У меня есть такой элемент управления, который может отображать загрузочный счетчик:
<?xml version="1.0" encoding="UTF-8"?>
<ContentView 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="Framework.Controls.Loading" x:Name="LoadingControl" IsVisible="{Binding LoadingIndicator}"
HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand">
<ContentView.Content>
<ActivityIndicator HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" Color="DarkBlue"
IsVisible="{Binding LoadingIndicator}"
IsRunning="{Binding LoadingIndicator}">
</ActivityIndicator>
</ContentView.Content>
</ContentView>
Я пытаюсь использовать его на странице, подобной этой:
<controls:Loading LoadingIndicator="{Binding IsLoading}"></controls:Loading>
Однако загрузкаспиннер не появляется на экране.
Когда я устанавливаю для свойства LoadingIndicator значение true, оно выглядит просто отлично:
<controls:Loading LoadingIndicator="true"></controls:Loading>
Моя привязка 'IsLoading' определенно работает правильно, потому что, если я помещаю следующий код непосредственно в мой XAMLстраница также работает нормально:
<ActivityIndicator HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand"
Color="DarkBlue" IsVisible="{Binding IsLoading}" IsRunning="{Binding IsLoading}">
</ActivityIndicator>
Поэтому, что в этом плохого?
<controls:Loading LoadingIndicator="{Binding IsLoading}"></controls:Loading>
Свойство IsLoading устанавливается на каждой из моих страниц из моей модели представления.Вот фрагмент из модели представления:
public ICommand OnSave => new Command(async () =>
{
IsLoading = true;
await CreateItem();
IsLoading = false;
});
Код для моего элемента управления выглядит следующим образом:
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Loading : ContentView
{
public static readonly BindableProperty LoadingIndicatorProperty =
BindableProperty.Create(
propertyName: nameof(LoadingIndicator), typeof(bool),
typeof(Loading), default(string), BindingMode.OneWayToSource);
public bool LoadingIndicator
{
get => (bool)GetValue(LoadingIndicatorProperty);
set => SetValue(LoadingIndicatorProperty, value);
}
public Loading()
{
InitializeComponent();
BindingContext = this;
}
}
Нужно ли мне писать код для обработки изменений, еслиСвязывание IsLoading обновляется?
Это полный код страницы, на которой я использую элемент управления:
ItemCreatePage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage Title="{Binding PageTitle}"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:userControls="clr-namespace:Framework.UserControls"
xmlns:converters="clr-namespace:Framework.ValueConverters"
xmlns:controls="clr-namespace:Framework.Controls;assembly=Framework.Android"
x:Class="Framework.Views.Item.ItemCreatePage">
<ContentPage.Resources>
<ResourceDictionary>
<converters:DoubleConverter x:Key="DoubleConverter"></converters:DoubleConverter>
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
<Grid>
<ScrollView>
<Grid RowSpacing="0" VerticalOptions="Start">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackLayout Grid.Row="1" Padding="20,20,20,0" VerticalOptions="Start">
<Label Text="Category" />
<userControls:BindablePicker
ItemsSource="{Binding Categories}"
SelectedItem="{Binding Path=Item.CategoryName, Mode=OneWay}"
DisplayMemberPath="Name"
SelectedValuePath="Id"
SelectedValue="{Binding Path=Item.CategoryId, Mode=TwoWay}"/>
<Label Text="Description" />
<Editor Text="{Binding Item.Description}" HeightRequest="100"/>
<Label Text="Area"/>
<Entry Text="{Binding Item.LineNumber}"/>
<Label Text="Identifier"/>
<Entry Text="{Binding Item.Identifier}"/>
<Label Text="Code"/>
<Entry Text="{Binding Item.Code}"/>
<Label Text="Priority" />
<userControls:BindablePicker
ItemsSource="{Binding Priorities}"
SelectedItem="{Binding Path=Item.ItemPriority, Mode=OneWay}"
DisplayMemberPath="Name"
SelectedValuePath="Id"
SelectedValue="{Binding Path=Item.ItemPriorityCode, Mode=TwoWay}"/>
<Label Text="Owner" />
<userControls:BindablePicker
ItemsSource="{Binding Users}"
SelectedItem="{Binding Path=Item.OwnerName, Mode=OneWay}"
DisplayMemberPath="Name"
SelectedValuePath="Id"
SelectedValue="{Binding Path=Item.OwnerId, Mode=TwoWay}"/>
<Label Text="Due Date" />
<DatePicker Date="{Binding Item.DateDue}" />
<Label Text="Date Identified" />
<DatePicker Date="{Binding Item.DateIdentified}" />
<Label Text="Status" />
<userControls:BindablePicker
ItemsSource="{Binding Statuses}"
SelectedItem="{Binding Path=Item.Status, Mode=OneWay}"
DisplayMemberPath="Name"
SelectedValuePath="Id"
SelectedValue="{Binding Path=Item.StatusCode, Mode=TwoWay}"/>
<Label Text="Comment" />
<Editor Text="{Binding Item.Comment}" HeightRequest="100"/>
<Label Text="IOM" />
<Entry Text="{Binding Item.OutcomeMeasurementInitial, Mode=TwoWay, Converter={StaticResource DoubleConverter}}" Keyboard="Numeric" />
<Label Text="FOM" />
<Entry Text="{Binding Item.OutcomeMeasurementFinal, Mode=TwoWay, Converter={StaticResource DoubleConverter}}" Keyboard="Numeric" />
<Label Text="Longitude" />
<Entry Text="{Binding Item.Longitude, Mode=TwoWay, Converter={StaticResource DoubleConverter}}" Keyboard="Numeric" />
<Label Text="Latitude" />
<Entry Text="{Binding Item.Latitude, Mode=TwoWay, Converter={StaticResource DoubleConverter}}" Keyboard="Numeric" />
<Button Margin="0,20,0,20" Command="{Binding OnSave}" BackgroundColor="{StaticResource Primary}"
BorderRadius="2" Text="Save" VerticalOptions="End" TextColor="White" ></Button>
</StackLayout>
</Grid>
</ScrollView>
<controls:Loading LoadingIndicator="{Binding IsLoading}"></controls:Loading>
</Grid>
</ContentPage.Content>
</ContentPage>
ItemCreatePage.xaml.cs
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class ItemCreatePage : ContentPage
{
public ItemCreatePage ()
{
InitializeComponent ();
}
protected override async void OnAppearing()
{
var vm = BindingContext as ItemCreateViewModel;
vm.Item = new Data.Entities.Item();
await vm?.GetDeviceLocation();
base.OnAppearing();
}
}
Код модели вида:
public class ItemCreateViewModel : FormViewModel<Data.Entities.Item>
{
public async Task GetDeviceLocation()
{
this.Item = await this.Item.AddDeviceLocation();
OnPropertyChanged(nameof(this.Item));
}
public ILookupService LookupService { get; set; }
public IItemService ItemService { get; set; }
#region selectLists
public List<EnumListItem<ItemPriority>> Priorities => EnumExtensions.ToEnumList<ItemPriority>();
public List<EnumListItem<ItemStatus>> Statuses => EnumExtensions.ToEnumList<ItemStatus>();
public string PageTitle => $"{PageTitles.ItemCreate}{this.OfflineStatus}";
public List<Data.Entities.User> Users => UserService.GetAll(this.Offline);
public List<Data.Entities.Lookup> Categories => LookupService.GetLookups(this.Offline, LookupTypeCode.ItemCategories);
#endregion
public Data.Entities.Item Item { get; set; }
public ICommand OnSave => new Command(async () =>
{
await Loading(CreateItem);
});
private async Task CreateItem()
{
// ... Save logic is here
}
FormViewModel:
public class FormViewModel<T> : BaseViewModel
{
public IValidator<T> Validator => Resolve<IValidator<T>>();
public bool IsLoading { get; set; }
/// <summary>
/// Render a loading spinner whilst we process a request
/// </summary>
/// <param name="method"></param>
/// <returns></returns>
public async Task Loading(Func<Task> method)
{
IsLoading = true;
await method.Invoke();
IsLoading = false;
}
}
BaseViewModel:
public class BaseViewModel : IViewModelBase
{
public BaseViewModel()
{
if (this.GetCurrentUserToken() != null && !UserService.IsActive())
{
SettingService.ClearToken();
Bootstrapper.MasterDetailPage.IsPresented = false;
Application.Current.MainPage = new LoginPage();
}
}
public T Resolve<T>() => AutofacBootstrapper.Container.Resolve<T>();
public IUserService UserService => Resolve<IUserService>();
public INavigator Navigator => AutofacBootstrapper.Navigator;
public IDisplayAlertFactory DisplayAlert { get; set; }
public INavigation MasterNavigation => Bootstrapper.MasterDetailPage?.Detail?.Navigation;
public bool Offline => SettingService.GetSetting<bool>(CacheProperties.Offline);
public string OfflineStatus => this.Offline ? " - Offline" : string.Empty;
public Token GetCurrentUserToken() => SettingService.GetToken() ?? null;
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyname = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyname));
}
}