[英]How to save a page state?
在Windows Runtime應用程序中,我像這樣加載數據:
private async void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
var userId = e.NavigationParameter as string;
List<User> followers = GetFollowers(userId);
this.DefaultViewModel["Followers"] = followers;
}
然后用戶可以從ListView
選擇一個項目:
private void ContentListView_ItemClick(object sender, ItemClickEventArgs e)
{
var selectedItem = e.ClickedItem as User;
if (!Frame.Navigate(typeof(FollowersPage), selectedItem.UserId))
{
throw new Exception(this.resourceLoader.GetString("NavigationFailedExceptionMessage"));
}
}
因此它向前導航到同一頁面,但顯示新的關注者。
問題在於,當它向后導航時,它將再次加載數據並從列表的開頭顯示,而不是顯示最后選擇的項目。
那么,如何在NavigationHelper_SaveState
保存數據List
,以及如何在NavigationHelper_LoadState
再次將數據加載到列表中的最后位置呢? 謝謝。
這是您可以開始的基本的半測試示例。 您需要對其進行修改以適合您的實際情況。 有些是從這里改編的。
void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
var isp = (ItemsStackPanel)listview.ItemsPanelRoot;
int firstVisibleItem = isp.FirstVisibleIndex;
e.PageState["FirstVisibleItemIndex"] = firstVisibleItem;
// This must be serializable according to the SuspensionManager
e.PageState["Followers"] = this.DefaultViewModel["Followers"];
}
void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
// Do we have saved state to restore?
if (e.PageState != null)
{
// Restore list view items
this.DefaultViewModel["Followers"] = (WhateverType)e.PageState["Followers"];
// Restore scroll offset
var index = (int)e.PageState["FirstVisibleItemIndex"];
var container = listview.ContainerFromIndex(index);
listview.ScrollIntoView(container);
}
else
{
// Load data for the first time
var userId = e.NavigationParameter as string;
List<User> followers = GetFollowers(userId);
this.DefaultViewModel["Followers"] = followers;
}
}
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