]];}
The Controller Class (in the -(void)awakeFromNib Method):
//Register for selection changed notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(selectionChanged:)
name:#"ASCollectionViewItemSetSelected"
object:nil];
And the -(void)selectionChanged:(NSNotification *)notification method:
- (void)selectionChanged:(NSNotification *)notification {
// * * Must get the selected item and set its properties accordingly
//Get the flag
NSNumber *flagNumber = [notification.userInfo objectForKey:#"flag"];
BOOL flag = flagNumber.boolValue;
//Get the view
ASListView *listView = [notification.userInfo objectForKey:#"view"];
//Set the view's selected property
[listView setIsSelected:flag];
[listView setNeedsDisplay:YES];
//Log for testing
NSLog(#"SelectionChanged to: %d on view: %#", flag, listView);}
The application that contains this code requires there to be no empty selection within the collection view at any time. This is where i get my problem. I've tried checking when a view's selection is changed and reselecting it if there is no selection, and manually selecting the views using NSCollectionView's
-(void)setSelectionIndexes:(NSIndexSet *)indexes
But there is always a situation which occurs that causes there to be an empty selection in the collection view.
So I was wondering if there is an easier way to prevent an empty selection occurring in an NSCollectionView? I see no checkbox in interface builder.
Thanks in advance!
Ben
Update
I ended up just subclassing my NSCollectionView, and overriding the - (void)mouseDown:(NSEvent *)theEvent method. I only then sent the method [super mouseDown:theEvent]; if the click was in one of the subviews. Code:
- (void)mouseDown:(NSEvent *)theEvent {
NSPoint clickPoint = [self convertPoint:theEvent.locationInWindow fromView:nil];
int i = 0;
for (NSView *view in self.subviews) {
if (NSPointInRect(clickPoint, view.frame)) {
//Click is in rect
i = 1;
}
}
//The click wasnt in any of the rects
if (i != 0) {
[super mouseDown:theEvent];
}}
I ended up just subclassing my NSCollectionView, and overriding the - (void)mouseDown:(NSEvent *)theEvent method. I only then sent the method [super mouseDown:theEvent]; if the click was in one of the subviews. Code:
- (void)mouseDown:(NSEvent *)theEvent {
NSPoint clickPoint = [self convertPoint:theEvent.locationInWindow fromView:nil];
int i = 0;
for (NSView *view in self.subviews) {
if (NSPointInRect(clickPoint, view.frame)) {
//Click is in rect
i = 1;
}
}
//The click wasnt in any of the rects
if (i != 0) {
[super mouseDown:theEvent];
}}
I also wanted to avoid empty selection in my collection view.
The way I did it is also by subclassing, but I overrode -hitTest: instead of -mouseDown: to return nil in case the click wasn't on an item :
-(NSView *)hitTest:(NSPoint)aPoint {
// convert aPoint in self coordinate system
NSPoint localPoint = [self convertPoint:aPoint fromView:[self superview]];
// get the item count
NSUInteger itemCount = [[self content] count];
for(NSUInteger itemIndex = 0; itemIndex < itemCount; itemIndex += 1) {
// test the point in each item frame
NSRect itemFrame = [self frameForItemAtIndex:itemIndex];
if(NSPointInRect(localPoint, itemFrame)) {
return [[self itemAtIndex:itemIndex] view];
}
}
// not on an item
return nil;
}
Although I'm late to this thread, I thought I'd just chime in because I've had the same problem recently. I got around it using the following line of code:
[_collectionView setValue:#NO forKey:#"avoidsEmptySelection"];
There is one caveat: the avoidsEmptySelection property is not part of the official API although I think that it's pretty safe to assume that its the type of property that will stick around for a while.
I'm trying to figure out how this is done the right way. I've tried to depict the situation:
I'm adding a UITableView as a subview of a UIView. The UIView responds to a tap- and pinchGestureRecognizer, but when doing so, the tableview stops reacting to those two gestures (it still reacts to swipes).
I've made it work with the following code, but it's obviously not a nice solution and I'm sure there is a better way. This is put in the UIView (the superview):
-(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
if([super hitTest:point withEvent:event] == self) {
for (id gesture in self.gestureRecognizers) {
[gesture setEnabled:YES];
}
return self;
}
for (id gesture in self.gestureRecognizers) {
[gesture setEnabled:NO];
}
return [self.subviews lastObject];
}
I had a very similar problem and found my solution in this SO question. In summary, set yourself as the delegate for your UIGestureRecognizer and then check the targeted view before allowing your recognizer to process the touch. The relevant delegate method is:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldReceiveTouch:(UITouch *)touch
The blocking of touch events to subviews is the default behaviour. You can change this behaviour:
UITapGestureRecognizer *r = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(agentPickerTapped:)];
r.cancelsTouchesInView = NO;
[agentPicker addGestureRecognizer:r];
I was displaying a dropdown subview that had its own tableview. As a result, the touch.view would sometimes return classes like UITableViewCell. I had to step through the superclass(es) to ensure it was the subclass I thought it was:
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
UIView *view = touch.view;
while (view.class != UIView.class) {
// Check if superclass is of type dropdown
if (view.class == dropDown.class) { // dropDown is an ivar; replace with your own
NSLog(#"Is of type dropdown; returning NO");
return NO;
} else {
view = view.superview;
}
}
return YES;
}
Building on #Pin Shih Wang answer. We ignore all taps other than those on the view containing the tap gesture recognizer. All taps are forwarded to the view hierarchy as normal as we've set tapGestureRecognizer.cancelsTouchesInView = false. Here is the code in Swift3/4:
func ensureBackgroundTapDismissesKeyboard() {
let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(handleTap))
tapGestureRecognizer.cancelsTouchesInView = false
self.view.addGestureRecognizer(tapGestureRecognizer)
}
#objc func handleTap(recognizer: UIGestureRecognizer) {
let location = recognizer.location(in: self.view)
let hitTestView = self.view.hitTest(location, with: UIEvent())
if hitTestView?.gestureRecognizers?.contains(recognizer) == .some(true) {
// I dismiss the keyboard on a tap on the scroll view
// REPLACE with own logic
self.view.endEditing(true)
}
}
One possibility is to subclass your gesture recognizer (if you haven't already) and override -touchesBegan:withEvent: such that it determines whether each touch began in an excluded subview and calls -ignoreTouch:forEvent: for that touch if it did.
Obviously, you'll also need to add a property to keep track of the excluded subview, or perhaps better, an array of excluded subviews.
It is possible to do without inherit any class.
you can check gestureRecognizers in gesture's callback selector
if view.gestureRecognizers not contains your gestureRecognizer,just ignore it
for example
- (void)viewDidLoad
{
UITapGestureRecognizer *singleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleSingleTap:)];
singleTapGesture.numberOfTapsRequired = 1;
}
check view.gestureRecognizers here
- (void)handleSingleTap:(UIGestureRecognizer *)gestureRecognizer
{
UIEvent *event = [[UIEvent alloc] init];
CGPoint location = [gestureRecognizer locationInView:self.view];
//check actually view you hit via hitTest
UIView *view = [self.view hitTest:location withEvent:event];
if ([view.gestureRecognizers containsObject:gestureRecognizer]) {
//your UIView
//do something
}
else {
//your UITableView or some thing else...
//ignore
}
}
I created a UIGestureRecognizer subclass designed for blocking all gesture recognizers attached to a superviews of a specific view.
It's part of my WEPopover project. You can find it here.
implement a delegate for all the recognizers of the parentView and put the gestureRecognizer method in the delegate that is responsible for simultaneous triggering of recognizers:
func gestureRecognizer(UIGestureRecognizer, shouldBeRequiredToFailByGestureRecognizer:UIGestureRecognizer) -> Bool {
if (otherGestureRecognizer.view.isDescendantOfView(gestureRecognizer.view)) {
return true
} else {
return false
}
}
U can use the fail methods if u want to make the children be triggered but not the parent recognizers:
https://developer.apple.com/reference/uikit/uigesturerecognizerdelegate
I was also doing a popover and this is how I did it
func didTap(sender: UITapGestureRecognizer) {
let tapLocation = sender.locationInView(tableView)
if let _ = tableView.indexPathForRowAtPoint(tapLocation) {
sender.cancelsTouchesInView = false
}
else {
delegate?.menuDimissed()
}
}
You can turn it off and on.... in my code i did something like this as i needed to turn it off when the keyboard was not showing, you can apply it to your situation:
call this is viewdidload etc:
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self selector:#selector(notifyShowKeyboard:) name:UIKeyboardDidShowNotification object:nil];
[center addObserver:self selector:#selector(notifyHideKeyboard:) name:UIKeyboardWillHideNotification object:nil];
then create the two methods:
-(void) notifyShowKeyboard:(NSNotification *)inNotification
{
tap.enabled=true; // turn the gesture on
}
-(void) notifyHideKeyboard:(NSNotification *)inNotification
{
tap.enabled=false; //turn the gesture off so it wont consume the touch event
}
What this does is disables the tap. I had to turn tap into a instance variable and release it in dealloc though.
I have an NSTableView, created from IB, that I want to only autohide the horizontal scroller on. The main reason I want to do this is because it seems the NSTableView corverView only get's displayed if there is a vertical scroller.
I can't find any method to do this with the base class. So I tried subclassing NSScrollView and observing the hidden key on the horizontal scroller (code below). This works; however, the view tries to reset the current visible options every time the user resizes the window. This makes my implementation somewhat expensive; and it seems inelegant. Any better ideas about how to do this?
Thanks in advance!
Current implementation:
#interface PVScrollView : NSScrollView {
BOOL autohidesHorizontalScroller;
}
#property(assign) BOOL autohidesHorizontalScroller;
- (void) viewResized:(NSNotification*)notification;
#end
#implementation PVScrollView
#synthesize autohidesHorizontalScroller;
- (void) setAutohidesHorizontalScroller:(BOOL)val
{
autohidesHorizontalScroller = val;
[self setAutohidesScrollers:NO];
[[self horizontalScroller] addObserver:self
forKeyPath:#"hidden"
options:0
context:nil];
}
- (void) observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
{
if (!([self documentVisibleRect].size.width < [[self documentView] frame].size.width) )
{
// remove observer
[[self horizontalScroller] removeObserver:self
forKeyPath:#"hidden"];
[[self horizontalScroller] setHidden:YES];
//[[self horizontalScroller] setNeedsDisplay:YES];
// add it back
[[self horizontalScroller] addObserver:self
forKeyPath:#"hidden"
options:0
context:nil];
}
}
#end
Give this a shot in your NSScrollView subclass:
- (void)setFrameSize:(NSSize)newSize;
{
NSSize minFrameSize = [NSScrollView frameSizeForContentSize:[self contentSize] hasHorizontalScroller:NO hasVerticalScroller:YES borderType:[self borderType]];
BOOL wantScroller = minFrameSize.width > newSize.width;
[self setHasHorizontalScroller:wantScroller];
[super setFrameSize: newSize];
}
You'll need to check "Show Vertical Scroller" and uncheck "Automatically Hide Scrollers" for it to work; I didn't bother making it robust to changes in IB. Also, you'll need to do the same thing when the window is first displayed (in the NSScrollView constructor).
I compared CPU usage with and without this change; it seems to vary at most 1% (19%→20%) in my test application.