【发布时间】：2020-09-21 19:07:51
【问题描述】：
我正在编写一个应用程序，该应用程序可以向用户显示可以浏览和放大的大图片，类似于照片应用程序或书籍。我正在尝试用 SwiftUI 编写这个。我一直在关注SwiftUI tutorials on apples site，并调整了代码以读取 json 文件以创建“Imageslides”数组 - 一种保存图像和有关它们的信息的方法。然后，我使用 PageView 和 PageViewController 来显示 ContentView> ContentView 显示图像和一些按钮，这些按钮显示关于我正在显示的图像的文本。我的问题是当我浏览页面时，内存会不断增加，直到应用程序崩溃。现在，如果我使用 UIKit，我可以使用
if let imgPath = Bundle.main.path(forResource: name, ofType: nil)
{
return UIImage(contentsOfFile: imgPath)
}
但我看不到如何在 swiftUI 中使用图像来使用 contentsOfFile，或者在不需要时让图像耗尽内存的另一种方式。我将图像放在资源文件夹中，而不是在资产库中。 感谢您的帮助。
//data.swift - reading from json, mainly from apple's tutorials
import Foundation
import UIKit
import SwiftUI
let imageData: [Imageslide] = load("imageData.json")
func load<T: Decodable>(_ filename: String) -> T {
let data: Data
guard let file = Bundle.main.url(forResource: filename, withExtension: nil)
else {
fatalError("Couldn't find \(filename) in main bundle.")
}
do {
data = try Data(contentsOf: file)
} catch {
fatalError("Couldn't load \(filename) from main bundle:\n\(error)")
}
do {
let decoder = JSONDecoder()
return try decoder.decode(T.self, from: data)
} catch {
fatalError("Couldn't parse \(filename) as \(T.self):\n\(error)")
}
}
final class ImageStore {
typealias _ImageDictionary = [String: CGImage]
fileprivate var images: _ImageDictionary = [:]
fileprivate static var scale = 2
static var shared = ImageStore()
func image(name: String) -> Image {
let index = _guaranteeImage(name: name)
return Image(images.values[index], scale: CGFloat(ImageStore.scale), label: Text(name))
}
static func loadImage(name: String) -> CGImage {
guard
let url = Bundle.main.url(forResource: name, withExtension: "png"),
let imageSource = CGImageSourceCreateWithURL(url as NSURL, nil),
let image = CGImageSourceCreateImageAtIndex(imageSource, 0, nil)
else {
fatalError("Couldn't load image \(name).jpg from main bundle.")
}
return image
}
fileprivate func _guaranteeImage(name: String) -> _ImageDictionary.Index {
if let index = images.index(forKey: name) { return index }
images[name] = ImageStore.loadImage(name: name)
return images.index(forKey: name)!
}
}
//imageslide.swift - abstract for holding my image slide and button info
import SwiftUI
struct buttonInfo: Hashable, Codable{
var text: String? = nil
var coords: [Int]? = nil
public enum CodingKeys : String, CodingKey {
case text, coords
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.text = try container.decodeIfPresent(String.self, forKey: .text)
self.coords = try container.decodeIfPresent([Int].self, forKey: .coords)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(self.text, forKey: .text)
try container.encode(self.coords, forKey: .coords)
}
}
struct Imageslide: Hashable, Codable, Identifiable {
public var imagename: String
public var id: Int
public var noButtons: Int
public var buttoninfo: [buttonInfo]? = nil
public enum CodingKeys : String, CodingKey {
case imagename, id, noButtons, buttoninfo
case imageslide = "Imageslide"
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
let imageslide = try container.nestedContainer(keyedBy:
CodingKeys.self, forKey: .imageslide)
self.imagename = try imageslide.decode(String.self, forKey: .imagename)
self.id = try imageslide.decode(Int.self, forKey: .id)
self.noButtons = try imageslide.decode(Int.self, forKey: .id)
self.buttoninfo = try imageslide.decodeIfPresent([buttonInfo].self, forKey: .buttoninfo)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
var imageslide = container.nestedContainer(keyedBy: CodingKeys.self, forKey: .imageslide)
try imageslide.encode(self.imagename, forKey: .imagename)
try imageslide.encode(self.id, forKey: .id)
try imageslide.encode(self.noButtons, forKey: .noButtons)
try imageslide.encode(self.buttoninfo, forKey: .buttoninfo)
}
}
extension Imageslide {
var image: Image {
ImageStore.shared.image(name: imagename)
}
}
struct ButtonDataStore: Codable{
var buttonData: [buttonInfo]
}
//contentview.swift - used to show the images and buttons
import SwiftUI
struct ContentView: View {
var imageslide: Imageslide
@State private var button1Visible = true
@State var scale: CGFloat = 1.0
var body: some View {
ZStack {
Image(uiImage: (UIImage(named: imageslide.imagename)!))
// imageslide.image
// Image(imageslide.imagename)
.resizable()
.frame(width: 2732/2, height: 2048/2)
//Pinch to zoom code goes here
.background(/*@START_MENU_TOKEN@*/Color.black/*@END_MENU_TOKEN@*/)
.edgesIgnoringSafeArea(.all)
.statusBar(hidden: true)
if (imageslide.noButtons != 0)
{
if imageslide.buttoninfo != nil
{
ForEach(imageslide.buttoninfo!, id: \.self) {count in
ButtonView(text: count.text!, xcoord: count.coords![0], ycoord: count.coords![1], xcoordo: count.coords![2], ycoordo: count.coords![3])
}
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
//ContentView(imageslide: imageData[0])
ContentView(imageslide: imageData[1]).previewLayout(
.fixed(width: 2732/2, height: 2048/2)
)
}
}
}
//PageViewController.swift
import SwiftUI
import UIKit
struct PageViewController: UIViewControllerRepresentable {
var controllers: [UIViewController]
@Binding var currentPage: Int
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIViewController(context: Context) -> UIPageViewController {
let pageViewController = UIPageViewController(
transitionStyle: .scroll,
navigationOrientation: .horizontal)
pageViewController.dataSource = context.coordinator
pageViewController.delegate = context.coordinator
return pageViewController
}
func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
pageViewController.setViewControllers(
[controllers[currentPage]], direction: .forward, animated: true)
}
class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
var parent: PageViewController
init(_ pageViewController: PageViewController) {
self.parent = pageViewController
}
func pageViewController(
_ pageViewController: UIPageViewController,
viewControllerBefore viewController: UIViewController) -> UIViewController?
{
guard let index = parent.controllers.firstIndex(of: viewController) else {
return nil
}
if index == 0 {
return parent.controllers.last
}
return parent.controllers[index - 1]
}
func pageViewController(
_ pageViewController: UIPageViewController,
viewControllerAfter viewController: UIViewController) -> UIViewController?
{
guard let index = parent.controllers.firstIndex(of: viewController) else {
return nil
}
if index + 1 == parent.controllers.count {
return parent.controllers.first
}
return parent.controllers[index + 1]
}
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
if completed,
let visibleViewController = pageViewController.viewControllers?.first,
let index = parent.controllers.firstIndex(of: visibleViewController)
{
parent.currentPage = index
}
}
}
}
//pageview.swift
import SwiftUI
struct PageView<Page: View>: View {
var viewControllers: [UIHostingController<Page>]
@State var currentPage = 0
init(_ views: [Page]) {
self.viewControllers = views.map { UIHostingController(rootView: $0) }
}
var body: some View {
PageViewController(controllers: viewControllers, currentPage: $currentPage)
}
}
struct PageView_Previews: PreviewProvider {
static var previews: some View {
PageView(imageData.map {ContentView(imageslide: $0)})
}
}
我正在使用的 JSON 示例。
{
"Imageslide":{
"imagename":"MOS_SHB_1",
"id":1001,
"noButtons":0
}
},
{
"Imageslide":{
"imagename":"MOS_SHB_2",
"id":1002,
"noButtons":0
}
},
{
"Imageslide":{
"imagename":"MOS_SHB_3",
"id":1003,
"noButtons":1,
"buttoninfo":[
{
"text":"The two halves of the arch touched for the first time. Workers riveted both top and bottom sections of the arch together, and the arch became self-supporting, allowing the support cables to be removed. On 20 August 1930 the joining of the arches was celebrated by flying the flags of Australia and the United Kingdom from the jibs of the creeper cranes.",
"coords":[
-150,
220,
200,
200
]
}
]
}
},
【问题讨论】：
标签： swift memory uikit swiftui uipageviewcontroller