When using setContentOffset, what's the range of contentOffset?
Normally it seems that there's no constraint, but I also found that when the scrollView is in a viewController which is embed in navigationController and the navigationBar is shown, the contentOffset must be smaller than contentSize.(eh,I actually means contentOffset.x < contentSize.width - scrollView.bounds.size.width and contentOffset.height < contentSize.height - scrollView.bounds.size.height). If the contentOffset.x or contentOffset.y is out of that range, then that value is the max value, i.e contentSize.width - scrollView.bounds.size.width.
But when setting the navigationBar hidden, the contentOffset has no constraint, I can set any value and the offset works as wanted.
So did I miss something? why the hidden of navigationBar has effects on scrollView's contentOffset?
I also create a project to illustrate this problem on github.
Related
This question is about supporting a variable-height, custom text view using constraints and the view's intrinsicContentSize for autolayout. Before you click that 'duplicate' button, hear me out.
I have a custom text view (from scratch, inherits from NSView). It supports many of the usual NSTextView features, the most relevant here being multiple lines and laying out its content based on width available. The app it's built for loads a couple of these text views into each row of a table view. The issue is that the height doesn't get set properly according to its intrinsicContentSize.
I created a sample project that simplifies the problem. It uses a "pseudo" text view with a fixed number and size of characters used to determine width/height required. In the sample, there is a table view of one column whose cell view has only one subview, a PseudoTextView. The text view is pinned to the edges of its cell view with a little padding. How can I get the system to recognize that the text view should abide by the constraints that define the width while allowing the text view to grow in height, wrapped tightly by the cell view? Here's the text view code:
class PseudoTextView: NSView {
#IBInspectable var characterCount: Int = 0
#IBInspectable var characterWidth: CGFloat = 5
#IBInspectable var characterHeight: CGFloat = 8
#IBInspectable var background: NSColor = .blue {
didSet {
layer?.backgroundColor = background.cgColor
}
}
required init?(coder decoder: NSCoder) {
super.init(coder: decoder)
wantsLayer = true
layer?.backgroundColor = background.cgColor
}
override var intrinsicContentSize: NSSize {
let requiredWidth = characterWidth * CGFloat(characterCount)
let lineCount = (requiredWidth / frame.width).rounded(.up)
let usedHeight = lineCount * characterHeight
let charactersPerLine = (frame.width / characterWidth).rounded(.down)
let usedWidth = charactersPerLine * characterWidth
return NSSize(width: usedWidth, height: usedHeight)
}
This version returns the appropriate size based on the frame of the view. This obviously doesn't work because it's accessed during the updateConstraints phase of layout when the frame hasn't been set. I've also tried using NSView.noIntrinsicMetric for the width, but this will drive the text view to zero width and the height never recovers. There are an enormous number of other attempts I've made, but I won't bore you with them all.
NSTextField does something different (assuming 'Editable' is off, 'Wrap' is on). It's intrinsicContentSize reports the full width of the text on a single line (even if it's much longer than the width available), but it is somehow resized to the correct width. Once resized, the intrinsicContentWidth then still reports the full single-line width, but the height is adjusted to account for multiple lines. There is some magic somewhere I haven't been able to divine.
I've read every line of related documentation. If there's a blog post on the topic, I've probably read it. If there's a question on SO on the topic, I've probably read it. If you wrote a book on the topic, I've probably bought it. All of these sources tease at the problem I'm having, but none of them answer the question of how to handle this particular situation. Desperate.
Update:
After reading an old blog post by Jonathon Mah (http://devetc.org/code/2014/07/07/auto-layout-and-views-that-wrap.html) I created an example that uses his approach. Here's another project that mimics his technique and works correctly. This is the top portion of the app. It's a fixed container view that's adjusted with a slider. The patchwork are the pseudo characters of the custom view whose background is the pink color.
However, when inserted into a self-sizing table view, the custom view correctly matches the width of its cell, but the cell is not adjusted to respect the intrinsic height. If you change the custom view's bottom constraint to be optional (say, with a >= relation) the custom view does shrink to the correct height, but the cell view remains fixed. How do I convince the cell view to shrink its height to respect the intrinsicContentSize.height of its subview?
I have a solution for your problem, although it may not be optimal, since I do not have too much experience with macos specifics. So, first of all, let's define that the table view should use automatic row heights:
override func awakeFromNib() {
super.awakeFromNib()
tableView.usesAutomaticRowHeights = true
}
In your second sample the tableView outlet was not not connected to TableViewController, but it probably should be, so do not forget to connect it.
Now, in your WrappingCellView, you override layout(), but the value that you set for preferredMaxLayoutWidth is incorrect. I think it should be the width of the superview:
override func layout() {
// 16 is used for the sake of example
wrappingView.preferredMaxLayoutWidth = (superview?.frame.width ?? 16) - 16
super.layout()
}
Next part is the one I am not sure about:
func tableViewColumnDidResize(_ notification: Notification) {
tableView.reloadData()
}
There should be a better API to recalculate row heights. I hope you or someone else can suggest something :)
These three adjustments result in proper recalculation of the cell height:
I have a tableView with a tableHeaderView that is assigned through a nib file. This tableHeaderView contains a TextView (orange background) that is sized with a height constraint using sizeThatFits.
let textViewSize = titleView.sizeThatFits(CGSize(width: titleView.frame.size.width, height: CGFloat(MAXFLOAT)))
textViewHeightConstraint.constant = textViewSize.height
The constraints of this header view are setup to properly drive it’s height.
When the tableView sizes the frame for the tableHeaderView i am getting very strange results from the headerView.systemLayoutSizeFitting when scrolling in the UITextView is no enabled.
if let headerView = tableView.tableHeaderView {
let height = headerView.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
var frame = headerView.frame
frame.size.height = height
if headerView.frame.height != height {
headerView.frame = frame
tableView.tableHeaderView = headerView
headerView.setNeedsLayout()
headerView.layoutIfNeeded()
}}
If scrolling in the textView is enabled the tableHeaderView scales as expected, but the textView is cutting off the top line.
If scrolling for the textView is disabled (desired setting) then the height for this headerView is calculated to be larger than the size required. The length of text seems to multiply this effect.
I should also add that the TextView is being assigned attributed text with various paragraph and line spacing options.
Any suggestions as to what could be going on are much appreciated.
I have resolved my issue. I am still not sure why the above problems were occurring, but when I applied the header view in a storyboard (vs loading it in via a nib file and assigning it to tableView.tableHeaderView at runtime) all of my autolayout issues disappeared.
Still would like to know why it was mis-behaving and if there is a way to get my table header views to work through a xib files
I use Autolayout for a fairly complex Menu and really need it. All Buttons, UIViews etc. of my Menu are in a separate UIView called "menuSubview".
If the user presses a button the whole "menuSubview" shifts to another position to reveal other parts of the menu. Sometimes the buttons in the menuSubview move as well. I always save the "Menu State" (with Userdefaults in the get-set variable "lastMenu") and have a function to set the alphas and centers according to the saved "Menu State".
I tried calling the "openLastMenu" function in viewDidAppear, viewDidLayoutSubview - all the "viewDid" functions of the ViewController. The "menuSubview" center and alphas of the buttons always behave as expected... but the centers of the buttons simply won't - no matter what "viewDid" I call the function in.
(the code is a lot more complex - I boiled it down to debug and state my point)
override func viewDidAppear(animated: Bool) {
if lastMenu != nil {openLastMenu()}
}
func openLastMenu(){
menuSubview.center.x = view.center.x //works
menuSubview.center.y = view.center.y + 200 //works
button1.center.x = view.center.x - 50 //why you no behave???
button2.center.x = view.center.x + 50 //why you no behave???
button3.alpha = 0 //works
button4.alpha = 0 //works
}
For debugging I even made a button Subclass to fetch the "center" values with a "didSet" if they change. Seems like after taking the correct values they change once more to their Autolayout-Position.
...oh and ignoring the constraints with "translatesAutoresizingMaskIntoConstraints" on the buttons always fucks up the whole menu. I'm starting to get crazy here :)
If you position views using autolayout, any changes to the frame, like what you do here with the center property, will be ignored.
What you need to do is identify the constraints that are you need to change to move the views in the desired position. Example:
You want to move button1 50 points to the left of view.center. Assuming view is the superview of menuSubview, you would
1) deactivate the the constraint responsible for button1's horizontal placement. How you do this mainly depends on whether you created the constraints in code or Interface Builder. The latter will require you to create outlets for some of the constraints.
2) create a new constraint between button1's centerX anchor and view's centerX anchor with a constant of -50, like so (iOS 9 code)
button1.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor, constant: -50.0).active = true
I changed the size of a NSButton when I clicked on it. But it's size is restored to default when I resize the window. I realised it's because of the Auto Layout option.
So, the question is, can't I change position or size of a control permanently with auto layout option enabled?
Declare an outlet:
#property(nonatomic,weak) IBOutlet NSLayoutConstraint *buttonWidthConstraint;
Go to NIB. Select your button and pin it's width (Editor - Pin - Width). This will add width constraint into button constraints. Connect newly created constraint to outlet above.
And in button click event:
- (IBAction)buttonDidClick:(id)sender
{
[self.buttonWidthConstraint setConstant:300]; // set new width
}
upd: The idea behind this is that auto layout engine overwrites view frames each time it is needed, so manual changes like [view setFrame:] do not apply. So the only way to change some properties of layout is to work on layout level instead. Layout constraint is just a formula like:
item1.attr1 {== | <= | >=} multiplier * {item2.attr2 | none} + constant
In your case, this constraint is as simple as MyButton.width = 1 * (none) + 70, where 70 is original width suggested by Xcode.
i have a view inside a viewController, i wanted to start the smaller view outside the viewController in the left, and animate it to the centre when i press a button. so i made it like this:
override func viewDidLayoutSubviews() {
smallView.center = CGPointMake(smallView.center.x - 400, smallView.center.y)
}
And it works perfectly!, the problem is i have a text view inside that smaller view, and every time i start editing it it jumps outside of the main viewController right where it was, and i have to press the button again to bring it inside.
How to fix this?
PS: i tried positioning it to the centre when i start editing the text view like this:
func textViewDidBeginEditing(textView: UITextView) {
smallView.center = CGPointMake(smallView.center.x + 400, smallView.center.y)
}
But it doesn't work. and the method is connected to the textView properly(delegate)
PS2: i also have imagePickerController inside my viewController.
OK, as you're using Auto Layout.
The first rule of Auto Layout (you will see this in any Auto Layout book) is that you absolutely cannot touch the frame or center of a view directly.
// don't do these
myView.frame = CGRectMake(0, 0, 100, 100);
// ever
myView.center = CGPointMake(50, 50);
You can get the frame and center but you can never set the frame or center.
In order to move stuff around using Auto Layout you need to update the constraints.
For instance if I set up a view called myView and want it to grow and shrink in height I would do something like...
Set the top constraint to the superview at 0.
Set the left constraint to the superview at 0.
Set the right constraint to the superview at 0.
Set the height constraint to 50 (for example) and save it in a property called heightConstraint.
Now to animate the change in height I do this...
self.heightConstraint.constant = 100;
[UIView animateWithDuration:1.0
animations:^ {
[self.view layoutIfNeeded];
}];
This will then animate the height from 50 (where it was when I set it) to 100.
This is the same for ANY animation of views using Auto Layout. If (for instance) I had saved the left constraint I could change that and it would increase and decrease the gap from the left edge of the superview to myView.
There are several really good tutorials about AutoLayout on the Ray Wenderlich site. I'd suggest you take a look at them.
Whatever you do, I'd strongly suggest not just disabling Auto Layout. If you don't know how to use Auto Layout then you will very quickly fall behind with iOS 8 and the new device sizes.