Java Doc for Button.java in  » 6.0-JDK-Core » AWT » java » awt » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The first view shows the button as it appears normally. The second view shows the button when it has input focus. Its outline is darkened to let the user know that it is an active object. The third view shows the button when the user clicks the mouse over the button, and thus requests that an action be performed.

The gesture of clicking on a button with the mouse is associated with one instance of ActionEvent, which is sent out when the mouse is both pressed and released over the button. If an application is interested in knowing when the button has been pressed but not released, as a separate gesture, it can specialize processMouseEvent, or it can register itself as a listener for mouse events by calling addMouseListener. Both of these methods are defined by Component, the abstract superclass of all components.

When a button is pressed and released, AWT sends an instance of ActionEvent to the button, by calling processEvent on the button. The button's processEvent method receives all events for the button; it passes an action event along by calling its own processActionEvent method. The latter method passes the action event on to any action listeners that have registered an interest in action events generated by this button.

If an application wants to perform some action based on a button being pressed and released, it should implement ActionListener and register the new listener to receive events from this button, by calling the button's addActionListener method. The application can make use of the button's action command as a messaging protocol.
version:
   1.89 05/05/07
author:
   Sami Shaio
See Also:   java.awt.event.ActionEvent
See Also:   java.awt.event.ActionListener
See Also:   java.awt.Component.processMouseEvent
See Also:   java.awt.Component.addMouseListener
since:
   JDK1.0

This method is not called unless action events are enabled for this button.

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
  l - the action listener
See Also:   Button.removeActionListener
See Also:   Button.getActionListeners
See Also:   java.awt.event.ActionListener
since:
   JDK1.1

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Button b for its action listeners with the following code:

ActionListener[] als = (ActionListener[])(b.getListeners(ActionListener.class));

This method is not called unless action events are enabled for this button. Action events are enabled when one of the following occurs:

• An ActionListener object is registered via addActionListener.
• Action events are enabled via enableEvents.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.
Parameters:
  e - the action event
See Also:   java.awt.event.ActionListener
See Also:   java.awt.Button.addActionListener
See Also:   java.awt.Component.enableEvents
since:
   JDK1.1

Note that if the event parameter is null the behavior is unspecified and may result in an exception.
Parameters:
  e - the event
See Also:   java.awt.event.ActionEvent
See Also:   java.awt.Button.processActionEvent
since:
   JDK1.1

Refer to AWT Threading Issues for details on AWT's threading model.
Parameters:
  l - the action listener
See Also:   Button.addActionListener
See Also:   Button.getActionListeners
See Also:   java.awt.event.ActionListener
since:
   JDK1.1