问题描述
我有一个使用 FreshMVVM 的 Xaml.Forms 应用程序。我像这样从 app.xaml.cs 打开某个页面:
firebase.auth().onAuthStateChanged(function(user) {
if (user) {
db.collection("users").doc(user.uid).get()
.then(snap => {
localStorage.setItem('userData',JSON.stringify(snap.data()));
});
} else {
// No user is signed in.
}
});
但是如果此页面已经打开,我需要添加一个检查以防止这样做。我怎样才能进行这样的检查?
解决方法
在App类中添加一个静态bool值来检查页面是否已经打开:
public partial class App : Application
{
public static bool isPageOpened;
public App()
{
InitializeComponent();
MainPage = new MainPage();
}
public void test()
{
if (App.isPageOpened = false)
{
Xamarin.Forms.Device.BeginInvokeOnMainThread(async () =>
{
var navService = FreshIOC.Container.Resolve<IFreshNavigationService>(FreshMvvm.Constants.DefaultNavigationServiceName);
Page page = FreshPageModelResolver.ResolvePageModel<SomePageModel>();
App.isPageOpened = true;
await navService.PushPage(page,null);
});
}
}
}
在页面的 OnDisappearing 方法中,将 isPageOpened
设置为 false:
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
protected override void OnDisappearing()
{
base.OnDisappearing();
App.isPageOpened = false;
}
}