StartButton

Button Component UnityEvent

UI Buttons: Unity Manual

UI Buttons can be configured to execute a public method when the Button's OnClick Event occurs.

Create UI Button GameObject

• Create a UI Button

• it will also have a child-gameObject that is UI Text

• Rename the Button to StartButton

• Set the RectTransform to position the StartButton.

• In the Inspector, make sure to set both Normal and Highlighted Colors

• Set Navigation to None

• Notice that OnClick( ) has: List is Empty

Create StartButton, Buttons Have a Child Text GameObject

Make Sure to Select a Highlighted Color that is different than the Normal Color

UnityEvent: onClick adds Listener Methods

UI-Button Components have an associated UnityEvent: onClick.

The Button Component can be considered as using the Observer Pattern. The Observer pattern provides a method to decouple logic when 2 objects need to communicate with each other.

In our case, the Button is the Event Subject or Publisher, our custom MiniGameManager script is the Event Listener. We must define a public method in the MiniGameManager class, to define a Listener method which will be configured to be executed when the Publisher's onClick event is invoked.

OnClick is a UnityEvent, it maintains a list of all Listener methods to be executed when the OnClick event is invoked. The Listener object must define a public method to be added as a listener to the Button's onClick Event list of listeners.

Game Programming Patterns: Observer Pattern

The observer pattern lets one piece of code announce that something interesting happened without actually caring who receives the notification.

In the code below, we have defined a function that we want to have executed when the button OnClick() event occurs. :

public void GameStartActions(){ //do game start things }

It is required that our function match the onClick event's delegate-type: in this case, a public method with a void return-type and no input parameters, in order to add our GameStartActions() method as a listener to the button's onClick event.

When the button object is clicked, we want our custom script component to be notified, we do so by creating a public method that is passed as a delegate to the button's onClick event. A Delegate provides a way to create a reference-type that refers to a method instead of a variable or object. Note, we're passing a method itself into the AddListener( ) method of the onClick event.

[SerializeField]
Button startButton;

void Start(){
startButton = GetComponent<Button> ();
startButton.onClick.AddListener (GameStartActions);
    }

public void GameStartActions(){
    // do game start things
}