I am working on a MAC application in which I need to get an event that user start resizing column of nstableview. I know there is a notification columnDidResize. But it get called when we ended resizing columns.
Solved the same problem using KVO notifications.
Set your table delegate as an observer for NSTableColumn width:
[column addObserver:self forKeyPath:#"width" options:0 context:nil];
Options argument could be adjusted to get the notification before an actual change takes place.
Then get notified when the width changes:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSInteger resizedColumn = tableView.headerView.resizedColumn;
if (resizedColumn != -1)
{
if (object == column &&
object == [tableView.tableColumns objectAtIndex:resizedColumn])
{
// User is resizing column
}
}
}
Using KVO, as indicated by #pointum works. If you get into troubles related to unregistering the observer, you can do what I actually ended up doing:
Subclass NSTableColumn and override the setter for the Width parameter and send a notification from there.
Related
I am not if this will work properly
[[cr1.crossRoad.trafficLights
objectForKey: [NSNumber numberWithInt:pedestrianTL]]
addObserver:view
forKeyPath:#"colorState"
options:NSKeyValueObservingOptionNew
context:nil];
The project I'm developing doesn't work properly. This way I was trying to add an observer to change the view with after every change happening to the cell of the colorState array.
-(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
[self refreshState:object];
}
The program never enters this method though I change values of the colorState cells. Maybe the problem is with me trying to observe array but not actually what it contains?
The problem was that I was trying to observe an array which was not possible that way.
How can I get a notification when the textfield has ended editing (enter key pressed, clicked outside the text field, clicked inside the same column, but outside the text field, etc)
I checked
- (void)textDidEndEditing:(NSNotification *)aNotification
{
//some code here
}
but this notification is only called when the text has actually changed. I need to be notified even if no text changes have been made.
Edit: Some sort of notification that the first responder has changed would work as well.
Any ideas?
Observe the firstResponder state of the window …
…
[theWindow addObserver:self forKeyPath:#"firstResponder" options:NSKeyValueObservingOptionOld context:NULL];
…
… and read the field editor's delegate:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if ([keyPath isEqualToString:#"firstResponder"])
{
NSResponder *oldResponder =change[NSKeyValueChangeOldKey];
if ([oldResponder isKindOfClass:[NSTextView class]])
{
NSTextView *editor = (NSTextView*)oldResponder;
NSTextField *textField = (NSTextField*)editor.delegate;
NSLog(#"This text field lost the focus: %#", textField.identifier);
}
}
}
in a slide menu I'm developing for my project i would like to add a black view over the content view when it's slide out. To do this i need to create a method that check continuously the view x-position and darken or brighten up the black layer. The position of this view is the same as the content view.
I thought i can use a NSNotificationCenter like this:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(incomingNotification:) name:#"notification" object: darkViewController.view.frame.origin.x]];
and a method:
- (void) incomingNotification:(NSNotification *)notification{
// the dark layer alpha will be 0 at origin=0 and 0.8 at bounds.size.width
float alphaToUse = (darkViewController.view.frame.origin.x / self.view.bounds.size.width) * 0.8;
[darkViewController.view setAlpha:alphaToUse];
}
The problem is that i must use an object as parameter.
I'm new to notifications so i'm asking: is it wrong to use them for this kind of things?
Is it better to solve this in another way?
EDIT:
Following Denis advice i'm now trying to use the key-value-observe solution.
My app is structured like this:
MenuViewController-->ContainerViewController-->DarkViewController
In MenuViewController.m :
#interface MenuViewController ()
#property (strong,nonatomic) ContainerViewController *containerViewController;
#property (strong,nonatomic) DarkViewController *darkViewController;
#end
#implementation MenuViewController
#synthesize containerViewController,darkViewController;
# pragma mark - Views
- (void)viewDidLoad{
[super viewDidLoad];
containerViewController = [[ContainerViewController alloc]init];
[self addChildViewController:containerViewController];
[self.view addSubview:containerViewController.view];
[containerViewController didMoveToParentViewController:self];
darkViewController = [[DarkViewController alloc]init];
[containerViewController addChildViewController:darkViewController];
[containerViewController.view addSubview:darkViewController.view];
[darkViewController didMoveToParentViewController:containerViewController];
[UIView animateWithDuration:slideDuration delay:0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
[darkViewController.view setAlpha:0.7];
containerViewController.view.frame = CGRectMake(self.view.frame.size.width - slideWidth, 0, self.view.frame.size.width, self.view.frame.size.height);
}
completion:^(BOOL finished) {
if (finished) {
}
}];
[darkViewController addObserver:self forKeyPath:#"darkViewController.view.frame.origin.x" options:NSKeyValueObservingOptionNew context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change: (NSDictionary *)change context:(void *)context
{
NSLog(#"x is changed");
}
When i run this i get this exception:
*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<DarkViewController 0x10962d280> addObserver:<MenuViewController 0x10922c890> forKeyPath:#"darkViewController.view.frame.origin.x" options:1 context:0x0] was sent to an object that is not KVC-compliant for the "darkViewController" property.'
Ok, it seems that i found a solution following this example Notificationsin IOS
I just added this in the viewDidLoad of my ContainerViewController
[self addObserver:self forKeyPath:#"view.frame" options:0 context:nil];
and implemented the observer method with a for cycle to find my DarkViewController view
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
for (UIViewController * vc in self.childViewControllers) {
if ([vc isKindOfClass:[DarkViewController class]]) {
float alphaToUse = (self.view.frame.origin.x / self.view.bounds.size.width) * 0.8;
[vc.view setAlpha:alphaToUse];
}
}
}
Now i just have to understand where to put the removeObserver method, since my ContainerViewController will be always loaded...
There is another machanism in iOS for such kind of things called Key value coding and Key value observing.
From Notification Center documentation:
As you design your application, do not simply assume that you should send a notification to communicate with interested parties. You should also consider alternatives such as key-value observing, key-value binding, and delegation.
Key-value binding and key-value observing were introduced in OS X version 10.3 and provide a way of loosely coupling data. With key-value observing, you can request to be notified when the properties of another object change. Unlike regular notifications, there is no performance penalty for unobserved changes. There is also no need for the observed object to post a notification because the key-value observing system can do it for you automatically, although you can still choose do it manually.
So if you'll have another notification observers while making slide menu animation it may reduce its handling performance.
And the best solution would be to invoke incomingNotification: method inside the animation block (the method where animation performs).
Apple docs again:
Though key-value coding is efficient, it adds a level of indirection that is slightly slower than direct method invocations. You should use key-value coding only when you can benefit from the flexibility that it provides.
ANSWERING EDITED QUESTION:
This answer describes exactly what you're trying to do. When add the observer on some object's property object's name shouldn't be included in the property key path. So in you case adding an observer looks like this:
[darkViewController addObserver:self forKeyPath:#"view.frame" options:NSKeyValueObservingOptionNew context:nil];
When trying to observe some object property don't forget to ensure the object's class is KVC compliant for that property!
And also don't forget to remove the observers after job is done.
I have an object that need to be notified when a QLPreviewController changes the shown document. QLPreviewController have the property currentPreviewItemIndex that is updated when the document change. I've added my object as observer for currentPreviewItemIndex and it receives the notification when in my code is changed the property, so far so good.
The problem is that the user can change the shown document swiping in the screen and I've found out that in this case the notification isn't generated.
Any solution to receive the notification also in this case? I suppose that the notification is generated when is called the setter of the property currentPreviewItemIndex and probably when the user swipe the property is changed internally in the object QLPreviewController.
Another solution may be to disable the horizontal swipe in QLPreviewController but preserving the vertical swipe (there are the arrows buttons to change the shown document). How do you do that?
Thanks in advance for the help.
Giannandrea
make a category on the QLPreviewController and swizzle the appropriate method and either add the willChange/didChange for KVO ;)
seriously though:
I tried KVO and it didnt work for me either.. 1) id file a bug with apple for that saying you need this
BUT as a workaround
(id )previewPanel:(QLPreviewPanel *)panel previewItemAtIndex:(NSInteger)index {
this is called ok and everytime we swipe so I would 'hack' this to FIRE your own correct KVO. something like
static NSInteger oldIndex = -1; //reset when the panel is hidden or shown
int newIndex = qlController.displayedIndex;
if(oldIndex != newIndex) {
oldIndex = newIndex;
[qlController willChangeValueForKey:#"displayedIndex"];
[qlController didChangeValueForKey:#"displayedIndex"];
}
I wrote it inline here so there are bound to be typos and mistakes but I think the general approach could work.
//1. Declare a static context:
static void *changePageContext = &changePageContext;
//2. In viewDidLoad add self as observer for currentPreviewItemIndex property of a strong ref to your QLPreviewController:
[self.previewController addObserver:self forKeyPath:#"currentPreviewItemIndex" options:(NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld) context:changePageContext];
//3. Implement the observer method:
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change context:(void *)context
{
if (context == changePageContext)
{
NSLog(#"newValue:%ld",(long)self.previewController.currentPreviewItemIndex);
}
else
{
// Any unrecognized context must belong to super
[super observeValueForKeyPath:keyPath
ofObject:object
change:change
context:context];
}
}
//4. Remove the observer in viewWillDisappear:
-(void)viewWillDisappear:(BOOL)animated
{
if (![[self.navigationController viewControllers] containsObject: self])
{
[self.previewController removeObserver:self forKeyPath:#"currentPreviewItemIndex"];
}
}
I have a uiview named subview1. I add this as subview to a couple of other views depending on certain situations. Now I have the following code
[subView1 addObserver:self forKeyPath:#"superview" options:NSKeyValueObservingOptionNew context:nil];
My problem is the obserValueForKeypath function is never called
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
if (self.subView1 == (UIView*)object) {
if ([keyPath isEqualToString:#"superview"]) {
NSLog(#"superview changed %#",change);
}
}
}
Am i doing something wrong here.
Just check that if it is going into first if block , the problem might be there.Also check if you have declared property for variable for which you are setting the observer if it is in different class.