I have a UIScrollView whose content size is 1200x480. I have some image views on it, whose width adds up to 600. When scrolling towards the right, I simply increase the content size and set the offset so as to make everything smooth (I then want to add other images, but that's not important right now). So basically, the images currently in the viewport remain somewhere on the left, eventually to be removed from the superview.
Now, the problem that I have happens when scrolling towards the left. What I do is I move the images to the end of the content size (so add 600 to each image view's origin.x), and then set the content offset accordingly. It works when the finger is on the screen and the user drags (scrollView.isTracking = YES). When the user scrolls towards the left and lets go (scrollView.isTracking = NO), the image views end up moving too fast towards the right and disappear almost instantly. Does anyone know how I could have the images move nicely and not disappear even when the user's not manually dragging the view and has already let go?
Here's my code for dragging horizontally:
-(void) scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint offset = self.scrollView.contentOffset;
CGSize size = self.scrollView.contentSize;
CGPoint newXY = CGPointMake(size.width-600, size.height-480);
// this bit here allows scrolling towards the right
if (offset.x > size.width - 320) {
[self.scrollView setContentSize:CGSizeMake(size.width+320, size.height)];
[self.scrollView setContentOffset: offset];
}
// and this is where my problem is:
if (offset.x < 0) {
for (UIImageView *imageView in self.scrollView.subviews) {
CGRect frame = imageView.frame;
[imageView setFrame:CGRectMake
(frame.origin.x+newXY.x, frame.origin.y, 200, frame.size.height)];
}
[self.scrollView setContentOffset:CGPointMake(newXY.x+offset.x, offset.y)];
}
}
EDIT: This is now working - I had a look at StreetScroller and it's all good now.
However, I now want to zoom in on the scrollview, but viewForZoomingInScrollView is never called. Is it not possible to zoom in on a scrollview with a large content size?
There are some approaches floating around here. Just use the site search …
If you want an more "official" example created by Apple take a look at the StreetScroller Demo. For some more information about this example take a look at last years WWDC session no. 104 Advanced Scroll View Techniques.
There is also an UIScrollView subclass on Github called BAGPagingScrollView, which is paging & infinite, but it has a few bugs you have to fix on your own, because it's not under active development (especially the goToPage: method leads to problems).
Related
I have a custom map of a limited area, and have it set up to correctly show the users' location. The map is a 1600px square image within a UIScrollView.
I have a crosshair image to show the current location of the user, which at zoomScale 1.0 is the desired size. When I pinch and zoom the scrollView, the crosshair scales with it. I would like to have the subview remain the same size on screen.
I haven't been able to find any information on this, what would be the best way to go about this?
If there is anything I can provide you with to help the answer, please let me know.
Many thanks!
EDIT -
Having looked in to this further, there is a UIScrollViewDelegate method - (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale which I tried using to take the marker's current center and size, then adjust, but this only scales at the end of the zoom. I would prefer to have the marker remain the same size while the user is zooming.
EDIT 2-
Cake has provided a great answer below, but I haven't been able to implement this in the way I imagined it would be.
I have the UIImageView as a placeholder, with alpha set to 0. This placeholder moves around relative to the map to show the user location. This operates as I expect it to. Unfortunately, this resizes with the map, as it is a subview of the map (so it stays in place).
Taking Cake's below answer, I have created the non-scaling crosshair image, and added it as a sibling subview to the scrollview. The maths, once Cake had pointed them out, were quite simple to get the new frame for the crosshair:
CGPoint ULPC = userLocationPlaceholder.center;
float zs = scrollView.zoomScale;
CGRect newFrame = CGRectMake(((ULPC.x * zs) - scrollView.contentOffset.x) - 20, ((ULPC.y * zs) - scrollView.contentOffset.y) - 20, 40, 40);
Where the image is 40points wide. This matches the centers perfectly.
The problem I now have is that I cannot get the crosshair image to stay locked to the placeholder.
I have tried using a self calling animation as such:
-(void)animeUserLocationAttachment
{
[UIView animateWithDuration:0.05
delay:0
options:(UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionCurveLinear )
animations:^{
userLocationDotContainer.frame = newFrame;
} completion:^(BOOL finished){
// Call self
[self animateUserLocationAttachment];
}];
}
As soon as I start scrolling/zooming, this locks the animation so that the crosshair just sits in place until I release the scrolling/zooming, then it correctly updates it's location.
Is there any way I can get around this, or an alternative method I can apply?
Many thanks
EDIT 3 -
I've re-accepted Cake's answer as it covers 90% of the issue. Further to his answer I have implemented the ScrollViewDelegate methods scrollViewWillBeginDragging: andscrollViewWillBeginDecelerating: to scale the placeholder to match the current size of the crosshair relative to the map, show the placeholder (that is a subview of the map image) and hide the crosshair image. The delegate method scrollviewWillBeginZooming:withView: does not show the placeholder because it scales with the map. As Cake recommends, I'll make a new question for this issue.
The counterpart methods (scrollViewDidEndZooming:withView:atScale:, scrollViewDidEndDragging:willDecelerate: and -scrollViewDidEndDecelerating:`) all hide the placeholder, and re-show the crosshair.
The question is old but for the future similar questions I've recently resolved a similar problem applying the hint of Andrew Madsen of another post.
I'had a UIScrollView, with an UIImageView in it. Attached to the UIImageView I had many MKAnnotationView (those are my subviews that I didn't want scaling with the superview).
I did subclass UIImageView and implement setTransform: method like here:
#import "SLImageView.h"
#implementation SLImageView
- (void)setTransform:(CGAffineTransform)transform
{
[super setTransform:transform];
CGAffineTransform invertedTransform = CGAffineTransformInvert(transform);
for (id obj in self.subviews)
{
if ([obj isKindOfClass:[MKAnnotationView class]])
{
[((UIView *)obj) setTransform:invertedTransform];
}
}
}
#end
This works perfectly!
Mick.
Create another crosshair image that's associated with the view or view controller that contains the scrollview. Then have this one always snap to the center of the crosshair image you already have. Then, hide your original crosshair image. Then you can avoid having the scrollview scale the disassociated crosshair, and it should stay the same size.
Relative coordinate systems
Each view in cocoa touch has a frame property that has an origin. In order to position an object owned by one view properly relative to another view, all you have to do is figure out the differences in their origins. If one view is a subview of another, then this isn't too difficult.
Get the origin of the container view
Get the location of the subview inside of the container view
Get the origin of the subview
Calculate the difference in the positions of the origins
Get the location of the object you want to overlap (relative to the subview)
Calculate the location of the object you want to overlap relative to the container view
Move your crosshair to this position
Swift equivalent for Mick's answer:
class MapContainerView:UIView {
#IBOutlet var nonScalingViews: [UIView]!
override var transform: CGAffineTransform {
didSet {
guard let nonScalingViews = nonScalingViews else {
return
}
let invertedTransform = CGAffineTransformInvert(transform)
for view in nonScalingViews {
view.transform = invertedTransform
}
}
}
}
I'm creating a drawing app on the iPad where the user can draw and scroll through the drawing. (Think of a canvas 4000 pixels wide with a view port width of 1024) At the moment, I'm using OpenGL for the drawing, and with a width of 1024, it works great. When I change the frame size of the UIView to 4000, I get "failed to make complete framebuffer object 8cd6". When I reduced it to a width of 2000, I ended up getting "wacky" results. I know I can manipulate the frame correctly, as having a frame width of 500 creates the correct result.
I was also thinking of leaving the width 1024 and moving the camera of the OpenGL layer, but how would that work with the UIScrollView that I setup? So I'm unsure on what to do at the moment. Any advice?
Thanks in advance
P.S. The code is largely based of GLPaint sample Apple provides here
I think you'd be best off with the scheme you suggest towards the end — keeping the OpenGL view static and outside of the scroll view, and moving its contents so as to match the movement of the scroll view.
Assuming you're using a GLKView, implement your glkView:drawInRect: so that it gets the contentOffset (and, probably, the bounds) properties from your scroll view and draws appropriately. E.g. (pretending you're using GLES 1.0 just because the matrix manipulation methods are so well known):
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// displayArea will be the area the scroll view is
// currently displaying; taking just the bounds would
// likely be fine too
CGRect displayArea;
displayArea.origin = scrollView.contentOffset;
displayArea.size = scrollView.bounds.size;
// assuming (0, 0) in the GL view is in the centre,
// we'll adjust things so that it's in the corner ala
// UIKit
CGPoint centre = CGPointMake(
displayArea.origin.x + displayArea.size.width*0.5f,
displayArea.origin.y + displayArea.size.height*0.5f);
glPushMatrix();
// apply the scroll as per the scroll view
// so that its centre is aligned with our centre
glTranslatef(-centre.x, -centre.y, -1);
/* rest of drawing here */
glPopMatrix();
}
Then connect yourself as a delegate to the scrollview and just perform:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
[glView setNeedsDisplay];
}
To ensure the GL redraws whenever the scroll view is scrolled.
I would strongly recommend to do your zooming in panning with your OpenGL camera instead of trying to use it in a UIScrollView. It will be a little more work to set up, but ultimately the way to go IMHO.
I have a UIScrollView which is scrollable both vertically and horizontally. This view is filled with lots of buttons, each of them with its own width (but all with the same height).
When one of these buttons gets tapped, a slider-like interface is brought to life. If this interface goes over the selected button, the whole scroll view must be scrolled so that the button becomes visible once again.
My app behaves as expected when the Y coordinate of the scroll view's content offset is set to a limit (this limit can be 0 or the view's height). But if the content offset is located in an intermediate vertical position, the scrolling just doesn't seem to happen.
At first, I tried the following approach:
CGPoint newOffset = CGPointMake(self.scrollView.contentOffset.x + horizontalVar,
self.scrollView.contentOffset.y);
[self.scrollView setContentOffset: newOffset animated: YES];
Which didn't work, as I mentioned.
Then, I tried to manually animate the view, using its property setter:
[UIView animateWithDuration: 0.3 animations: ^{
CGPoint newOffset = CGPointMake(self.scrollView.contentOffset.x + horizontalVar, self.scrollView.contentOffset.y);
self.scrollView.contentOffset = newOffset;
}];
That approach produced the following result: if the scroll view is in an intermediate vertical position when one of its buttons gets tapped, the content offset update causes a visual change, but the view almost immediately returns to its original state.
I have no other clues on the subject. Could you please help me?
Maybe it's because you didn't set the ContentSize of your scrollView.
I have two instances of NSScrollView both presenting a view on the same content. The second scroll view however has a scaled down version of the document view presented in the first scroll view. Both width and height can be individually scaled and the original width - height constraints can be lost, but this is of no importance.
I have the synchronised scrolling working, even taking into account that the second scroll view needs to align its scrolling behaviour based on the scaling. There's one little snag I've been pulling my hairs out over:
As both views happily scroll along the smaller view needs to slowly catch up with the larger view, so that they both "arrive" at the end of their document at the same time. Right now this is not happening and the result is that the smaller view is at "end-of-document" before the larger view.
The code for synchronised scrolling is based on the example found in Apple's documentation titled "Synchronizing Scroll Views". I have adapted the synchronizedViewContentBoundsDidChange: to the following code:
- (void) synchronizedViewContentBoundsDidChange: (NSNotification *) notification {
// get the changed content view from the notification
NSClipView *changedContentView = [notification object];
// get the origin of the NSClipView of the scroll view that
// we're watching
NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;
// get our current origin
NSPoint curOffset = [[self contentView] bounds].origin;
NSPoint newOffset = curOffset;
// scrolling is synchronized in the horizontal plane
// so only modify the x component of the offset
// "scale" variable will correct for difference in size between views
NSSize ownSize = [[self documentView] frame].size;
NSSize otherSize = [[[self synchronizedScrollView] documentView] frame].size;
float scale = otherSize.width / ownSize.width;
newOffset.x = floor(changedBoundsOrigin.x / scale);
// if our synced position is different from our current
// position, reposition our content view
if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
// note that a scroll view watching this one will
// get notified here
[[self contentView] scrollToPoint:newOffset];
// we have to tell the NSScrollView to update its
// scrollers
[self reflectScrolledClipView:[self contentView]];
}
}
How would I need to change that code so that the required effect (both scroll bars arriving at an end of document) is achieved?
EDIT: Some clarification as it was confusing when I read it back myself: The smaller view needs to slow down when scrolling the first view reaches the end. This would probably mean re-evaluating that scaling factor... but how?
EDIT 2: I changed the method based on Alex's suggestion:
NSScroller *myScroll = [self horizontalScroller];
NSScroller *otherScroll = [[self synchronizedScrollView] horizontalScroller];
//[otherScroll setFloatValue: [myScroll floatValue]];
NSLog(#"My scroller value: %f", [myScroll floatValue]);
NSLog(#"Other scroller value: %f", [otherScroll floatValue]);
// Get the changed content view from the notification.
NSClipView *changedContentView = [notification object];
// Get the origin of the NSClipView of the scroll view that we're watching.
NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;
// Get our current origin.
NSPoint curOffset = [[self contentView] bounds].origin;
NSPoint newOffset = curOffset;
// Scrolling is synchronized in the horizontal plane so only modify the x component of the offset.
NSSize ownSize = [[self documentView] frame].size;
newOffset.x = floor(ownSize.width * [otherScroll floatValue]);
// If our synced position is different from our current position, reposition our content view.
if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
// Note that a scroll view watching this one will get notified here.
[[self contentView] scrollToPoint: newOffset];
// We have to tell the NSScrollView to update its scrollers.
[self reflectScrolledClipView:[self contentView]];
}
Using this method the smaller view is "overtaken" by the larger view when both scrollers reach a value of 0.7, which is not good. The larger view then scrolls past its end of document.
I think you might be approaching this in the wrong way. I think you should be getting a percentage of how far down each scroll be is scrolled in relation to itself and apply that to the other view. One example of how this could be done is this way using NSScroller's -floatValue:
NSScroller *myScroll = [self verticalScroller];
NSScroller *otherScroll = [otherScrollView verticalScroller];
[myScroll setFloatValue:otherScroll.floatValue];
I finally figured it out. The answer from Alex was a good hint but not the full solution as just setting the float value of a scroller doesn't do anything. That value needs translation to specific coordinates to which the scroll view needs to scroll its contents.
However, due to differences in size of the scrolled document view, you cannot just simply use this value, as the scaled down view will be overtaken by the "normal" view at some point. This will cause the normal view to scroll past its end of document.
The second part of the solution was to make the normal sized view wait with scrolling until the scaled down view has scrolled its own width.
The code:
// Scrolling is synchronized in the horizontal plane so only modify the x component of the offset.
NSSize ownSize = [[self documentView] frame].size;
newOffset.x = MAX(floor(ownSize.width * [otherScroll floatValue] - [self frame].size.width),0);
The waiting is achieved by subtracting the width of the scroll view from the width times the value of the scroller. When the scaled down version is still traversing its first scroll view width of pixels, this calculation will result in a negative offset. Using MAX will prevent strange effects and the original view will quietly wait until the value turns positive and then start its own scrolling. This solution also works when the user resizes the app window.
I have a UIViewController one UIWebView in it. I'd like the UIWebView to be positioned in the centre of the iPad screen in landscape and portrait modes. So, I've implemented it like this
// UIViewController
// InfoGraphicView is the UIWebView
-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Overriden to allow any orientation.
return YES;
}
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
duration:(NSTimeInterval)duration {
if (toInterfaceOrientation == UIInterfaceOrientationPortrait ||
toInterfaceOrientation == UIInterfaceOrientationPortraitUpsideDown) {
[self layoutPortrait];
} else {
[self layoutLandscape];
}
}
- (void)layoutLandscape {
NSLog(#"Layout Landscape");
infoGraphicView.frame = CGRectMake(100, 100, 936, 700);
}
- (void)layoutPortrait {
NSLog(#"Layout Portrait");
infoGraphicView.frame = CGRectMake(100, 100, 700, 936);
}
However, it's not behaving as I expected. In the above code, I would expectt he UIWebView to be 100px (or points or whatever the unit is) away from the top and the left. But it's not. In Portrait mode it appears flush with the top left of the screen, and in Landscape mode it seems to be partially offscreen in the top left.
If I set the frame as CGRectMake(-100, 100, 700, 936) then I get it positioned in the center of the screen as I'd like it to be, but I've no idea why.
As usual, there's most likely something simple I'm overlooking but I can't figure it out. Any help greatly appreciated as always.
The coordinates you set on infoGraphicView are relative to its superview, not to the screen generally. And views don't necessarily clip their subviews. Furthermore, the shape set automatically to self.view will depend on the scaling flags set in Interface Builder. However, I think that by default it is set to fill the whole screen.
That said, I think the mistake is in your use of willRotateToInterfaceOrientation:duration:. That is called before the rotation begins, so self.view has the old size (ie, it'll still be portrait sized if rotating from portrait to landscape and vice versa). Probably better to hook willAnimateRotationToInterfaceOrientation:duration: — then the correct size has been set and you'll be within the CoreAnimation block so your view will grow/shrink as part of the rotation animation.
It's also worth checking which resizing flags you have set on infoGraphicView. They'll take effect automatically, in addition to any changes you make. So you probably want to disable them all.
This probably is an issue with the view that the web view is in. The coordinate system used is that of the view’s superview. If that view isn’t being resized on rotation, then you’ll see unexpected layout like this. You can access the superview of a view through the superview property; one way to see its frame would be to use its description. Put this line in one of your layout methods:
NSLog(#"Superview: %#", [infoGraphicView superview]);
That should print out a description of the view.
Once you get that figured out, if you want the web view to have the same layout, you can use its autoresizingMask property. If you set it like this:
infoGraphicView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
Then the view will automatically change its width and height to keep the top, left, right, and bottom margins the same.