使用Switch语句从Xcassets加载imageView

Question

我在Xcassets中有@1 @2和@3的图像，我试图使用下面的代码将图像加载到滚动视图页面上，该代码根据图像的年龄切换图像。页面由位置决定，switch语句在viewWillLoad函数中调用。图像没有加载，但声音正在工作，所以我知道这是图像加载的问题。你能帮忙吗?

override func viewDidDisappear(animated: Bool) {
    self.imageView.removeFromSuperview()
    self.imageView.image = nil
}

override func viewWillAppear(animated: Bool) {
    showImageView()
    let tapGestureImage = UITapGestureRecognizer(target: self, action: Selector("handleTapGestureImage:"))
    imageView.addGestureRecognizer(tapGestureImage)
    imageView.userInteractionEnabled = true
}


// MARK: BWWalkthroughPage Implementation
func walkthroughDidScroll(position: CGFloat, offset: CGFloat) {
    // getting the page number from the scroll position. First page loads as nil so want it to be zero.
    screenPage  = Int(((position / view.bounds.size.width) + 1) - 1)
}

func showImageView() {
    // change imageView in bundle depending on which scrollview page you are.
    switch screenPage {
    case 0:
        self.imageView.image = UIImage(named: "Aligator", inBundle: NSBundle.mainBundle(), compatibleWithTraitCollection: self.traitCollection)
        self.view.addSubview(imageView)
    case 1:
        self.imageView.image = UIImage(named: "Bear", inBundle: NSBundle.mainBundle(), compatibleWithTraitCollection: self.traitCollection)
        self.view.addSubview(imageView)
    default:
        self.imageView.image = nil
    }
}

Answer 1

有几件事对你来说很重要。您不需要从视图层次结构中一遍又一遍地添加/删除图像视图。只要调用imageView.image = nil就足够了。

第二件事是，您不需要使用完整的方法UIImage(named:inBundle:compatibleWithTraitCollection:)。你应该能够简单地使用UIImage(named:)。如果你发现自己不得不使用前者，那么在你职业生涯的这个阶段，你可能承受了超出你能力范围的压力。

第三件事是，当你重写一个方法时，你必须在99%的情况下调用super。

下面是一个可以工作的例子:

import UIKit
class MyViewController: UIViewController {
    override fun viewDidLoad() {
        super.viewDidLoad()
        let gestureRecognizer = UITapGestureRecognizer(target: self, action: Selector("handleTapGestureImage:"))
        imageView.addGestureRecognizer(gestureRecognizer)
        imageView.userInteractionEnabled = true
    }
    override func viewDidDisappear(animated: Bool) {
        super.viewDidDisappear(animated: animated)
        self.imageView.image = nil
    }
    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated: animated)
        showImageView()
    }
    func walkthroughDidScroll(position: CGFloat, offset: CGFloat) {
        screenPage  = Int(((position / view.bounds.size.width) + 1) - 1)
    }
    func showImageView() {
        switch screenPage {
        case 0:
            imageView.image = UIImage(named: "Aligator")
        case 1:
            imageView.image = UIImage(named: "Bear")
        default:
            imageView.image = nil
        }
    }
}