[英]How to write an Int value from struct to Xaml Page Text Box?
I have a structure like this 我有这样的结构
struct struValues
{
public int a;
}
I want to write it to a textcell in Xaml Page. 我想将其写入Xaml页面中的文本单元。 How can I do it?
我该怎么做? I tried
我试过了
{Bind struValues.a}
but it did not worked. 但是没有用。
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:i18n="clr-namespace:test_Trade.Localization;assembly=test_Trade"
xmlns:puser="clr-namespace:test_Trade.Classes"
x:Class="test_Trade.Views.Durumpg">
<ContentPage.Content>
<TableView Intent="Form">
<TableRoot>
<TableSection Title="{i18n:TranslateExtension Text=Stats}">
<ImageCell ImageSource="Euro.png" Detail="{Here Should be money}" x:Name="imgCelleuro"/>
</TableSection>
</TableRoot>
</TableView>
</ContentPage.Content>
</ContentPage>
Here is an MVVM example of how I would bind a TextCell "Text" Property to an int property of a struct-typed instance. 这是一个MVVM示例,说明如何将TextCell“ Text”属性绑定到结构类型实例的int属性。 I put out comments for important lines.
我对重要内容发表了评论。
The visual outcome should be a table view with one section titled as "Cool Struct Section" and one Text Cell as a child, showing the text "123" which is the structs current value. 视觉结果应该是一个表格视图,其中一个标题为“ Cool Struct Section”的区域,一个文本单元格作为子级,显示文本“ 123”,它是结构的当前值。
XAML Page Content: XAML页面内容:
<ContentPage.Content>
<TableView Intent="Settings">
<TableRoot>
<TableSection Title="{Binding TableSectionTitle}">
<TextCell Text="{Binding StruValues.A}" />
</TableSection>
</TableRoot>
</TableView>
</ContentPage.Content>
C# Page code behind: C#页面代码背后:
using MVVMExample.ViewModel;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace MVVMExample
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class TableViewPage : ContentPage
{
public TableViewPage()
{
InitializeComponent();
BindingContext = new TableViewPageVM(); //Assing the ViewModel to the binding context!
}
}
}
C# ViewModel (also BindingContext of the Page) : C#ViewModel (也是页面的BindingContext) :
using MVVMExample.Utils;
namespace MVVMExample.ViewModels
{
public class TableViewPageVM : BindableBase
{
//Simple text to bind to the TableSection Title property
private string tableSectionTitle;
public string TableSectionTitle { get { return tableSectionTitle; } set { SetProperty(ref tableSectionTitle, value); } }
//Property that will hold our struValues instance. The TextCell "Text" Property will be bound to the A property of this instance.
//The A property exposes the value of the actual "a" property of the facades struct instance
private struValuesFacade _struValues;
public struValuesFacade StruValues { get { return _struValues; } set { SetProperty(ref _struValues, value); } }
public TableViewPageVM()
{
TableSectionTitle = "Cool Struct Section"; //Set the title text
StruValues = new struValuesFacade(123); //Create an instance of our facade
}
/// <summary>
/// A "facade" of the actual struct, that exposes the "a" property of the struct instance
/// Also holds the instances of the struct
/// </summary>
public class struValuesFacade : BindableBase
{
struValues origin;
public int A
{
get { return origin.a; }
set
{
SetProperty(ref origin.a, value);
}
}
public struValuesFacade(int value)
{
origin = new struValues() { a = value };
}
}
/// <summary>
/// Your beloved struct
/// </summary>
struct struValues
{
public int a;
}
}
}
C# "BindableBase" class, inherits from INotifyPropertyChanged (credits to msdn.microsoft.com) (mandatory to update the view when properties change in an MVVM environment) C#“ BindableBase”类继承自INotifyPropertyChanged(提供给msdn.microsoft.com) (强制在MVVM环境中更改属性时更新视图)
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace MVVMTest.Utils
{
public class BindableBase : INotifyPropertyChanged
{
///
/// Multicast event for property change notifications.
///
public event PropertyChangedEventHandler PropertyChanged;
///
/// Checks if a property already matches a desired value. Sets the property and
/// notifies listeners only when necessary.
///
///Type of the property.
///Reference to a property with both getter and setter.
///Desired value for the property.
///Name of the property used to notify listeners. This
/// value is optional and can be provided automatically when invoked from compilers that
/// support CallerMemberName.
///True if the value was changed, false if the existing value matched the
/// desired value.
protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
{
if (object.Equals(storage, value)) return false;
storage = value;
this.OnPropertyChanged(propertyName);
return true;
}
///
/// Notifies listeners that a property value has changed.
///
///Name of the property used to notify listeners. This
/// value is optional and can be provided automatically when invoked from compilers
/// that support .
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
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