I have an entry on the top of a page and a listview on below of that. When doing pull down refresh I want to clear the text on that entry.
Following is my entry code:
<Entry
x:Name="SearchEntry"
HorizontalOptions="FillAndExpand"
VerticalOptions="Center"
PlaceholderColor="Black"
FontFamily="Bold"
TextColor="Black"
Placeholder="Search a Directory"/>
Thanks in advance
I assume that you use MVVM and have a ViewModel.
Create and bind a property of type string from your ViewModel to Entry.Text. Inside refresh method set this property to null or string.Empty.
Example:
class MyViewModel : INotifyPropertyChanged
{
// TODO: Handle INotifyPropertyChanged correctly
public string EntryTextProp { get; set; }
public async Task<?> UpdateList()
{
// ...
EntryTextProp = null;
// ...
}
}
<Entry
x:Name="SearchEntry"
Text="{Binding EntryTextProp}"
HorizontalOptions="FillAndExpand"
VerticalOptions="Center"
PlaceholderColor="Black"
FontFamily="Bold"
TextColor="Black"
Placeholder="Search a Directory"/>
Updating the complete code here, this might help others.
class MyViewModel : INotifyPropertyChanged
{
string _entrytext = "";
public string EntryText
{
protected set
{
if (_entrytext != value)
{
_entrytext = value;
OnPropertyChanged("EntryText");
}
}
get { return _entrytext; }
}
public ICommand RefreshCommand
{
get
{
return new Command(async () =>
{
IsRefreshing = true;
EntryText = null;
MyList();
IsRefreshing = false;
});
}
}
}
<Entry
x:Name="SearchEntry"
Text="{Binding EntryTextProp}"
HorizontalOptions="FillAndExpand"
VerticalOptions="Center"
PlaceholderColor="Black"
FontFamily="Bold"
TextColor="Black"
Placeholder="Search a Directory"/>
Related
This is the short code for testing purpose. The problem is that the UI is not displaying the Text from the Label which is binded with ViewModelB. In debugging when I hover the mouse in xaml over the Text from the Label I see the right binding data is there, but the UI simply won't display. With ViewModelA there are no problems.
In XAML:
<StackLayout>
<StackLayout>
<StackLayout.BindingContext>
<testbinding:ViewModelA/>
</StackLayout.BindingContext>
<Button Command ="{Binding Get}"/>
</StackLayout>
<StackLayout>
<StackLayout.BindingContext>
<testbinding:ViewModelB/>
</StackLayout.BindingContext>
<Label Text="{Binding Metadata}"/>
</StackLayout>
ViewModelA: where BaseViewModel is a INotifyPropertyChanged interface
public ViewModelA:BaseViewModel
{
public ViewModelA()
{
Get = new Command(SendText);
vmB = new ViewModelB();
}
ViewModelB vmB;
public ICommand Get { get; }
private void SendText()
{
string data = "someText";
vmB.GetMetadata(data);
}
}
ViewModelB is like this:
class ViewModelB:BaseViewModel
{
private string _metadata = string.Empty;
public string Metadata
{
get { return _metadata; }
set
{
_metadata = value;
OnPropertyChanged();
}
}
GetMetadata()
{
Metadata = "Some text";
}
}
In ViewModelA there are more properties which I need and in ViewModelB is just one property which gets data from a function. I could make just one ViewModel from both of them which works fine, but I'm trying to keep them smaller and organized. I already tried so many scenarios and is getting really frustrating.
Thanks for helping.
In the second StackLayout in your xaml file you're not binding it's BindingContext property to the ViewModelB instance from ViewModelA but instead you are creating a new one.
Here's a working solution for you:
public class ViewModelA : BaseViewModel
{
public ViewModelB ViewModelB { get; }
public ICommand GetMetadataCommand { get; }
public ViewModelA()
{
ViewModelB = new ViewModelB();
GetMetadataCommand = new Command((_) => GetMetadata());
}
private void GetMetadata()
{
string data = "someText";
ViewModelB.GetMetadata(data);
}
}
public class ViewModelB : BaseViewModel
{
private string _metadata;
public string Metadata
{
get { return _metadata; }
set
{
_metadata = value;
OnPropertyChanged();
}
}
public void GetMetadata(string data)
{
Metadata = data;
}
}
XAMl:
<StackLayout>
<StackLayout x:Name="StackLayout1">
<StackLayout.BindingContext>
<local:ViewModelA />
</StackLayout.BindingContext>
<Button Command ="{Binding GetMetadataCommand}"/>
</StackLayout>
<StackLayout BindingContext="{Binding Source={x:Reference StackLayout1}, Path=BindingContext.ViewModelB}">
<Label Text="{Binding Metadata}" />
</StackLayout>
</StackLayout>
I want to bind my MenuItem from my ViewCell which has a ViewModel.
This is my View cell, Do any one know the proper way do this type of binding?
I have an ObservableCollection<object> that populate my ListView, this the cell I need to bind.
<?xml version="1.0" encoding="UTF-8" ?>
<ViewCell
x:Class="DataTemp.Controls.DeviceViewCell"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Name="this">
<ViewCell.ContextActions>
// I've been trying these two ways
<MenuItem Command="{Binding Source={x:Reference this}, Path=BindingContext.DeviceCommand}" Text="Call" />
<MenuItem Command="{Binding DeviceCommand}" Text="Call" />
</ViewCell.ContextActions>
<ViewCell.View>
<StackLayout Padding="10">
<Label Text="{Binding Name}" />
<Label Text="{Binding Number}" />
</StackLayout>
</ViewCell.View>
</ViewCell>
Here is my view model
I'm trying to catch the event with a a breakpoint, but i never get into the method OnDeviceCommnad.
public class DeviceViewCellViewModel : BaseViewModel, IDevice
{
public string Number
{
get
{
return _numberDevice;
}
set
{
_numberDevice = value;
OnPropertyChanged("Number");
}
}
public string Name
{
get
{
return _nameDevice;
}
set
{
_nameDevice = value;
OnPropertyChanged("Number");
}
}
public ICommand DeviceCommand { get; set; }
private string _nameDevice;
private string _numberDevice;
public DeviceViewCellViewModel()
{
DeviceCommand = new Command(OnDeviceCommnad);
}
private void OnDeviceCommnad()
{
}
}
If you not need to pass a parameter, the second way should work.
<MenuItem Command="{Binding DeviceCommand}" Text="Call" />
And in Model sample code could as follows:
public Command DeviceCommand { get; private set; }
public DeviceViewCellViewModel()
{
DeviceCommand = new Command(() =>
{
// Execute logic here
});
}
=============================Update==================================
From shared sample, I found that the binded MainViewModel not using DeviceViewCellViewModel, therefore the command will not be invoked.
Modify the folloing code inside MainViewModel:
PaymentsAndDevices.Add(new Devices()
{
Number = rdn.Next().ToString(),
Name = "I'm a device"
});
as follows:
PaymentsAndDevices.Add(new DeviceViewCellViewModel()
{
Number = rdn.Next().ToString(),
Name = "I'm a device"
});
Then OnDeviceCommnad method will be invoked.
I am working on providing wishlist feature for my app by tapping wishlist icon on each product in list through MVVM. Once tapped, an API call is made to update database(add/remove from wishlist table). Based on result from api call, I updated the specific product's respective property to either 'True' or 'False'. Once property updated, I want to change the icon image source of corresponding product. I am using trigger on wishlist icon to differentiate non-wishlist and wiahlist products while binding the list itself.
My code is below,
MODEL
public class PublisherProducts
{
public long ProductId { get; set; }
public string ProductName { get; set; }
public string ImageURL { get; set; }
public decimal Price { get; set; }
public bool IsWishlistProduct { get; set; }
}
VIEWMODEL
public class OnlineStoreViewModel : BaseViewModel
{
private ObservableCollection<PublisherProducts> publisherProducts;
public Command<long> WishlistTapCommand { get; }
public OnlineStoreViewModel()
{
publisherProducts = new ObservableCollection<PublisherProducts>();
WishlistTapCommand = new Command<long>(OnWishlistSelected);
}
public ObservableCollection<PublisherProducts> PublisherProducts
{
get { return publisherProducts; }
set
{
publisherProducts = value;
OnPropertyChanged();
}
}
public async Task GetProducts(long selectedCategoryId)
{
try
{
...
PublisherProducts = new ObservableCollection<PublisherProducts>(apiresponse.ProductList);
...
}
catch (Exception ex) { ... }
finally { ... }
}
async void OnWishlistSelected(long tappedProductId)
{
if (tappedProductId <= 0)
return;
else
await UpdateWishlist(tappedProductId);
}
public async Task UpdateWishlist(long productId)
{
try
{
var wishlistResponse = // api call
var item = PublisherProducts.Where(p => p.ProductId == productId).FirstOrDefault();
item.IsWishlistProduct = !item.IsWishlistProduct;
PublisherProducts = publisherProducts; *Stuck here to toggle wishlist icon*
await App.Current.MainPage.DisplayAlert("", wishlistResponse.Message, "Ok");
}
catch (Exception ex) { ... }
finally { ... }
}
}
XAML
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" ... >
<ContentPage.Content>
<ScrollView>
<StackLayout Padding="15,0,15,10">
<FlexLayout x:Name="flxLayout" BindableLayout.ItemsSource="{Binding PublisherProducts}" ...>
<BindableLayout.ItemTemplate>
<DataTemplate>
<AbsoluteLayout Margin="6" WidthRequest="150">
<Frame Padding="0" WidthRequest="150" CornerRadius="10" HasShadow="True">
<StackLayout Orientation="Vertical" Padding="10" HorizontalOptions="FillAndExpand">
<Image Source="{Binding ImageURL}" WidthRequest="130" HeightRequest="130" HorizontalOptions="Center"/>
<Label Text="{Binding ProductName}" Style="{StaticResource ProductNameStyle}"></Label>
...
<StackLayout ...>
...
<Frame x:Name="wlistFrame" Padding="0" WidthRequest="30" HeightRequest="30" CornerRadius="10" BorderColor="#02457A">
<StackLayout Orientation="Horizontal" VerticalOptions="Center" HorizontalOptions="Center">
<Image x:Name="wlImage" WidthRequest="13" HeightRequest="12" HorizontalOptions="Center" VerticalOptions="Center" Source="ic_wishlist_open">
<Image.Triggers>
<DataTrigger TargetType="Image" Binding="{Binding IsWishlistProduct}" Value="true">
<Setter Property="Source" Value="ic_wishlist_close" />
</DataTrigger>
</Image.Triggers>
</Image>
</StackLayout>
<Frame.GestureRecognizers>
<TapGestureRecognizer Command="{Binding Source={RelativeSource AncestorType={x:Type local:OnlineStoreViewModel}}, Path=WishlistTapCommand}" CommandParameter="{Binding ProductId}" NumberOfTapsRequired="1" />
</Frame.GestureRecognizers>
</Frame>
</StackLayout>
</StackLayout>
</Frame>
</AbsoluteLayout>
</DataTemplate>
</BindableLayout.ItemTemplate>
</FlexLayout>
</StackLayout>
</ScrollView>
</ContentPage.Content>
</ContentPage>
I am stuck at this place to change wishlist icon, when 'IsWishlistProduct' property value is changed in UpdateWishlist().
Guessing through your code, the BaseViewModel contains code similar to the following:
public class BaseViewModel : INotifyPropertyChanged
{
...
public event PropertyChangedEventHandler PropertyChanged;
...
public void OnPropertyChanged(string name)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
...
}
And your viewmodel should be like this:
...
public ObservableCollection<PublisherProducts> PublisherProducts
{
get { return publisherProducts; }
set
{
publisherProducts = value;
OnPropertyChanged(nameof(PublisherProducts));
}
}
...
As Jason mentioned, If there is a change in data in the ViewModel, it is reflected in the UI when it is notified to the View through NotifyPropertyChanged. You already implemented "OnPropertyChanged" function in your BaseViewModel but it seems you don't pass the object name.
Following this example to create a grouping for CollectionView, I notice that none of the properties are INotifyPropertyChanged, nor is the base class an ObservableCollection.
While the latter is easy to fix by changing List to ObservableCollection:
public class AnimalGroup : ObservableCollection<Animal>
{
public string Name { get; private set; }
public AnimalGroup(string name, ObservableCollection<Animal> animals) : base(animals)
{
Name = name;
}
private string _someOtherPropertyIWantToChangeAtRuntime = "hey";
public string SomeOtherPropertyIWantToChangeAtRuntime { get => _someOtherPropertyIWantToChangeAtRuntime, set => SetProperty(ref _someOtherPropertyIWantToChangeAtRuntime, value); }
}
It isn't clear how to make Name, or any other property (e.g. SomeOtherPropertyIWantToChangeAtRuntime), I want to associate with the group as an INotifyPropertyChanged. Treating it is as a normal class by adding the interface to base causes this warning:
Base interface 'INotifyPropertyChanged' is redundant because AnimalGroup inherits 'ObservableCollection'
Yet, there is nothing for the setter to call, such as SetProperty(ref _name, Value) and the existing PropertyChanged object is just for monitoring a group's collection changes. It isn't invokable, just handleable.
If I ignore the warning and implement INotifyPropertyChanged anyway (and name my event PropChanged to avoid colliding with ObservableCollection.PropertyChanged),
protected bool SetProperty<T>(ref T backingStore, T value, [CallerMemberName]string propertyName = "", Action onChanged = null)
{
if (EqualityComparer<T>.Default.Equals(backingStore, value))
return false;
backingStore = value;
onChanged?.Invoke();
PropChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
return true;
}
public event PropertyChangedEventHandler PropChanged;
and let my ViewModel manage the value of SomeOtherPropertyIWantToChangeAtRuntime, the bound <Label> never sees any changes.
<CollectionView ItemsSource="{Binding AnimalGroups}" HorizontalOptions="FillAndExpand">
<CollectionView.ItemsLayout>
<LinearItemsLayout Orientation="Vertical"/>
</CollectionView.ItemsLayout>
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout>
<StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand">
<Label
Text="{Binding Name}"
HorizontalOptions="Start"
FontSize="24.44"
TextColor="Black"
FontAttributes="Bold"
Margin="0,0,0,10"/>
<Label
Text="{Binding SomeOtherPropertyIWantToChangeAtRuntime}" FontSize="15"
TextColor="Black"
Margin="0,0,0,0">
<Label.GestureRecognizers>
<TapGestureRecognizer Command="{Binding BindingContext.FindGroupAndChangeTextCommand, Source{x:Reference thisPageName}" CommandParameter="{Binding Name}"/>
</Label.GestureRecognizers>
</Label>
...
ViewModel:
public ObservableCollection<AnimalGroup> AnimalGroups {get; private set;}
public ICommand FindGroupAndChangeTextCommand {get; private set;}
public void FindGroupAndChangeText(string name)
{
var group = AnimalGroups.FirstOrDefault(t => t.Name == name);
if (group != null)
group.SomeOtherPropertyIWantToChangeAtRuntime = DateTime.Now.ToString();
}
ViewModel()
{
AnimalGroups = LoadData(); // not shown
FindGroupAndChangeTextCommand = new Command(FindGroupAndChangeText);
}
The result is that the label remains "hey" (which is the default value) and never changes even though I can see that the above command fires and the code finds the group and sets the text.
Agree with Jason, ObservableCollection has inherited INotifyPropertyChanged interface , So you will get the warning
Base interface 'INotifyPropertyChanged' is redundant because AnimalGroup inherits 'ObservableCollection'
And please see following screenshot about ObservableCollection<T>.
If you want to change the item at the runtime like this GIF.
Based on your code. I add two properties in the Animal class. For achieve the change the text of properties at the runtime, we can achieve the INotifyPropertyChanged in Animal class. Here is AnimalGroup.cs
public class AnimalGroup : ObservableCollection<Animal>
{
public string Name { get; private set; }
public AnimalGroup(string name, ObservableCollection<Animal> animals) : base(animals)
{
Name = name;
}
}
public class Animal : INotifyPropertyChanged
{
string animalName;
public string AnimalName
{
set
{
if (animalName != value)
{
animalName = value;
OnPropertyChanged("AnimalName");
}
}
get
{
return animalName;
}
}
string animalArea;
public string AnimalArea
{
set
{
if (animalArea != value)
{
animalArea = value;
OnPropertyChanged("AnimalArea");
}
}
get
{
return animalArea;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
For testing click the command, I achieve the MyAnimalViewModel.cs like following code.
public class MyAnimalViewModel
{
public ObservableCollection<AnimalGroup> AnimalGroups { get; private set; } = new ObservableCollection<AnimalGroup>();
public ICommand FindGroupAndChangeTextCommand { protected set; get; }
public MyAnimalViewModel()
{
ObservableCollection<Animal> ts = new ObservableCollection<Animal>();
ts.Add(new Animal() { AnimalArea = "Asia", AnimalName = "cat" });
ts.Add(new Animal() { AnimalArea = "Asia", AnimalName = "dog" });
ObservableCollection<Animal> ts2 = new ObservableCollection<Animal>();
ts2.Add(new Animal() { AnimalArea = "Eourp", AnimalName = "keep" });
ts2.Add(new Animal() { AnimalArea = "Eourp", AnimalName = "gggg" });
AnimalGroups.Add(new AnimalGroup("Animal1", ts));
AnimalGroups.Add(new AnimalGroup("Animal2", ts2));
FindGroupAndChangeTextCommand = new Command<Animal>((key) =>
{
key.AnimalName = "testggggg";
});
}
}
I notice you want to achieve the group for CollectionView. Here is my edited layout.
<ContentPage.Content>
<CollectionView x:Name="MyCollectionView" ItemsSource="{Binding AnimalGroups}" IsGrouped="True" HorizontalOptions="FillAndExpand">
<CollectionView.ItemsLayout>
<LinearItemsLayout Orientation="Vertical"/>
</CollectionView.ItemsLayout>
<CollectionView.GroupHeaderTemplate>
<DataTemplate>
<Label Text="{Binding Name}"
BackgroundColor="LightGray"
FontSize="Large"
FontAttributes="Bold" >
</Label>
</DataTemplate>
</CollectionView.GroupHeaderTemplate>
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout>
<StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand">
<Label
Text="{Binding AnimalArea}"
HorizontalOptions="Start"
FontSize="24.44"
TextColor="Black"
FontAttributes="Bold"
Margin="0,0,0,10"/>
<Label
Text="{Binding AnimalName}" FontSize="15"
TextColor="Black"
Margin="0,0,0,0">
<Label.GestureRecognizers>
<TapGestureRecognizer NumberOfTapsRequired="1"
Command="{ Binding BindingContext.FindGroupAndChangeTextCommand, Source={x:Reference Name=MyCollectionView} }" CommandParameter="{Binding .}"
/>
</Label.GestureRecognizers>
</Label>
</StackLayout>
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</ContentPage.Content>
Here is layout background code.
public partial class Page2 : ContentPage
{
public Page2()
{
InitializeComponent();
this.BindingContext = new MyAnimalViewModel();
}
}
In my Xamarin.Forms app, I have a ListView and am binding to the SelectedItem property:
<ListView x:Name="MyListView" ItemsSource="{Binding MyItems}" IsVisible="{Binding Expanded}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}" SelectionMode="Single" SeparatorVisibility="None">
<!-- not relevant code -->
</ListView>
When I run it on UWP, my SelectedItem property in my view model gets set when I select an item in the list. But not in ios. Am I doing something wrong? Or is there a work around?
I wrote a simple demo and it works on my side. Here is the code:
<ListView x:Name="testListView"
Style="{StaticResource ListStyle}" SelectedItem="{Binding YourSelectedItem, Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout>
<Label Text="{Binding Name}"/>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Then in your view-model(viewModel should implement INotifyPropertyChanged):
class testViewModel : INotifyPropertyChanged
{
public string Name { get; set; }
private testViewModel _yourSelectedItem { get; set; }
public testViewModel YourSelectedItem
{
get
{
return _yourSelectedItem;
}
set
{
_yourSelectedItem = value;
OnPropertyChanged("YourSelectedItem");
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
And in the MainPage, set the BindingContext = new testViewModel();:
public partial class MainPage : ContentPage
{
ObservableCollection<testViewModel> myModels = new ObservableCollection<testViewModel>();
testViewModel model;
public MainPage()
{
InitializeComponent();
myModels.Add(new testViewModel { Name = "age" });
myModels.Add(new testViewModel { Name = "gender" });
myModels.Add(new testViewModel { Name = "name" });
testListView.ItemsSource = myModels;
BindingContext = new testViewModel();
}
}
Try it and let me know if it works for you.