#collection view

Hi friends, here is a new post I wrote about implementing Infinite Scroll With the Xamarin Forms Collection View. #XamarinForms #Xamarin

Implementing Infinite Scroll with the Xamarin Forms Collection View

Hello friends, Xamarin Forms is continuously getting better and it comes with a lot of improvements in every new release. Be it in performance aspects or the addition of new controls, we Xamarin Forms developers have several brand new features. Last year I wrote an article about the new paradigm (Shell)for building apps with…

IOS 9 introduces reordering of Collection View Cells. This is enabled by default, selecting a cell with a long press enables the user to reorder the cells. All that's needed is to update the order of the item in the data model. In this tutorial some cells containing alphabet letters will be displayed, these cells can be easily reordered. This tutorial is made with Xcode 10 and built for iOS 12.

Open Xcode and create a new Single View App.

For product name, use IOSReorderCollectionViewTutorial and then fill out the Organization Name and Organization Identifier with your customary values. Enter Swift as Language and choose Next.

Go to the Storyboard and delete the View Controller. Drag a Collection View Controller from the Object Library to the Storyboard. Select the Collection View Controller and navigate to the Editor  menu and select Embed in -> Navigation Controller. Select the Navigation Controller and go to the Attribute Inspector. In the View Controller section select the "Is Initial View Controller" checkbox.

Double-click the Navigation Bar in the Collection View Controller and change the title to "Alphabet". Select the Collection View and go to the Size inspector. In the Collection View Section set the Cell size to a width and height of 100 points. Also change the Min Spacing to 1 for cells and lines. This will decrease the spacing between the cells.

Select the Collection View Controller Cell and go to the Attributes inspector. In the View section change the background to green.

Go to the Attribute Inspector and in the Collection Reusable View section set the Identifier to "Cell"

Drag a Label from the Object Library and place it in the center of the Collection View Cell. Double-click the label and enter the letter "A". The storyboard should now look like this.

Since the View Controller is deleted in the Storyboard the ViewController.swift file can also be deleted. Add a new file to the project. Select File -> New File -> iOS -> Source -> Cocoa Touch Class. Name the class AlphabetViewController and make it a subclass of UICollectionViewController.

Next, create a class for the Collection View Cell. Add a new file to the project. Select File -> New File -> iOS -> Source -> Cocoa Touch Class. Name the class AlphabetCell and make it a subclass of UICollectionViewCell.

These newly created classes need to connect to the objects in the Storyboard. Select the Collection View Controller and go to the Identity Inspector. Change the custom Class to AlphabetViewController.

Select the Collection View Cell and go to the Identity inspector. Change the custom Class to AlphabetCell.

Select the Assistant Editor and make sure the AlphabetCell.swift file is visible. Ctrl-drag from the Label to the AlphabetCell class  and create the following Outlet.

Go to the AlphabetViewController.swift class. Navigate to the viewDidLoad class and delete the following line. 

self.collectionView!.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)

The reuse identifier is already made in the Interface Builder. so it's not needed anymore. Add a property to store the Alphabet letters

var alphabet = [String]()

Change the viewDidLoad method to

override func viewDidLoad() { super.viewDidLoad() let str: String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" for i in str { alphabet.append(String(i)) } }

Each letter in the alphabet is assigned to the characterArray array. Next, change the predefined Collection View delegate methods.

override func numberOfSections(in collectionView: UICollectionView) -> Int { // 1 // return the number of sections return 1 } override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { // 2 // return the number of items return alphabet.count } override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { // 3 let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! AlphabetCell // Configure the cell cell.alphabetLabel.text = alphabet[indexPath.row] return cell }

The Collection View contains only one section

26 items will be created in the Collection View

Each cell will contain a letter from the alphabet.

When reordering the cells the content needs to be changed. This can be done in the CollectionView:moveItemAtIndexPath:toIndexPath method.

override func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) { let temp = alphabet.remove(at: sourceIndexPath.item) alphabet.insert(temp, at: destinationIndexPath.item) }

When the cell is moved to a new postion, the original index position in the array is removed and the new index position Is inserted in the array.

Build and Run the project, long-press a cell and reorder it.

The Collection View provides a flexible way to present content to the user. Similar to a table view, a collection view gets data from custom data source objects and displays it using a combination of cell, layout, and supplementary views. A collection view can display items in a grid or in a custom layout that you design. In this tutorial we will create a custom collection view cell by adding an image to it. This tutorial is made with Xcode 10 and built for iOS 12.

Open Xcode and create a new Single View App.

For product name, use IOSCustomCollectionViewCellTutorial and then fill out the Organization Name and Organization Identifier with your customary values. Enter Swift as Language and choose Next.

We need an image to display in our Collection View Cells. so download the image and add it to the Assets folder.

Go to the Storyboard and delete the View Controller. Drag a Collection View Controller from the Object Library to the Storyboard. Select the Collection View Controller and go to the Attribute Inspector. In the View Controller section select the "Is Initial View Controller" checkbox.

Select the Collection View and go to the Size Inspector. In the Collection View Section set the Cell size to a width and height of 50 points.

Drag an Image View from the Object Library inside the Collection View Cell and make sure the height and width is also 50 points. Select the Image View and go to the Attribute Inspector. In the View Section set the Mode to "Aspect Fit"

The Storyboard should look like this.

Since the View Controller is deleted in the Storyboard the ViewController.swift file can also be deleted. Add a new file to the project. Select File -> New File -> iOS -> Source -> Cocoa Touch Class. Name the class CollectionViewController and make it a subclass of UICollectionViewController.

Go back to the Storyboard, select the Collection View Controller and go to the Identity Inspector. Change the custom Class to CollectionViewController.

Go to the CollectionViewController.swift file and in the viewDidLoad method delete the following line.

self.collectionView!.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)

We will set the reuse Identifier in Interface Builder, so this line isn't needed. Go back to the Storyboard and select the Collection View Cell. Go to the Attribute Inspector and in the Collection Reusable View section set the Identifier to "Cell"

Next, create a class for the custom Collection View Cell. Add a new file to the project. Select File -> New File -> iOS -> Source -> Cocoa Touch Class. Name the class CollectionViewCell and make it a subclass of UICollectionViewCell.

Go back to the Storyboard and select the Collection View Cell. Go to the Identity Inspector and in the Custom Class section change the Class to "CollectionViewCell"

Select the Assistant Editor and make sure the CollectionViewCell.swift file is visible. Ctrl and drag from the Image View to the CollectionViewCell class  and create the following Outlet.

Go to CollectionViewController.swift file and add the following property

let myImage = UIImage(named: "Apple_Swift_Logo")

Next we will change the predefined methods.

override func numberOfSections(in collectionView: UICollectionView) -> Int { // 1 return 1 } override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { // 2 return 100 } override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { // 3 let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionViewCell cell.imageView.image = myImage return cell }

The Collection View has only one section

There will be 100 images displayed

First a cell with the type of CollectionViewCell is defined. Then of each cell the image is assigned to the imageView property of the CollectionViewCell class.

Build and Run the project. there will be 100 Swift logos displayed.

original source : https://stackoverflow.com/questions/18113872/uicollectionviewcell-with-rounded-corners-and-drop-shadow-not-working

#1 answer

https://stackoverflow.com/a/44820559

collection view 에서 cell을 둥글게 하고 drop shadow를 만드는 방법 (cell.contentView를 cell self로 바꾸어 적용)

original source : https://stackoverflow.com/questions/28325277/how-to-set-cell-spacing-and-uicollectionview-uicollectionviewflowlayout-size-r

#1 answer 

https://stackoverflow.com/a/28327193

property를 조정해서 구현할수도 있고 conform하는 func의 리턴값을 변경해서 구현할수도 있다.

Add these 2 lines

layout.minimumInteritemSpacing = 0 layout.minimumLineSpacing = 0

So you have:

  // Do any additional setup after loading the view, typically from a nib.        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()        layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)        layout.itemSize = CGSize(width: screenWidth/3, height: screenWidth/3)        layout.minimumInteritemSpacing = 0        layout.minimumLineSpacing = 0        collectionView!.collectionViewLayout = layout

That will remove all the spaces and give you a grid layout:

If you want the first column to have a width equal to the screen width then add the following function:

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {    if indexPath.row == 0    {        return CGSize(width: screenWidth, height: screenWidth/3)    }    return CGSize(width: screenWidth/3, height: screenWidth/3); }

Grid layout will now look like (I've also added a blue background to first cell):

original source : https://stackoverflow.com/questions/29773787/collectionview-controller-vs-collectionview

UICollectionViewController 와 UICollectionView 의 차이점

UICollectionView inherits from UIScrollView (just another UIView)

UICollectionViewController inherits from UIViewController.. and it implements some protocols.. like UICollectionViewDelegate and UICollectionViewDataSource .. it means everything is already done for you.. and you just have to use it.. but as everything is already done for you.. you may not be able to do some stuff.. like resizing your collectionView ..

How to create Collection View from Scratch using Swift

tvOS Focus Engine and Collection View

I recently did some consulting work for a new startup here in San Francisco. I built for them a couple of quite complex UI animations for an Apple TV app. Doing so, I was able to work very closely with tvOS and its very interesting interaction mechanism: the Focus Engine. I am quite fascinated by this new interaction model. After spending almost 8 years with touch-based devices, this new toy brings to my work some fresh air. I am going to demonstrate you how the Focus Engine works using the Watch OS UI example I built it here some month ago. Please, review that example if you haven't done it so far, because I am going to use it as it is without going again into details. There is some math involved, but complex UI animations sometimes require some math.