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I've got a VC with a table view. When an event occurs, I want to drop in a UIView from the top of the main view. When the user scrolls the table view, I want to re-layout the view so that the dropped in view "scrolls away". I figured I'd do this by moving the upperView's frame and resizing the table view (both in relation to the scroll offset). I've got it almost working as follows:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGFloat contentOffsetY = scrollView.contentOffset.y;
if (contentOffsetY > 0) {
CGFloat upperHeight = self.upperView.frame.size.height;
CGFloat fullTableHeight = self.view.frame.size.height;
CGFloat offsetY = (contentOffsetY < upperHeight)? -scrollView.contentOffset.y : -upperHeight;
self.upperView.frame = CGRectMake(0, offsetY, 320, upperHeight);
scrollView.frame = CGRectMake(0, upperHeight+offsetY, 320, fullTableHeight-(upperHeight+offsetY));
}
NSLog(#"%f", self.upperView.frame.origin.y);
}
The upper view origin starts at 0,0.
The problem is, after a little dragging back and forth, I lose the top few pixels of that upper view. It can't seem to get it's origin y back to zero. The logging reads negative values, and only gets to -1, with the most careful dragging. Has anybody done something like this? Much obliged if you can help.
It sounds like you always scroll the table view to the top when you show the drop-in view. Assuming that's the case, there is a better way to do this.
UITableView inherits the contentInset property from UIScrollView. The contentInset property defines a border on each edge of the scroll view. Each border has its own thickness, which is zero by default. These borders just affect how far the scroll view is willing to let the user scroll the content - they don't hide the content! If you set the top inset larger than zero, and give the scroll view a subview with a negative Y origin, that subview can be visible in the border, and will scroll with the rest of the scroll view's content.
So we'll set the table view's top inset to the height of the drop-in view, and add the drop-in view as a subview of the table view with its origin set to the negative of its height. This will make it fit perfectly on the screen above the first row of the table view, and it will scroll with the table view. When we detect that the drop-in view has been scrolled fully off-screen, we can just remove it from the table view and set the table view's top inset back to zero.
We'll need an instance variable that tracks the current state of the drop-in view:
typedef enum {
DropInViewStateHidden,
DropInViewStateAppearing,
DropInViewStateVisible
} DropInViewState;
#implementation ViewController {
DropInViewState _dropInViewState;
}
In my test project, I just used a button to trigger the drop-in view. Here's the action:
- (IBAction)dropIn {
if (_dropInViewState != DropInViewStateHidden)
return;
CGRect frame = self.dropInView.frame;
frame.origin.y = -frame.size.height;
self.dropInView.frame = frame;
[self.tableView addSubview:self.dropInView];
self.tableView.contentInset = UIEdgeInsetsMake(frame.size.height, 0, 0, 0);
[self.tableView setContentOffset:frame.origin animated:YES];
_dropInViewState = DropInViewStateAppearing;
}
When the table view scrolls, we check the state of the drop-in view. If it is in the “visible” state and has been scrolled off-screen, we hide it. There's a tricky bit because when we make the drop-in view visible, and scroll it onto the screen, we can receive scrollViewDidScroll: messages that would make us think the drop-in view has been hidden. That's why we start out in the DropInViewStateAppearing state, and transition to the DropInViewVisible state when we know the view has appeared.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
switch (_dropInViewState) {
case DropInViewStateHidden:
break;
case DropInViewStateVisible:
if (scrollView.contentOffset.y >= 0) {
// dropInView has been scrolled off-screen
self.tableView.contentInset = UIEdgeInsetsZero;
[self.dropInView removeFromSuperview];
_dropInViewState = DropInViewStateHidden;
break;
}
case DropInViewStateAppearing:
// When I first add dropInView to tableView and tell tableView
// to scroll to reveal dropInView, I may get a bunch of
// scrollViewDidScroll: messages with contentOffset.y >= 0.
// I don't want those messages to hide dropInView, so I sit in
// DropInViewStateAppearing until contentOffset.y goes negative,
// which means at least part of dropInView is actually on-screen.
if (scrollView.contentOffset.y < 0)
_dropInViewState = DropInViewStateVisible;
break;
}
}
Figured this out: The UITableView doesn't thoroughly message didScroll during the bounce. This is why I was missing a few pixels. Resizing during the bounce makes the bounce get mixed up and stop. This fix on my code above allows the bounce to work (by moving, not resizing the table) and makes sure the upper view is correctly placed during the bounce (when contentOffset.y <= 0).
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGFloat contentOffsetY = scrollView.contentOffset.y;
CGFloat upperHeight = self.upperView.frame.size.height;
CGFloat fullTableHeight = self.view.frame.size.height;
CGFloat offsetY = (contentOffsetY < upperHeight)? -scrollView.contentOffset.y : -upperHeight;
if (contentOffsetY > 0) {
self.upperView.frame = CGRectMake(0, offsetY, 320, upperHeight);
scrollView.frame = CGRectMake(0, upperHeight+offsetY, 320, fullTableHeight-(upperHeight+offsetY));
} else {
self.upperView.frame = CGRectMake(0, 0, 320, upperHeight);
scrollView.frame = CGRectMake(0.0, upperHeight, 320, scrollView.frame.size.height);
}
[super scrollViewDidScroll:scrollView];
}
I'm making an app what contains a scroll view with some subviews what are built up on UIGestures...
The idea is to be able to use it in both orientations, in portrait.. it would be full screen but in landscape the user would have to scroll to access all the content however I have had some issues trying to get it to work correctly.
Here is how I have my view laid out:
UIView -> UIScrollView -> UIView -> UIImageView -> Subviews with Gesture recognisers.
the first UIView is just the UIViewControllers View, the UIScrollView is what will/should handle the difference in orientation, the second UIView is just a container to stop positioning screwing up and the UIImageView holds my image what is a diagram where I have placed a series of custom checkboxes and labels into/over the UIImageView to display content and receive and handle interaction...
In Portrait, this will work flawlessly however when I rotate to landscape, the content inside the UIScrollView is shifted up by 128pixels so the top is inaccessible... this also makes the bottom 128pixels too big so there is a transparent gap..
I can fix this by running this code on the didRotateFromInterfaceOrientation: function:
int offset = 0;
if (UIInterfaceOrientationIsLandscape([[UIApplication sharedApplication] statusBarOrientation]))
offset = 128;
else
offset = 0;
[scrollView setContentInset:UIEdgeInsetsMake(offset, 0, -offset, 0)];
The code above just alters the ContentInset's top and bottom property to adjust the postion by 128 pixels each way... the scroll view will then display the content fine...
However, when I attempt to touch any of the gestures within 128pixels from the bottom, they will not work!
I've tried so much to get it working but also if i don't alter the contentInset they will still not work (within 128 from the bottom)... It's really confusing me as I have userInteractionEnabled set to YES on all of my views but it still wont work, anything else will and content is displayed fine within this 128pixels area...
Does anybody know what is wrong with this or have anything I can try as I feel that I have tried everything possible.
Thanks for reading,
Liam
I figured it out in the end... It was an issue with the frame size changing... all I had to do was run this code on the didRotate function:
int offset = 0;
if (UIInterfaceOrientationIsLandscape([[UIApplication sharedApplication] statusBarOrientation])) {
[scrollView setFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
offset = 128;
} else {
[scrollView setFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
offset = 0;
}
[scrollView setContentInset:UIEdgeInsetsMake(offset, 0, -offset, 0)];
It just makes sure that the frame is reset back to the size of the view once rotated... I figure it was an issue with autoresize masks but I didn't have the time to play around with them and this works just as well.
This should be a pretty common thing to do, but I haven't been able to get it to work exactly right.
I have rectangular content. It normally fits in 320x361: portrait mode minus status bar minus ad minus tab bar.
I have put that content in a UIScrollView and enabled zooming. I also want interface rotation to work. The content will always be a tall rectangle, but when zoomed users might want to see more width at a time and less height.
What do I need to do in Interface Builder and code to get this done? How should I set my autoresizing on the different views? How do I set my contentSize and contentInsets?
I have tried a ton of different ways and nothing works exactly right. In various of my solutions, I've had problems with after some combination of zooming, interface rotation, and maybe scrolling, it's no longer possible to scroll to the entire content on the screen. Before you can see the edge of the content, the scroll view springs you back.
The way I'm doing it now is about 80% right. That is, out of 10 things it should do, it does 8 of them. The two things it does wrong are:
When zoomed in portrait mode, you can scroll past the edge of the content, and see a black background. That's not too much to complain about. At least you can see all the content. In landscape mode, zoomed or not, seeing the black background past the edge is normal, since the content doesn't have enough width to fill the screen at 1:1 zoom level (the minimum).
I am still getting content stuck off the edge when it runs on a test device running iOS 3.0, but it works on mine running 4.x. -- Actually that was with the previous solution. My tester hasn't tried the latest solution.
Here is the solution I'm currently using. To summarize, I have made the scroll view as wide and tall as it needs to be for either orientation, since I've found resizing it either manually or automatically adds complexity and is fragile.
View hierarchy:
view
scrollView
scrollableArea
content
ad
view is 320x411 and has all the autoresizing options on, so conforms to screen shape
scrollView is 480 x 361, starts at origin -80,0, and locks to top only and disables stretching
scrollableArea is 480 x 361 and locks to left and top. Since scrollView disables stretching, the autoresizing masks for its subviews don't matter, but I tell you anyway.
content is 320x361, starts at origin 80,0, and locks to top
I am setting scrollView.contentSize to 480x361.
shouldAutorotateToInterfaceOrientation supports all orientations except portrait upside down.
In didRotateFromInterfaceOrientation, I am setting a bottom content inset of 160 if the orientation is landscape, resetting to 0 if not. I am setting left and right indicator insets of 80 each if the orientation is portrait, resetting if not.
scrollView.minimumZoomScale = 1.0
scrollView.maximumZoomScale = 2.0
viewForZoomingInScrollView returns scrollableArea
// in IB it would be all options activated
scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
scrollView.contentSize = content.frame.size; // or bounds, try both
what do you mean with scrollableArea?
your minZoomScale is set to 1.0 thats fine for portrait mode but not for landscape. Because in landscape your height is smaller than in portrait you need to have a value smaller than 1.0. For me I use this implementation and call it every time, the frame of the scrollView did change:
- (void)setMaxMinZoomScalesForCurrentBounds {
CGSize boundsSize = self.bounds.size; // self is a UIScrollView here
CGSize contentSize = content.bounds.size;
CGFloat xScale = boundsSize.width / contentSize.width;
CGFloat yScale = boundsSize.height / contentSize.height;
CGFloat minScale = MIN(xScale, yScale);
if (self.zoomScale < minScale) {
[self setZoomScale:minScale animated:NO];
}
if (minScale<self.maximumZoomScale) self.minimumZoomScale = minScale;
//[self setZoomScale:minScale animated:YES];
}
- (void)setFrame:(CGRect)rect { // again, this class is a UIScrollView
[super setFrame:rect];
[self setMaxMinZoomScalesForCurrentBounds];
}
I don't think I understood the entire problem from your post, but here's an answer for what I did understand.
As far as I know (and worked with UIScrollView), the content inside a UIScrollView is not automatically autoresized along with the UIScrollView.
Consider the UIScrollView as a window/portal to another universe where your content is. When autoresizing the UIScrollView, you are only changing the shape/size of the viewing window... not the size of the content in the other universe.
However, if needed you can intercept the rotation event and manually change your content too (with animation so that it looks good).
For a correct autoresize, you should change the contentSize for the scrollView (so that it knows the size of your universe) but also change the size of UIView. I think this is why you were able to scroll and get that black content. Maybe you just updated the contentSize, but now the actuall content views.
Personally, I haven't encountered any case that required to resize the content along with the UIScrollView, but I hope this will get you started in the right direction.
If I understand correctly is that you want a scrollview with an image on it. It needs to be fullscreen to start with and you need to be able to zoom in. On top of that you want it to be able to rotate according to orientation.
Well I've been prototyping with this in the past and if all of the above is correct the following code should work for you.
I left a bit of a white area for the bars/custombars.
- (void)viewDidLoad
{
[super viewDidLoad];
//first inits and allocs
scrollView2 = [[UIScrollView alloc] initWithFrame:self.view.frame];
imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"someImageName"]];
[scrollView2 addSubview:imageView];
[self drawContent]; //refreshing the content
[self.view addSubview:scrollView2];
}
-(void)drawContent
{
//this refreshes the screen to the right sizes and zoomscales.
[scrollView2 setBackgroundColor:[UIColor blackColor]];
[scrollView2 setCanCancelContentTouches:NO];
scrollView2.clipsToBounds = YES;
[scrollView2 setDelegate:self];
scrollView2.indicatorStyle = UIScrollViewIndicatorStyleWhite;
[scrollView2 setContentSize:CGSizeMake(imageView.frame.size.width, imageView.frame.size.height)];
[scrollView2 setScrollEnabled:YES];
float minZoomScale;
float zoomHeight = imageView.frame.size.height / scrollView2.frame.size.height;
float zoomWidth = imageView.frame.size.width / scrollView2.frame.size.width;
if(zoomWidth > zoomHeight)
{
minZoomScale = 1.0 / zoomWidth;
}
else
{
minZoomScale = 1.0 / zoomHeight;
}
[scrollView2 setMinimumZoomScale:minZoomScale];
[scrollView2 setMaximumZoomScale:7.5];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
if (interfaceOrientation == UIInterfaceOrientationPortrait || interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown) {
// Portrait
//the 88pxls is the white area that is left for the navbar etc.
self.scrollView2.frame = CGRectMake(0, 88, [UIScreen mainScreen].bounds.size.width, self.view.frame.size.height - 88);
[self drawContent];
}
else {
// Landscape
//the 88pxls is the white area that is left for the navbar etc.
self.scrollView2.frame = CGRectMake(0, 88, [UIScreen mainScreen].bounds.size.height, self.view.frame.size.width);
[self drawContent];
}
return YES;
}
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return self.imageView;
}
I hope this will fix your troubles. If not leave a comment.
When you want to put a content (a UIView instance, let's call it theViewInstance ) in a UIScrollView and then scroll / zoom on theViewInstance , the way to do it is :
theViewInstance should be added as the subview of the UIScrollView
set a delegate to the UIScrollView instance and implement the selector to return the view that should be used for zooming / scrolling:
-(UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return theViewInstance;
}
Set the contentSize of the UIScrollView to the frame of the theViewInstance by default:
scrollView.contentSize=theViewInstance.frame.size;
(Additionally, the accepted zoom levels can be set in the UIScrollView :)
scrollView.minimumZoomScale=1.0;
scrollView.maximumZoomScale=3.0;
This is the way a pinch to zoom is achieved on a UIImage : a UIImageView is added to a UIScrollView and in the UIScrollViewDelegate implementation, the UIImageView is returned (as described here for instance).
For the rotation support, this is done in the UIViewController whose UIView contains the UIScrollView we just talked about.
I have about 50 images of 50 x 50 pixel size each. I want the user to pick one of them. So first I thought about an UITableView, but that's just not the right thing. It wastes a lot of screen space. Rather than putting all images one below the other, it would be better to show a grid of lets say 6 columns and n rows.
I would use an UIScrollView and fill it up with UIView objects which I automatically arrange so that they appear like a grid. Is that the way to go? Or any other suggestions?
I'm doing something very similar in my app- an NxN grid with an image underneath, and another subview on top to draw the "lines", all owned by a UIScrollView. I recommend having a separate view to draw the images, something like:
-(void) drawRect(CGRect rect) {
CGRect smallerRect = CGRectMake(x, y, width, height);
[yourImage drawRect: smallerRect];
// repeat as needed to draw the grid
}
Another poster mentioned that you won't be able to get touch events if your view is owned by a UIScrollView- this is simply not true. I have it working. You might need to set the following though:
[yourScrollView setUserInteractionEnabled: YES]
[yourGridView setUserInteractionEnabled: YES]
The three20 library has a class that does this.
A table view doesn't necessarily imply showing one image per row, as you suggest. Table cells can be customized, and a cell subclass with six 50x50 UIImageViews would be pretty simple. It's maybe less flexible than a scroll view but if six images per row is your goal then a table view is the quickest way to get it.
three20 is horrible,ive used it, i dont recommend it... displaying a grid is easy...
- (void) reloadGridView
{
scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(5, 54, scrollViewWidth, scrollViewHeight8)];
scrollView.delegate = self;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.userInteractionEnabled = YES;
scrollView.scrollEnabled = YES;
[self.view addSubview:scrollView];
int x = 10;
int y = 10;
divisor = 1;
for (int i = 0; i < [self.photosArray count]; i++) {
int buttonTag = divisor;
UIImage *thumb = [UIImage imageWithContentsOfFile:[self thumbPathAtIndex:i]];
//********* CREATE A BUTTON HERE **********
//********* use the thumb as its backgroundImage *******
if(divisor%4==0){
y+=70;
x = 10;
}else{
x += 70;
}
divisor++;
}
[scrollView setContentSize:CGSizeMake(scrollViewWidth, ([self.photosArray count]%4 == 0) ? y : y+100)];
}
and if you want 6 images when in landscape - setup a BOOL for isLandscape
if (isLandscape) {
//change the divisor to change # 6 instead of 4
}
if you need a more advanced gridView check out AQGridView (Google it)
UIScrollView in paging mode assumes the pages are located right next to each other, with no gap. However if you open a photo in the Photos app and swipe through photos, you can see that it has some gap between pages. I want these gaps too.
I'm looking for existing solutions if any, or for some more bizarre ideas about implementing the page gaps besides the one I have explained below. Or maybe there's some obvious easy way I am missing?
To be clear: I want the gap to only be visible while scrolling, so I cannot simply inset the page content.
My plan is to try moving the page content from inside scrollViewDidScroll callback, so that (assuming you're scrolling to the right) initially the target page is slightly offset to the right of its page boundaries, and by the time you arrive at the target page it's back at its proper location, and the source page is slightly offset to the left of its boundaries. (Or maybe instead of moving things continuously, I'll be better off shifting the offsets, say, exactly halfway between pages.)
I'm the author of the ScrollingMadness article+example that I've been referring some people to here. I've implemented progammatic zooming, and got in-photo zooming+scrolling working together with inter-photo paging. So I know how to play with UIScrollView, and am looking for the advanced stuff.
Please don't point me at TTScrollView. I've already pointed many people to it myself, but I consider it's feel too far from the native UIScrollView behaviour, and do not want to use it in my projects.
Note that this answer is quite old. The basic concept still works but
you should not be hard coding view sizes in iOS7 and 8. Even if you ignore
that advice, you should not use 480 or 330.
Have you tried making the frame of the UIScrollView slightly larger than the screen (assuming that you want to display your images fullscreen and then arranging your subviews on the same slightly-larger-than-the-screen boundaries.
#define kViewFrameWidth 330; // i.e. more than 320
CGRect scrollFrame;
scrollFrame.origin.x = 0;
scrollFrame.origin.y = 0;
scrollFrame.size.width = kViewFrameWidth;
scrollFrame.size.height = 480;
UIScrollView* myScrollView = [[UIScrollView alloc] initWithFrame:scrollFrame];
myScrollView.bounces = YES;
myScrollView.pagingEnabled = YES;
myScrollView.backgroundColor = [UIColor redColor];
UIImage* leftImage = [UIImage imageNamed:#"ScrollTestImageL.png"];
UIImageView* leftView = [[UIImageView alloc] initWithImage:leftImage];
leftView.backgroundColor = [UIColor whiteColor];
leftView.frame = CGRectMake(0,0,320,480);
UIImage* rightImage = [UIImage imageNamed:#"ScrollTestImageR.png"];
UIImageView* rightView = [[UIImageView alloc] initWithImage:rightImage];
rightView.backgroundColor = [UIColor blackColor];
rightView.frame = CGRectMake(kViewFrameWidth * 2,0,320,480);
UIImage* centerImage = [UIImage imageNamed:#"ScrollTestImageC.png"];
UIImageView* centerView = [[UIImageView alloc] initWithImage:centerImage];
centerView.backgroundColor = [UIColor grayColor];
centerView.frame = CGRectMake(kViewFrameWidth,0,320,480);
[myScrollView addSubview:leftView];
[myScrollView addSubview:rightView];
[myScrollView addSubview:centerView];
[myScrollView setContentSize:CGSizeMake(kViewFrameWidth * 3, 480)];
[myScrollView setContentOffset:CGPointMake(kViewFrameWidth, 0)];
[leftView release];
[rightView release];
[centerView release];
Apologies if this doesn't compile, I tested it in a landscape app and hand edited it back to portrait. I'm sure you get the idea though. It relies on the superview clipping which for a full screen view will always be the case.
So I don't have enough "rep" to post a comment on the answer above. That answer is correct, but there is a BIG issue to be aware of:
If you're using a UIScrollView in a viewController that's part of a UINavigationController, the navigation controller WILL resize the frame of your scrollView.
That is, you have an app that uses a UINavigationController to switch between different views. You push a viewController that has a scrollView and you create this scrollView in the viewController's -init method. You assign it a frame of (0, 0, 340, 480).
Now, go to your viewController's -viewDidAppear method, get the frame of the scrollView you created. You'll find that the width has been reduced to 320 pixels. As such, paging won't work correctly. You'll expect the scrollView to move 340 pixels but it will, instead, move 320.
UINavigationController is a bit notorious for messing with subviews. It moves them and resizes them to accommodate the navigation bar. In short, it's not a team player -- especially in this case. Other places on the web suggest that you not use UINavigationController if you need precise control over your views' size and locations. They suggest that, instead, you create your own navigationController class based on UINavigationBar.
Well that's a ton of work. Fortunately, there's an easier solution: set the frame of the scrollView in your viewController's -viewDidAppear method. At this point, UINavigationController is done messing with the frame, so you can reset it to what it should be and the scrollView will behave properly.
This is relevant for OS 3.0. I have not tested 3.1 or 2.2.1. I've also filed a bug report with Apple suggesting that they modify UINavigationController with a BOOL such as "-shouldAutoarrangeSubviews" so that we can make that class keep its grubby hands off subviews.
Until that comes along, the fix above will give you gaps in a paginated UIScrollView within a UINavigationController.
Apple has released the 2010 WWDC session videos to all members of the iphone developer program. One of the topics discussed is how they created the photos app!!! They build a very similar app step by step and have made all the code available for free.
It does not use private api either. Here is a link to the sample code download. You will probably need to login to gain access.
http://connect.apple.com/cgi-bin/WebObjects/MemberSite.woa/wa/getSoftware?code=y&source=x&bundleID=20645
And, here is a link to the iTunes WWDC page:
http://insideapple.apple.com/redir/cbx-cgi.do?v=2&la=en&lc=&a=kGSol9sgPHP%2BtlWtLp%2BEP%2FnxnZarjWJglPBZRHd3oDbACudP51JNGS8KlsFgxZto9X%2BTsnqSbeUSWX0doe%2Fzv%2FN5XV55%2FomsyfRgFBysOnIVggO%2Fn2p%2BiweDK%2F%2FmsIXj
The way to do this is like you said, a combination of a few things.
If you want a gap of 20px between your images, you need to:
First, expand your scroll view's total width by 20px and move it left by 10px.
Second, when you lay out the xLoc of your images, add 20px for each image so they're spaced 20px apart.
Third, set the initial xLoc of your images to 10px instead of 0px.
Fourth, make sure you set the content size of your scroll view to add 20px for each image. So if you have kNumImages images and each is kScrollObjWidth, then you go like this:
[scrollView setContentSize:CGSizeMake((kNumImages * (kScrollObjWidth+20)), kScrollObjHeight)];
It should work after that!
This is just a hunch, so apologies if completely wrong, but is it possible that the contentSize is just set to slightly wider than the screen width.
The correct information is then rendered within the view to the screen width and UIScrollView takes care of the rest ?
Maybe you want to try UIScrollView's contentInset property?
myScrollView.contentInset = UIEdgeInsetsMake(0, 0, 0, 10.0);
I just thought I'd add here for posterity the solution I ended up going with. For a long time I've been using Bryan's solution of adjusting the frame in -viewDidAppear, and this has worked brilliantly. However since iOS introduced multitasking I've been running into a problem where the scroll view frame gets changed when the app resumes from the background. In this case, -viewDidAppear was not being called and I couldn't find a delegate method that would be called at the right time to reverse the change. So I decided to make my scroll view a subview of my View Controller's view, and this seemed to fix the problem. This also has the advantage of not needing to use -viewDidAppear to change the frame - you can do it right after you create the scroll view. My question here has the details, but I'll post them here as well:
CGRect frame = CGRectMake(0, 0, 320, 460);
scrollView = [[UIScrollView alloc] initWithFrame:frame];
// I do some things with frame here
CGRect f = scrollView.frame;
f.size.width += PADDING; // PADDING is defined as 20 elsewhere
scrollView.frame = f;
[self.view addSubview:scrollView];
To avoid messing with UIScrollView's frame, you could subclass UIScrollView and override layoutSubviews to apply an offset to each page.
The idea is based on the following observations:
When zoomScale !=1, the offset is zero when it is at the left / right edge
When zoomScale ==1, the offset is zero when it is at the visible rect centre
Then the following code is derived:
- (void) layoutSubviews
{
[super layoutSubviews];
// Find a reference point to calculate the offset:
CGRect bounds = self.bounds;
CGFloat pageGap = 8.f;
CGSize pageSize = bounds.size;
CGFloat pageWidth = pageSize.width;
CGFloat halfPageWidth = pageWidth / 2.f;
CGFloat scale = self.zoomScale;
CGRect visibleRect = CGRectMake(bounds.origin.x / scale, bounds.origin.y / scale, bounds.size.width / scale, bounds.size.height / scale);
CGFloat totalWidth = [self contentSize].width / scale;
CGFloat scrollWidth = totalWidth - visibleRect.size.width;
CGFloat scrollX = CGRectGetMidX(visibleRect) - visibleRect.size.width / 2.f;
CGFloat scrollPercentage = scrollX / scrollWidth;
CGFloat referencePoint = (totalWidth - pageWidth) * scrollPercentage + halfPageWidth;
// (use your own way to get all visible pages, each page is assumed to be inside a common container)
NSArray * visiblePages = [self visiblePages];
// Layout each visible page:
for (UIView * view in visiblePages)
{
NSInteger pageIndex = [self pageIndexForView:view]; // (use your own way to get the page index)
// make a gap between pages
CGFloat actualPageCenter = pageWidth * pageIndex + halfPageWidth;
CGFloat distanceFromRefPoint = actualPageCenter - referencePoint;
CGFloat numOfPageFromRefPoint = distanceFromRefPoint / pageWidth;
CGFloat offset = numOfPageFromRefPoint * pageGap;
CGFloat pageLeft = actualPageCenter - halfPageWidth + offset;
view.frame = CGRectMake(pageLeft, 0.f, pageSize.width, pageSize.height);
}
}