I have a horizontal UIScrollview set up (meaning its not one that scrolls up and down but one that only scrolls left-right) and upon the app launching, I want this scrollview to scroll itself left, then right - kind of "demonstrating" its ability to scroll - and finally then stop, letting the user then take over and control the scroll manually with their finger.
Everything works - except for this on-load left-right demo-scrolling.
I'm not using Interface Builder for any of this, I'm doing everything with code:
//(this is in viewDidLoad:)
// Create the scrollView:
UIScrollView *photosScroll = [[UIScrollView alloc] initWithFrame: CGRectMake(0, 0, 320, 200)];
[photosScroll setContentSize: CGSizeMake(1240, 200)];
// Add it as a subview to the mainView
[mainView addSubview:photosScroll];
// Set the photoScroll's delegate:
photosScroll.delegate = self;
// Create a frame to which to scroll:
CGRect frame = CGRectMake(10, 10, 80, 150);
// Scroll to that frame:
[photosScroll scrollRectToVisible: frame animated:YES];
So the scrollView loads successfully and I'm able to scroll it left and right with my finger - but it doesn't do this "auto-scroll" like I was hoping it would.
I tried calling the scrollRectToVisible before and after adding the
scrollView as a subview - didn't work.
Thinking maybe this should
happen in loadView and not in viewDidLoad? But if so, how?
Any ideas?
A couple of ways to do this:
Use scrollRectToVisible:animated: for a zero X value and then a largeish positive one, then set it back to your middle point. You can call the method after the scroll view is added as a subview (probably before too, but best be safe). You'll need to calculate what value of X is off-screen to the left using your contentSize and knowledge about how wide your various elements inside the scroll view are.
Since you're just doing a quick animation and will give the user control, this can really be a quick-and-dirty animation, so you could use setContentOffset:animated: to force the content of the scrollview to move relative to your current view position. Move the elements right for a left scroll (positive X value), then left twice as far for a right scroll (negative X value), then set the offset back to zero.
You shouldn't put either of these in viewDidLoad or loadView; put them in viewDidAppear, which is after your scrollview is actually drawn on screen. You only care about animations when the user can see them!
Related
I am trying to generate a scroll controller in a window with the UIScrollView class, which will contain numerous UIButtons, placed vertically. I set the size of the scroll view equal to the current view controller's root view, so that the scroll view covers the entire visible window. Then I generate the UIButtons I am going to add to the scroll view: I add each UIButton just in the below of the previous UIButton and I add the height of the current UIButton to a variable called "totalContentHeight". Finally, I set the height of the contentSize of the scroll view to this value, in the following line of code:
self.scrollViewForNewsButtons.contentSize = CGSizeMake(self.view.frame.size.width, totalContentHeight);
totalContentHeight is equal to numOfButtons*eachButtonsHeight after I add all the buttons to the scroll view.
The problem is, in the simulator, when I run the app and scroll until the end of the last button and release the mouse, the last two buttons bounces back such that they lie outside of the visible window. It is somewhat hard to express with mere words, so here are the images:
1)This is what I get when I scrolled until the end of the content and held the content at the last possible position it could be pushed:
2)This is what I get after I released the mouse and the scroll view bounced back to its final position:
As you can see, the last two buttons are drawn outside of the visible area. It is like the scroll view's area covers the whole window plus the button area of the IPhone. I could not find a reasonable explanation for this. Am I setting the area size wrong or am I missing something else?
just set content size with calculation with your total button and its height...For Ex..
float yheight = totalButton * yourButtonHeight;
[yourScrollView setContentSize:CGSizeMake(320, yheight + 44)];
try this code...
And if you set the scrollview frame size the same as
self.view.bounds
I have image that needs to be scrolled in uiscrollview but scrolling needs to be stopped only at specific points. Imagine I have long image of uitableview so I need to scroll it. What I'm thinking about: is it possible to stop scroll only at points where full row is visible at the top? If yes, then how to do it?
You need to set the coordinates to where you want the scroll to move. This is done here -
[scrollView scrollRectToVisible:CGRectMake(0, 50, 1536, 939) animated:NO];
So you need to specify the exact CGRect specs you need. But this will work for you.
If you turn animated:YES then the scroll to this new position is smoothly animated.
I have a UIScrollView in which vertical only scrolling is enabled. I'm displaying a grid of buttons (similar to the photo viewer image grid). The grid has to be drawn differently based on screen orientation, so that all of the screen real estate is used. Given the size of my buttons, I can fit 3 per row in portrait, and 4 per row in landscape.
I reposition all of the buttons in: willRotateToInterfaceOrientation:duration and then call: setContentSize: on my UIScrollView. Everything seems to work just fine, with the exception of the auto-scrolling that occurs after the call to SetContentSize:. In other words, let's say I was in portrait, and scrolled 3/4 of the way down the list, when I rotate to landscape, it auto-scrolls all the back up to the top.
The interesting thing is, in the same scenario, if I were to do a small flick scroll up or down, and then immediately rotate the device, the scroll view redraws correctly, and retains the current scroll position!
So, to be clear, the culprit here seems to be SetContentSize:, but obviously I have to call that for the scroll view to scroll correctly.
Any ideas on how I can retain the current scroll position?
Thanks!
You might try implementing the UIScrollViewDelegate method scrollViewShouldScrollToTop:, which tells the caller whether to scroll to the top or not. You may have to have some flag in your delegate that indicates if a rotation is underway or not, because under normal conditions you may actually want the ability to tap the status bar and have the scroll view scroll to the top.
If, on the other hand, you don't ever want the scroll view to scroll to the top automaticlly, simply implement that delegate method and have it return NO.
I had this problem, just did this and it works well for me
- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
//calculate percentage down scrollview currently at
float c = self.scrollView.contentOffset.y / self.scrollView.contentSize.height;
//reposition subviews in the scrollview
[self positionThumbnails:toInterfaceOrientation];
//set the new scrollview offset to the same percentage,
// using the new scrollview height to calculate
self.scrollView.contentOffset =
CGPointMake(0, c * self.scrollView.contentSize.height);
}
In my case, I have a scrollview with a fixed width to device size, and variable height
I'm now trying to create my own Text panel (with code highlighting and so on).
In fact everything is ready except one thing - scrolling
What I've done:
created UIScrollView and inserted my own view as a subview using Interface builder.
in ViewController viewDidLoad method I've pointed initial textfield size to be the UIScrollView content size.
And when user writes too much into my text field. I call delegate (which is ViewController) to change size.
To do that I simply write
[scrollView setContentSize:newSize];
And what I get is increasing of the scroll view but not my text field - just blank lines appears. I think I need to set my view's size too but I can't figure out how...
And a second part of my question:
Every time I call [textField setNeedsDisplay] it calls drawRect: method with rectangle which is equal to the whole size of my view (which is much bigger than it's visible part). What will it look like if I try to use my view to modify file which size is more than 3 mb? How can I force it to redraw only visible part?
Thanks for your attention.
Part 1:
The scroll view's content size is not actually related to the size or position of the views it contains. If you want to change the size of the content view as well as the scroll view's content, you need to call two different methods.
CGSize newSize;
UIScrollView *scrollView;
// assume self is the content view
CGRect newFrame = (CGRect){CGPointZero,newSize}; // Assuming you want to start at the top-left corner of the scroll view. Change CGPointZero as appropriate
[scrollView setContentSize:newSize]; // Change scroll view's content size
[self setFrame:newFrame]; // Change views actual size
Part 2:
setNeedsDisplay marks the entire view as needing display. To cause it to display only the visible part, you need to use setNeedsDisplayInRect:visibleRect.
Assuming the view is at the top-left corner (its frame's origin is 0) and the scroll view does not allow zooming, the visible rect can be found using the scroll view's content offset and bounds size.
CGRect visibleRect;
visibleRect.origin = [scrollView contentOffset];
visibleRect.size = [scrollView bounds].size;
[self setNeedsDisplayInRect:visibleRect];
You could also choose to draw a part of the visible rect if only part changes.
It's simpler than you think, for example you have an UITextView called "textDesc" inside your UIScrollView, and you want to know the size of content, so next step will looks like that:
int contentHeight = textDesc.frame.size.height + textDesc.frame.origin.y;
After calculating the size of textDesc, just set it:
[scrollView setContentSize:(CGSizeMake(320, contentHeight))];
That's all, now your scrollView know the size of your text inside him, and will resize automatically, hope this helps, good luck.
Set your text field autoresizingMask property to flexible height and width:
[textField setAutoResizingMask:UIViewAutoResizingFlexibleHeight | UIViewAutoResizingFlexibleWidth];
This should expand the view automatically when you change it's parent's size (the scrollView's contentSize)
Otherwise try:
[textField setFrame:CGRectMake(0, 0, scrollView.contentSize.width, scrollView.contentSize.height)];
just after you change the scroll view's contentsize.
I have an UIViewController that has two UIViews inside, whose layout (set in Interface Builder) is something like this (the magenta colored view is the UIViewController default view):
and I added the main view to a root view obtaining this effect (by not showing the darker view placing its frame at the bottom):
Now when the device rotates, what I obtain is this:
whereas I'd like to still hide the darker view.
This is the code I use to hide it when it appears (I use it in the viewDidLoad method):
- (void)hideAll:(float)time{
CGRect hiddenFrame = CGRectMake(0, 1024, self.view.frame.size.width, self.view.frame.size.height);
[self.view setFrame:hiddenFrame];
[self.view setNeedsDisplay];
}
and it appears to work, but when I call a variant of it when rotating (in willRotateToInterfaceOrientation:duration:), nothing happens:
CGRect hiddenFrame = CGRectMake(0, 748, self.view.frame.size.width, self.view.frame.size.height);
[self.view setFrame:hiddenFrame];
[self.view setNeedsDisplay];
What am I missing? have I to set some other view property in Interface Builder?
UPDATE
It seems to me that the coordinate system does not change after the device has been rotated (ie the origin set in the upper-left corner in portrait mode will become the upper-right after a clockwise rotation in landscape mode)
Check your struts and springs in IB. It maybe that when you autorotate, the strut fixing you to the top of the screen moves your frame back to the top.
Try adding your code to the didRotateToInterfaceOrientation method so it can run after rotation has occurred.
Why to you change the frame to hide it, and not just
[self.view setHidden:YES];
second thing is that you should try to set the "Autoresizing" panel to handle the orientation changes, and not by changing the frame of the view.
hope i understood you right.
shani
The problem I encountered can be faced in two ways (I hope this can save some time for someone in the future):
using an UIViewcontroller (loaded from xib) and only its view as the rotating view, that is my original attempt to solve it. In this case you have to programmatically set the frame for the view when you want to hide it, and by doing so you have to consider that the coordinate system for the controller remains untouched and does not rotate (ie. it is always originated from the same corner)
using a UIView (loaded from xib) inside an already existing UIViewcontroller, in this way the view will automatically rotate and resize and you will not have to take the proper coordinates value into account at each rotation (this is by far the simplest way)