I am having a upperview with height 60 and i have placed tableview at y = 60.I want when i scroll the table my upperview should be hide and when i scroll down it should be visible again.But i can not make this upperview as header of tableview.Please help me how i can i detect the direction of scrollview within tableview that is it moving up or down.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
int scrollPosition = scrollView.contentOffset.y;
if(upperview.frame.size.height<scrollPosition>1 && moveDirection = movingup){
//code to make hide
}else if(upperview.frame.size.height==scrollPosition>1 && moveDirection = movingDown){
//code to show again
}
// But i have no idea how can i get this direction moveDirection = movingup or moveDirection = movingDown
}
Thanks
I have seen this tried but it always had the problem that the overlaying view could not gain the acceleration of the scroll view. It would mismatch during very quick changes of scrolling speed by the user.
If you cannot use the table's header view, you could add your view as a subview of the scroll view above coordinate zero, then change the UIScrollView's contentInset to allow it to scroll into sight.
Related
I have two scrollview, one scrollview inside another and I want to scroll my main scrollview content first after that only I want to scroll subview scroll
CGFloat scrollOffset = texscrl.contentOffset.y;
if (scrollOffset == 0)
{
//This condition will be true when scrollview will reach to bottom
self.ArtistScroll.scrollEnabled=YES;
texscrl.scrollEnabled=YES;
}else
{
self.ArtistScroll.scrollEnabled=NO;
texscrl.scrollEnabled=YES;
}
Here, am using content offset for this.. so can anyone help me?
You can achieve the affect you describe by using a third scrollview to actually handle the touch gestures and manually set the contentOffset of the other scrollviews.
Here is how to achieve this for vertically scrolling content, which is I think what you are describing. In the code, outerScrollView is the main scrollview, innerScrollView is the sub-scrollview that is contained by the outer scrollview, and trackingScrollView is the third scrollview that only handles the touches - it has no content.
Create the three scrollviews such that trackingScrollView exactly covers outerScrollView. (I assume you will do this in XIB or storyboard so there is no code.)
Once your scrollviews have content (and whenever their contentSize or bounds change) you should set the contentSize of trackingScrollView:
self.trackingScrollView.contentSize = CGSizeMake(self.trackingScrollView.bounds.size.width,
self.outerScrollView.contentSize.height + self.innerScrollView.contentSize.height - self.innerScrollView.bounds.height);
This makes the content height be that of outerScrollView plus the scrollable distance of innerScrollView, allowing trackingScrollView to scroll over the total travel distance of both scrollviews.
Delegate for trackingScrollView and implement scrollViewDidScroll:
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView == self.trackingScrollView) {
CGFloat const offsetY = self.trackingScrollView.contentOffset.y;
// Calculate the maximum outer scroll offset
CGFloat const maxOuterOffsetY = self.outerScrollView.contentSize.height - self.outerScrollView.bounds.height;
// Calculate the maximum inner scroll offset
CGFloat const maxInnerOffsetY = self.innerScrollView.contentSize.height - self.innerScrollView.bounds.height;
if (offsetY < maxOuterOffsetY) {
// Scroll is within the outer scroll area or the top bounce zone
self.outerScrollView.contentOffset = CGPointMake(0, offsetY);
self.innerScrollView.contentOffset = CGPointZero;
} else if (offsetY < maxOuterOffsetY + maxInnerOffsetY) {
// Scroll is within the inner scroll area
self.outerScrollView.contentOffset = CGPointMake(0, maxOuterOffsetY);
self.innerScrollView.contentOffset = CGPointMake(0, offsetY - maxOuterOffsetY);
} else {
// Scroll is within the bottom bounce zone
self.outerScrollView.contentOffset = CGPointMake(0, offsetY - maxInnerOffsetY);
self.innerScrollView.contentOffset = CGPointMake(0, maxInnerOffsetY);
}
} else {
// Handle other scrollviews as required
}
}
Effectively we divide the tracking scroll area into two parts. The top part controls the scrolling within the outer scrollview and the bottom part controls the inner scrollview.
Assuming bounce is turned on (which generally it should be) we also need to handle scrolling outside the scroll area. We want the bounce to show on the outer scrollview so the top bounce is handled implicitly by the first conditional. However, the bottom bounce has to be handled explicitly by the third conditional, otherwise we would see the bounce on the inner scrollview.
To be clear, in this solution the two content scrollviews (outerScrollView and innerScrollView) do not receive any touches at all; all input is going to trackingScrollView. If you want input to subviews of the content scrollviews you will need a more advanced solution. I believe this can be done by putting trackingScrollView behind outerScrollView, removing outerScrollView's gesture recognizers and replacing them with those from trackingScrollView. I have seen this technique presented in an old WWDC session on UIScrollView but I have not tried it myself.
Anyone has an idea how to control two scroll views while one in on the top of the other. One scrolls, the other one scrolls too. Same with zoom, gesture recognisers, etc ... Kinda like passing replica of the touches received by the first view onto the the one underneath. Subclass of the top scroll view has got a weak reference to the "dependant" scroll view underneath. Very important is to get the delegate methods working for both scrollviews as there is a lot of logic in these ...
use the scrollView Delegate methood
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if([scrollView isEqual:scrollViewA]) {
CGPoint offset = scrollViewB.contentOffset;
offset.y = scrollViewA.contentOffset.y;
[scrollViewB setContentOffset:offset];
} else {
CGPoint offset = scrollViewA.contentOffset;
offset.y = scrollViewB.contentOffset.y;
[scrollViewA setContentOffset:offset];
}
}
or simply in the same method for both horizontal an vertical scrolling
if([scrollView isEqual:scrollViewA]) {
scrollViewB.contentOffset = scrollViewA.contentOffset;
}
and viceVersa
My collection view begins life short, at the bottom of it's view controller's view. When the user scrolls up a little bit, I'd like the collection to fill the view. I'd like it to shrink again when the user pulls down into the bounce area.
Here's the code that I'd like to make work (and I think should work):
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView == self.collectionView) {
CGFloat offsetY = self.collectionView.contentOffset.y;
if (offsetY > 20.0) {
[self setCollectionViewExpanded:YES];
} else if (offsetY < -10.0) {
[self setCollectionViewExpanded:NO];
}
}
}
- (void)setCollectionViewExpanded:(BOOL)expanded {
// avoid starting a do-nothing animation
BOOL currentlyExpanded = self.collectionView.frame.origin.y == 0.0;
if (expanded == currentlyExpanded) return;
// note: the collection view is the uppermost subview of the vc's view
// expanding to view bounds makes it cover every other view
CGRect newFrame = (expanded)? self.view.bounds : CGRectMake(0.0, 240.0, 320.0, self.view.bounds.size.height-240.0);
[UIView animateWithDuration:0.3 animations:^{
self.collectionView.frame = newFrame;
}];
}
But after the expand happens, the cells remain in the same position relative to the parent view (still near the bottom) and the collection view stops responding to panning touches and sends no further didScroll notification.
I can get the content repositioned properly by doing a reloadData in an animation completion block, but the scrolling touches stop working either way.
A while back, I tried something like this with a table view (or another kind of scroll view) and ran into a similar hangup. Much obliged if anyone has this solved...
Can you describe your view hierarchy a bit better? Is the UICollectionView a subview of the UIScrollView?
Is self.view a UIScrollView?
In that case, the bounds origin is the scrollview's contentOffset (not 0,0). That could give your UICollectionView an unexpected frame.
If the UICollectionView is a subview of the scrollview, the frame origin is the origin of the view in the scrollview-space. So don't change the frame's origin (just its size) and set the contentOffset of the scrollView to make it visible.
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 have the UIScrollView with pagingEnabled set to YES, and programmatically scroll its content to bottom:
CGPoint contentOffset = scrollView.contentOffset;
contentOffset.y = scrollView.contentSize.height - scrollView.frame.size.height;
[scrollView setContentOffset:contentOffset animated:YES];
it scrolls successfully, but after that, on single tap its content scrolls up to offset that it has just before it scrolls down. That happens only when I programmaticaly scroll scrollView's content to bottom and then tap. When I scroll to any other offset and then tap, nothing is happened.
That's definitely not what I'd like to get. How that should be fixed?
Much thanks in advance!
Timur.
This small hack prevents the UIScrollView from scrolling when tapped. Looks like this is happening when the scroll view has paging enabled.
In your UIScrollView delegate add this method:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
scrollView.pagingEnabled = self.scrollView.contentOffset.x < (self.scrollView.contentSize.width - self.scrollView.frame.size.width);
}
This disables the paging when the scroll view reaches the right end in horizontal scrolling (my use case, you can adapt it to other directions easily).
I just figured out what causes this problem, and how to avoid it. If you having pagingEnabled set to YES on a scroll view, you must set the contentOffset to be a multiple of the scroll view's visible size (i.e. you should be on a paging boundary).
Concrete example:
If your scroll view was (say) 460 pixels high with a content area of 920, you would need to set the content offset to EITHER 0 or 460 if you want to avoid the "scroll to beginning on tap" problem.
As a bonus, the end result will probably look better since your scroll view will be aligned with the paging boundaries. :)
The following workaround did help (assume that one extends UIScrollView with a category, so 'self' refers to its instance):
-(BOOL) scrolledToBottom
{
return (self.contentSize.height <= self.frame.size.height) ||
(self.contentOffset.y == self.contentSize.height - self.frame.size.height);
}
Then, one should sometimes turn pagingEnabled off, just at the position where scroll view reaches its bottom. In the delegate (pagingEnabled is initialy on of course, since the problem occurs only when it is enabled):
-(void) scrollViewDidScroll:(UIScrollView *)scrollView
{
if (scrollView.pagingEnabled == YES)
{
if ([scrollView scrolledToBottom] == YES)
scrollView.pagingEnabled = NO;
}
else
{
if ([scrollView scrolledToBottom] == NO)
scrollView.pagingEnabled = YES;
}
}
This seems to be a bug:
UIScrollView doesn't remember the position
I have tested this on iOS 4.2 (Simulator) and the issue remains.
When scrolling a ScrollView I would suggest using
[scrollView scrollRectToVisible:CGRectMake(0,0,1,1) animated:YES];
Where the rect is the position you're after. (In this case the rect would be the top of the scrollview).
Changing the content offset is not the correct way of scrolling a scrollview.