【发布时间】：2020-06-22 22:39:44
【问题描述】：
好的，这就是我的应用程序的基本内容：在 AcceuilPage.xaml 中打开 im 时，我单击 + 图标将新项目添加到集合中。
然后它把我带到我用来填写数据表单的 NewFormPage.xaml，然后当我单击保存时，我从 NewFormPage.xaml.cs 调用 SaveButtonClicked 方法，但我的应用程序崩溃了，我得到：未处理的异常：系统.InvalidCastException：指定的强制转换无效。但我不知道为什么？
感谢您的帮助！
另外，我尝试了这个以查看是否创建了数据并且一切正常：
private void CreateSampleData()
{
base.OnAppearing();
ObservableCollection<Agenda> list = new ObservableCollection<Agenda>();
list.Add(new Agenda { Topic = "Journée au chantier", Duration = "07:30 UTC - 11:30 UTC", Color = "#B96CBD", Date = new DateTime(2020, 3, 23) });
list.Add(new Agenda { Topic = "Journée au chantier", Duration = "07:30 UTC - 11:30 UTC", Color = "#B96CBD", Date = new DateTime(2020, 3, 23) });
AgendaCollection.ItemsSource = list;
}
代码如下：
数据库文件夹中的 AgendaDatabase.cs
using System;
using System.Collections.Generic;
using System.Text;
using SQLite;
using Calculette.Models;
using System.Threading.Tasks;
namespace Calculette.Database
{
public class AgendaDatabase
{
readonly SQLiteAsyncConnection database;
public AgendaDatabase(string dbPath)
{
database = new SQLiteAsyncConnection(dbPath);
database.CreateTableAsync<Agenda>().Wait();
}
// Get all agenda
public Task<List<Agenda>> GetAgendasAsync()
{
return database.Table<Agenda>().ToListAsync();
}
// Get specific agenda
public Task<Agenda> GetAgendaAsync(int id)
{
return database.Table<Agenda>()
.Where(i => i.ID == id)
.FirstOrDefaultAsync();
}
// Insert new agenda (save)
public Task<int> SaveAgendaAsync(Agenda agenda)
{
if (agenda.ID != 0)
{
return database.UpdateAsync(agenda);
}
else
{
return database.InsertAsync(agenda);
}
}
//Delete specific agenda
public Task<int> DeleteAgendaAsync(Agenda agenda)
{
return database.DeleteAsync(agenda);
}
}
}
模型文件夹中的 Agenda.cs
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
using SQLite;
using Calculette.Database;
namespace Calculette.Models
{
public class Agenda
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public string Topic { get; set; }
public string Duration { get; set; }
public DateTime Date { get; set; }
}
}
视图文件夹中的NewFormPage.xaml
<ContentPage.Content>
<StackLayout>
<StackLayout >
<Label Text="Date de calcul:" FontAttributes="Bold" FontFamily="ROBOTO" TextColor="#000000"></Label>
<DatePicker x:Name="Datepicker" Date="{Binding Date}" FontFamily="ROBOTO" Format="yyyy-MM-dd" ></DatePicker>
</StackLayout>
<StackLayout >
<Label Text="Description" FontAttributes="Bold" FontFamily="ROBOTO" TextColor="#000000"></Label>
<Entry x:Name="Description" Text="{Binding Topic}"/>
</StackLayout>
<StackLayout>
<Label Text="Durée quotidienne" FontAttributes="Bold" FontFamily="ROBOTO" TextColor="#000000"></Label>
<Entry x:Name="Duree" Placeholder="HH:MM:SS" Text="{Binding Duration}"/>
</StackLayout>
<StackLayout>
<Label Text="Niveau de pression dB(A)" FontAttributes="Bold" FontFamily="ROBOTO" TextColor="#000000"></Label>
<Entry x:Name="Pression" Text="{Binding Pression}"/>
</StackLayout>
<Editor Text="{Binding Commentary}"
x:Name="Commentary"
AutoSize="TextChanges"
Placeholder="Commentaires" />
<StackLayout>
<Button Text="Save" x:Name="SaveButton" TextColor="#008A00" BackgroundColor="#FFFFFF" BorderWidth="1" BorderColor="#1A961A" Clicked="SaveButtonClicked"></Button>
<ActivityIndicator IsRunning="{Binding IsBusy}"/>
</StackLayout>
</StackLayout>
</ContentPage.Content>
视图文件夹中的NewFormPage.xaml.cs
using Calculette.Models;
using Calculette.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace Calculette.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class NewFormPage : ContentPage
{
public NewFormPage ()
{
InitializeComponent ();
BindingContext = new FormViewModel();
}
async void SaveButtonClicked(object sender, EventArgs e)
{
var agenda = (Agenda)BindingContext;
//agenda.Date = DateTime.UtcNow;
await App.Database.SaveAgendaAsync(agenda);
await Navigation.PopAsync();
}
}
}
AcceuilPage.xaml
<ContentPage.Content>
<!-- ScrollView nous permet d'avoir une page scrollable-->
<ScrollView Orientation="Vertical">
<CollectionView Grid.Row="2" Margin="25" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"
SelectionMode="None" x:Name="AgendaCollection"> <!--ItemsSource="{Binding AngedaCollection}" -->
<CollectionView.Header>
<StackLayout Orientation="Horizontal" Spacing="220">
<Label Text="Agenda" TextColor="Black" FontSize="18"/>
<ImageButton Source="iconplus.png" HeightRequest="30" WidthRequest="30" Clicked="GoToNewFormPage"></ImageButton>
</StackLayout>
</CollectionView.Header>
<CollectionView.ItemsLayout>
<LinearItemsLayout Orientation="Vertical" ItemSpacing="20"/>
</CollectionView.ItemsLayout>
<CollectionView.ItemTemplate >
<DataTemplate>
<pv:PancakeView HasShadow="True" BackgroundColor="White" VerticalOptions="StartAndExpand "
HorizontalOptions="FillAndExpand">
<Grid VerticalOptions="StartAndExpand" HorizontalOptions="FillAndExpand">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<BoxView BackgroundColor="{Binding Color}" WidthRequest="3" HorizontalOptions="Start"
VerticalOptions="FillAndExpand"/>
<Expander Grid.Column="1">
<Expander.Header>
<Grid HorizontalOptions="FillAndExpand">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="3.5*"/>
</Grid.ColumnDefinitions>
<StackLayout HorizontalOptions="Center" VerticalOptions="Center">
<Label Text="{Binding Date, StringFormat='{0:dd}'}" TextColor="#008A00" FontSize="27"
HorizontalOptions="Center"/>
<Label Text="{Binding Date, StringFormat='{0:MMMM}'}" TextColor="Black" FontSize="10"
HorizontalOptions="Center" Margin="0,-10,0,0" FontAttributes="Bold"/>
<ImageButton Source="iconplus.png" HorizontalOptions="Center" HeightRequest="30" WidthRequest="30" Clicked="GoToFormPage"></ImageButton>
</StackLayout>
<BoxView Grid.Column="1" BackgroundColor="#F2F4F8" WidthRequest="1" HorizontalOptions="Start"
VerticalOptions="FillAndExpand"/>
<StackLayout Grid.Column="2" HorizontalOptions="Start" VerticalOptions="Center" Margin="20">
<Label Text="{Binding Topic}" TextColor="#008A00" FontSize="15" FontAttributes="Bold"/>
<Label Text="{Binding Duration}" TextColor="#2F3246" FontSize="12" Margin="0,-10,0,0"/>
</StackLayout>
</Grid>
</Expander.Header>
<Grid HorizontalOptions="FillAndExpand">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="3.5*"/>
</Grid.ColumnDefinitions>
<BoxView Grid.Column="1" BackgroundColor="#F2F4F8" WidthRequest="1" HorizontalOptions="Start"
VerticalOptions="FillAndExpand"/>
<StackLayout Grid.Column="2" Spacing="10">
<Label Text="Tâches" TextColor="Black" FontSize="15" Margin="20,0"/>
<StackLayout BindableLayout.ItemsSource="{Binding Speakers}" HorizontalOptions="Start" VerticalOptions="Center" Margin="20,0,0,20">
<BindableLayout.ItemTemplate>
<DataTemplate>
<Label TextColor="#2F3246" FontSize="12">
<Label.FormattedText>
<FormattedString>
<FormattedString.Spans>
<Span Text="{Binding Time}"/>
<Span Text=" - "/>
<Span Text="{Binding Name}" FontAttributes="Bold"/>
</FormattedString.Spans>
</FormattedString>
</Label.FormattedText>
</Label>
</DataTemplate>
</BindableLayout.ItemTemplate>
</StackLayout>
</StackLayout>
</Grid>
</Expander>
</Grid>
</pv:PancakeView>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</ScrollView>
</ContentPage.Content>
AcceuilPage.xaml.ca
public partial class MainPage : TabbedPage
{
public MainPage()
{
InitializeComponent();
this.BindingContext = this;
}
protected async void GoToFormPage(object sender, EventArgs e)
{
await Navigation.PushAsync(new Views.AgendaItemDetailPage());
}
protected async void GoToNewFormPage(object sender, EventArgs e)
{
await Navigation.PushAsync(new Views.NewFormPage());
}
protected override async void OnAppearing()
{
base.OnAppearing();
AgendaCollection.ItemsSource = await App.Database.GetAgendasAsync();
}
}
【问题讨论】：
标签： sqlite xamarin xamarin.forms