根据Xamarin Forms中的选项卡页面工具栏选择器值更改更改子页面数据

Question

我有一个选项卡页面在我的Xamarin表单应用程序。我有两个孩子的内容页面。在选项卡页面的工具栏中有两个选择器和一个按钮。我想要的是根据值填充来自服务器的数据，这是在选择器中更改的。我正在使用MVVM设计模式。如何将选择器值传递给子页面?我试着使用MessagingCenter，它有时工作，但不是所有的时间。

Tabbedpage

public partial class LifekpiRankingTabbedRM : ZeroTabbarHeight
{
public LifekpiRankingTabbedRM(string uRegion)
{
InitializeComponent();
BindingContext = new LifekpiRankingRmTabbedViewModel(uRegion);
Children.Add(new LifeKpiRankingViewRM(uRegion));
Children.Add(new LifeKpiRankingViewRMsBM(uRegion));
} 
}

Tabbedpage VM

public class LifekpiRankingRmTabbedViewModel : BaseViewModelHelper
{
public MonthData2 SelectedMonth
{
get => _selectedMonth;
set
{
_selectedMonth = value;
GenerateData(_selectedMonth.mIndex, SelectedKpi).Await(CompletedTask, ErrorHandle);
OnPropertyChanged();
}
}
public string SelectedKpi
{
get => _selectedKpi;
set
{
_selectedKpi = value;
GenerateData(SelectedMonth.mIndex, _selectedKpi).Await(CompletedTask, ErrorHandle);
OnPropertyChanged();
}
}
public LifekpiRankingRmTabbedViewModel(string uRegion)
{
this.uRegion = uRegion;
SelectedMonth = GetCurrentMonth();
SelectedKpi = KpiList.First();
reportType = "Monthly";
ReportTypeTapCommand = new Command(ChangeTypeCommand);
}
private async Task GenerateData(int selectedMonth, string selectedKpi)
{
AcrDialogClass.ShowLoadingDialog("Loading...");
if (runCount > 2)
{
var resRmData = await _apiServices.GetLifeRegionalKpiWiseRanking(selectedMonth, selectedKpi, isCumulative);
var resBmForRmData = await _apiServices.GetLifeBranchKpiWiseRankingForRM(selectedMonth, selectedKpi, uRegion, isCumulative);
if (resRmData != null)
{
MessagingCenter.Send<App, string>(App.Current as App, "KPI_REGINAL_RANKING", resRmData);
}
if (resBmForRmData != null)
{
MessagingCenter.Send<App, string>(App.Current as App, "KPI_BM_RANKING_FOR_RM", resBmForRmData);
}
}
else
{
runCount++;
}
}
private MonthData2 GetCurrentMonth()
{
var months = Enumerable.Range(1, 12).Select(i => new { I = i, M = DateTimeFormatInfo.InvariantInfo.GetMonthName(i) });
foreach (var ss in months)
{
MonthList.Add(new MonthData2() { mIndex = ss.I, mName = ss.M });
}
return MonthList.Find(r => r.mIndex == dt.Month);
}
private void ChangeTypeCommand()
{
if (isCumulative)
{
reportType = "Monthly";
isCumulative = false;
}
else
{
reportType = "Cumulative";
isCumulative = true;
}
GenerateData(SelectedMonth.mIndex, SelectedKpi).Await(CompletedTask, ErrorHandle);
}
private void CompletedTask()
{
AcrDialogClass.HideLoadingDialog();
}
private void ErrorHandle(Exception ex)
{
AcrDialogClass.HideLoadingDialog();
}
}

标签1

public partial class LifeKpiRankingViewRM : ContentPage
{
private LifeKpiRankingViewModelRM vm;
public LifeKpiRankingViewRM(string uRegion)
{
InitializeComponent();
BindingContext = new LifeKpiRankingViewModelRM(uRegion);
vm = BindingContext as LifeKpiRankingViewModelRM;
}
protected override void OnAppearing()
{
base.OnAppearing();
MessagingCenter.Subscribe<App, string>(App.Current, "KPI_REGINAL_RANKING", (snd, arg) =>
{
vm.SetValues(arg);
});
}
protected override void OnDisappearing()
{
base.OnDisappearing();
MessagingCenter.Unsubscribe<App, string>(App.Current, "KPI_REGINAL_RANKING");
}
}

标签2

public partial class LifeKpiRankingViewRMsBM : ContentPage
{
private LifeKpiRankingViewModelBMForRM vm;
public LifeKpiRankingViewRMsBM(string uRegion)
{
InitializeComponent();
BindingContext = new LifeKpiRankingViewModelBMForRM(uRegion);
vm = BindingContext as LifeKpiRankingViewModelBMForRM;
}
protected override void OnAppearing()
{
base.OnAppearing();
MessagingCenter.Subscribe<App, string>(App.Current, "KPI_BM_RANKING_FOR_RM", (snd, arg) =>
{
vm.SetValues(arg);
});
}
protected override void OnDisappearing()
{
base.OnDisappearing();
MessagingCenter.Unsubscribe<App, string>(App.Current, "KPI_BM_RANKING_FOR_RM");
}
}

Answer 1

首先，您可以尝试获取子页面的实例，然后设置其值。如果你在app.cs中使用MainPage = new LifekpiRankingTabbedRM():

设置选项卡页面

var tabbedpage = App.Current.MainPage as LifekpiRankingTabbedRM;
var childpage1 = tabbedpage.Children[0];
var vm1 = childpage1.BindingContext as LifeKpiRankingViewModelRM;
vm1.SetValues(...);

一般来说，当您有TabbedPage的实例时，您可以获取它的子页面并更新子页面的值。

此外，您可以显示更多关于MessageCenter不工作的细节，我们可以帮助您继续使用MessageCenter。