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https://github.com/nugmanoff/DropdownTransition

Simple and elegant Dropdown Transition
https://github.com/nugmanoff/DropdownTransition

custom-transition ios swift uikit

Last synced: 7 days ago
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Simple and elegant Dropdown Transition

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	DropdownTransition width=









Simple and elegant dropdown transition for iOS




    

    

    

    

    




## Why?



I needed to perform the dropdown transition in the app I was building and I've found many great libraries out there that provide desired functionality. But all of them had one flaw in them: they were *NOT* implemented as custom transitions, but rather as some view animations.



This library solves this problem by providing you custom modal transition that is implemented using `UIPresentationController` and `UITransitionCoordinator`. It provides you with greater flexibility and is more suitable for the use in projects that follow some standard architecture & navigation patterns (e.g. `Router`, `Navigator` & `Coordinator` patterns)



## Demo



 

## Installation

There are multiple options for installing DropdownTransition:



Using **Carthage** dependency manager, add following line to `Cartfile`:

```shell

github "nugmanoff/DropdownTransition" ~> 1.0.0

```



Using **CocoaPods** add following line to your project `Podfile`:

```shell

pod 'DropdownTransition', '~> 1.0.0'

```



Using **Swift Package Manager**, add the following line to your `Package.swift`:

```swift

dependencies: [

  .package(url: "https://github.com/nugmanoff/DropdownTransition.git", .exact("1.0.0")),

]

```

Or just simply drag `*.swift` files from `DropdownTransition` folder to your project (my favorite option).



## Usage



1. You need to conform to `DropdownPresentable` protocol in the `UIViewController` subclass you wish to present.

```swift

class SomeViewController: UIViewController, DropdownPresentable {

    // ...

}

```

2. You need to store instance variable of `DropdownTransitioningDelegate` somewhere accessible form your call to `present` method (e.g. in `Coordinator` pattern that'd be inside `Router` implementation)

```swift

let dropdownTransitioningDelegate = DropdownTransitioningDelegate()`

```

3. As the final step, you need to perform the actual transition by assigning the tweaking the options of view controller that is going to be presented, and calling the `present` function with it.

```swift

let someViewController = SomeViewController()

someViewController.transitioningDelegate = dropdownTransitioningDelegate

someViewController.modalPresentationStyle = .custom

navigationController?.present(someViewController, animated: true, completion: nil)

```

If you are using Auto Layout and wondering how to present controller with the proper height, take a look at the [Pro tip](#pro-tip)



### Advanced usage



In order to customize various presentation parameters, you need to override implement needed variables from `DropdownPresentable` protocol, otherwise their values will be set to some sensible defaults.

```swift

var isDraggingEnabled: Bool { get } // option that indicates whether you can drag (pan gesture) the dropdown controller or not

var dismissAfterRelease: Bool { get } // when enabled automatically dismisses controller when it surpasses threshold value

var dismissDraggingTranslationThreshold: CGFloat { get } // threshold value for dismissals

var stretchableBackgroundColor: UIColor { get } // background color of the view that stretches at the top of the controller (if dragging is enabled)

var dismissAfterTappingDimmingView: Bool { get } // when enabled automatically dismisses controller upon tap on the dimmed (black) area

var isFeedbackEnabled: Bool { get } // whether or not haptic feedback is generated on reaching threshold value

var feedbackStyle: UIImpactFeedbackGenerator.FeedbackStyle { get } // haptic feedback style

```




Demo above shows the presented controller with `dismissAfterRelease` set to `false`, as you see controller is not dismissed automatically as opposed to the default state shown in the first demo.



### Pro tip



Intrinsic height of the presented `UIViewController` needs to be set correctly in order to attain the desired height and behavior of the transition.

Luckily you can do that easily by calling this function in `viewDidLayoutSubviews` and `viewDidLoad` methods of the `UIViewController`



```swift

private func updatePreferredContentSize() {

        view.updateConstraintsIfNeeded()

        let viewSize = CGSize(width: UIScreen.main.bounds.width, height: .leastNonzeroMagnitude)

        preferredContentSize = view.systemLayoutSizeFitting(viewSize,

                                                            withHorizontalFittingPriority: .required,

                                                            verticalFittingPriority: .defaultLow)

```



If you are still experiencing issues with the height of the controller not being set correctly, make sure that you got your constraints right and they are feasibly satisfiable.



In case if you are looking for into more details I've added demonstrated [Example](https://github.com/nugmanoff/DropdownTransition/tree/master/DropdownTransitionExample) to the repo.



## Support



If you have any questions regarding the library, found a bug or want to contribute, please open an [issue on GitHub](https://github.com/nugmanoff/DropdownTransition/issues/new).



Author of the project is [@nugmanoff](https://github.com/nugmanoff)



This project is licensed under [MIT License](/LICENSE)