如何解决如何以 xamarin 形式将数据绑定到可绑定属性
我有两个使用相同表单的页面，因此我创建了表单的内容视图并应用了如下所示的可绑定属性：
<ContentView xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ListContact.Extension.EditForm">
<StackLayout Padding="20">
<Label Text="Edit Contact Forms"
HorizontalOptions="Center"
FontSize="20"
TextColor="Blue"
VerticalOptions="Start"/>
<Label Text="Name"/>
<Entry x:Name="txtName" Text="{Binding NameText}" Placeholder="Name"/>
<Label Text="Phone number"/>
<Entry x:Name="txtPhoneNumber" Text="{Binding PhoneNumberText}" Placeholder="Phone number" Keyboard="Telephone"/>
<Label Text="Email"/>
<Entry x:Name="txtEmail" Text="{Binding EmailText}" Placeholder="Email" Keyboard="Email"/>
<Label Text="Description"/>
<Editor x:Name="txtDescription" Text="{Binding DescriptionText}" Placeholder="Description"
HeightRequest="70"/>
</StackLayout>
</ContentView>
这是后面的代码：
using ListContact.viewmodel;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace ListContact.Extension
{
[XamlCompilation(XamlCompilationoptions.Compile)]
public partial class EditForm : ContentView
{
private static readonly BindableProperty NameProperty = BindableProperty.Create("NameText",typeof(object),typeof(EditForm));
public string NameText { get => (string)GetValue(NameProperty); set => SetValue(NameProperty,value); }
private static readonly BindableProperty PhoneProperty = BindableProperty.Create("PhoneNumberText",typeof(string),typeof(EditForm));
public string PhoneNumberText { get => (string)GetValue(PhoneProperty); set => SetValue(PhoneProperty,value); }
private static readonly BindableProperty EmailProperty = BindableProperty.Create("EmailText",typeof(EditForm));
public string EmailText { get => (string)GetValue(EmailProperty); set => SetValue(EmailProperty,value); }
private static readonly BindableProperty DescriptionProperty = BindableProperty.Create("DescriptionText",typeof(EditForm));
public string DescriptionText { get => (string)GetValue(DescriptionProperty); set => SetValue(DescriptionProperty,value); }
public EditForm()
{
InitializeComponent();
BindingContext = this;
}
}
}
在视图中，我回调我之前创建的这个表单并将数据绑定到可绑定属性，如下所示：
这是xaml文件：
<ContentPage xmlns:local="clr-namespace:ListContact.Extension"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ListContact.View.ListContactAddingForm">
<local:EditForm NameText="{Binding Name,Mode=TwoWay}" PhoneNumberText="egwebwev" EmailText="ưewevefqwf" DescriptionText="ewebe"/>
<ContentPage.Content>
<Button Text="Save"
HorizontalOptions="Center"
TextColor="White"
Command="{Binding AddContactCommand}"
BackgroundColor="#0A7CFF"/>
</ContentPage.Content>
</ContentPage>
这是背后的代码：
namespace ListContact.View
{
[XamlCompilation(XamlCompilationoptions.Compile)]
public partial class ListContactAddingForm : ContentPage
{
private sqliteAsyncConnection connection;
public ListContactAddingForm()
{
connection = new sqliteAsyncConnection(BaseConnection.DatabasePath);
viewmodel = new Contactviewmodel(new PageService());
InitializeComponent();
}
private Contactviewmodel viewmodel
{
get => BindingContext as Contactviewmodel;
set => BindingContext = value;
}
}
}
`
这是我的视图模型：
namespace ListContact.viewmodel
{
public class Contactviewmodel : Baseviewmodel
{
public int Id { get; set; }
private string name;
public string Name
{
get => name;
set
{
SetValue(ref name,value);
}
}
private string description;
public string Description
{
get => description;
set
{
SetValue(ref description,value);
}
}
private string phoneNumber;
public string PhoneNumber
{
get => phoneNumber;
set
{
SetValue(ref phoneNumber,value);
}
}
private string email;
public string Email
{
get => email;
set
{
SetValue(ref email,value);
}
}
public ICommand AddContactCommand { get; private set; }
private IPageService pageService;
public object Alert { get; private set; }
public Contactviewmodel(IPageService pageService)
{
this.pageService = pageService;
AddContactCommand = new Command(async () => await AddContacts());
}
private async Task AddContacts()
{
var newContact = new Contact()
{
Name = Name,PhoneNumber = PhoneNumber,Email = Email,Description = Description
};
var result = await connection.InsertAsync(newContact);
if (result == 1)
await App.Current.MainPage.displayAlert("Successfully","","OK");
await pageService.PopAsycn();
}
}
}
未找到“NameText”的属性、可绑定属性或事件，或者值和属性之间的类型不匹配
在我将表单分离到另一个内容视图并从视图中调用它之前，我的代码没问题
所以我的问题是： 我创建表单和可绑定属性的方式是否正确？ 我可以将数据绑定到表单中的可绑定属性吗？可以的话怎么做？ 以及如何修复上述错误？
我使用 MVVM 构建此代码
顺便说一句，对不起我的英语不好
解决方法
从 Xamarin.Forms Bindable Properties 开始，可以通过声明 BindableProperty 类型的公共静态只读属性来创建可绑定属性。
public static readonly BindableProperty NameTextProperty = BindableProperty.Create
("NameText",typeof(string),typeof(EditForm),"",BindingMode.OneWay,propertyChanged:NamePropertychanged);
然后你需要处理 BindableProperty Name，例如，PropertyNameProperty
public static readonly BindableProperty NameTextProperty = BindableProperty.Create
("NameText",propertyChanged:NamePropertychanged);
public string NameText
{
get => (string)GetValue(NameTextProperty);
set => SetValue(NameTextProperty,value);
}
最后，你不需要在 EditForm 中使用 Binding，只需使用 propertyChanged 事件来通知属性值已更改。
private static void NamePropertychanged(BindableObject bindable,object oldValue,object newValue)
{
var control = (EditForm)bindable;
control.txtName.Text = (string)newValue;
}
做一个你可以看看的样本：
EditForm xaml。
<ContentView.Content>
<StackLayout Padding="20">
<Label
FontSize="20"
HorizontalOptions="Center"
Text="Edit Contact Forms"
TextColor="Blue"
VerticalOptions="Start" />
<Label Text="Name" />
<Entry x:Name="txtName" Placeholder="Name" />
<Label Text="Phone number" />
<Entry
x:Name="txtPhoneNumber"
Keyboard="Telephone"
Placeholder="Phone number" />
<Label Text="Email" />
<Entry
x:Name="txtEmail"
Keyboard="Email"
Placeholder="Email" />
<Label Text="Description" />
<Editor
x:Name="txtDescription"
HeightRequest="70"
Placeholder="Description" />
</StackLayout>
</ContentView.Content>
public partial class EditForm : ContentView
{
public static readonly BindableProperty NameTextProperty = BindableProperty.Create
("NameText",value);
}
public static readonly BindableProperty PhoneNumberTextProperty = BindableProperty.Create
("PhoneNumberText",propertyChanged:PhoneNumberchanged);
public string PhoneNumberText
{
get => (string)GetValue(PhoneNumberTextProperty);
set => SetValue(PhoneNumberTextProperty,value);
}
public static readonly BindableProperty EmailTextProperty = BindableProperty.Create
("EmailText",propertyChanged:Emailpropertychanged);
public string EmailText
{
get => (string)GetValue(EmailTextProperty);
set => SetValue(EmailTextProperty,value);
}
public static readonly BindableProperty DescriptionTextProperty = BindableProperty.Create
("DescriptionText",propertyChanged: Descriptionchanged);
public string DescriptionText
{
get => (string)GetValue(DescriptionTextProperty);
set => SetValue(DescriptionTextProperty,value);
}
private static void NamePropertychanged(BindableObject bindable,object newValue)
{
var control = (EditForm)bindable;
control.txtName.Text = (string)newValue;
}
private static void PhoneNumberchanged(BindableObject bindable,object newValue)
{
var control = (EditForm)bindable;
control.txtPhoneNumber.Text = (string)newValue;
}
private static void Emailpropertychanged(BindableObject bindable,object newValue)
{
var control = (EditForm)bindable;
control.txtEmail.Text = (string)newValue;
}
private static void Descriptionchanged(BindableObject bindable,object newValue)
{
var control = (EditForm)bindable;
control.txtDescription.Text = (string)newValue;
}
public EditForm()
{
InitializeComponent();
}
}
<StackLayout>
<local:EditForm
DescriptionText="{Binding option}"
EmailText="{Binding Email}"
NameText="{Binding Name}"
PhoneNumberText="{Binding Phone}" />
</StackLayout>
public partial class Page5 : ContentPage
{
public Contact contact1 { get; set; }
public Page5()
{
InitializeComponent();
contact1 = new Contact() { Name = "cherry",Phone = "1234567",Email = "xxxxxxxx",option = "this is test" };
this.BindingContext = contact1 ;
}
}
public class Contact:ViewModelBase
{
private string _name;
public string Name
{
get { return _name; }
set
{
_name = value;
RaisePropertyChanged("Name");
}
}
private string _phone;
public string Phone
{
get { return _phone; }
set
{
_phone = value;
RaisePropertyChanged("Phone");
}
}
private string _email;
public string Email
{
get { return _email; }
set
{
_email = value;
RaisePropertyChanged("Email");
}
}
private string _option;
public string option
{
get { return _option; }
set
{
_option = value;
RaisePropertyChanged("option");
}
}
}
实现 INotifyPropertyChanged 的 ViewModelBase
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this,new PropertyChangedEventArgs(propertyName));
}
}
}
截图：
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