For Xamarin Forms for Android and IOS, how do I display a status indicator (not an activity indicator) showing up to 4 unique states of the server, data or other objects, all set in the code behind with binded objects/strings/ints?
Skia sharp and RoundedBoxView are two libraries that I've found, however they're significantly more complex to implement that I was hoping for.
Essentially what I'm looking for is to display one of the following in a grid:
Error (Red)
Warning (Yellow)
No problems (Green)
Other/TBD (Grey)
Thank you for your time and assistance. The answer MUST be in Xamarin.Forms instead of native platform specific. I also greatly prefer something that already exists in Xamarin.Forms instead of getting another library and implementing it but not opposed to it.
how do I display a status indicator (not an activity indicator) showing up to 4 unique states of the server, data or other objects, all set in the code behind with binded objects/strings/ints?
But is there a way to disable the animation and fill it so its solid.
If just want to display a Solid circle, then the BoxView can also do it and change the color.
Set CornerRadius property of BoxView can show as a circle .
Just binding Color property of BoxView to ViewModel,and converting the value of Color by IValueConverter.
If want color dynamic changed, also need to use INotifyPropertyChanged in ViewModel.
Xmal file:
<?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:PickerCase="clr-namespace:PickerCase" //PickerCase is project namespace
x:Class="PickerCase.NextPage"> //NextPage is current page name
<ContentPage.Resources>
<ResourceDictionary>
<PickerCase:StringToColorConverter x:Key="StringToColorConverter"/>
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
<StackLayout>
<BoxView Color="{Binding MyColor, Converter={StaticResource StringToColorConverter}}"
HorizontalOptions="Center"
WidthRequest="40"
HeightRequest="40"
CornerRadius="20"/>
</StackLayout>
</ContentPage.Content>
Creating a StringToColorConverter.cs file to convert color by string value:
public class StringToColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
//throw new NotImplementedException();
string valueAsString = value.ToString();
switch (valueAsString)
{
case ("Red"):
{
return Color.Red;
}
case ("Yellow"):
{
return Color.Yellow;
}
case ("Green"):
{
return Color.Green;
}
case ("Gray"):
{
return Color.Gray;
}
default:
{
return Color.FromHex(value.ToString());
}
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
//throw new NotImplementedException();
return null;
}
}
ViewModel add MyColor property ,and OnPropertyChanged it.
class SecondDataModel : INotifyPropertyChanged
{
private string mycolor = "Gray"; //Default color is Gray
public string MyColor
{
set
{
if (mycolor != value)
{
mycolor = value;
OnPropertyChanged("MyColor");
}
}
get
{
return mycolor;
}
}
public SecondDataModel()
{
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Finally in ContentPage bind this ViewModel:
SecondDataModel secondDataModel;
...
secondDataModel = new SecondDataModel();
BindingContext = secondDataModel;
When the data from API Server, you can change color as follow:
secondDataModel.MyColor = "Red";
...
secondDataModel.MyColor = "Yelow";
...
secondDataModel.MyColor = "Green";
An alternative/slightly different implementation to Junior Jiang's solution is to have a Converter which converts to an Image rather than converting colours. You can then have a different Image asset for each status.
Note using an ActivityIndicator would be horrible! The implementation on different platforms is different, and would just not look right.
I am struggling how I could replicate the drop-down ToolbarItem from Xamarin.Forms when a ToolbarItem's order is set to Secondary for IOS, in order for it to look like it does for Android.
Here are some images to better explain what I am looking for:
How it works on Android:
Code:
ToolbarItem toolbarItem = new ToolbarItem()
{
Text = "ToolbarItem",
Order = ToolbarItemOrder.Secondary
};
Images on how it looks on Android:
Image showing the "More" icon
Image showing the "More" icon expanded to show more toolbar items
There is no default "More" icon on the toolbar when setting the Order to Secondary in iOS. Instead what happens, is that a bar below the navigation bar is created, which includes all of the toolbar items - something I do not wish to have for my Application.
This is an example of how it has been achieved before on IOS:
A screenshot I took from one of my Apps that implements this
effect
In native iOS, you can use UIPopoverController to achieve your effect. But please notice that this control can only be used in iPad.
Since you are using Xamarin.Forms, we can create a custom renderer in iOS platform to get this.
Firstly, create a page renderer to display the UIPopoverController. We can show it from a UIBarButtonItem or a UIView depending on your request. Here I use UIBarButtonItem like:
//I defined the navigateItem in the method ViewWillAppear
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
rightItem = new UIBarButtonItem("More", UIBarButtonItemStyle.Plain, (sender, args) =>
{
UIPopoverController popView = new UIPopoverController(new ContentViewController());
popView.PopoverContentSize = new CGSize(200, 300);
popView.PresentFromBarButtonItem(rightItem, UIPopoverArrowDirection.Any, true);
});
NavigationController.TopViewController.NavigationItem.SetRightBarButtonItem(leftItem, true);
}
Secondly, construct the content ViewController in the UIPopoverController(just like the secondary list in android):
public class ContentViewController : UIViewController
{
public override void ViewDidLoad()
{
base.ViewDidLoad();
UITableView tableView = new UITableView(new CGRect(0, 0, 200, 300));
tableView.Source = new MyTableViewSource();
View.AddSubview(tableView);
}
}
public class MyTableViewSource : UITableViewSource
{
public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
{
UITableViewCell cell = tableView.DequeueReusableCell(new NSString("Cell"));
if (cell == null)
{
cell = new UITableViewCell(UITableViewCellStyle.Default, new NSString("Cell"));
}
cell.TextLabel.Text = "Item" + indexPath.Row;
return cell;
}
public override nint RowsInSection(UITableView tableview, nint section)
{
return 10;
}
}
At last we can show it on the screen by calling PresentFromBarButtonItem.
Lets say there is a login page with username\password TextFields and login Button. When the button is pressed a request is set to a server and ActivityIndicator is shown.
Currently I put StackLayout on top of all other controls not to give the user a possibility to click on them while processing the request. But in some cases TextField stays focused and the user can type there.
I'm already using a component to wrap all TextFields to show validation errors:
#Component({
selector: "field",
template: "<grid-layout><ng-content></ng-content>...</grid-layout>"
})
export class FieldComponent {
#ContentChild(NgModel) private input: NgModel;
...
}
My question is can I set isEnabled property to false on TextField inside ng-content from FieldComponent having NgModel or in some another way?
If it is impossible what is the best practices in this case to disable inputs when an app is busy?
Here is my solution for NativeScript+Angular:
setControlInteractionState() is recursive.
the TextField cursor is hidden (using native android API).
XML:
<GridLayout #mainGrid rows="*" columns="*">
<!-- Main page content here... -->
<GridLayout *ngIf="isBusy" rows="*" columns="*">
<GridLayout rows="*" columns="*" style="background-color: black; opacity: 0.35">
</GridLayout>
<ActivityIndicator width="60" height="60" busy="true">
</ActivityIndicator>
</GridLayout>
</GridLayout>
or
<GridLayout #mainGrid rows="*" columns="*">
<!-- Main page content here... -->
</GridLayout>
<GridLayout *ngIf="isBusy" rows="*" columns="*">
<GridLayout rows="*" columns="*" style="background-color: black; opacity: 0.35">
</GridLayout>
<ActivityIndicator width="60" height="60" busy="true">
</ActivityIndicator>
</GridLayout>
TypeScript:
import { Component, ViewChild, ElementRef } from "#angular/core";
import { View } from "ui/core/view";
import { LayoutBase } from "ui/layouts/layout-base";
import { isAndroid, isIOS } from "platform";
#Component({
templateUrl: "./SignIn.html"
})
export class SignInComponent {
#ViewChild("mainGrid")
MainGrid: ElementRef;
isBusy: boolean = false;
submit() : void {
try {
this.isBusy = true;
setControlInteractionState(<View>this.MainGrid.nativeElement, false);
//sign-in here...
}
finally {
this.isBusy = false;
setControlInteractionState(<View>this.MainGrid.nativeElement, true);
}
}
setControlInteractionState(view: View, isEnabled: boolean) : void {
view.isUserInteractionEnabled = isEnabled;
if (isAndroid) {
if (view.android instanceof android.widget.EditText) {
let control = <android.widget.EditText>view.android;
control.setCursorVisible(isEnabled);
}
}
if (view instanceof LayoutBase) {
let layoutBase = <LayoutBase>view;
for (let i = 0, length = layoutBase.getChildrenCount(); i < length; i++) {
let child = layoutBase.getChildAt(i);
setControlInteractionState(child, isEnabled);
}
}
}
}
NS 2.5.0
There are a couple way you can do this;
You can use a ngIf or binding on isEnabled to disable it based on a data bound value.
You can create a simple routine that you call (my preferred method).
require("nativescript-dom");
function screenEnabled(isEnabled) {
runAgainstTagNames('TextEdit', function(e) { e.isEnabled = isEnabled; });
runAgainstTagNames('Button', function(e) { e.isEnabled = isEnabled; });
}
The nativescript-dom plugin has the runAgainst*, or getElementBy* wrappers to talk to the native layer like you were talking to a html dom.
Full disclosure, I'm the author of nativescript-dom, it is one of the plugins that I use in almost every app/demo I do.
I found an easiest solution in Angular, so i am posting here for any future reference. First in app.component.html file i added a Grid and ScrollView like following:
<GridLayout>
<page-router-outlet></page-router-outlet>
<!-- hack to block UI -->
<ScrollView isUserInteractionEnabled="false" *ngIf="isLoading">
<ActivityIndicator busy="true"></ActivityIndicator>
</ScrollView>
</GridLayout>
Notice the page-router-outlet which is inside the Grid. By default it will be place at row="0". The next thing is ScrollView which has isUserInteractionEnabled set to false.
Now in your app.component.ts file add a a variable called isLoading and toggle it using some kind of events e.g RxJs Observable events
Expanding #KTCO's answer to get the size of the overlay exactly the same as the main grid:
import { Size, View } from "tns-core-modules/ui/core/view";
import { GridLayout } from "tns-core-modules/ui/layouts/grid-layout/grid-layout";
...
...
dialogSize: Size;
mainGrid: GridLayout;
...
submit() {
this.mainGrid = <GridLayout>this.MainGrid.nativeElement;
this.dialogSize = this.mainGrid.getActualSize();
.....
.....
<GridLayout *ngIf="isBusy" rows="auto" columns="auto">
<GridLayout rows="*" columns="*" [width]="dialogSize.width" [height]="dialogSize.height" style="background-color: black; opacity: 0.35">
</GridLayout>
<ActivityIndicator width="50" height="50" busy="true">
</ActivityIndicator>
</GridLayout>
I know this is a little old, but sometimes I just got to do things my way. If you want to accomplish this programmatically:
const excludedView = someViewToBeExcluded;
const enabler = (parentView:View, enable:boolean) => {
parentView.eachChildView(childView => {
if (childView != excludedView) {
enabler(childView, enable);
childView.isEnabled = enable;
}
return true;
});
};
enabler(page, false);
Note: This will not disable/enable the initial parentView (ie. the page in this example)
When I write text in entry view in xamarin.forms I alway have underline under the text
I search all the web for a solution - it was to change the background to null or transparent BUT its not working.
is there any other solution ?
I know this is an old question but it seems to get viewed/asked a lot, and Xamarin still hasn't added built-in support for customizing this very basic UI feature, so I will post an answer here that will hopefully be helpful. Also most answers you will find online (including the Microsoft documentation) show you how to create a static custom renderer, but what we really want is a control where we can set properties in shared code like with any other control. I figured out how to do this so I will share here. I've also included a property for setting border color and width since this is a common UI element we like to set.
In your shared project create a class called CustomEntry (you can rename this later if you wish).
using Xamarin.Forms;
namespace CustomizedControl
{
public class CustomEntry : Entry
{
public Color BorderColor { get; set; }
public int BorderThickness { get; set; }
public bool HasUnderline { get; set; }
}
}
In your Android project create a class called CustomEntryAndroid and paste in this code:
using Android.Content;
using Android.Graphics;
using Android.Graphics.Drawables;
using CustomizedControl;
using CustomizedControl.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
[assembly: ExportRenderer(typeof(CustomEntry), typeof(CustomEntryAndroid))]
namespace CustomizedControl.Droid
{
public class CustomEntryAndroid : EntryRenderer
{
public CustomEntryAndroid(Context context) : base(context)
{ }
private bool HasUnderline;
protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
{
base.OnElementChanged(e);
if (Control != null)
{
var element = (CustomEntry)Element;
HasUnderline = element.HasUnderline;
var BorderClr = element.BorderColor.ToAndroid();
if (HasUnderline == false)
{
GradientDrawable gd = new GradientDrawable();
gd.SetColor(Android.Graphics.Color.Transparent);
Control.SetBackgroundDrawable(gd); //this is depreciated but it doesn't matter, the new method SetBackgroud simply calls SetBackgroundDrawable
} //Else maintain default underline
if (BorderClr != Android.Graphics.Color.Transparent)
{
int borderThickness = element.BorderThickness;
if (borderThickness == 0) { borderThickness = 1; } //in case border thickness was not set then default to 1
var brdr = new ShapeDrawable(new Android.Graphics.Drawables.Shapes.RectShape());
brdr.Paint.Color = BorderClr;
brdr.Paint.SetStyle(Paint.Style.Stroke);
Control.Background = brdr;
GradientDrawable gd = new GradientDrawable();
gd.SetColor(Android.Graphics.Color.Transparent);
gd.SetStroke(borderThickness, BorderClr);
Control.SetBackground(gd);
}
}//end if
}//end OnElementChanged
}//end public class CustomEntryAndroid
}//end NameSpace
You can now use the custom entry in any xaml page and get rid of the underline like this:
<local:CustomEntry HasUnderline="False" />
Here is a very simple content page with pretty much nothing on it but an entry:
<?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:local="clr-namespace:CustomizedControl"
x:Class="CustomizedControl.MainPage">
<StackLayout Padding="30">
<local:CustomEntry Text="Test text" WidthRequest="250" HorizontalOptions="Start" HasUnderline="False" />
</StackLayout>
</ContentPage>
Note the import statement xmlns:local="clr-namespace:CustomizedControl". Here is the output:
Now with the underline attribute set to true:
<local:CustomEntry Text="Test text" WidthRequest="250" HorizontalOptions="Start" HasUnderline="True" />
And finally with a border:
<local:CustomEntry Text="Test text" WidthRequest="250" HorizontalOptions="Start" BorderColor="Purple" />
Notice I did not specify a width in the xaml but the border still appeared. This is because I set the default width to 1 in the Android custom renderer. But you can set the width thicker like this BorderThickness="6" or modify the default behavior if you wanted to.
One final note: the namespace I used for this project is "CustomizedControl", so you will of course need to replace "CustomizedControl" with whatever your namespace is.
Take a look here
http://geeks.ms/xamarinteam/2015/04/20/branding-a-xamarin-forms-app-on-android-accent-color/
Your ask was a little obscure, but I think the link above can help you ... you just need to set the underline color for all status as same to the background or transparent.
in Android 5.0 devices, which use the specified accent color you can just change the color, another hand, in androids 4.< you need to create an image
Using Xamarin.Forms, how can I define the highlight/background color of a selected/tapped ListView item?
(My list has a black background and white text color, so the default highlight color on iOS is too bright. In contrast, on Android there is no highlighting at all - up to a subtle horizontal gray line.)
Example: (left: iOS, right: Android; while pressing "Barn2")
In Android simply edit your styles.xml file under Resources\values adding this:
<resources>
<style name="MyTheme" parent="android:style/Theme.Material.Light.DarkActionBar">
<item name="android:colorPressedHighlight">#color/ListViewSelected</item>
<item name="android:colorLongPressedHighlight">#color/ListViewHighlighted</item>
<item name="android:colorFocusedHighlight">#color/ListViewSelected</item>
<item name="android:colorActivatedHighlight">#color/ListViewSelected</item>
<item name="android:activatedBackgroundIndicator">#color/ListViewSelected</item>
</style>
<color name="ListViewSelected">#96BCE3</color>
<color name="ListViewHighlighted">#E39696</color>
</resources>
It looks like there is actually a cross-platform way to do this that works on both iOS and Android (not sure about Windows). It uses only binding and does not require custom renderers (which seems rare). This is a mash-up of lots of googling, so thanks to anyone who I may have borrowed from...
I am assuming ViewCells, but this should work for Text or Image cells as well. I am only including the relevant code here beyond the typical text, image, etc.
On your page do something like this:
MyModel model1 = new MyModel();
MyModel model2 = new MyModel();
ListView list = new ListView
{
ItemsSource = new List<MyModel> { model1, model2 };
ItemTemplate = new DataTemplate( typeof(MyCell) )
};
Your custom Model might look something like this:
public class MyModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private Color _backgroundColor;
public Color BackgroundColor
{
get { return _backgroundColor; }
set
{
_backgroundColor = value;
if ( PropertyChanged != null )
{
PropertyChanged( this, new PropertyChangedEventArgs( "BackgroundColor" ) );
}
}
}
public void SetColors( bool isSelected )
{
if ( isSelected )
{
BackgroundColor = Color.FromRgb( 0.20, 0.20, 1.0 );
}
else
{
BackgroundColor = Color.FromRgb( 0.95, 0.95, 0.95 );
}
}
}
Then for your ItemTemplate you need a custom cell class something like this:
public class MyCell : ViewCell
{
public MyCell() : base()
{
RelativeLayout layout = new RelativeLayout();
layout.SetBinding( Layout.BackgroundColorProperty, new Binding( "BackgroundColor" ) );
View = layout;
}
}
Then in your ItemSelected event handler, do the following. Note that 'selected' is an instance of MyModel used to track the currently selected item. I am only showing background color here, but I also use this technique to reverse highlight the text and detail text colors.
private void ItemSelected( object sender, ItemTappedEventArgs args )
{
// Deselect previous
if ( selected != null )
{
selected.SetColors( false );
}
// Select new
selected = (list.SelectedItem as MyModel);
selected.SetColors( true );
}
iOS
Solution:
Within a custom ViewCellRenderer you can set the SelectedBackgroundView. Simply create a new UIView with a background color of your choice and you're set.
public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell, UITableView tv)
{
var cell = base.GetCell(item, reusableCell, tv);
cell.SelectedBackgroundView = new UIView {
BackgroundColor = UIColor.DarkGray,
};
return cell;
}
Result:
Note:
With Xamarin.Forms it seems to be important to create a new UIView rather than just setting the background color of the current one.
Android
Solution:
The solution I found on Android is a bit more complicated:
Create a new drawable ViewCellBackground.xml within the Resources>drawable folder:
<?xml version="1.0" encoding="UTF-8" ?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true" >
<shape android:shape="rectangle">
<solid android:color="#333333" />
</shape>
</item>
<item>
<shape android:shape="rectangle">
<solid android:color="#000000" />
</shape>
</item>
</selector>
It defines solid shapes with different colors for the default state and the "pressed" state of a UI element.
Use a inherited class for the View of your ViewCell, e.g.:
public class TouchableStackLayout: StackLayout
{
}
Implement a custom renderer for this class setting the background resource:
public class ElementRenderer: VisualElementRenderer<Xamarin.Forms.View>
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.View> e)
{
SetBackgroundResource(Resource.Drawable.ViewCellBackground);
base.OnElementChanged(e);
}
}
Result:
To change color of selected ViewCell, there is a simple process without using custom renderer. Make Tapped event of your ViewCell as below
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell Tapped="ViewCell_Tapped">
<Label Text="{Binding StudentName}" TextColor="Black" />
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
In your ContentPage or .cs file, implement the event
private void ViewCell_Tapped(object sender, System.EventArgs e)
{
if(lastCell!=null)
lastCell.View.BackgroundColor = Color.Transparent;
var viewCell = (ViewCell)sender;
if (viewCell.View != null)
{
viewCell.View.BackgroundColor = Color.Red;
lastCell = viewCell;
}
}
Declare lastCell at the top of your ContentPage like this ViewCell lastCell;
Only for Android
Add in your custom theme or your default theme under ProjectName.Android/Resources/values/styles.xml
<item name="android:colorActivatedHighlight">#android:color/transparent</item>
I have a similar process, completely cross platform, however I track the selection status myself and I have done this in XAML.
<ListView x:Name="ListView" ItemsSource="{Binding ListSource}" RowHeight="50">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<ContentView Padding="10" BackgroundColor="{Binding BackgroundColor}">
<Label Text="{Binding Name}" HorizontalOptions="Center" TextColor="White" />
</ContentView>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Then in the ItemTapped Event
ListView.ItemTapped += async (s, e) =>
{
var list = ListSource;
var listItem = list.First(c => c.Id == ((ListItem)e.Item).Id);
listItem.Selected = !listItem.Selected;
SelectListSource = list;
ListView.SelectedItem = null;
};
As you can see I just set the ListView.SelectedItem to null to remove any of the platform specific selection styles that come into play.
In my model I have
private Boolean _selected;
public Boolean Selected
{
get => _selected;
set
{
_selected = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("BackgroundColor"));
}
}
public Color BackgroundColor
{
get => Selected ? Color.Black : Color.Blue;
}
I had this same issue and I solved it as well by creating a custom renderer for iOS as Falko suggests, however, I avoided the styles modification for Android, I figured out a way to use a custom renderer for Android as well.
It is kind of funky how the selected flag is always false for the android view cell that's why I had to create a new private property to track it. but other than that I think this follows a more appropriate pattern if you want to use custom renderers for both platforms, In my case I did it for TextCell but I believe it applies the same way for other CellViews.
Xamarin Forms
using Xamarin.Forms;
public class CustomTextCell : TextCell
{
/// <summary>
/// The SelectedBackgroundColor property.
/// </summary>
public static readonly BindableProperty SelectedBackgroundColorProperty =
BindableProperty.Create("SelectedBackgroundColor", typeof(Color), typeof(CustomTextCell), Color.Default);
/// <summary>
/// Gets or sets the SelectedBackgroundColor.
/// </summary>
public Color SelectedBackgroundColor
{
get { return (Color)GetValue(SelectedBackgroundColorProperty); }
set { SetValue(SelectedBackgroundColorProperty, value); }
}
}
iOS
public class CustomTextCellRenderer : TextCellRenderer
{
public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell, UITableView tv)
{
var cell = base.GetCell(item, reusableCell, tv);
var view = item as CustomTextCell;
cell.SelectedBackgroundView = new UIView
{
BackgroundColor = view.SelectedBackgroundColor.ToUIColor(),
};
return cell;
}
}
Android
public class CustomTextCellRenderer : TextCellRenderer
{
private Android.Views.View cellCore;
private Drawable unselectedBackground;
private bool selected;
protected override Android.Views.View GetCellCore(Cell item, Android.Views.View convertView, ViewGroup parent, Context context)
{
cellCore = base.GetCellCore(item, convertView, parent, context);
// Save original background to rollback to it when not selected,
// We assume that no cells will be selected on creation.
selected = false;
unselectedBackground = cellCore.Background;
return cellCore;
}
protected override void OnCellPropertyChanged(object sender, PropertyChangedEventArgs args)
{
base.OnCellPropertyChanged(sender, args);
if (args.PropertyName == "IsSelected")
{
// I had to create a property to track the selection because cellCore.Selected is always false.
// Toggle selection
selected = !selected;
if (selected)
{
var customTextCell = sender as CustomTextCell;
cellCore.SetBackgroundColor(customTextCell.SelectedBackgroundColor.ToAndroid());
}
else
{
cellCore.SetBackground(unselectedBackground);
}
}
}
}
...then, in the .xaml page, you need to add an XMLNS reference back to the new CustomViewCell...
xmlns:customuicontrols="clr-namespace:MyMobileApp.CustomUIControls"
And don't forget to make actual use of the new Custom comtrol in your XAML.
Here is the purely cross platform and neat way:
1) Define a trigger action
namespace CustomTriggers {
public class DeselectListViewItemAction:TriggerAction<ListView> {
protected override void Invoke(ListView sender) {
sender.SelectedItem = null;
}
}
}
2) Apply the above class instance as an EventTrigger action in XAML as below
<ListView x:Name="YourListView" ItemsSource="{Binding ViewModelItems}">
<ListView.Triggers>
<EventTrigger Event="ItemSelected">
<customTriggers:DeselectListViewItemAction></customTriggers:DeselectListViewItemAction>
</EventTrigger>
</ListView.Triggers>
</ListView>
Don't forget to add xmlns:customTriggers="clr-namespace:CustomTriggers;assembly=ProjectAssembly"
Note: Because none of your items are in selected mode, selection styling will not get applied on either of the platforms.
I have & use a solution similar to #adam-pedley.
No custom renderers, in xaml i bind background ViewCell Property
<ListView x:Name="placesListView" Grid.Row="2" Grid.ColumnSpan="3" ItemsSource="{Binding PlacesCollection}" SelectedItem="{Binding PlaceItemSelected}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid BackgroundColor="{Binding IsSelected,Converter={StaticResource boolToColor}}">
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Label Grid.Row="1" Grid.ColumnSpan="2" Text="{Binding DisplayName}" Style="{StaticResource blubeLabelBlackItalic}" FontSize="Default" HorizontalOptions="Start" />
<Label Grid.Row="2" Grid.ColumnSpan="2" Text="{Binding DisplayDetail}" Style="{StaticResource blubeLabelGrayItalic}" FontSize="Small" HorizontalOptions="Start"/>
<!--
<Label Grid.RowSpan="2" Grid.ColumnSpan="2" Text="{Binding KmDistance}" Style="{StaticResource blubeLabelGrayItalic}" FontSize="Default" HorizontalOptions="End" VerticalOptions="Center"/>
-->
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
In code (MVVM) i save the lastitemselected by a boolToColor Converter i update background color
public class BoolToColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (bool)value ? Color.Yellow : Color.White;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return (Color)value == Color.Yellow ? true : false;
}
}
PlaceItem LastItemSelected;
PlaceItem placeItemSelected;
public PlaceItem PlaceItemSelected
{
get
{
return placeItemSelected;
}
set
{
if (LastItemSelected != null)
LastItemSelected.IsSelected = false;
placeItemSelected = value;
if (placeItemSelected != null)
{
placeItemSelected.IsSelected = true;
LastItemSelected = placeItemSelected;
}
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(PlaceItemSelected)));
}
}
My example is extracted by a listview of places which are in a Xamarin Forms Maps (same contentpage).
I hope this solution will be usefull for somebody
In order to set the color of highlighted item you need to set the color of cell.SelectionStyle in iOS.
This example is to set the color of tapped item to transparent.
If you want you can change it with other colors from UITableViewCellSelectionStyle. This is to be written in the platform project of iOS by creating a new Custom ListView renderer in your Forms project.
public class CustomListViewRenderer : ListViewRenderer
{
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (Control == null)
{
return;
}
if (e.PropertyName == "ItemsSource")
{
foreach (var cell in Control.VisibleCells)
{
cell.SelectionStyle = UITableViewCellSelectionStyle.None;
}
}
}
}
For android you can add this style in your values/styles.xml
<style name="ListViewStyle.Light" parent="android:style/Widget.ListView">
<item name="android:listSelector">#android:color/transparent</item>
<item name="android:cacheColorHint">#android:color/transparent</item>
</style>
This solution works fine, but if you change the caching strategy of the ListView away from the default value it stops working. It works if you new up your ListView like this:
listView = new ListView() { ... };
But if you do this it does not work (the background stays grey for the selected item):
listView = new ListView(cachingStrategy:ListViewCachingStrategy.RecycleElement) { ... };
Below is a solution that works even with a non-standard cachingStrategy. I prefer this to other solutions like having code in the OnItemSelected method coupled with a binding from the ViewModel for the background color.
Credit to #Lang_tu_bi_dien who posted the idea here: Listview Selected Item Background Color
The final code then looks like this:
Xamarin.Forms code:
namespace MyProject
{
public class ListView2 : ListView
{
public ListView2(ListViewCachingStrategy cachingStrategy) : base(cachingStrategy)
{
}
}
}
XAML on your page:
<ListView2 x:Name="myListView" ListViewCachingStrategy="RecycleElement" ItemsSource="{Binding ListSource}" RowHeight="50">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<Label Text="{Binding Name}" HorizontalOptions="Center" TextColor="White" />
</ContentView>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView2>
iOS-specific renderer:
[assembly: ExportRenderer(typeof(ListView2), typeof(ListView2Renderer))]
namespace MyProject.iOS
{
public partial class ListView2Renderer : ListViewRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<ListView> e)
{
base.OnElementChanged(e);
if (Control != null && e != null)
{
//oldDelegate = (UITableViewSource)Control.Delegate;
Control.Delegate = new ListView2Delegate(e.NewElement);
}
}
}
class ListView2Delegate : UITableViewDelegate
{
private ListView _listView;
internal ListView2Delegate(ListView listView)
{
_listView = listView;
}
public override void WillDisplay(UITableView tableView, UITableViewCell cell, Foundation.NSIndexPath indexPath)
{
cell.SelectedBackgroundView = new UIView()
{
BackgroundColor = Color.Red.ToUIColor()
};
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
_listView = null;
}
base.Dispose(disposing);
}
}
}
Note: you may run into some issues due to the fact that you are replacing the default delegate, for more info on this see Setting delegate of control in custom renderer results in lost functionality. In my project it all works as it should if I do this:
Use the normal ListView together with the ListItemViewCellRenderer code given in in the earlier posts on this thread for ListViews that use the default caching strategy ListViewCachingStrategy.RetainElement.
Use this ListView2 together for ListViews that use a non-default caching strategy i.e. ListViewCachingStrategy.RecycleElement or ListViewCachingStrategy.RecycleElementAndDataTemplate.
I am also filing a feature request with Xamarin, please upvote it if you feel this should be added to the standard ListView: ListView desperately needs a SelectedItemBackgroundColor property
Found this lovely option using effects here.
iOS:
[assembly: ResolutionGroupName("MyEffects")]
[assembly: ExportEffect(typeof(ListViewHighlightEffect), nameof(ListViewHighlightEffect))]
namespace Effects.iOS.Effects
{
public class ListViewHighlightEffect : PlatformEffect
{
protected override void OnAttached()
{
var listView = (UIKit.UITableView)Control;
listView.AllowsSelection = false;
}
protected override void OnDetached()
{
}
}
}
Android:
[assembly: ResolutionGroupName("MyEffects")]
[assembly: ExportEffect(typeof(ListViewHighlightEffect), nameof(ListViewHighlightEffect))]
namespace Effects.Droid.Effects
{
public class ListViewHighlightEffect : PlatformEffect
{
protected override void OnAttached()
{
var listView = (Android.Widget.ListView)Control;
listView.ChoiceMode = ChoiceMode.None;
}
protected override void OnDetached()
{
}
}
}
Forms:
ListView_Demo.Effects.Add(Effect.Resolve($"MyEffects.ListViewHighlightEffect"));
The easiest way to accomplish this on android is by adding the following code to your custom style :
#android:color/transparent
The previous answers either suggest custom renderers or require you to keep track of the selected item either in your data objects or otherwise. This isn't really required, there is a way to link to the functioning of the ListView in a platform agnostic way. This can then be used to change the selected item in any way required. Colors can be modified, different parts of the cell shown or hidden depending on the selected state.
Let's add an IsSelected property to our ViewCell. There is no need to add it to the data object; the listview selects the cell, not the bound data.
public partial class SelectableCell : ViewCell {
public static readonly BindableProperty IsSelectedProperty = BindableProperty.Create(nameof(IsSelected), typeof(bool), typeof(SelectableCell), false, propertyChanged: OnIsSelectedPropertyChanged);
public bool IsSelected {
get => (bool)GetValue(IsSelectedProperty);
set => SetValue(IsSelectedProperty, value);
}
// You can omit this if you only want to use IsSelected via binding in XAML
private static void OnIsSelectedPropertyChanged(BindableObject bindable, object oldValue, object newValue) {
var cell = ((SelectableCell)bindable);
// change color, visibility, whatever depending on (bool)newValue
}
// ...
}
To create the missing link between the cells and the selection in the list view, we need a converter (the original idea came from the Xamarin Forum):
public class IsSelectedConverter : IValueConverter {
public object Convert(object value, Type targetType, object parameter, CultureInfo culture) =>
value != null && value == ((ViewCell)parameter).View.BindingContext;
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
throw new NotImplementedException();
}
We connect the two using this converter:
<ListView x:Name="ListViewName">
<ListView.ItemTemplate>
<DataTemplate>
<local:SelectableCell x:Name="ListViewCell"
IsSelected="{Binding SelectedItem, Source={x:Reference ListViewName}, Converter={StaticResource IsSelectedConverter}, ConverterParameter={x:Reference ListViewCell}}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
This relatively complex binding serves to check which actual item is currently selected. It compares the SelectedItem property of the list view to the BindingContext of the view in the cell. That binding context is the data object we actually bind to. In other words, it checks whether the data object pointed to by SelectedItem is actually the data object in the cell. If they are the same, we have the selected cell. We bind this into to the IsSelected property which can then be used in XAML or code behind to see if the view cell is in the selected state.
There is just one caveat: if you want to set a default selected item when your page displays, you need to be a bit clever. Unfortunately, Xamarin Forms has no page Displayed event, we only have Appearing and this is too early for setting the default: the binding won't be executed then. So, use a little delay:
protected override async void OnAppearing() {
base.OnAppearing();
Device.BeginInvokeOnMainThread(async () => {
await Task.Delay(100);
ListViewName.SelectedItem = ...;
});
}
The easiest way to change the selection color is adding these to your Android.Resources.values.styles
<item name="android:colorPressedHighlight">#android:color/holo_blue_bright</item>
<item name="android:colorFocusedHighlight">#android:color/holo_blue_bright</item>
<item name="android:colorActivatedHighlight">#android:color/holo_blue_bright</item>