Desired Scenario: create a custom Alert View via iOS6's AutoLayout vs Frames:
1) Create an empty UIView upon the host view (UIController.view):
alertView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 0, 0)];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[alertView(==300)]" options:0 metrics:nil views:viewsDict]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-[alertView]-|" options:0 metrics:nil views:viewsDict]];
This works: I see my alert UIView upon (subview) the host view.
However, attempting to add UILabel to the Alert view bombs.
Seeing that the UIView (1) was drawn, I merely substituted the UILabel in its stead to see if I can get something:
- (UILabel *)createLabelWithMessage:(NSString *)message {
if (!message) return nil;
UILabel *myLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, 0,0)];
myLabel.text = message;
[myLabel setFont:[UIFont systemFontOfSize:12.0]];
[myLabel setAutoresizingMask:UIViewAutoresizingNone];
myLabel.backgroundColor = [UIColor clearColor];
return myLabel;
}
...
titleLabel = [self createLabelWithMessage:#"Danger"];
...
// ...replacing 'alertView' (UIView) with 'titleView' (UILabel):
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|-[titleLabel(==300)]" options:0 metrics:nil views:viewsDict]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|-[titleLabel]-|" options:0 metrics:nil views:viewsDict]];
Question: Why would the UILabel bomb but the UIView appears to be drawing okay?
Here's the hint from Xcode:
AutoLayoutContraints[3828:11303] Unable to simultaneously satisfy
constraints.
Probably at least one of the constraints in the
following list is one you don't want. Try this:
(1) look at each
constraint and try to figure out which you don't expect;
(2) find the
code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you
don't understand, refer to the documentation for the UIView property
translatesAutoresizingMaskIntoConstraints) (
"",
"",
"" )
Will attempt to recover by breaking constraint
(Names: '|':UIView:0x128727a0 )>
There must be a hidden property within UILabel that's screwing up my 'Visual-Formatting' language.
..I created another subview of "alertView"; and I get the same error. So apparently I'm only getting a 'good' result when I merely display one (1) UIView (the 'alertView') upon (subview) of the UIController's view; nothing more.
Something hidden is conflicting the simple constraints. And I don't know what.
BTW: I'm using a NIB as the host UIView, with 'use autoLayout' 'ON'.
However, I'll be using this within larger code without 'autolayout' (iOS 4.3+), within
an iOS6-checked routine.
Solution: (per my comment) I had missed setting the 'setTranslatesAutoresizingMaskIntoConstraints' flag to 'NO' for the particular subview; albeit I had done it for its super container.
Example:
[testView setTranslatesAutoresizingMaskIntoConstraints:NO];
Don't forget to use 'setTranslatesAutoresizingMaskIntoConstraints' for ALL member UIViews!
Related
I have prepared one view controller file named "CncWindowController" and In XIB file, i take window object (instead of UIView) and connected it to view outlet. So when I access its view, i get window object.
I'm accessing like it in AppDelegate.m file :
self.windowController = [[CncWindowController alloc] initWithNibName:#"CncWindowController" bundle:nil];
self.window = (UIWindow*) self.windowController.view;
Here, view is actually referring to window. But Rotation is not working in iOS6.0 and shouldAutorotate method is also not called.
If i will use window object like below then it works fine :
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
What is wrong with my approach ? Any help of ideas how i should work autorotation in iOS-6 too using above approach ?
Thanks!
I have some data that is fetched in another thread that updates a UICollectionView's header. However, I've not found an efficient way of reloading a supplementary view such as a header or footer.
I can call collectionView reloadSections:, but this reloads the entire section which is unnecessary. collectionView reloadItemsAtIndexPaths: only seems to target cells (not supplementary views). And calling setNeedsDisplay on the header itself doesn't appear to work either. Am I missing something?
You can also use (the lazy way)
collectionView.collectionViewLayout.invalidateLayout() // swift
[[_collectionView collectionViewLayout] invalidateLayout] // objc
More complex would be to provide a context
collectionView.collectionViewLayout.invalidateLayout(with: context) // swift
[[_collectionView collectionViewLayout] invalidateLayoutWithContext:context] // objc
You can then make a or configure the context yourself to inform about what should be updated see: UICollectionViewLayoutInvalidationContext
It has a function in there that you can override:
invalidateSupplementaryElements(ofKind:at:) // swift
Another option is (if you have already loaded the correct header/footer/supplementary view) and you only want to update the view with the new data than you can use one of the following functions to retrieve it:
supplementaryView(forElementKind:at:) // get specific one
visibleSupplementaryViews(ofKind:) // all visible ones
Same goes for visible cells with visibleCells. The advantage of just getting the view and not reloading a view entirely is that the cells retains it state. This is espically nice with table view cells when they use swipe to delete/edit/etc since that state is lost after reloading the cell.
If you feel fanatic you can of course also write some extensions to retrieve only cells/supplementary views of a given kind using generics
if let view = supplementaryView(forType: MySupplementaryView.self, at: indexPath) {
configure(view, at indexPath)
}
this assumes that you have a function that registers/dequeues views in example with their class name. I made a post about this here
I just ran into the same problem, and I ended up looking up the view using its tag to edit a label:
UICollectionReusableView *footer = (UICollectionReusableView*)[self.collectionView viewWithTag:999];
UILabel *footerLabel = (UILabel*)[footer viewWithTag:100];
Like you said it is unnecessary to reload an entire section, which cancels out any animation on cells as well. My solution isn't ideal, but it's easy enough.
Swift 3/4/5 version:
collectionView.collectionViewLayout.invalidateLayout()
Caution!
If you change the number of collectionView items at the same time (for example you show the footer only if all cells were loaded), it will crash. You need to reload the data first, to make sure that the number of items is the same before and after invalidateLayout():
collectionView.reloadData()
collectionView.collectionViewLayout.invalidateLayout()
I got the same problem. I tried #BobVorks's answer and it is working fine, if only the cell was reused else it won't. So, I tried finding a more cleaner way to achieve this and I came up reloading the whole UICollectionView after the performBatchUpdate (completion block) and it is working great. It reloads the Collection Without any cancellation of animation in the insertItemsAtIndexPath. Actually I personally up voted recent 2 answers cause i find it working but in my case, this is the cleanest way to do it.
[self.collectionView performBatchUpdates:^{
// perform indexpaths insertion
} completion:^(BOOL finished) {
[self.collectionView reloadData];
}];
[UIView performWithoutAnimation:^{
[self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:4]];
}];
[UIView performWithoutAnimation:^{
[self.collectionView reloadData];
}];
Here are two ways you could do it.
1.
Create a mutable model to back the data that will eventually be available. Use KVO in inherited class of UICollectionReusableView to observe the changes and update the header view with the new data as it comes available.
[model addObserver:headerView
forKeyPath:#"path_To_Header_Data_I_care_about"
options:(NSKeyValueObservingOptionNew |
NSKeyValueObservingOptionOld)
context:NULL];
then implement listener method in header view
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context
2.
add notification listener to the view and post a notification when the data has successfully come available. Downside is that this is application wide and not a clean design.
// place in shared header file
#define HEADER_DATA_AVAILABLE #"Header Data Available Notification Name"
// object can contain userData property which could hole data needed.
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(headerDataAvailable:) name:HEADER_DATA_AVAILABLE object:nil];
[[NSNotificationCenter defaultCenter] postNotificationName:HEADER_DATA_AVAILABLE object:nil];
let headerView = collectionView.visibleSupplementaryViews(ofKind: UICollectionView.elementKindSectionHeader)[0] as! UICollectionReusableView
I've used above method to get current header, and successfully updated subviews on it.
Here's what I did to update only the section headers that are currently loaded in memory:
Add a weakToStrong NSMapTable. When you create a header, add the header as the weakly held key, with the indexPath object. If we reuse the header we'll update the indexPath.
When you need to update the headers, you can now enumerate the objects/keys from the NSMapTable as needed.
#interface YourCVController ()
#property (nonatomic, strong) NSMapTable *sectionHeaders;
#end
#implementation YourCVContoller
- (void)viewDidLoad {
[super viewDidLoad];
// This will weakly hold on to the KEYS and strongly hold on to the OBJECTS
// keys == HeaderView, object == indexPath
self.sectionHeaders = [NSMapTable weakToStrongObjectsMapTable];
}
// Creating a Header. Shove it into our map so we can update on the fly
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
PresentationSectionHeader *header = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:#"presentationHeader" forIndexPath:indexPath];
// Shove data into header here
...
// Use header as our weak key. If it goes away we don't care about it
// Set indexPath as object so we can easily find our indexPath if we need it
[self.sectionHeaders setObject:indexPath forKey:header];
return header;
}
// Update Received, need to update our headers
- (void) updateHeaders {
NSEnumerator *enumerator = self.sectionHeaders.keyEnumerator;
PresentationSectionHeader *header = nil;
while ((header = enumerator.nextObject)) {
// Update the header as needed here
NSIndexPath *indexPath = [self.sectionHeaders objectForKey:header];
}
}
#end
This question is very old but a simple way to do it is to just set a delay that covers the time your view is animating and disabling the animation while you update the view...usually a delete or insert takes about .35 seconds so just do:
delay(0.35){
UIView.performWithoutAnimation{
self.collectionView.reloadSections(NSIndexSet(index: 1))
}
My problem arose when frame sizes for the supplementary views changed upon invalidating the layout. It appeared that the supplementary views were not refreshing. It turns out they were, but I was building the UICollectionReusableView objects programmatically, and I was not removing the old UILabel subviews. So when the collection view dequeued each header view, the UILabels would pile up, causing erratic appearance.
The solution was to build each UICollectionReusableView completely inside the viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath method, starting by a) removing all subviews from the dequeued cell, then b) getting the frame size from the item's layout attributes to allow adding the new subviews.
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
yourClass *header = (yourClass *)[collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:#"identifier" forIndexPath:indexPath];
[[header viewWithTag:1] removeFromSuperview]; // remove additional subviews as required
UICollectionViewLayoutAttributes *attributes = [collectionView layoutAttributesForSupplementaryElementOfKind:kind atIndexPath:indexPath];
CGRect frame = attributes.frame;
UILabel *label = [[UILabel alloc] initWithFrame: // CGRectMake based on header frame
label.tag = 1;
[header addSubview:label];
// configure label
return header;
}
I have got a Perfect solution:
let footerView = self.collectionView.visibleSupplementaryViews(ofKind: UICollectionView.elementKindSectionFooter)
Now you can access all subview of footerView by using:
footerView[0].subviews[0]
If you have label in your footerView then :
let label: UILabel = footerView[0].subviews[0] as? UILabel ?? UILabel()
Final Step:
label.text = "Successfully Updated Footer."
if let footerView = collectionView.subviews.first(where: {$0 is LoadingFooterCell}) as? LoadingFooterCell {
footerView.isLoading = .loading
}
Can someone PLEASE help me out here. I've been scouring the internet for 2 days now looking for ways on how to do this. It seems like it should be simple enough, but it's not.
Just like many others, I'm following along the Stanford iOS 5 tutorials and got to Lecture 8: Controller Lifecycle & Image/Scroll/WebViews. I know in this example, he's using springs and struts, but I'd like to see it get done just as easily in iOS 6.
So, in iOS 5, we just set the contentSize of our UIScrollView = to the size of our UIImageView. However, in iOS 6, we're told NOT to set contentSize.
So, I start off with a new project, drag in the UIImageView, embed it into a UIScrollView. I make sure that Auto Layout is enabled. I create outlets in my view controller for both the scroll view and the image view, then I look to my constraints. This is where I get stuck.
With how great everyone says the new constraints are, I can't believe that something as simple as this can't be so straight forward. I've gone through all my constraints. I've made sure that they're all adequate, yet when I run my app, the scroll view doesn't pan the image.
Now, if I implement the following:
- (void)viewDidLoad
{
[super viewDidLoad];
[self.scrollView removeConstraints:self.scrollView.constraints];
[self.imageView removeConstraints:self.imageView.constraints];
NSDictionary *viewsDictionary = [NSDictionary dictionaryWithObjectsAndKeys:self.scrollView, #"sv", self.imageView, #"iv", nil];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[sv]|" options:0 metrics:nil views:viewsDictionary]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[sv]|" options:0 metrics:nil views:viewsDictionary]];
[self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[iv]|" options:0 metrics:nil views:viewsDictionary]];
[self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[iv]|" options:0 metrics:nil views:viewsDictionary]];
}
It works fine, but look at the constraints I set up. It's not like they're complicated. So why can't this be done easily in IB (at least not from everything I've tried)?
If this CAN be done in IB, can someone please show me how?!?!
I want to implement pull-down-to-refresh in a UICollectionViewController under iOS 6. This was easy to achieve with a UITableViewController, like so:
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:#selector(startRefresh:)
forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
The above implements a nice liquid-drop animation as part of a native widget.
As UICollectionViewController is a "more evolved" UITableViewController one would expect somewhat of a parity of features, but I can't find a reference anywhere to a built-in way to implement this.
Is there a simple way to do this that I'm overlooking?
Can UIRefreshControl be used somehow with UICollectionViewController despite the header and docs both stating that it's meant to be used with a table view?
The answers to both (1) and (2) are yes.
Simply add a UIRefreshControl instance as a subview of .collectionView and it just works.
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:self action:#selector(startRefresh:)
forControlEvents:UIControlEventValueChanged];
[self.collectionView addSubview:refreshControl];
That's it! I wish this had been mentioned in the documentation somewhere, even though sometimes a simple experiment does the trick.
EDIT: this solution won't work if the collection is not big enough to have an active scrollbar. If you add this statement,
self.collectionView.alwaysBounceVertical = YES;
then everything works perfectly. This fix taken from another post on the same topic (referenced in a comment in the other posted answer).
I was looking for the same solution, but in Swift. Based on the above answer, I have done the following:
let refreshCtrl = UIRefreshControl()
...
refreshCtrl.addTarget(self, action: "startRefresh", forControlEvents: .ValueChanged)
collectionView?.addSubview(refreshCtrl)
Not forgetting to:
refreshCtrl.endRefreshing()
I was using Storyboard and setting self.collectionView.alwaysBounceVertical = YES; did not work. Selecting the Bounces and Bounces Vertically does the job for me.
The refreshControl property has now been added to UIScrollView as of iOS 10 so you can set the refresh control directly on collection views.
https://developer.apple.com/reference/uikit/uiscrollview/2127691-refreshcontrol
UIRefreshControl *refreshControl = [UIRefreshControl new];
[refreshControl addTarget:self action:#selector(refreshControlAction:) forControlEvents:UIControlEventValueChanged];
self.collectionView.refreshControl = refreshControl;
mjh's answer is correct.
I ran into the issue where if the the collectionView.contentSize was not larger then the collectionView.frame.size, you can not get the collectionView to scroll. You can not set the contentSize property either (at least I couldn't).
If it can't scroll, it won't let you do the pull to refresh.
My solution was to subclass UICollectionViewFlowLayout and overide the method:
- (CGSize)collectionViewContentSize
{
CGFloat height = [super collectionViewContentSize].height;
// Always returns a contentSize larger then frame so it can scroll and UIRefreshControl will work
if (height < self.collectionView.bounds.size.height) {
height = self.collectionView.bounds.size.height + 1;
}
return CGSizeMake([super collectionViewContentSize].width, height);
}
I am setting up routing to a TTTableViewController as follows:
[map from:#"myurl://filter/(initWithName:)"
toViewController:[FilterViewController class]];
and then, in another view controller I set up a mutable dictionary to pass through as my query:
// Set up dictionary and populate a field
NSMutableDictionary *filterDictionary;
filterDictionary = [[NSMutableDictionary alloc] init];
[filterDictionary setObject:#"test entry" forKey:#"test key"];
// Attach a query to the URL and open it
TTURLAction *theAction = [[TTURLAction actionWithURLPath:#"myurl://filter/search"]
applyQuery:filterDictionary];
[[TTNavigator navigator] openURLAction:theAction];
Finally, in the filter view controller, I can correctly access the values:
in .h:
#property (nonatomic, retain) NSMutableDictionary *filterDictionary;
in .m:
- (id)initWithName:(NSString *)filterName query:(NSMutableDictionary *)filters {
if (self = [self init]) {
self.filterDictionary = filters;
NSLog(#"Filter Dictionary assigned : %#", self.filterDictionary);
}
return self;
}
- (BOOL)textFieldShouldReturn:(UITextField *)textField {
if (filterDictionary)
[filterDictionary setObject:textField.text forKey:#"searchAddress"];
[textField resignFirstResponder];
return YES;
}
The dictionary is correctly mutable and I can add values etc. without problem. However, when my filterViewController is dismissed, I assumed the changed dictionary would be reflected in the parent - it was passed by reference correctly.
Am I missing something? Is my dictionary in the filterVC actually a copy due to a base class of Three20 somewhere?
I'm running into a similar issue. I suspect we may need to pass in a delegate (via that query), along with your dictionary as a separate object. Then have the parent honor a protocol defined in this new VC, wherein you can now pass back that dictionary at the proper time.
TTNavigator also has viewControllerForURL:query: (among others) for obtaining a VC without opening it, but perhaps passing in the query and having the VC "do the right thing" is enough, plus I think - accent on think - the idea is to start using URL Actions and not just URLs (in the Three20 sense).