“不知道Xamarin.Forms.Color”
为什么给我这个代码“不知道关于Xamarin.Forms.Color”的例外？
例外细节：
System.AggregateException Zpráva=One or more errors occurred. (Don't know about Xamarin.Forms.Color) Zdroj= StackTrace: at System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions) [0x00011] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2027 at System.Threading.Tasks.Task.Wait (System.Int32 millisecondsTimeout, System.Threading.CancellationToken cancellationToken) [0x00043] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2759 at System.Threading.Tasks.Task.Wait () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2625 at Notes.Data.NoteDatabase..ctor (System.String dbPath) [0x00015] in C:\Users\foksak\source\repos\Notes\Notes\Notes\Data\NoteDatabase.cs:15 at Notes.App.get_Database () [0x0000e] in C:\Users\foksak\source\repos\Notes\Notes\Notes\App.xaml.cs:18 at Notes.NotesPage.OnAppearing () [0x0001b] in C:\Users\foksak\source\repos\Notes\Notes\Notes\NotesPage.xaml.cs:19 at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.39(intptr,intptr at (wrapper native-to-managed) Android.Runtime.DynamicMethodNameCounter.39(intptr,intptr)
注模式：
namespace Notes.Models
{
public class Note
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public string Text { get; set; }
public string Title { get; set; }
public string Picture { get; set; }
public string Colorr { get; set; }
public Color Colorrr { get; set; }
}
}数据输入页面的c#：
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class NoteEntryPage : ContentPage
{
Dictionary<string, string> dic = new Dictionary<string, string>() {
{"Color1","#d8daea"},
{"Color2", "#ecd67b"},
{"Color3", "#3f6018"},
{"Color4", "#ff8847" }
};
public NoteEntryPage()
{
InitializeComponent();
}
async void OnSaveButtonClicked(object sender, EventArgs e)
{
var note = (Note)BindingContext;
string x = dic[note.Colorr];
note.Colorrr = Color.FromHex(x);
await App.Database.SaveNoteAsync(note);
await Navigation.PopAsync();
}
async void OnDeleteButtonClicked(object sender, EventArgs e)
{
var note = (Note)BindingContext;
await App.Database.DeleteNoteAsync(note);
await Navigation.PopAsync();
}
}输入有效。当我用手写"#ff8847" 而不是 x**.**的时候，的问题也出现了。
数据是页中的去播放机，下面是代码。C#中的数据种子：
protected override async void OnAppearing()
{
base.OnAppearing();
listView.ItemsSource = await App.Database.GetNotesAsync();
}Xaml：
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="Notes.NotesPage">
<ContentPage.ToolbarItems>
<ToolbarItem Text="+"
Clicked="OnNoteAddedClicked" />
</ContentPage.ToolbarItems>
<ListView x:Name="listView"
Margin="20" RowHeight="80"
ItemSelected="OnListViewItemSelected">
<ListView.ItemTemplate>
<DataTemplate >
<ViewCell>
<Grid VerticalOptions="FillAndExpand" HorizontalOptions="Fill">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="auto"/>
<ColumnDefinition Width="auto"/>
<ColumnDefinition Width="auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions >
<RowDefinition Height="auto"/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<StackLayout Orientation="Horizontal" Grid.Column="1" Grid.Row="0">
<Label Text="{Binding Title}" FontSize="22" FontAttributes="Bold" />
</StackLayout>
<Label Text="{Binding Text}" Grid.Column="1" Grid.Row="1" Grid.ColumnSpan="2"/>
<Frame CornerRadius="5" HasShadow="true" Grid.RowSpan="2" BackgroundColor="{Binding Colorrr}" Margin="7" WidthRequest="35">
<Image Source="{Binding Picture}" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="30"/>
</Frame>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage>回答 1
Stack Overflow用户
发布于 2020-02-06 09:47:20
在sqlite中不能有一个Color字段，所以忽略它。
namespace Notes.Models
{
public class Note
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public string Text { get; set; }
public string Title { get; set; }
public string Picture { get; set; }
public string Colorr { get; set; }
[Ignore]
public Color Colorrr { get; set; }
}
}还必须在将Colorrr字段绑定到视图之前初始化它，如下所示：
note.Colorrr = note.Colorr.FromHex(x);然后命名您的框架以更新颜色，并删除绑定：
<Frame x:Name="ColorFrame" CornerRadius="5" HasShadow="true" Grid.RowSpan="2" Margin="7" WidthRequest="35">
<Image Source="{Binding Picture}" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="30"/>
</Frame>并在保存方法中更新它：
async void OnSaveButtonClicked(object sender, EventArgs e)
{
var note = (Note)BindingContext;
string x = dic[note.Colorr];
ColorFrame.BackgroundColor = Color.FromHex(x);
await App.Database.SaveNoteAsync(note);
await Navigation.PopAsync();
}那么它应该会像预期的那样起作用。
另一个更清晰的路径:使用MVVM模式并创建一个NoteViewModel实现INotifyPropertyChanged，它将包装您的Note对象。
https://stackoverflow.com/questions/60089355
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