A UIView subview doesn't show in UIScrollView - iphone

I'm a newbe on iOS development, I'm trying to make a scroll header like Engadget's app for iPhone, i created a custom UIView to act as a subview for UIScrollView, the algorithm for placing the subviews seems to be ok as I can Scroll the subviews, programatically i change the background color of the views, but the problem is that I can't see anything of the content, just gray backgrounds what am I doing wrong?
Thanks in advance.
This is my code:
Promoted is a UIView with two labels and a UIImageView.
- (void)layoutScrollSubViews
{
promoted *view = nil;
NSArray *subviews = [sView1 subviews];
// reposition all image subviews in a horizontal serial fashion
CGFloat curXLoc = 0;
for (view in subviews)
{
if ([view isKindOfClass:[promoted class]] && view.tag > 0)
{
CGRect frame = view.frame;
frame.origin = CGPointMake(curXLoc, 0);
frame.size.height = kScrollObjHeight;
frame.size.width = kScrollObjWidth;
view.frame = frame;
curXLoc += (kScrollObjWidth);
}
}
// set the content size so it can be scrollable
[sView1 setContentSize:CGSizeMake((kNumImages * kScrollObjWidth), [sView1 bounds].size.height)];
}
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad{
NSUInteger i;
for (i = 1; i <= kNumImages; i++)
{
promoted *p = [[promoted alloc] initWithFrame:CGRectMake(0, 0, 320, 187)];
p.title.text = #"Test 1";
p.num.text = #"1/1";
p.num.backgroundColor = [UIColor whiteColor];
// setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
p.backgroundColor = [UIColor colorWithRed:(.9/i) green:(.9/i) blue:(.9/i) alpha:1];
p.tag = i; // tag our images for later use when we place them in serial fashion
[sView1 addSubview:p];
[p release];
}
[self layoutScrollSubViews];
[super viewDidLoad];
}

You can do two things:
1. Add your image view and labels directly to scrollView
2. also alloc your label and ImageView before adding them to your UIView(and don't forgot to release them when requirement is finish, in respective scope)

As per my experience, UIScrollView is a weird buggy control released by apple. Don't know why it behaves abnormal when added through nib file. I always try to create UIScrollView programmatically and add subviews to it by allocating them programmatically as well.
May be it would sound strange, but it works for me most of the time!

Related

Is it possible to add fixed content to a UIScrollView?

I want to create a subclass of UITableView or UIScrollView that will have some shading at the top when the content offset is > 0 to indicate that the content is scrollable. (See image attached)
The way I'm implementing it right now is using the UIViewController that is the delegate of the tableView. I simply have a GradientView on top of the tableView, and I intercept scrollViewDidScroll: to animate the visibility of that top gradient.
My problem with this implementation is that it's not "clean". I want my UIViewControllers to take care of logic, and not to deal with applying gradients and stuff. I wish I could just drop a subclass of UITableView that will do that for me.
The challenge for me is that I can't figure out how the tableView could add to itself a fixed content on top of the scrollable content.
Another question is what method/s of UIScrollView should I override to intercept the scrolling event. Obviously I don't want the tableView to be the delegate of itself...
Any ideas?
Thanks!
Ok, so I found the solution on Apple's WWDC 2011 Session 104 video - Advanced Scroll View Techniques.
There is a whole section in this video about "Stationary Views" inside a scroll view.
According to Apple, the way to go here is to override layoutSubviews and put there all the code to position whatever you want - wherever you want.
I tried it and it's actually pretty easy and it's working as expected.
So for example if I would like a shadowed header on top of the table when the content is being scrolled, this is the code I should write:
-(void) layoutSubviews
{
[super layoutSubviews];
[self positionTopShadow];
}
-(void) positionTopShadow
{
CGFloat yOffset = self.contentOffset.y;
// I'm doing some limiting so that the maximum height of the shadow view will be 40 pixels
yOffset = MIN(yOffset, 40);
yOffset = MAX(0, yOffset);
CGRect frame = self.topShadowView.frame;
// The origin should be exactly like the content offset so it would look like
// the shadow is at the top of the table (when it's actually just part of the content)
frame.origin = CGPointMake(0, self.contentOffset.y);
frame.size.height = yOffset;
frame.size.width = self.frame.size.width;
self.topShadowView.frame = frame;
if (self.topShadowView.superview == nil)
{
[self addSubview:self.topShadowView];
}
[self bringSubviewToFront:self.topShadowView];
}
I've managed to figure out a much simpler way of doing this then what Avraham did.
I use the fact that the UIScrollView calls scrollViewDidScroll: ever pixel the scrolling changes to set the object at the location of the offset. Below is my full code to keep a gray bar at the top of the scrollview as you move around:
- (void)viewDidLoad {
UIScrollView* scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(5.0, 50.0, self.bounds.size.width - 15.0, self.bounds.size.height - 60.0)];
[scrollView setBackgroundColor:[UIColor colorWithRed:251.0/255.0 green:251.0/255.0 blue:251.0/255.0 alpha:1.0]];
[scrollView setContentSize:CGSizeMake(scrollView.frame.size.width + 500, 1000.0)];
[scrollView setDelegate:self];
[self addSubview:scrollView];
UIView* header = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, scrollView.contentSize.width, 40.0)];
[header setTag:100];
[header setBackgroundColor:[UIColor darkGrayColor]];
[scrollView addSubview:header];
}
-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
UIView* header = [self viewWithTag:100];
[header setFrame:CGRectMake(0.0, scrollView.contentOffset.y, header.bounds.size.width, header.bounds.size.height)];
}
You could try using viewForHeaderInSection method of tableView for the shaded view(and also heightForHeaderInSection)... Make the shaded portion as a header.That way there is a fixed content on top of the scrollable content.
#define kImageOriginHight 300
- (void)scrollViewDidScroll:(UIScrollView *)scrollView1{
CGFloat yOffset = scrollView1.contentOffset.y;
// NSLog(#" y offset := %f", yOffset);
//zoom images and hide upper view while scrooling to down position
if (yOffset < 0) {//-kImageOriginHight
CGRect f = imgV.frame;
f.origin.y = yOffset;
f.size.height = -yOffset + kImageOriginHight;
imgV.frame = f;
//viewTableUpperView.alpha = 1.5 - (yOffset/-kImageOriginHight);
//viewTableUpperView.userInteractionEnabled = NO;
if(yOffset+0.5 == -kImageOriginHight){
[UIView animateWithDuration:0.1 animations:^{
//viewTableUpperView.alpha = 1.0;
}];
//viewTableUpperView.userInteractionEnabled = YES;
}
}
}

Reuse cells of a scroll view

I am using a scrollview to display various items in a horizontal fashion.
How can I "reuse the cells" to conserve memory:
Edit: Apologies for not being clear. I plan to place a few labels and and another ImageView inside each ImageView so I am keen to reuse this each time instead of instantiating new items each time. e.g. change the image's and update the labels instead of re-create it.
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{
[super viewDidLoad];
// load all the images from our bundle and add them to the scroll view
// NSUInteger i;
for (int i = 0; i <= 150; i++)
{
NSString *imageName = #"tempImage.jpg";
UIImage *image = [UIImage imageNamed:imageName];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
// setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
CGRect rect = imageView.frame;
rect.size.height = kScrollObjHeight;
rect.size.width = kScrollObjWidth;
imageView.frame = rect;
imageView.tag = i; // tag our images for later use when we place them in serial fashion
[self.bestSellScrollView addSubview:imageView];
[imageView release];
}
[self layoutScrollImages]; // now place the photos in serial layout within the scrollview
}
- (void)layoutScrollImages
{
UIImageView *view = nil;
NSArray *subviews = [self.bestSellScrollView subviews];
// reposition all image subviews in a horizontal serial fashion
CGFloat curXLoc = 0;
for (view in subviews)
{
if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
{
CGRect frame = view.frame;
frame.origin = CGPointMake(curXLoc, 0);
view.frame = frame;
curXLoc += (kScrollObjWidth);
}
}
// set the content size so it can be scrollable
[self.bestSellScrollView setContentSize:CGSizeMake((150 * kScrollObjWidth),
[self.bestSellScrollView bounds].size.height)];
}
If you mean like what happens with respect UITableViewCell in a UITableView, then its not possible in the horizontal scroller.
The reusable cells property for a table view is provided by the system and it not applicable for horizontal scroller.
You have to write on your own logic in order to achieve it, perhaps! Its a good question though. Will be tuned to other answers just in case if anything is possible.
If you mean you'd like to keep the UIImageView(s) where they are in the scrollview, but you'd like to change the UIImage that they show, try something like this:
-(void)changeImageViewWithTag:(NSInteger)aTag toImage:(UIImage *)anImage
{
UIImageView *theView = [self.bestSellScrollView viewWithTag:aTag];
if (theView)
{
[theView setImage:anImage];
}
}
I am assuming that you intend to reuse the UIImageView cell instances in the UIScrollView.
I hope that Daniel Tull's implementation may be helpful--
https://github.com/danielctull/DTGridView
You may like to see an Apple sample code on UIScrollView as well(I don't have the link, but u can easily find it on the web)
Thanks!
Ishank

UIScrollView Rotation Issues

I have a scrollview that automatically generates a series of subviews containing imageviews. The concept is that it's pretty much a custom PDF style reader, where each page is loaded in to an imageview as an image. There are three "layers" - the outer UIScrollView, the automatically generated subViews and the imageview inside the subview.
I've been having some trouble with this, I've asked the question previously, but unfortunately, the core of my question was in the wrong place. Here is my second attempt:
On rotate, everything is rotated as needed. Unfortunately, this is what I'm getting:
Obviously, I would like Image 1 to be centred and for there to be no hint of image 2 until you flick the view across.
Here is my code for setting up the view:
- (void)loadView {
[self setUpView];
}
- (void)setUpView {
//INITIALISE PAGING SCROLL VIEW
CGRect pagingScrollViewFrame = [[UIScreen mainScreen] bounds];
pagingScrollViewFrame.origin.x -= 10;
pagingScrollViewFrame.size.width += 20;
pagingScrollView = [[UIScrollView alloc] initWithFrame:pagingScrollViewFrame];
pagingScrollView.contentMode = UIViewContentModeScaleAspectFit;
//CONFIGURE PAGING SCROLL VIEW
pagingScrollView.pagingEnabled = YES;
pagingScrollView.backgroundColor = [UIColor blackColor];
pagingScrollView.contentSize = CGSizeMake(pagingScrollViewFrame.size.width*7, pagingScrollViewFrame.size.height);
//ACTIVATE PAGING SCROLL VIEW
self.view = pagingScrollView;
//ADD PAGES TO SCROLL VIEW
for (int i = 0; i < 7; i++){
ImageScrollView *page = [[[ImageScrollView alloc] init] autorelease];
[self configurePage:page forIndex:i];
[pagingScrollView addSubview:page];
}
}
How do I re-define the size of the frame? What function should I call etc. How do I centre the image?
I'm new to this so I apologise for the ambiguity of my question.
Cheers
I've figured it out. It was the Frame of the individual pages that I needed to change, so (with the help gained from another question) I wrote a re-orient method.
The first step to this came because I figured out that I needed to iterate through and re-size each frame for each of my pages and then re-apply the frames to the view. For this to happen I needed to create an array which I would fill in the For Loop above. I have 7 total pages.
Then I could (on rotate) call the below re-orient method to re-size each view:
- (void) reOrient{
if(UIInterfaceOrientationIsPortrait(self.interfaceOrientation)){
CGRect f;
int i = 0;
for (ImageScrollView *page in pageArray) {
f = page.frame;
f.size.width = 320;
f.origin.x = (f.size.width * i);
page.frame = f;
pagingScrollView.contentSize = CGSizeMake(f.size.width * 7, 480);
i++;
}
}else{
CGRect f;
int i = 0;
for (ImageScrollView *page in pageArray) {
f = page.frame;
f.size.width = 480;
f.origin.x = (f.size.width * i);
page.frame = f;
pagingScrollView.contentSize = CGSizeMake(f.size.width * 7, 480);
i++;
}
}
}
This worked for me:
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
[super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
//get current page based on offset before rotation
NSInteger currentPage = self.scrollView.contentOffset.x / self.scrollView.bounds.size.width;
//set anticipated scrollview content size by switching width and height (they will be switched after rotation)
[self.scrollView setContentSize:CGSizeMake(totalPages * self.view.bounds.size.height, self.view.bounds.size.width)];
//set the anticipated content offset based on height before rotation
[self.scrollView setContentOffset:CGPointMake(currentPage * self.scrollView.bounds.size.height, 0.0f)];
}
Basically I am setting the content offset for the new scrollview content size before rotating (I'm switching height and width for the anticipated height and width).
This worked for me when rotating a full-screen paged UIScrollView.
All of the paged subviews have the following autoresizing mask so that they neatly fall into place after rotation:
UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleRightMargin

uiscrollview not switching image subviews

I'm building a comic viewer app, that consists of two view controllers, the root viewcontroller basically displays a view where a user decides what comic they want to read by pressing a button. The second viewController actually displays the comic as a uiscrollview with a toolbar and a title at the top.
So the problem I am having is that the comic image panels themselves are not changing from whatever the first comic you go to if you select another comic after viewing the first one. The way I set it up, and I admit it's not exactly mvc, so please don't hate, anyway the way I set it up is each comic uiscrollview consists of x number of jpg images where each comic set's image names have a common prefix and then a number like 'funny1.jpg', 'funny2.jpg', 'funny3.jpg' and 'soda1.jpg', 'soda2.jpg', 'soda3.jpg', etc...
so when a user selects a comic to view in the root controller it makes a call to the delegate and sets ivars on instances of the comicviewcontroller that belongs to the delegate (mainDelegate.comicViewController.property) I set the number of panels in that comic, the comic name for the title label, and the image prefix.
The number of images changes(or at least the number that you can scroll through), and the title changes but for some reason the images are the same ones as whatever comic you clicked on initially.
I'm basing this whole app off of the 'scrolling' code sample from apple.
I thought if I added a viewWillAppear:(BOOL) animated call to the comicViewController everytime the user clicked the button that would fix it but it didn't, after all that is where the scrollview is laid out.
Anyway here is some code from each of the two controllers:
RootController:
-(IBAction) launchComic2{
AppDelegate *mainDelegate = [(AppDelegate *) [UIApplication sharedApplication] delegate];
mainDelegate.myViewController.comicPageCount = 3;
mainDelegate.myViewController.comicTitle.text = #"\"Death by ETOH\"";
mainDelegate.myViewController.comicImagePrefix = #"etoh";
[mainDelegate.myViewController viewWillAppear:YES];
[mainDelegate.window addSubview: mainDelegate.myViewController.view];
comicViewController:
-(void) viewWillAppear:(BOOL)animated {
self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor];
// 1. setup the scrollview for multiple images and add it to the view controller
//
// note: the following can be done in Interface Builder, but we show this in code for clarity
[scrollView1 setBackgroundColor:[UIColor whiteColor]];
[scrollView1 setCanCancelContentTouches:NO];
scrollView1.indicatorStyle = UIScrollViewIndicatorStyleWhite;
scrollView1.clipsToBounds = YES; // default is NO, we want to restrict drawing within our scrollview
scrollView1.scrollEnabled = YES;
// pagingEnabled property default is NO, if set the scroller will stop or snap at each photo
// if you want free-flowing scroll, don't set this property.
scrollView1.pagingEnabled = YES;
// load all the images from our bundle and add them to the scroll view
NSUInteger i;
for (i = 1; i <= self.comicPageCount; i++)
{
NSString *imageName = [NSString stringWithFormat:#"%#%d.jpg", self.comicImagePrefix, i];
NSLog(#"%#%d.jpg", self.comicImagePrefix, i);
UIImage *image = [UIImage imageNamed:imageName];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
// setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
CGRect rect = imageView.frame;
rect.size.height = kScrollObjHeight;
rect.size.width = kScrollObjWidth;
imageView.frame = rect;
imageView.tag = i; // tag our images for later use when we place them in serial fashion
[scrollView1 addSubview:imageView];
[imageView release];
}
[self layoutScrollImages]; // now place the photos in serial layout within the scrollview
}
- (void)layoutScrollImages
{
UIImageView *view = nil;
NSArray *subviews = [scrollView1 subviews];
// reposition all image subviews in a horizontal serial fashion
CGFloat curXLoc = 0;
for (view in subviews)
{
if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
{
CGRect frame = view.frame;
frame.origin = CGPointMake(curXLoc, 0);
view.frame = frame;
curXLoc += (kScrollObjWidth);
}
}
// set the content size so it can be scrollable
[scrollView1 setContentSize:CGSizeMake((self.comicPageCount * kScrollObjWidth), [scrollView1 bounds].size.height)];
}
Any help would be appreciated on this.
Nick
So what I ended up doing is just making multiple instances of the comic controller inside the delegate instead of just re-using the one. Will update this if I run into problems.
Nick

iPhone UIScrollView - how to get an image title

I'm ATTEMPTING to learn UIScrollview using Apple's Docs and their sample code http://developer.apple.com/iphone/library/samplecode/Scrolling/index.html but something SO simple is escaping me.
How do you tell what image is currently on the screen, so that if I selected one of the images in the horizontal scrolling view, how would I get the filename of the image, or even a pointer in the array, to then do something further with the image?
I thought with Page Control enable I might be able to find a page # and map it to the image. I thought about counting deceleration to count pages, but a flick no full enough will increment it and give a false number.
The last thing I could think of is to get contentOffSet and divide by image size which will give a 1, 2, 3 and I could point to the array (too tired to try tonight... thought I might ask before I waste a lot more time ;-) ).
Any other ideas? I thought there would be a method somewhere that they use in the photo album app.
PS: Here's the code:
- (void)layoutScrollImages
{
UIImageView *view = nil;
NSArray *subviews = [scrollView1 subviews];
// reposition all image subviews in a horizontal serial fashion
CGFloat curXLoc = 0;
for (view in subviews)
{
if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
{
CGRect frame = view.frame;
frame.origin = CGPointMake(curXLoc, 0);
view.frame = frame;
curXLoc += (kScrollObjWidth);
}
}
// set the content size so it can be scrollable
[scrollView1 setContentSize:CGSizeMake((kNumImages * kScrollObjWidth), [scrollView1 bounds].size.height)];
}
- (void)viewDidLoad
{
self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor];
// 1. setup the scrollview for multiple images and add it to the view controller
//
// note: the following can be done in Interface Builder, but we show this in code for clarity
[scrollView1 setBackgroundColor:[UIColor blackColor]];
[scrollView1 setCanCancelContentTouches:NO];
scrollView1.indicatorStyle = UIScrollViewIndicatorStyleWhite;
scrollView1.clipsToBounds = YES; // default is NO, we want to restrict drawing within our scrollview
scrollView1.scrollEnabled = YES;
// pagingEnabled property default is NO, if set the scroller will stop or snap at each photo
// if you want free-flowing scroll, don't set this property.
scrollView1.pagingEnabled = YES;
// load all the images from our bundle and add them to the scroll view
//NSUInteger i;
for (i = 1; i <= kNumImages; i++)
{
NSString *imageName = [NSString stringWithFormat:#"Card %d.png", i];
UIImage *image = [UIImage imageNamed:imageName];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
// setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
CGRect rect = imageView.frame;
rect.size.height = kScrollObjHeight;
rect.size.width = kScrollObjWidth;
imageView.frame = rect;
imageView.tag = i; // tag our images for later use when we place them in serial fashion
[scrollView1 addSubview:imageView];
[imageView release];
}
[self layoutScrollImages]; // now place the photos in serial layout within the scrollview
This was easy after a good sleep!
CGPoint p = scrollView1.contentOffset;
NSLog(#"x = %f, y = %f", p.x, p.y);
Now just divide by 320 (if horizontal and full screen image) and add 1 (because it starts at 0).
Hope this helps someone else!
Paul