[英]How do I change a button in SwiftUI after a button is pressed
当我按下按钮时,我希望一张卡片图像变为另一张卡片图像。 这是我当前的代码:
import SwiftUI
var leftCard = "green_back"
var rightCard = "blue_back"
func dealCards() {
leftCard = "1C"
print("deal")
}
struct GameView: View {
var body: some View {
VStack {
HStack(alignment: .center, spacing: 20) {
Image(leftCard)
.resizable()
.aspectRatio(contentMode: .fit)
Image(rightCard)
.resizable()
.aspectRatio(contentMode: .fit)
}
.padding(.all, 25)
Button(action: dealCards) {
Text("Deal Cards")
.fontWeight(.bold)
.font(.title)
.padding(10)
.background(Color.blue)
.foregroundColor(.white)
.padding(10)
.border(Color.blue, width: 5)
}
}
}
}
struct GameView_Previews: PreviewProvider {
static var previews: some View {
GameView()
}
}
当我按下按钮时,此代码会打印“交易”,但不会更改图像。
我正在使用 MacOS Big Sur beta 3 和 Xcode 12 beta 2。
编辑:我只需将变量移动到 GameView 结构中并向它们添加@State
修饰符。 感谢所有回答的人。 :D
您甚至可以删除 function 并将代码直接添加到按钮
struct GameView: View {
@State var leftCard = "green_back"
@State var rightCard = "blue_back"
var body: some View {
VStack {
HStack(alignment: .center, spacing: 20) {
Image(leftCard)
.resizable()
.aspectRatio(contentMode: .fit)
Image(rightCard)
.resizable()
.aspectRatio(contentMode: .fit)
}
.padding(.all, 25)
Button(action: {
self.leftCard = "1C"
}) {
Text("Deal Cards")
.fontWeight(.bold)
.font(.title)
.padding(10)
.background(Color.blue)
.foregroundColor(.white)
.padding(10)
.border(Color.blue, width: 5)
}
}
}
}
以下代码应更新您的Images
,并应在deal()
function 中为您提供一个随机值。
在View
或组件中定义属性和函数非常重要。 全局变量一般不推荐使用,可能会导致意想不到的结果。
import SwiftUI
struct GameView: View {
// 1. Add ImageName to handle names via dot (.) to avoid mistyping strings. CaseIterable allow you to get an array of all the values defined.
enum ImageName: String, CaseIterable {
case greenBack = "green_back"
case blueBack = "blue_back"
case other = "1C"
}
// 2. Add @State to update the GameView() automatically when any of the properties are updated.
@State private var leftCard: ImageName = .greenBack
@State private var rightCard: ImageName = .blueBack
var body: some View {
VStack {
HStack(alignment: .center, spacing: 20) {
// 3. Add .rawValue to get the raw String value
Image(leftCard.rawValue)
.resizable()
.aspectRatio(contentMode: .fit)
Image(rightCard.rawValue)
.resizable()
.aspectRatio(contentMode: .fit)
}
.padding(.all, 25)
Button(action: dealCards) {
Text("Deal Cards")
.fontWeight(.bold)
.font(.title)
.padding(10)
.background(Color.blue)
.foregroundColor(.white)
.padding(10)
.border(Color.blue, width: 5)
}
}
}
func dealCards() {
// 4. Update the name via dot(.) of any card that you want.
// You can also randomise the card doing .allCases.randomElement()
leftCard = ImageName.allCases.randomElement() ?? .greenBack
print("deal")
}
}
struct GameView_Previews: PreviewProvider {
static var previews: some View {
GameView()
}
}
您可以将变量移动到GameView
并添加@State
修饰符:
struct GameView: View {
@State var leftCard = "green_back"
@State var rightCard = "blue_back"
var body: some View {
...
}
func dealCards() {
leftCard = "1C"
print("deal")
}
}
这样 SwiftUI 将在您的@State
变量更改时刷新视图。
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