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Xamarin Forms how to add behaviors to custom control
DimitrisMylonas
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USMember ✭✭✭
I have created a custom control,which is a ContentView with a Label and an Entry
The xaml of the custom controls looks like this:
<Label Text="{Binding Source={x:Reference ValidationControl}, Path=Caption}"/>
<Entry Text="{Binding Source={x:Reference ValidationControl}, Path=Value, Mode=TwoWay}" />
The code behind of the custom control looks like this:
public static readonly BindableProperty CaptionProperty = BindableProperty.Create(
nameof(Caption), typeof(string), typeof(ValidationEntry), default(string));
public string Caption
{
get => (string)GetValue(CaptionProperty);
set => SetValue(CaptionProperty, value);
}
public static readonly BindableProperty ValueProperty = BindableProperty.Create(
nameof(Value), typeof(string), typeof(ValidationEntry), default(string));
public string Value
{
get => (string)GetValue(ValueProperty);
set => SetValue(ValueProperty, value);
}
I’m using the custom control in the following way
<controls:ValidationEntry Caption=”Name:” Value="{Binding FullName, Mode=TwoWay}" />
My question is how to add behaviors to the custom control?
I would like to add them in the place that I’m using the control. i.e.
<controls:ValidationEntry Caption="Name:"
Value="{Binding FullName, Mode=TwoWay}">
<controls:ValidationEntry.EntryBehaviors>
<behaviors:EntryLengthValidatorBehavior IgnoreSpaces="True"/>
</controls:ValidationEntry.EntryBehaviors>
</controls:ValidationEntry>
Tagged:
0
Answers
What's the problem you're facing ? What exactly do you want to achieve ?
Add behaviors to the custom control that I can apply to the
Entry.I wasn't able to find a way to populate the
IList<Behaviors>of theEntryinside the custom control by adding the behaviors in the custom control.Create behavior for your custom control , and find the Entry inside it ..
class CustomBehavior : Behavior<ValidationEntry> { protected override void OnAttachedTo(ValidationEntry view) { StackLayout stack = view.Content as StackLayout; Entry e = stack.Children[0] as Entry; //handle the logic base.OnAttachedTo(view); } }So you mean, that there is no way to add behaviors to my custom control like I do with an
Entry?You mean, that if I have a behavior for an
Entryand I need it also for my custom control then I cannot reuse it and I should create a different behavior doing the same thing but for my custom control?You mean that if I have another custom control with 2
Entries(i.e. phone number with National prefix and the phone number) and I need the same behavior then I should create a third for that particular custom control?Why don't you use behavior with Entry in your custom control directly?
// inside your control <Label Text="{Binding Source={x:Reference ValidationControl}, Path=Caption}"/> <Entry Text="{Binding Source={x:Reference ValidationControl}, Path=Value, Mode=TwoWay}"> <Entry.Behaviors> <local:NumericValidationBehavior /> </Entry.Behaviors> </Entry>local:NumericValidationBehavioris Behavior is for Entry , and it is reusable.I made the custom control in order to use it in multiple cases. Different cases need different behaviors.
As a result, I would like to add the behaviors that I want depending on the use of the custom control.
That is the reason that we can add behaviors to a simple
Entrycontrol depending on the situation.I suggest you handle the logic in custom renderer code behind.
if (A) { entry.Behaviors.Add(new BehaviorA()); } else if (B) { entry.Behaviors.Add(new BehaviorB()); } else { entry.Behaviors.Add(new BehaviorC()); }What is the
if (A)?Don't you think that this is a very cumbersome and unpractical solution that also needs a lot of maintenance?
Behavior A is created and used for Control A , you can't add Behavior of Entry on your custom control .
Did you ever find a solution for this?
@IeuanWalker ...not a good one… but I realized also that I made some mistakes.
Firstly, just to describe the solution, is to create a
bindable propertyof type bool to specify if I want to attach thebehavior(or theeffect)On property change of the
bindable propertyI add thebehaviorby code.It’s not a pretty solution. I can re-use the
behaviorsor theeffectswhich is good but I need to create a fewbindable properties… which is not good.The default value of the
bindable propertyisfalseso myXAMLis not that verbose. In my case I only had 2behaviorsand 1effectso it worked for me.I think that one mistake that I did is that the
behaviors(or theeffects) should be for theContentViewthat contains the entry instead of theentry.I'm was searching to the same thing. My solution was:
1 - Create a List<Behavior> as a Bindable property inside the component
2- Name you entry in code behind
3- Enter the following code when creting the bindable property
public static readonly BindableProperty EntryBehaviorsProperty = BindableProperty.Create(nameof(EntryBehaviors), typeof(List<Behavior<Entry>>), typeof(List<Behavior<Entry>>), null, BindingMode.OneTime, propertyChanged: (bindable, oldValue, value) => { var view = bindable as FloatingLabelInput; if (view.EntryBehaviors != null && view.EntryBehaviors.Count >0) { foreach (var item in view.EntryBehaviors) { view.EntryField.Behaviors.Add(item); } } });4- Populate the list in the viewModel (with any behaviors you need) and binding to the component
<customcontrolwithentryinside EntryBehaviors="{Binding EntryBehavior}">Hi
can you share an example of how you did it, I am new to xamarin and I need to do this, thanks for your help