I'm having a really hard time trying to animate the resizing of a UIWebView, and just don't know where else to go.
Here's what I want to accomplish: I have two views, one above the other (imagine two squares, one on the top of the other). The top view is a UIWebView, and the bottom one will be referred to as a general UIView (I'm not having any problems with the bottom one). I adjust the two views every time new content is loaded just fine. I also have a button that should hide the bottom view or show it, depending on its previous state.
That's where the problem kicks in. When the bottom view is hidden, pressing the button will enlarge its frame and reduce the UIWebView frame. That's fine. But if the bottom view is being shown and the button is pressed, the UIWebView frame will become larger, and there are some issues with it:
If the UIWebView is scrolled all the way to the bottom, it "jumps" up a little bit before coming down (becoming larger);
If the UIWebView is scrolled all the way to the top, it comes down as expected, as long as there is enough content to be scrolled behind the bottom view.
In general, what I've learned is that if the content yet behind the bottom view is LARGER than the amount of resizing happening, no jumping happens. Otherwise, it does.
I've done a lot of research, asked a previous question and so I'm assuming this is a consequence of lazy loading the UIWebView. This "jump" happens so that it is automatically resized (showing all the content, even if some of it is offscreen) and then moves down. Otherwise, it would be expanding and loading new content at the same time, requiring a lot more processor power.
I've experimented with frames, bounds and centers, and so far have got nowhere. Is my assumption correct? Is there no simple way to resize way to resize the UIWebView so that it goes only down (when becoming larger) and keeps the bottom scroll?
In theory, I think the right way would be to make the UIWebView larger to the top, keeping its current bottom position, and then animate bringing it down. This way, the top content would already be loaded. But I haven't had any success with it.
If anyone has any experience with this, please share. And thanks a lot.
If scrolled to the bottom of a tall enough web page, try animating the web view downwards without changing it's size, then change the web views height so that the top goes back to where it should be. You can temporarily fill the space left as the web view moves down with some sort of pattern.
Related
I have a paged scroll view in my app and it works almost perfectly... Usually one page looks like this:
There is no content below this, but when i move it as if it should scroll down (clicking and swiping upwards) it stops moving at this stage:
It's as if its decided that that is an acceptable page loaction or something. If i drag it part way up it snaps the rest of the way up, and if i drag it part way down it snaps all the way down.
Why is it considering this an acceptable place to stop? Is there an easy property to set im missing? Or is there a way to allow only horizontal scrolling?
Thanks
Check the contentSize property of the scroll view. That determines how far it will scroll, and you can manually set it to control exactly where it will scroll to.
Is the scroll view on 0,0 on the canvas? It looks like it is not actually centered on the screen.
I know that I asked a question a few minutes ago, but I want to make a few points clearer before asking for the community's help. I'm new to iOS development, close to finishing my first app. The only thing standing in my way is this UIScrollView. I simply do not understand it, and could use your help.
This is in the detail view controller of a drill-down app with a tab bar. I have approximately 8 fields (for things like phone numbers and such) drawing from a .plist. Obviously, those take up enough room that I could use a little extra real estate. I would guess that it needs to be about the size of two views vertically, but I do not understand how to allocate that sort of space to a UIScrollView. Some tutorials I have read say that you don't even need to define it in the header, which I doubt and do not understand. Additionally, I do not understand how to simply get the app to smoothly scroll up-and down only. Apple's examples have constant move cycles that flip between horizontal pictures.
I doubt it makes very much a difference, but I have an image that is in the background. I'm going to load the view on top of that.
My question is broad, so I don't expect you to take the time to sit down and write out all of the code for me (and I wouldn't ask you to). Just an outline of quick, helpful tips would help me understand how to get this view to load in the context of my project.
Many thanks!
It's fairly simple. Add a UIScrollView to your view. Add your fields and such to the scrollview. In viewDidLoad or somewhere similar, you need to set the contentSize on your scrollview. This is the "virtual" area that will be scrollable. This will generally be larger than the frame of the scrollview. In your case, you indicated it should be roughly double the width.
For instance, if you had a scrollview with a view inside, and you wanted to make sure the entire view is visible via scrolling:
self.scrollView.contentSize = self.contentView.frame.size;
//setting scrollview zoom level
self._scrollview.minimumZoomScale=0.5;
self._scrollview.maximumZoomScale=6.0;
self._scrollview.contentSize=CGSizeMake(320,500 );
you have to outlet scroll view in .h class and #property #synthesis this scroll view.then you can able to scroll up and down,if u want only vertical scrolling ,then u have to go to interface builder and uncheck the horizontal scrolling.
You can set a few settings for your scrollview to limit the scrolling to horizontal or vertical. A few important ones are:
// pseudcode here, start typing "[scrollView " then press escape to get a intelli-sense of all // the things you can set for the scrollview.
// values could be YES/NO or TRUE/FALSE, I can't remember which one but
// I think it's YES/NO. Once you start scrolling, the phone will determine
// which way you're scrolling then lock it to that direction
[scrollView setDirectionalLockEnabled:YES];
// when you slide the view, if enough of the next part of the view is visible,
// the scrollview will snap or bounce the scrollview to fit this new "page".
// think of swiping feature to navigate the iPhone home screens
// to show different "pages" of iphone apps
[scrollView setPagingEnabled:YES];
// as a safe guard, make sure the width of your scrollview fits snuggly with the content
// it is trying to display. If the width is more than necessary to display your table of
// data vertically, sometimes the scrollview will cause the
// horizontal scrolling that you don't want to happen and you get bi-directional scrolling
Just set the content size of UIScrollView after adding all the controls/button/textfields etc. for example you add 10 textfields in UIScrollview then content size of UIScrollView will be
lastTextField.frame.origin.y+lastTextField.frame.size.height+20; 20 is for margin.
That's it let me know if you want to know something more related to your app.
Ok, I have a complicated scenario here. I have a scrollview which scrolls horizontally and contains tiles, 1 centered on the screen at a time with the user still able to see if there are more to the left or right by way of having the edges of the 2 views visible on either side. I am able to add the views programmatically to the scrollview and have paging work properly, so the user can swipe back and forth between them. Another requirement is to have an initial animation where the first view slides in, then is bounced off to the left by the second view. I accomplished this by using a series of UIView animations, and it works well.
Here is my problem: After the animation completes, you cannot scroll left to get to the first UIView that was created. I suspect that this is because it was animated out to the left of the content area of the scrollview. I have tried to increase the contentSize of the scrollview, but I still get the same behavior.Once the initial scrollview has been moved off to the left, I cannot swipe to page to it.
Is there a common pattern I could use to accomplish this in a better way?
It sounds to me like you're animating the child view's frame to the left so that the x coordinate of that first view's frame is negative, instead of animating the scroll view's contentOffset to the right. If that's the case, is there a reason you aren't just setting the scroll view's contentOffset inside an animation block? If there is a reason, what if after the animation completes you "fix up" the content offset and the frames of the child views so that none of the views are in a negative position.
But, I guess I have more questions than answers right now, so it might help to post the code showing how you do your animations to make it easier to answer your question.
I want to display a handle at the corners of a UIView that can be used to resize the view. How can I display the handles floating on the top of everything else and still have a connection to and be in sync with a view?
The solution I implemented before looks like this:
alt text http://bayimg.com/image/dalipaacn.jpg
I put the view into another view that shows the handles on top of the corners. The problem with this approach is that the handles add extra space to the original view's size. Since Apple recommends at least 40 x 40 px for the size of a button, it is not very little space and also goes beyond the visible bounds of the original view. Also when I want to align the original views border with its superviews border, parts of the handle buttons become untouchable. Another problem is that the original view has to be encapsulated in this 'helper view' object and thus becomes a part of something although it really is the main component.
You could make your frame view larger than the actual content, and then inset the content. That's probably the simplest way. You could also use views that weren't subviews of the frame view, but then you run into problems of synchronizing the handle with the content view, as you mentioned. I'd recommend the first option.
I would like to be able to build a scroll view capable of scrolling an unbounded (infinite) distance (this is question number one, how to do this with the contentSize property). The reason for this is so that I can implement a scrolling calendar view, which the user can use to scroll through time along a single axis.
Now, I need to put a view/s in there to mark the dates as they scroll by. My second question is how to implement a view like this in a scroll view. I could have a long view, 3 or 4 times wider than the scrollview frame and just reposition and update that every time the scrolling stops, faking a continuous bar. Any other ideas?
Thanks!
I know it's been a while since you posted this question, but just for future reference:
At WWDC 2011, Apple gave a great presentation called "Session 104 - Advanced Scroll View Techniques". The video can be seen from developer.apple.com or from iTunes.
The main concept:
1 - Start off with a subview that is larger than your scrollView's bounds.
2 - In -layoutSubViews from the scrollView, you check whether the contentOffset in the direction you want to scroll infinitely is past some threshold that you specify (this doesn't have to be any specific value, it could be 1 point in the extreme).
3 - If this is the case, you reset the contentOffset to zero, and you adjust the subview's frame by the same amount.
These last two steps happen within the same run loop cycle, hence the transition will not be visible. Beware that the scrollBar will jump, though. But as your scrollView is infinite, there is no visual feedback the scrollBars could give, anyway, so you'd better hide them when you've finished implementing this.
Not sure it can be... You could try CGSizeZero
http://developer.apple.com/library/ios/#documentation/uikit/reference/UIScrollView_Class/Reference/UIScrollView.html#//apple_ref/occ/instp/UIScrollView/contentSize
contentSize
The size of the content view. #property(nonatomic) CGSize contentSize Discussion
The unit of size is points. The default size is CGSizeZero.
The real question is do you truely want "infinate" or do you want mostly infinate and just make the view ungodly large? Or do you want auto-resizing.
Also a continuous bar for an infinite scrollview? The bar would never move as it wouldn't get any closer to the beginning or the end... You could make a bar that dragging to the right would go into the future and dragging it to the left would go back and then just always reposition it in the center.... Other then that I dunno what would make sense here.
Looping UIScrollView Horizontally sounds like the same sort of problem, hopefully my comments there might give you some ideas as well.
Making an 'infinite' scrollview doesn't work - the memory requirements get way too large. The best way to do it is fake it.
3 screen scrollview:
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Make a scrollview that is 3 times as large as one screen, then when the user finishes scrolling to the next third of the scrollview, move the scroll position back to the center third and scoot the content over to the left. This happens so fast that there is no visible feedback to the user that the scrollview & content was just recentered.
Similarly, when the user scrolls back to the first third, change the scroll position to the center third and move all the content to the right.
For memory management, you should only load as much content as will fit onto those three screens. When you scroll to the next third, you'll reposition, and load the next screen of content.