I want to redraw a view.
When I touch a button, my view have to redraw itself. (have to call viewWillAppear)
But view's setNeedDisplay method doesn't redraw itself immediately.
Because I have to redraw it immediately, the method is not suitable to me.
I tried to remove all of viewController's view's subviews and to change viewController's
view to other view.
But these didn't work. (don't redraw)
I need your help acutely.
Thank you for your reading.
I think there are some misunderstandings here. Let's set things straight:
viewWillAppear: has nothing to do with the drawing of the view.
It's true that setNeedsDisplay doesn't redraw the view instantly, but we're talking milliseconds. So that's not even relevant.
Since you want viewWillAppear: to be called I'm assuming that what you call redrawing the view really should be referred to as relayouting the view. I assume that what you do in viewWillAppear: is setting the frames of you're views and possibly add/remove and/or show/hide some views.
I suggest that you move that code out of viewWillAppear: and into it's own method that will be called from viewWillAppear: and when you tap the button.
Since you don't provide your viewWillAppear: code this is all based on assumptions, so if my assumptions are wrong, please let me know and please do provide your "redraw" code.
Without more details it's hard to know exactly what you need but I might suggest you look at UIView::setNeedsDisplay. This will in turn cause your views drawRect: to be called where you can update the drawing.
[yourViewName setNeedsDisplay];
Related
I have a simple question regarding the method removeFromSuperview()
When for example I use it to remove a UIView, do I remove also all of this view subviews?
I tried to search online but didn't find anything explanatory at least to me.
Yes. Basically, that is what a subview is. What you do to a superview, qua view, you do its subviews. Move it, hide it, show it, transform it, change its alpha, whatever.
Another way to think about it: what does it mean for a subview to have no superview in the interface? It means the subview is not in the interface. Well, you just took the superview out of the interface.
And we can go further. The superview owns the subview. If you remove the superview, by default, it is destroyed. In that case, the subview is destroyed too; it has no owner any more.
I'm trying to make a custom table view. I have a UIScrollView loaded up with UIViews. I would like to recreate the reusable cell functionality that a tableview has. And I'm wondering what might be a good way to do this.
I was thinking that when the UIViews are scrolled off screen I'll remove them from the Subview, and when I need another I'll just add it. However I'm not sure what method might be the best to do this in.
I could check to see the views location in scrollViewDidScroll: but I'm not sure if this would be the best thing to check over and over again. If anyone has any suggestions or helpful tips that would be really awesome.
Thanks!
One reason why scrollViewDidScroll is less than ideal choice is that your scroll view subclass will then need to be its own delegate. That will deny the users of that class the chance to be the delegate (easily, at least).
The better place to check this is in overriding layoutSubviews. And yes, like scrollViewDidScroll, it gets called a lot! But if you think about it, the only way to detect with certainty if any subview has been scrolled off, is to check when any scrolling occurs.
So the key is to be as efficient as you can checking. The first thing I'd try is fast enumeration of the subviews, asking if each frame transformed by contentOffset falls within the parent's bounds (using CGRectIntersectsRect). If not, add it to your reuse pool and remove it from superview.
Subclass UIScrollView and override setContentOffset. That's where the scrollViewDidScroll message comes from in the original UITableView, and that's where you can implement your own logic.
Edit: you might want to study the source code for PSTCollectionView, which is not a custom UITableView but a custom UICollectionView.
I'm developing an iPhone app, i have a UIViewController class where some coverflow animations are there and according to design i have some 5 buttons on top of my view each button have an IBAction method on clicking a button i need to display different set of coverflow with different data and the count of coverflow also changes from 1 button action to another. My problem is how can i refresh my page(reload) on click of these buttons, as i know calling explicitly viewDidLoad is a very bad idea, so how can i accomplish this? Any help is appreciated in advance thank you.
The easiest way to get a view to re-draw itself is to call [UIView setNeedsDisplay] or by using [UIView setNeedsDisplayInRect]. This method tells the view that it needs to re-draw itself and it's subviews. However you shouldn't always have to call this. There are other methods that can cause views to redraw themselves. For instance if you add or remove a view to the view hierarchy using [UIView addSubview:] or [UIView removeFromSuperview].
These methods cause the system to call your view's drawInRect: method (assuming you overrode it with custom drawing code). If you did not override this method for custom drawing then it should cause your subviews to receive the same message so that they can get a chance to redraw.
Additional information here. Specifically read the section labeled "The View Drawing Cycle".
http://developer.apple.com/library/ios/#documentation/uikit/reference/uiview_class/uiview/uiview.html
Why do you want to reload the page?, if it is because you are changing your view and you want it to be redrawn, you can call:
setNeedsDisplay();
But that is often not needed, as whenever a views bounds change that is called automatically for you.
If there's too much other stuff rather than refreshing/reloading the part of your interest in your viewDidLoad method, you can extract the refreshing part into a private method, say methodA. Every time you click your button, you call that methodA. However I think methodA still need call setNeedsDisplay or re-draw the the part of your interest. Hope it helps.
If your point is to refresh "UIViewController", then:
[self viewDidLoad];
Source: How to refresh UIViewController programmatically?
To Refresh your UIViewController, When Clicking the button >>
Add the below code into your UIButton method,
-(IBAction)button:(id)sender{
[self viewDidLoad];
[self viewWillAppear:YES];
}
Now Build and Run Your Code.
Use function viewWillAppear().This function is called everytime the view is called.
is there a possibility to determine if an uiview obj is going to be displayed. imagine: you have 2 uiviews in an uiscrollview. now you are going to switch per gesture from the first view to the second. the first view now is NOT in the viewport. now you are going to go back to the first view. and now I want to be notified that this view is in viewport, or is redisplayed. the same has to be for the second view. I have not found any callback or something like this.
You make sure your UiViewController overrides viewWillAppear: (before it appears this method is called) or viewDidAppear: (after this method is called).
See: http://developer.apple.com/iphone/library/documentation/uikit/reference/UIViewController_Class/Reference/Reference.html#//apple_ref/occ/instm/UIViewController/viewWillAppear:
That depends what you mean by "switch". If one view is just scrolled out of the visible area of the scrollview, but still remains attached as a subview to it, then you may want to check if the bounds of your view overlap those of the scrollviews visible area.
You could do this by using UIScrollView Delegate's scrollViewDidScroll: method to implement a check for overlaps while the user is scrolling.
If however your view is actually removed from the viewstack, then you may want to subclass UIView and implement willMoveToSuperview: to check if the view has been added to the scrollview again.
I have a series of UIViews inside a UIScrollView, and the UIViewControllers for those views are not receiving the touch events. If I take the views out of the scroll view then it works.
I have enabled userInteraction on the views but it's still not working!
This must be possible and I'd be really grateful if someone could point me in the right direction!
Thanks,
Mike
Do the views have their own touch handlers, or are you relying on the viewcontroller to get the touches? Depending on how you have set things up, the views may be handling the touches without passing through to the view controller.
I have overcome this issue by overriding the loadView method of the view controller, and setting the view's instance variable to a simple UIView subclass which passes on the touches.
Check what you are returning in scrollview delegate method view for scrollin in scroll view.
As mahboudz mentioned - check if you have any custom handler for touch event. If not, please have one. Its far more relief to do whatever you want to do with your view. Check out Apples sample app from scrollViewSuite. They have tapDetectingImageView delegate. I used the same in my app it worked great! Hope this helps!
You may find this post useful. It's an example of a pretty clean way of intercepting events.
Have touch handlers for view for which you want to receive touch events and that will work.