I'm making a music app that displays musical notation. Currently the notation is in a very large view that extends horizontally until the music ends. Obviously this isn't a good solution because I quickly run out of memory when display large scores of music.
My question is how I can implement my view such that the view where I do my drawing is only the size of the screen, but the content gets scrolled across it (The view is contained in a scrollview)? I imagine I could just only draw stuff on the screen and redraw the view as it gets scrolled with different x coordinates, but this seems ugly and would be pretty slow.
Thanks for any suggestions. : )
There are a number of solutions around. Usually these involve drawing one-or-two screen widths past the edges, then scrolling as needed, and drawing again into the area that was previously visible. In essence, using the scroll-view as a circular buffer.
Try a Google search for UIScrollView infinite scroll.
Also, see Infinite horizontal scrolling UIScrollView.
Related
So I am trying to figure out how to make a circular scrolling system. So I have for example a wheel like this http://static.cubiq.org/uploads/2009/04/Rotating-wheel.jpeg and you scroll between options (like an old school ipod) Now I currently already have this working with positions. So I have positions 1-6 and as you scroll down, it moves everything down a position and I animate this transition. I am wondering if there is a way to do this using the actual scroll function. So that you can scroll up and down freely while holding down, rather then doing up or down actions and waiting for animation.
So given that information how could I convert a standard vertical scroll up->down and down->up into a circle structure. Thanks for any info
I have a screen in my app that consists of a UITableView with another opaque view overhanging on the top (which is also interactive). The content offset is set correctly such that the entire tableView is visible to a sighted user.
However, when using VoiceOver and paging up/down with three fingers the default scroll distance will place part of the tableView under the overhanging view, and thus prevent VoiceOver from reading part of the tableView[1].
Is there any way to change how tall a "page" is when using VoiceOver?
[1]: I know that there are still ways to cycle through all the elements, etc, but it's far easier and more discoverable for partially sighted users to skim over elements with their finger.
I think you are looking for this: https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIAccessibilityAction_Protocol/index.html#//apple_ref/occ/instm/NSObject/accessibilityScroll:
Re implement that method and scroll the amount of pixels you require instead of a whole page
I have a page in a UIWebview whose main element is taller and wider than the webview itself. I'd like to be able to "pan" around the page smoothly in any way the user chooses: horizontally, vertically, diagonally or swiping in a circular motion.
Usually it works, however around once in every three gestures, the UIWebView scrolls on only one axis (sometimes x, sometimes y), despite gesturing on both simultaneously.
The problem tends to happen most often just after the webview has loaded. After a successful two-dimensional scroll it tends not to happen so often again.
Has anybody else seen this problem or any idea what to do about it?
Found out what it was. I had a UIScrollViewDelegate listening to the UIWebView's UIScrollView for doing all sorts of other stuff I probably shouldn't. And the symptoms in the question are why!
I have a myriad of UIImageViews that act as 'tiles' on a map. They align up next to one another to form a grid of images.
Ordinarily, the grid images are flush against each other, but whenever the iPhone or iPad device is rotated, or if a UIView is applied to the view that contains these tiles, the spaces between the UIImageViews become momentarily visible, showing off the grid pattern that I'd like to be invisible.
Any ideas what might be causing this?
Thanks
Consider using CATiledLayer to draw all the images in a single view instead of using multiple subviews. There's a nice writeup on using it at Cocoa Is My Girlfriend. CATiledLayer makes it easy to build an image out of smaller tiles, display higher resolution images as the user zooms in, and avoid memory problems that come from keeping too much of a large image loaded.
this is happening because you are using different views (here uiimageview). Since they are not part of the same fabric during any animation or change in view hierarchy there is a chance that the gap between them would be visible.
This is a very common problem in graphics programming. The way to fix this problem is to have one single view and add these uiimageviews as sub-layers to this view. That way all the imageviews are part of the same fabric and the gap would not be visible.
I did not post any code but then so did you ;)
Scenario:
Horizontally scrolling UIScrollView with reused page views (so that there are only few page viewcontrollers which are being reused similar way like UITableView cells). So that they are able to be updated with new content and reused I need to know exact position of UIScrollView's content view (offset). This works great.
Now I need to implement custom scrolling animation - I mean to programatically move the content view, so that user touches some buttons, and the scroll view scrolls to desired position with this custom animation. The movement can be very quick and very far. I can not use Core Animation for this, as I could not track position during animation (CA reports you only start and end of the movement). So I decided to use CADisplayLink, and calculate each UIScrollView content for each position. This works great too.
The only problem is, that sometimes I see stroboscopic effect - say I am moving the content to the right, and it looks like it is moving to left. If I look at builtin animation within UISCrollView using setContentOffset:animated:, the animation is smooth and nice. Does anyone know, how to get rid of this stroboscopic effect?
Most likely your issue is that timestamp is a double and you're assigning it to a float
Floats have 7 digits while Doubles have 15-16 digits.
So in other words you're experiencing data loss. By using double you should see a silky smooth animation.