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Converters
A converter that can be used with a Binding to a boolean value. The converter will return a inverted boolean value.
<Label Text="Welcome to Xamarin"
IsVisible="{Binding SomeLogicalProperty, Converter={dui:InvertedBoolConverter}}" />A converter that can be used with different input values. It will return a boolean value indicating whether or not the input value is empty. It also has the ability to be inverted.
<Label Text="Is visible if list is empty"
IsVisible="{Binding EmptyListOfStrings, Converter={dui:IsEmptyConverter}}" />Converter that takes different input input types and returns a true/false object to indicate if it is empty or not. It also has the ability to be inverted.
<Label Opacity="{Binding MyText, Converter=IsEmptyToObjectConverter TrueObject=0, FalseObject=1}" />Converters a boolean input value to its respective TrueObject/FalseObject. Can be used with any object and has the ability to be inverted.
<Label Opacity="{Binding SomeLogicalProperty, Converter={dui:BoolToObjectConverter TrueObject=0.5, FalseObject=1}}"
Text="My opacity changes" />Attempts to convert an object into its respective bool value based on its own equality implementation.
<Label IsVisible="{Binding SomeObjectProperty, Converter={dui:ObjectToBoolConverter TrueObject='Hello'}}"
Text="I'm visible because SomeObjectProperty is 'Hello'!" /><Label IsVisible="{Binding SomeObjectProperty, Converter={dui:ObjectToBoolConverter TrueObject=0.5}}"
Text="I'm visible because SomeObjectProperty is 0.5!" />Converts an DateTime object with a format and convert it to a readable time string. By default the time will first be converted to the systems local timezone.
| Format | English-GB | English-US | Norwegian | Remarks |
|---|---|---|---|---|
| Default / Short | 12th Dec 2019 | Dec 12th, 2019 | 12. des 2019 | |
| Text | Today | Today | I dag | Will return different texts based on the date based on todays date |
To skip converting to local time zone use the IgnoreLocalTime property
<Label Text="{Binding Date, Converter={dxui:DateConverter Format=Default}}"Converts an DateTime or TimeSpan object with a format and convert it to a readable time string. By default the time will first be converted to the systems local timezone
| Format | English-GB | English-US | Norwegian | Remarks |
|---|---|---|---|---|
| Default | 13:00 | 01:00 PM | 13:00 |
To skip converting to local time zone use the IgnoreLocalTime property
<Label Text="{Binding Time, Converter={dui:TimeConverter Format=Default}}" />Converters a DateTime object with an format and convert it to a readable string. By default the time will first be converted to the systems local timezone.
| Format | English-GB | English-US | Norwegian | Remarks |
|---|---|---|---|---|
| Default / Short | 12th Dec 1990 13:00 | Dec 12th, 1990 01:00 PM | 12. des 1990 13:00 | |
| Text | Today 13:00 | Today 01:00 PM | I dag, kl 13:00 | Will return different date texts based on the date based on todays date |
To skip converting to local time zone use the IgnoreLocalTime property
<Label Text="{Binding Date, Converter={dui:DateAndTimeConverter Format=Default}}" />Multiplies the input value with a provided factor.
<Label Text="{Binding Value, Converter={dui:MultiplicationConverter Factor=2}}" />Adds the provided value (a term) with a Addend to create a sum
<Label Text="{Binding Value, Converter={dui:AdditionConverter Addend=2}}" />Converters a input string to a desired string case
<Label Text="{Binding MyString, Converter={dui:StringCaseConverter StringCase=Upper}}"/>Checks the type of the binding against a Type and returns a True / False object accordingly to the type check.
<Frame BackgroundColor="{Binding CurrentTypeClass, Converter={dui:TypeToObjectConverter Type={x:Type valueconverters:OneTypeClass}, TrueObject=Red, FalseObject=Green}}" />Converter that takes multiple boolean inputs, runs it through a LogicalGate and returns a True/FalseObject.
👉 If
True/FalseObjectis not set, it will return booleantrue/false
<Label Text="MyText">
<Label.IsVisible>
<MultiBinding Converter="{dui:LogicalExpressionConverter
LogicalGate=Or}">
<Binding Path="SomeBoolProperty" />
<Binding Path="SomeOtherBoolProperty" />
</MultiBinding>
</Label.IsVisible>
</Label>These are the different options for logical gates:
| A | B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 1 | 1 |
| A | B | Output |
|---|---|---|
| 0 | 0 | 1 |
| 1 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 1 | 0 |
| A | B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 1 | 1 |
| A | B | Output |
|---|---|---|
| 0 | 0 | 1 |
| 1 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 1 | 0 |
| A | B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 1 | 0 |
| A | B | Output |
|---|---|---|
| 0 | 0 | 1 |
| 1 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 1 | 1 |
A converter that takes a item and a list as bindings and compare the index of the item with a Position and return a True/FalseObject
👉 If
True/FalseObjectis not set, it will return booleantrue/false
You are displaying a list of items and you want all of the items to have a bottom separator except the last item in the list. This can be achieved by using this converter to set a separator for each item but not the last item by doing so:
<StackLayout x:Name="ItemsStackLayout"
BindableLayout.ItemsSource="{Binding Items}"
Orientation="Vertical">
<BindableLayout.ItemTemplate>
<DataTemplate x:DataType="{x:Type x:String}">
<StackLayout Margin="15,0,0,0">
<Label Text="{Binding .}"/>
<BoxView HeightRequest="1"
Color="Black">
<BoxView.IsVisible>
<MultiBinding Converter="{dui:PositionInListConverter Position=Last, Inverted=True}">
<Binding /> <!-- The item -->
<Binding Path="BindingContext.Items"
Source="{x:Reference ItemsStackLayout}"/> <!-- The list -->
</MultiBinding>
</BoxView.IsVisible>
</BoxView>
</StackLayout>
</DataTemplate>
</BindableLayout.ItemTemplate>
</StackLayout>In this example we are using the
Invertedproperty to make sure it returnstruefor all items except theLastitem.
This is a string and it accepts both First / Last and indexes that are inside of the bounds of the list. This means that you can write Position=1 to have it return true for the item at position = 1 and false for the rest.
If you do not set the Position property it will default to Last.
When dealing with an ObservableCollection managing items with the Add() / Remove() method, you will have to force the layout to redraw all items to get the effect. This is because converters does not fire again magically by a ObservableCollection.CollectionChanged.
The workaround is to set the entire list with a new modified list and raise property changed to make the UI redraw:
Add (example)
private void AddItem()
{
var newList = new ObservableCollection<string>(Items);
newList.Add(<item>);
Items = newList; //Raises property changed in the `Items.Set`
...Remove (example)
private void RemoveItem()
{
var newList = new ObservableCollection<string>(Items);
newList.Remove(<item>);
Items = newList; //Raises property changed in the `Items.Set`
...Takes a list of converters and pipes the value through all of them, from first to last.
<Label.Opacity>
<Binding Path="Digits">
<Binding.Converter>
<essentials:ValueConverterGroup>
<dui:IsEmptyConverter />
<dui:BoolToObjectConverter TrueObject="0.5" FalseObject="1" />
</essentials:ValueConverterGroup>
</Binding.Converter>
</Binding>
</Label.Opacity>