接下来介绍的同样是 RxSwift 的官方样例，演示的是如何对 UIImagePickerControllerDelegate 进行 Rx 封装，方便我们在RxSwift项目中选择图片（可以通过拍照、或者从相簿中选取）
三、从本地相册、或摄像头获取图片
1，效果图
（1）点击“拍照”按钮，会打开摄像头进行拍照，拍照后自动将照片显示在下方的 imageView 中。
（2）而点击“选择照片”或“选择照片并裁剪”按钮后，会打开本地相册选择照片，选择后自动将照片显示在下方的 imageView 中。不过后者在选择完毕后还多了个编辑步骤，可以把照片裁剪成正方形再显示。
2，准备工作
（1）RxImagePickerDelegateProxy.swift
首先我们继承 DelegateProxy 创建一个关于图片选择的代理委托，同时它还要遵守 DelegateProxyType、UIImagePickerControllerDelegate、UINavigationControllerDelegate 协议。
import RxSwift
import RxCocoa
import UIKit
//图片选择控制器（UIImagePickerController）代理委托
public class RxImagePickerDelegateProxy :
DelegateProxy<UIImagePickerController,
UIImagePickerControllerDelegate & UINavigationControllerDelegate>,
DelegateProxyType,
UIImagePickerControllerDelegate,
UINavigationControllerDelegate {
public init(imagePicker: UIImagePickerController) {
super.init(parentObject: imagePicker,
delegateProxy: RxImagePickerDelegateProxy.self)
}
public static func registerKnownImplementations() {
self.register { RxImagePickerDelegateProxy(imagePicker: $0) }
}
public static func currentDelegate(for object: UIImagePickerController)
-> (UIImagePickerControllerDelegate & UINavigationControllerDelegate)? {
return object.delegate
}
public static func setCurrentDelegate(_ delegate: (UIImagePickerControllerDelegate
& UINavigationControllerDelegate)?, to object: UIImagePickerController) {
object.delegate = delegate
}
}
（2）UIImagePickerController+Rx.swift
接着我们对 UIImagePickerController 进行 Rx 扩展，作用是将 UIImagePickerController 与前面创建的代理委托关联起来，将图片选择相关的 delegate 方法转为可观察序列。
注意：下面代码中将 methodInvoked 方法替换成 sentMessage 其实也可以，它们的区别可以看我的另一篇文章：
import RxSwift
import RxCocoa
import UIKit
//图片选择控制器（UIImagePickerController）的Rx扩展
extension Reactive where Base: UIImagePickerController {
//代理委托
public var pickerDelegate: DelegateProxy<UIImagePickerController,
UIImagePickerControllerDelegate & UINavigationControllerDelegate > {
return RxImagePickerDelegateProxy.proxy(for: base)
}
//图片选择完毕代理方法的封装
public var didFinishPickingMediaWithInfo: Observable<[String : AnyObject]> {
return pickerDelegate
.methodInvoked(#selector(UIImagePickerControllerDelegate
.imagePickerController(_:didFinishPickingMediaWithInfo:)))
.map({ (a) in
return try castOrThrow(Dictionary<String, AnyObject>.self, a[1])
})
}
//图片取消选择代理方法的封装
public var didCancel: Observable<()> {
return pickerDelegate
.methodInvoked(#selector(UIImagePickerControllerDelegate
.imagePickerControllerDidCancel(_:)))
.map {_ in () }
}
}
//转类型的函数（转换失败后，会发出Error）
fileprivate func castOrThrow<T>(_ resultType: T.Type, _ object: Any) throws -> T {
guard let returnValue = object as? T else {
throw RxCocoaError.castingError(object: object, targetType: resultType)
}
return returnValue
}
3，使用样例
（1）要获取照片或者进行拍照，首先我们需要在 info.plist里加入相关的描述：
-
Privacy - Camera Usage Description：App 需要访问您的相机 -
Privacy - Photo Library Usage Description：App 需要访问您的照片
（2）Main.storyboard
在 StoryBoard中添加 3 个 Button 以及 1 个 ImageView，并将它们与代码做 @IBOutlet 绑定。
（3）ViewController.swift
主视图控制器代码如下，可以看到原来图片选择完毕这个代理方法现在已经变成响应式的了。
import UIKit
import RxSwift
import RxCocoa
class ViewController: UIViewController {
//拍照按钮
@IBOutlet weak var cameraButton: UIButton!
//选择照片按钮
@IBOutlet weak var galleryButton: UIButton!
//选择照片并裁剪按钮
@IBOutlet weak var cropButton: UIButton!
//显示照片的imageView
@IBOutlet weak var imageView: UIImageView!
let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
//初始化图片控制器
let imagePicker = UIImagePickerController()
//判断并决定"拍照"按钮是否可用
cameraButton.isEnabled = UIImagePickerController.isSourceTypeAvailable(.camera)
//“拍照”按钮点击
cameraButton.rx.tap
.bind { [weak self] _ -> Void in
imagePicker.sourceType = .camera //来源为相机
imagePicker.allowsEditing = false //不可编辑
//弹出控制器，显示界面
self?.present(imagePicker, animated: true)
}
.disposed(by: disposeBag)
//“选择照片”按钮点击
galleryButton.rx.tap
.bind { [weak self] _ -> Void in
imagePicker.sourceType = .photoLibrary //来源为相册
imagePicker.allowsEditing = false //不可编辑
//弹出控制器，显示界面
self?.present(imagePicker, animated: true)
}
.disposed(by: disposeBag)
//“选择照片并裁剪”按钮点击
cropButton.rx.tap
.bind { [weak self] _ -> Void in
imagePicker.sourceType = .photoLibrary //来源为相册
imagePicker.allowsEditing = true //不可编辑
//弹出控制器，显示界面
self?.present(imagePicker, animated: true)
}
.disposed(by: disposeBag)
//图片选择完毕后，将其绑定到imageView上显示
imagePicker.rx.didFinishPickingMediaWithInfo
.map { info in
//根据情况选择是使用原始图片还是编辑后的图片
if imagePicker.allowsEditing {
return info[UIImagePickerControllerEditedImage] as! UIImage
} else {
return info[UIImagePickerControllerOriginalImage] as! UIImage
}
}
.bind(to: imageView.rx.image)
.disposed(by: disposeBag)
//图片选择完毕后，退出图片控制器
imagePicker.rx.didFinishPickingMediaWithInfo
.subscribe(onNext: { _ in
imagePicker.dismiss(animated: true)
})
.disposed(by: disposeBag)
}
}
附：功能改进
虽然前面我们对 UIImagePickerController 进行了 Rx 扩展，但使用起来还是有些不便，比如图片选择完毕后还需要在代码中手动退出选择器。下面对它做个功能改进，让其可以自动关闭退出。
1，UIImagePickerController+RxCreate.swift
这里再一次对 UIImagePickerController 进行 Rx 扩展，增加一个创建图片选择控制器的静态方法，后面当我们使用该方法初始化 ImagePickerController 时会自动将其弹出显示，并且在选择完毕后会自动关闭。
import UIKit
import RxSwift
import RxCocoa
//取消指定视图控制器函数
func dismissViewController(_ viewController: UIViewController, animated: Bool) {
if viewController.isBeingDismissed || viewController.isBeingPresented {
DispatchQueue.main.async {
dismissViewController(viewController, animated: animated)
}
return
}
if viewController.presentingViewController != nil {
viewController.dismiss(animated: animated, completion: nil)
}
}
//对UIImagePickerController进行Rx扩展
extension Reactive where Base: UIImagePickerController {
//用于创建并自动显示图片选择控制器的静态方法
static func createWithParent(_ parent: UIViewController?,
animated: Bool = true,
configureImagePicker: @escaping (UIImagePickerController) throws -> () = { x in })
-> Observable<UIImagePickerController> {
//返回可观察序列
return Observable.create { [weak parent] observer in
//初始化一个图片选择控制器
let imagePicker = UIImagePickerController()
//不管图片选择完毕还是取消选择，都会发出.completed事件
let dismissDisposable = Observable.merge(
imagePicker.rx.didFinishPickingMediaWithInfo.map{_ in ()},
imagePicker.rx.didCancel
)
.subscribe(onNext: { _ in
observer.on(.completed)
})
//设置图片选择控制器初始参数，参数不正确则发出.error事件
do {
try configureImagePicker(imagePicker)
}
catch let error {
observer.on(.error(error))
return Disposables.create()
}
//判断parent是否存在，不存在则发出.completed事件
guard let parent = parent else {
observer.on(.completed)
return Disposables.create()
}
//弹出控制器，显示界面
parent.present(imagePicker, animated: animated, completion: nil)
//发出.next事件（携带的是控制器对象）
observer.on(.next(imagePicker))
//销毁时自动退出图片控制器
return Disposables.create(dismissDisposable, Disposables.create {
dismissViewController(imagePicker, animated: animated)
})
}
}
}
2，ViewController.swift
主视图控制器代码如下，可以看到我们现在不需要去关心图片选择界面如何关闭了。
import UIKit
import RxSwift
import RxCocoa
class ViewController: UIViewController {
//拍照按钮
@IBOutlet weak var cameraButton: UIButton!
//选择照片按钮
@IBOutlet weak var galleryButton: UIButton!
//选择照片并裁剪按钮
@IBOutlet weak var cropButton: UIButton!
//显示照片的imageView
@IBOutlet weak var imageView: UIImageView!
let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
//判断并决定"拍照"按钮是否可用
cameraButton.isEnabled = UIImagePickerController.isSourceTypeAvailable(.camera)
//“拍照”按钮点击
cameraButton.rx.tap
.flatMapLatest { [weak self] _ in
return UIImagePickerController.rx.createWithParent(self) { picker in
picker.sourceType = .camera
picker.allowsEditing = false
}
.flatMap { $0.rx.didFinishPickingMediaWithInfo }
}
.map { info in
return info[UIImagePickerControllerOriginalImage] as? UIImage
}
.bind(to: imageView.rx.image)
.disposed(by: disposeBag)
//“选择照片”按钮点击
galleryButton.rx.tap
.flatMapLatest { [weak self] _ in
return UIImagePickerController.rx.createWithParent(self) { picker in
picker.sourceType = .photoLibrary
picker.allowsEditing = false
}
.flatMap { $0.rx.didFinishPickingMediaWithInfo }
}
.map { info in
return info[UIImagePickerControllerOriginalImage] as? UIImage
}
.bind(to: imageView.rx.image)
.disposed(by: disposeBag)
//“选择照片并裁剪”按钮点击
cropButton.rx.tap
.flatMapLatest { [weak self] _ in
return UIImagePickerController.rx.createWithParent(self) { picker in
picker.sourceType = .photoLibrary
picker.allowsEditing = true
}
.flatMap { $0.rx.didFinishPickingMediaWithInfo }
}
.map { info in
return info[UIImagePickerControllerEditedImage] as? UIImage
}
.bind(to: imageView.rx.image)
.disposed(by: disposeBag)
}
}
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