...frustration. I want my game to be run only in landscape mode. I have added the appropriate key/value to the Info.plist file that forces the device orientation to be correct at launch.
I'm now trying to rotate the OpenGL coordinate space to match that of the device. I'm trying to use the code I found here, but it's not working. My test case draws a square at the center, and with all of that code included, I see nothing drawn; if I comment out the 2nd part (only setting the GL_PROJECTION matrix mode), the coordinate system does appear to be correct. But I'd like it rotated as well. I'm a little puzzled on how to do this, as well as setting up the view nib correctly as well. Tips, please?
Also, in the future, I'm going to be swapping out the EAGLView with another UIView subclass; is doing this going to require anything different?
Thanks!
randy
You have the plist set correctly.
Now make sure ALL your view controllers have the following:
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
{
return (toInterfaceOrientation==UIInterfaceOrientationLandscapeRight) ? YES : NO;
}
A child view without it can muck things up.
Also if you have a UINavigationController or similar you NEED to subclass it and implement shouldAutorotateToInterfaceOrientation because its dead stupid on its own and will default to portrait and ruin things.
Then for viewdidload
- (void)viewDidLoad {
[super viewDidLoad];
CGRect rect = [[UIScreen mainScreen] bounds];
rect.size.height = 320;
rect.size.width = 480;
rect.origin.x = 0;
rect.origin.y = 0;
glView = [[EAGLView alloc] initWithFrame:rect pixelFormat:GL_RGB565_OES depthFormat:GL_DEPTH_COMPONENT16_OES preserveBackbuffer:NO];
[self.view addSubview: glView];
[glView addSubview: minimapView];
//etc...
}
Related
I'm making one app in phone-gap so I've to deal in web-views only. In this app I need to put ads in the bottom of the screen. I'm using google admob for this. This generates floating ad window. I've put this window in bottom of the screen but problem is my webview content is hiding behind this window.
So, I've make one rectangle and add this google admob window in this rectangle. It solved my data hiding problem, but now it is not click able.
My code:
- (void)webViewDidFinishLoad:(UIWebView*)theWebView
{
theWebView.backgroundColor = [UIColor blackColor];
CGRect viewBounds = CGRectMake([[UIScreen mainScreen] applicationFrame].origin.x, [[UIScreen mainScreen] applicationFrame].origin.y, [[UIScreen mainScreen] applicationFrame].size.width, [[UIScreen mainScreen] applicationFrame].size.height-CGSizeFromGADAdSize(kGADAdSizeBanner).height);
self.view.frame = viewBounds;
CGPoint origin = CGPointMake(0.0,theWebView.frame.size.height);
bannerView_ = [[[GADBannerView alloc] initWithAdSize:kGADAdSizeBanner origin:origin] autorelease];
bannerView_.adUnitID = #"___ADMOBID___";
bannerView_.rootViewController = self;
[self.view addSubview:bannerView_];
[bannerView_ loadRequest:[GADRequest request]];
return [super webViewDidFinishLoad:theWebView];
}
How to make admob clickable inside rectangle (CGRect)???
Thanks in advance...
You're actually making the main view smaller, which basically - I guess - rescales its contents (including the webview Then you're placing the banner view right under the webview, but it'll show up anyways as you most probably have the clipsToBounds flag set to NO in your main view.
What you need to do is to make the webview (not the main view) smaller using CGRectGetHeight(self.view.bounds) - CGRectGetHeight(kGADAdSizeBanner) (and not the application frame) and then lay them both out accordingly.
Check the self.view.clipsToBounds flag and set it to YES whether in code or in IB in order to test correct behaviour, what you don't see in screen won't get any touches.
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 started by creating a universal window based app. Starting with the iPhone version I created a UIViewController and associated nib.
My App delegate:
rootViewController = [[RootViewController alloc] initWithNibName:nil bundle:nil];
[window makeKeyAndVisible];
[window addSubview:rootViewController.view];
return YES;
My RootViewController:
- (void)viewDidLoad {
[super viewDidLoad];
adBannerView = [[ADBannerView alloc] initWithFrame:CGRectZero()];
[self.view addSubview:adBannerView];
}
I've tried instanciating buttons instead of the adBanner and I get the same result.
My RootViewController's nib has not been changed since x-code created it for me.
My MainWindow_iPhone.xib also is stock.
What's causing this?
Update
After changing the app's orientation the adBannerView (or button...) will snap into the correct place at y=0. I've tried setting adBannerView's y location to 20 presumably to compensate for the status bar and that makes everything display correctly until I change orientation. Then everything moves down 20 pixels and will leave a 20 pixel space between the adBannerView and the status bar.
Try to add the next line in your viewDidLoad (right after [super viewDidLoad];):
self.view.frame = [[UIScreen mainScreen] applicationFrame];
CGRectZero is literally a zero rect (0, 0, 0, 0), so ADBannerView should never show up if it really has a width and height of 0. You probably want to try initWithFrame:self.view.frame or so…
You should set the size identifier before adding the view:
- (void)viewDidLoad {
[super viewDidLoad];
adBannerView = [[ADBannerView alloc] initWithFrame:CGRectZero()];
if(UIInterfaceOrientationIsPortrait([[UIDevice currentDevice] orientation]))
adBannerView.currentContentSizeIdentifier = ADBannerContentSizeIdentifier320x50;
else
adBannerView.currentContentSizeIdentifier = ADBannerContentSizeIdentifier480x32;
[self.view addSubview:adBannerView];
// now you can treat it like any other subview
// For example, if you want to move it to the bottom of the view, do this:
CGRect frame = adBannerView.frame;
frame.origin.y = self.view.frame.size.height - frame.size.height;
[adBannerView setFrame:frame];
}
Whenever the interface rotates, you should notify the banner to change its size.
Assuming you have access to WWDC videos (which is available for free), check video session 305. It demos adding the banner.
Having trouble getting the correct bounds for my iPad application when launching it in landscape mode. I have the proper keys set in my Info.plist file, and my view controllers launch properly in landscape (and portrait, natch).
In my applicationDidFinishLaunching: method I'm calling a selector after a 3 second delay, and that method makes a call to [[UIScreen mainScreen] applicationFrame], but it's returning me a portrait frame (ie height > width).
Does anyone know how to fix this? It smells like a bug to me (if so I'll file a radar), but if it's intended behaviour, where is it documented?
I never rely on [[UIScreen mainScreen] applicationFrame], especially during app launch.
When creating views in code, use the superview to set your frame.
If you're using xibs with "simulated interface elements" they will be correctly sized and everything will work great.
UINavigationController based apps
In the case of a UINavigationController based app, grab the frame directly from self.navigationController.view, don't try to use [self loadView] and self.view.superview. UINavigationController uses "hidden" subviews to do it's job--so the direct superview will not work.
UINavigationController is special because during app launch, the navigation controller resizes your views after loadView gets called. When autoresizing kicks in you end up with a small margin at the bottom of the screen.
Why not UIScreen
[[UIScreen mainScreen] applicationFrame] doesn't work reliably (especially during app launch in landscape). My experience is that the viewcontroller's interfaceOrientation property will not match the applicationFrame orientation.
CGRect bounds = [[UIScreen mainScreen] bounds]; // portrait bounds
if (UIInterfaceOrientationIsLandscape([[UIApplication sharedApplication] statusBarOrientation])) {
bounds.size = CGSizeMake(bounds.size.height, bounds.size.width);
}
When you are holding the iPad in landscape orientation and launch an app, the view controller initially sees bounds for a portrait view (even though orientation reports landscape). The view controller will then get a message to rotate to landscape orientation before it appears.
This is the way I get the correct CGRect when the view controller is on landscape:
CGRect landscapeBounds;
if (self.view.frame.size.width < self.view.frame.size.height)
landscapeBounds = CGRectMake(self.view.frame.origin.y, self.view.frame.origin.x, self.view.frame.size.height, self.view.frame.size.width);
else
landscapeBounds = CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y, self.view.frame.size.width, self.view.frame.size.height);
This is as designed. You should query the size of your superview and adjust as necessary.
[[UIScreen mainScreen] applicationFrame] will always return the portrait rectangle even if the app is in landscape mode. This is related to the fact that UIWindow never actually rotates, but just changes the transform of rootViewController.view instead.
To make sure, you can print the root view object in portrait and landscape modes, and you'll see something like this:
Portrait:
<UIView: 0x96290e0; frame = (0 20; 768 1004); ...
Landscape:
<UIView: 0x96290e0; frame = (0 20; 768 1004); transform = [0, 1, -1, 0, 0, 0]; ...
So, add a launch image and give it the suffix -568h, according to Apple's guides.
I don't understand why anyone with a sound mind would make a system setting depend on a graphic; but I just tested and it worked.
Here is the spot that taught me after a quick search I didn't see this answer above, figured it'd be useful to someone.
S
I got into same problem when dismissing view with dismissViewControllerAnimated in Cordova plugin.
I modified singingAtom code for viewWillAppear method in MainViewController, which got resized after dismissing modal view:
- (void)viewWillAppear:(BOOL)animated
{
CGRect appFrame = [[UIScreen mainScreen] applicationFrame];
UIDeviceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];
if (UIDeviceOrientationLandscapeLeft == orientation ||
UIDeviceOrientationLandscapeRight == orientation)
{
if (appFrame.size.width < appFrame.size.height)
{
appFrame = CGRectMake(appFrame.origin.y, appFrame.origin.x, appFrame.size.height, appFrame.size.width);
}
}
self.view.frame = appFrame;
[super viewWillAppear:animated];
}
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);
}
}