I am trying to go through some collection view Swift tutorials, but they always show up as blank/black pages as if I have not set an initial view controller. However I have, I only drug out 1 UICollectionViewController and set the custom class to my CollectionViewController. In this class I implemented the numberOfSectionsInCollectionView: method and just to make sure it is working I just returned 3. However when I build and run the project all that should up is a blank/black screen...
Can someone please help? I have been searching through info with no luck...
Don't forget to connect the delegate and the dataSource to your
viewcontroller
Easy way to be done is to right click on your UICollectionView then drag to the yellow circle on the top of ViewController.
Repeat this step twice once choose dataSource and once choose delegate.
Step 1: Click on your view controller in storyBoard.
Step 2: Go to Attributes Inspector( Right hand side in xcode) then change background color from default to white color
It will show white color.
You have to implement at least 3 of the UICollectionViewDataSource methods to get anything to display.
It sounds like you are only telling it how many sections you want, but you have not told it how many views in each section or provided views for it to display.
Try this:
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
return 2
}
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 3
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = UICollectionViewCell()
cell.backgroundColor = UIColor.redColor()
return cell
}
Related
I wrote a simple app with two view controllers:
TableViewController with a table of websites to select
ViewController with a WKWebView that loads the website. This ViewController also has a key-value observer that refuses to load websites not in an approvedWebsites array that is filled from the TableViewController upon selecting a website.
Here's the most relevant code, can add more as requested. This is the didSelectRowAt function in TableViewController:
override func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
if let vc = storyboard?.instantiateViewController(withIdentifier: "Browser") as? ViewController {
vc.approvedWebsites = websites
vc.selectedWebsite = websites[indexPath.row]
navigationController?.pushViewController(vc, animated: true)
}
Currently, when I run the program and select any row, that row will remain highlighted and not respond. I added a print function to the row (above the if let) and it will not print.
However, the next row I select will respond, but with the website from the row I previously selected. I've tested this vigorously and it always will load the website of what I selected previous. When I back out of the webView screen, it'll reset everything and I can recreate the same error without reloading the app.
Any ideas as to what's happening?
Figured it out. Make sure you used DidSelectRowAt not DidDeselectRowAt.
I have some quite simple doubt regarding optional binding,global variable & wrapping and unwrapping . Since I am new to SWIFT, its very important to understand the tits & bits of their concepts.
1) In Swift if I declare a global variable, I have 2 options either to make it optional or non optional, so let I am having 2-4 or more optional variables . So is it advisable to optional bind all those variables in
viewDidLoad() method// so that I could use them without any problem of unwrapping and fatal error in my program.
2) Let me make myself more clear by the following example- I have 2 VC in my project VC1 & VC2 . VC2 has a text field in which user enters some value and displays it in a tabelview in VC1.
In Vc1
var namevc1 = NSMutableArray?//holds the input of textfield to be passed from VC2.
As you can see, my VC1 is the first view controller that loads when my project runs and I am using an optional variable to populate my tabke vuew that is
'arr'
So when the app runs for the first time its empty . So it might cause a fatal error while using its value in the code. So what is its solution whether to unbind it in the
viewDidLoad()
method or in all total declare an empty NSMutable array type in place of optional type .
Thanks in advance.
I'll start by repeating the my comment from above.
Possibly you've misunderstanding the concept of global variables in Swift.
If you have a global variable, you won't have to "pass" it between any views/methods/classes etc, because the variable is defined at global scope (accessible everywhere).
Generally global variables is not a good idea, and something that you want to avoid.
Regarding the matter of global variables and swift, you really should include singletons into the discussion. See e.g. the following existing SO thread(s):
Any reason not use use a singleton "variable" in Swift?
(How to create a global variable?)
(Declaring Global Variables in Swift)
Communication between TableViewController and ViewController by means of segues (prepare for & unwind segues)
(This answer ended up being very and probably a bit too thorough, as I didn't know in detail what your current tableview/viewcontroller program state looks like. Sorry for the lengthy answer and any inconvenience it might bring to readers of it).
Now, lets leave global variables and discuss one (among other) viable options for the communication between the two controllers in your example. From your question, I'll summarize your example as follows
VC1: storyboard entry point, a UITableViewController consisting of UITableViewCells, where, in these cells, you display some text, say, via instances of UILabel.
VC2: a UIViewController, accessible from the cells of VC1, containing an UITextField instance. When user enters text into this text field, your want the text to be displayed in the associated cell in VC2 (associated in the sense that it was the cell in VC1 that was used to access VC2).
We'll associate VC1 and VC2 with (cocoa touch) classes TableViewController (TableViewController.swift) and ViewController (ViewController.swift), respectively. The cells in the table view controller will be associated with (cocoa touch) class TableViewCell (TableViewCell.swift). Details for these classes follow below.
For this simple example, note that we will not embed VC1 into a navigation controller (which is otherwise appropriate for table view -> view navigation).
We'll start in the storyboard, adding objects (drag-and-drop from object library) for a Table View Controller and a View Controller. The table view container will also, automatically, contain, in its Table View, a TableViewCell. Continuing in the storyboard:
Add a UILabel object to the TableViewCell container in the Table View Controller (align it as you wish)
In the View Controller, add a Text Field object and a Button object (align them as you wish).
Set the entry point to the Table View Controller.
Thereafter Ctrl-drag a 'Show' segue from the TableViewCell to the View Controller.
Select the Show segue and, from the Attributes inspector, enter an identifier for it, say, ShowDetail.
Finally, with the TableViewCell selected, (as above; from the attribute inspector), enter an identifier for the cell. Here, we'll use simply use identifier TableViewCell.
We now leave the storyboard for now and implement three classes, associated with the Table View Controller, the View Controller and the formers' TableViewCell.
We start with the Table View Controller, and implement our UITableViewController sub-class. Note that here, instead of using an NSMutableArray to hold the texts of the UITextLabel in each cell, we'll simply use a String array.
// TableViewController.swift
Import UIKit
class TableViewController: UITableViewController {
// Properties
var userTextLabels = [String]()
var numberOfCells: Int?
override func viewDidLoad() {
super.viewDidLoad()
numberOfCells = loadSampleTextLabels() // Load sample labels.
}
func loadSampleTextLabels() -> Int {
userTextLabels += ["Label #1", "Label #2", "Label #3"]
return userTextLabels.count
}
// func numberOfSectionsInTableView(tableView: UITableView) ...
// func tableView(tableView: UITableView, numberOfRowsInSection section: Int) ...
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cellIdentifier = ("TableViewCell")
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! TableViewCell
// Text for current cell
let cellText = userTextLabels[indexPath.row]
cell.userSuppliedTextLabel.text = cellText
return cell
}
// ... communication?
}
Where the two commented out methods are standard methods used in any UITableViewController, for number of sections (e.g. return 1) and cells (e.g. return (numberOfCells ?? 0)) in the table, respectively. I'll leave fixing these to you.
Now, we associate the TableViewCell object(s) in the table view with instances of a subclass to UITableViewCell. Here, we'll use a very simple class for our cells; each cell just containing a single UILabel instance (created via storyboard Ctrl-drag as an #IBOutlet from the UILabel in the table view cells).
// TableViewCell.swift
import UIKit
class TableViewCell: UITableViewCell {
// Properties
#IBOutlet weak var userSuppliedTextLabel: UILabel!
// Ctrl-drag from UILabel (in TableViewCell) in storyboard
override func awakeFromNib() {
super.awakeFromNib()
}
override func setSelected(selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
}
}
Finally, for the view controller that is accessed from the table view cells: use a single #IBOutlet to the UITextField used for user text input, and handle events in this text field using the pre-existing UITextFieldDelegate. E.g.:
// ViewController.swift
import UIKit
class ViewController: UIViewController, UITextFieldDelegate {
// Properties
#IBOutlet weak var userSuppliedText: UITextField!
// Ctrl-drag from storyboard...
var cellText: String?
override func viewDidLoad() {
super.viewDidLoad()
userSuppliedText.text = cellText ?? "..."
// Handle the user input in the text field through delegate callbacks
userSuppliedText.delegate = self
}
// UITextFieldDelegate
func textFieldShouldReturn(textField: UITextField) -> Bool {
// User finished typing (hit return): hide the keyboard.
textField.resignFirstResponder()
return true
}
func textFieldDidEndEditing(textField: UITextField) {
cellText = textField.text
}
}
We've also declared a string property (cellText) here, that will as act as container for communication between VC1 and VC2.
We return to the storyboard and---from the Identity inspector---associate the three storyboard objects (Table View Controller, View Controller, TableViewCell) with their associated classes that we've just written above.
We're now almost at our goal; it only remains to specify how to communicate between the two controllers.
We'll begin with communication from VC1 to VC2. In your comment above, you were on the right track (for this specific solution, anyway) by looking at the prepareForSegue(...) method. In the class for the Table View Controller, we add the following method:
// ... add to TableViewController.swift
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
if segue.identifier == "ShowDetail" {
let viewController = segue.destinationViewController as! ViewController
if let selectedCell = sender as? TableViewCell {
let indexPath = tableView.indexPathForCell(selectedCell)!
let currentTextInCell = userTextLabels[indexPath.row]
viewController.cellText = currentTextInCell // <-- note this
}
}
}
Hence, for VC1->VC2 communication, we can (in this example) bring whatever existing text that is currently occupying the UILabel in the sender cell (as is specified by the String array userTextLabels). Look at the viewDidLoad(...) method in the ViewController.swift to see how this value is passed from VC1 and set as default text in the UITextField in VC2.
Now, for communication VC2->VC1, which was the specific communication direction you were asking about, add another method (programmatically), again to TableViewController.swift:
// ... add to TableViewController.swift
#IBAction func unwindToTableView(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? ViewController,
text = sourceViewController.cellText {
// ^ note 2nd clause of if let statement above
if let selectedIndexPath = tableView.indexPathForSelectedRow {
// Update cell text
userTextLabels[selectedIndexPath.row] = text
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
}
}
Here, we define an unwind action that, when triggered, retrieves the cellText property of the view controller that was the source of the segue, i.e., in our case, the instance of ViewController. But how do we trigger this action?
Return to the storyboard and the View Controller. Note the three little icons in the top of the View Controller object, more specifically, the right-most of these, named Exit. Ctrl-drag an action from your Button to the Exit icon, and select the unwindToTableView Action Segue. When you click your button the view controller, the view unwind (exit) and land at the unwindToTableView method in the TableViewController.
The resulting app should look something like this:
This was way longer than I had expected, but once you get started writing... Anyway, the method above uses, naturally, no global variables, but make use of references to future (prepareForSegue) or historic (unwindToTableView) views to get (generally from current or historic view) or set (generally in current of future view) values by using these references (to future/historic view).
Apple has their own very thorough tutorial on an example app in the tableviewcontroller/viewcontroller context that I would recommend going over. I found it very valuable myself when I started coding Swift.
Start Developing iOS Apps (Swift)
I'm building a typical Xcode 6 iOS app.
My goal is:
A screen that has an sub-area that can be swiped to change the content.
For example, the home screen has a logo image, a middle area that I want to be swipeable, and a bottom button.
When the user swipes (or taps) the middle area, the area shows the next (or previous) information, which is a typical UIImage and UILabel caption.
The rest of the screen stays the same, i.e. there is no navigation change.
The code is here. It use the recommendations from the StackOverflow post here.
My question: how can I implement the code below better, while still using an XIB?
My current implementation does work, and uses this approach...
A typical Swift Demo.swift file that is a UIViewController that has:
the page index, min, and max
outlets for the PageControl, UIImageView, and UILabel
actions for the page control change, and the image swipe or tap
A typical Demo.xib file that has:
a typical UIViewController for the entire screen
a UIImageView and UILabel for the changeable image and caption text
a PageControl to indicate what tutorial page the user is viewing
I am seeking better ways to accomplish this; I've read many of Xcode tutorials and so far none seem definitive for Xcode 6, XIBs, and Swift.
Here are some implementations that I've researched that seem promising...
Is there a way to implement a subview area in the XIB?
For example, can Xocde show the XIB with a rectangular area that is intended for the changeable content?
Is there an idiomatic way to write the code for changeable content?
For example, by using a ScrollView, perhaps that contains a UIPageViewController?
Is there a way to make a PageControl XIB object large enough to cover the entire UIImageView and UILabel, so I can skip making the UIImageView respond to gestures.
In my Xcode, the PageControl seems to have an uneditable height that is always 37.
The bounty will be for expert advice.
To make a UIPageViewController swipe-able you should implement the UIPageViewControllerDataSource protocol and provide a view controller for the pageViewController(pageViewController:viewControllerBeforeViewController) -> UIViewController? and the ...viewControllerAfterViewController) methods.
Provide a custom view controller for each page that presents an image and label and takes them as properties so you can provide them from the PageViewController.
My trick it to create a method that instantiates a new view controller in these methods:
// MARK:- UIPageViewControllerDataSource
extension MyPageViewController: UIPageViewControllerDataSource {
func viewControllerWithIndex(var index: Int) -> UIViewController! {
let viewController = storyboard?.instantiateViewControllerWithIdentifier("MyViewController") as! MyViewController // This VC has to be in the storyboard, otherwise just use MyVC()
// Adjust the index to be cyclical, not required
if let count = data?.endIndex {
if count == 1 && index != 0 { return nil }
if index < 0 { index += count }
index %= count
}
viewController.view.tag = index
viewController.record = data?[index]
return viewController
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
let index = viewController.view?.tag ?? 0
return viewControllerWithIndex(index + 1)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
let index = viewController.view?.tag ?? 0
return viewControllerWithIndex(index - 1)
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
return countAndSetupPageControl()
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
return viewController?.view.tag ?? 0
}
}
Now for the "sub-area" you will need to implement a ChildViewController. If you're using storyboards you can just drag a Container View and put PageViewController in the embedded view controller, otherwise you need to add the PageViewController.view as a subview and set the frame to the middle.
You can find more info in the apple documentation but basically you MUST call these methods:
addChildViewController(pageViewController)
view.addSubView(pageViewController.view)
pageViewController.view.frame = ... // This is your "sub-area"
pageViewController.didMoveToParentViewController(self)
If you add a height constraint to PageControl you can set it's height to whatever you want.
I don't see a problem with your current implementation. Changing it to use a PageViewController would be quite more work.
If I were you I would add an animation in pageUpdate function so the image would fade in or slide in...
It would only make sense to use a PageViewController if you want to be able to scroll to the next page (as in content moving in the same time your finger is moving onscreen). And you can use a PageViewController or a CollectionView with paging enabled.
I've searched a lot on the internet for a solution to this problem but I can't figure it out. I'm trying to create a custom cell in a table view.
I made a CustomCell.swift class to configure the labels I want in my custom cell, created it via storyboard (the first prototype cell in the tableview) and linked it with a identifier to the cellForRowAtIndexPath method
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {
let cellIdentifier = "huisCell"
var cell: CustomCell? = tableView.dequeueReusableCellWithIdentifier(cellIdentifier) as? CustomCell
if cell == nil {
cell = CustomCell(style: UITableViewCellStyle.Value1, reuseIdentifier: cellIdentifier)
}
cell!.huisAdresLabel.text = "123"
cell!.huisDetailLabel.text = "456"
return cell
}
My CustomCell.swift code is like this:
class CustomCell: UITableViewCell {
#IBOutlet var huisAdresLabel: UILabel
#IBOutlet var huisDetailLabel: UILabel
}
It's very basic now, but I just want it to work because than I can expand the cell with more attributes and style it better.
Pictures via DropBox because I need 10 reputation to properly document my problem :)
https://www.dropbox.com/sh/5v9jb6cqp80knze/AAD5-yPR8-KoStQddkqKIbcUa
I hope someone can explain what I'm doing wrong.
Edit:
To clear up some things, before my try to make a custom cell, I got it working with the basic cells, with the one label on the left hand side. But when I tried to style the tableview and created a custom cell it won't work.
Also, when testing different solutions I came across the problem that de two labels in CustomCell.swift are nil. Even when I made a custom init and did like a
self.huisAdresLabel = UILabel()
it was still nil. in the code that I showed you it prints the following:
<UILabel: 0xb2aadc0; frame = (0 -21; 42 21); text = '123'; clipsToBounds = YES; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0xb2aa3a0>>
I resolved this issue by overriding the following function, setting the height of the cells manually:
override func tableView(tableView:UITableView!, heightForRowAtIndexPath indexPath:NSIndexPath)->CGFloat
{
return 44
}
Try using a xib file and adding your custom cell class to the
"Table View Cell" that you create in your xib file.
(Make sure you reconnect it to the outlets in your custom cell class ;)
This link may help.
http://www.weheartswift.com/swifting-around/
I had the same Problem, but after disabling the "Use Auto Layout" under the "File Inspector", it did work!! and the Custom Cells are displayed
Note: I made the Custom Cells in the Builder, not in Code. Using Xcode beta 3
Working w/ Custom table cells in Xcode 6 Beta-4's IB, I found they all rendered on top of each other and my non-Custom cell.
I fixed my problem by...
selecting the Custom cell in IB
selecting the Size inspector (Option-Command-5)
in the Table View Cell section
checking the Custom box
keeping the default-provided 44 Row Height
Quick workaround: disable Use Size Classes, but still don't know is it bug or feature :-) needs more investigation or man reading.
First of all, let me say I'm an absolute beginner, so please forgive me if this is a stupid questions to be asking. And let me just add that I've spent hours/days trying to figure out how to solve this problem - including extensive searches on stackoverflow (maybe the answer is somewhere and I just don't now exactly what to search for :)...
But, let's continue: I have a small (?) problem with an Xcode storyboard project. Basically my project looks like this:
Navigation Controller -> View Controller 0 -> Tab Bar Controller -< View Controller 1, View Controller 2, View Controller 3.
When the user pushes 'button #2' in the View Controller 0, I'd like him/her to jump directly to 'View Controller 2'.
Would that be possible at all, and if so what code should use and excatly where should I put it.
Hope someone out there will help a newbie out :)
Regards,
Ulrik
Yes it is possible. You may show any view controller from any other.
You should simply add a segue from button #2 to View Controller 2. (I assume you have all your controllers in single storyboard)
Update: the above solution will show you View Controller 2 itself without tab bar controller.
Hard to tell in details without seeing the actual code. For more details you may refer to these documents:
View Controller Basics (especially part "Storyboards Help You Design Your User Interface")
Presenting View Controllers from Other View Controllers
Using View Controllers in Your App
Probably you'll come up with more concrete question.
Update
If you want to preselect desired view controller inside tabbar controller you may use the following code sketch. Here you can programmatically initiate a segue and do the desired pre-initialization inside prepareForSegue:sender: method.
static NSString * const kShowTabSegueID = #"ShowTab";
#interface ViewController ()
- (IBAction)buttonOnePressed;
- (IBAction)buttonTwoPressed;
- (IBAction)buttonThreePressed;
#end
#implementation ViewController
- (IBAction)buttonOnePressed
{
[self performSegueWithIdentifier:kShowTabSegueID
sender:#0];
}
- (IBAction)buttonTwoPressed
{
[self performSegueWithIdentifier:kShowTabSegueID
sender:#1];
}
- (IBAction)buttonThreePressed
{
[self performSegueWithIdentifier:kShowTabSegueID
sender:#2];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue
sender:(id)sender
{
if ([segue.identifier isEqual:kShowTabSegueID]) {
NSNumber *indexToShow = sender;
UITabBarController *tabBar = segue.destinationViewController;
[tabBar setSelectedIndex:indexToShow.unsignedIntegerValue];
}
}
#end
If you are simply trying to programatically switch tabs, its as simple as:
[self.tabBarController setSelectedIndex:1];
If I am understanding your flow correctly, from ViewController0 you would present ViewController1(that has a UITabBarController). In the viewWillAppear: set the selectedIndex for the tab controller (code above) to index 1, which would be ViewController2.
EDIT
After looking at your project, add this code to your BrainBreaksViewController.m
- (void)viewWillAppear:(BOOL)animated
{
[self.tabBarController setSelectedIndex:1];
}
I added this, and it switches to the 2nd tab after pressing "Press this button to goto tab #1". Follow Max Ks answer if you would like to be able to have a button to open each specific tab.
So if I understand correctly you have a view controller outside the tabbar controller and you want to navigate to the second tab in the tabbar controller from that (outside)view controller, if that is the problem then, this is my solution and I hope it helps someone as I spent some time on this issue myself.
First connect the (outside)Viewcontroller 0 to the tabbar controller in the storyboard with modal segue and give it identifier - "showTabBar" (not as one of the tabs just a modal segue).
Then:
in Viewcontroller 0 declare:
var tabBarIndex: Int?
//function that will trigger the **MODAL** segue
private func loadTabBarController(atIndex: Int){
self.tabBarIndex = atIndex
self.performSegue(withIdentifier: "showTabBar", sender: self)
}
//in here you set the index of the destination tab and you are done
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showTabBar" {
let tabbarController = segue.destination as! UITabBarController
tabbarController.selectedIndex = self.tabBarIndex!
}
}
then you can navigate to ViewController 2 like that(don't forget it is 0 indexed):
self.loadTabBarController(atIndex: 1)
This is tested and working as of the day I am posting this answer using
Swift 3.0.2 / Xcode 8.2.1