What is "actionlistener"

An action event occurs whenever an action is performed by the user. For example, when the user clicks a button, chooses a menu item, or presses Enter in a text field. The result is that a message through the method actionPerformed is sent to all action listeners who are registered in the relevant component.

A class that aims to manipulate an action event, must implement the interface ActionListener, and the object created with that class is registered to a component, using the method addActionListener since component. When the action event occurs, the method actionPerformed of this object is invoked, as the example below shows:

• creating the implementing class ActionListener

  public class MyClass implements ActionListener { 
  ...
  }
  

• Registering an instance of the event handler class as a "listener" in one or more components:

  someComponent.addActionListener(instanceOfMyClass);
  

• Define what will occur when the action is executed within the method implemented by the class ActionListener:

  public void actionPerformed(ActionEvent e) { 
      ...//Código que reage à ação... 
  }
  

Already in this other example below, demonstrates how to implement a ActionListener directly through the use of anonymous classes:

myButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
       System.out.println("Hey!");
    }
});