如果有任何更改,我会在出现选项卡项时调用 API。为什么在调用onDisappear 之后调用onAppear?
这是一个简单的例子:
struct ContentView: View {
var body: some View {
TabView {
NavigationView {
Text("Home")
.navigationTitle("Home")
.onAppear {
print("Home appeared")
}
.onDisappear {
print("Home disappeared")
}
}
.tabItem {
Image(systemName: "house")
Text("Home")
}.tag(0)
NavigationView {
Text("Account")
.navigationTitle("Account")
.onAppear {
print("Account appeared")
}
.onDisappear {
print("Account disappeared")
}
}
.tabItem {
Image(systemName: "gear")
Text("Account")
}.tag(1)
}
}
}
只需运行上面的代码,我们将在 onDisappear 之后看到 onAppear。Home appeared
---After switch tab to Account---
Home disappeared
Account appeared
Home appeared
有什么办法可以避免这种情况吗?
最佳答案
这是非常烦人的错误,想象一下这种情况:Home
查看 onAppear
方法包含一个重复获取数据的计时器。
通过切换到 Account
来无形地触发计时器看法。
解决方法:
NavigationView
创建一个独立 View 内容 @Binding
传递到独立 View 参数例如。:
struct ContentView: View {
@State var selected: MenuItem = .HOME
var body: some View {
return TabView(selection: $selected) {
HomeView(selectedMenuItem: $selected)
.navigationViewStyle(StackNavigationViewStyle())
.tabItem {
VStack {
Image(systemName: "house")
Text("Home")
}
}
.tag(MenuItem.HOME)
AccountView(selectedMenuItem: $selected)
.navigationViewStyle(StackNavigationViewStyle())
.tabItem {
VStack {
Image(systemName: "gear")
Text("Account")
}
}
.tag(MenuItem.ACCOUNT)
}
}
}
enum MenuItem: Int, Codable {
case HOME
case ACCOUNT
}
主页 View :struct HomeView: View {
@Binding var selectedMenuItem: MenuItem
var body: some View {
return Text("Home")
.onAppear(perform: {
if MenuItem.HOME == selectedMenuItem {
print("-> HomeView")
}
})
}
}
帐户 View :struct AccountView: View {
@Binding var selectedMenuItem: MenuItem
var body: some View {
return Text("Account")
.onAppear(perform: {
if MenuItem.ACCOUNT == selectedMenuItem {
print("-> AccountView")
}
})
}
}
关于ios - 为什么在 SwiftUI 的 TabView 中切换选项卡时 onDisappear 之后再次调用 onAppear?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/63252499/