How to wait until Widget blueprint is constructed / initialized?

Development Programming & Scripting C++
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1

Hi everyone,

I am working on a project that uses widget blueprints for UI element layout and C++ for all logic. A simple example is a widget blueprint that consists of a checkbox (UCheckBox) and another widget blueprint.

I created a parent class that has two variables that hold the two UI elements (checkbox and other blueprint) and a method, and I want to manipulate the UI elements from the method. I also created a parent class for the other blueprint the same way.

Here’s how my class looks:

QuestCheckbox.h
UCLASS()
class UNREALQUESTBP56_API UQuestCheckbox : public UUserWidget
{
	GENERATED_BODY()
	
public:
	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (BindWidget), Category="UI Setup")
	UQuestBasicText* BasicTextWidget_Answer;
	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (BindWidget), Category="UI Setup")
	UCheckBox* CheckBox_Answer;
	
	UFUNCTION(BlueprintCallable)
	void SetText(FString Answer) const;
};

QuestCheckbox.cpp
void UQuestCheckbox::SetText(const FString Answer) const
{
	BasicTextWidget_Answer->DisplayedText = FText::FromString(Answer);
}

QuestBasicText.h

UCLASS()
class UNREALQUESTBP56_API UQuestBasicText : public UUserWidget
{
	GENERATED_BODY()
	
public:
	UPROPERTY(BlueprintReadWrite)
	FText DisplayedText;
	UPROPERTY(BlueprintReadWrite, EditAnywhere, meta = (BindWidget))
	UTextBlock* TextBlock;
};

And here’s how I use those:

UQuestCheckbox* checkBox = CreateWidget<UQuestCheckbox>(this, UQuestCheckbox::StaticClass());
checkBox->SetText("LULZ");

The second call crashes because BasicTextWidget_Answer is null. So I assumed elements in widget blueprints are not constructed immediately when the widget is instanced. I added checkBox->Construct(); before calling SetText() but that did not help. What am I missing here?

2

You need to do something that adds it to the viewport/widget tree. That’s what causes the widget to be fully constructed and BindWidget properties to have something that can be assigned.

That could be calling AddToViewport (but for a checkbox that’s probably not the right solution) or adding the widget to some sort of container widget like a canvas panel or a vertical/horizontal box.