Click function on Toggle Buttons in Unreal Engine 4 C++

Question

I have a doubt about CheckBoxes and click events. I have some button which executes a function OnClick, something like this on code:

SomeButton->OnClicked.AddDynamic(this, &ClassName::FunctionToExecute);

For style reasons, I thought that I should use a Toggle Button, implemented with a CheckBox, instead of a regular Button. However, I am having trouble finding the correct method to bind the function to each click. So far, I tried something like this, but it doesn't work. I also tried declaring a delegate, but it won't work either.

SomeCheckBox->OnCheckStateChanged.Add(&ClassName::FunctionToExecute);

What is the correct way to bind the function to the OnCheckStateChanged() event? Thanks a lot in advance :smile:

Answer 1

If you are using a UMG Check box (which it sounds like you are), than we can look at the delegate declaration:

// In Checkbox.h 
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam( FOnCheckBoxComponentStateChanged, bool, bIsChecked );

and notice that we need a bool input parameter for our callback function.

So that means that our callback function has to look like this:

void UYourWidget::OnCheckboxChanged(bool bIsChecked) {}

You can then bind your widget like this:

if(CheckBox)
{
    CheckBox->OnCheckStateChanged.AddDynamic(this, &UTextChatWidget::Test);
}

If you are using a slate check box, then the callback function declaration is a bit different. It uses the ECheckBoxState enum instead of a boolean.

SNew(SCheckBox)
   .OnCheckStateChanged(this, &SFoo::OnStateChanged)

void SFoo::OnStateChanged(ECheckBoxState NewState) {}

My typical approach for figuring this stuff out is to simply do a CTRL+SHIFT+F search for the delegate in Visual Studio to find other examples of it.