import java.awt.*; import java.util.*; import java.io.*; import java.applet.Applet; public class myButton extends Applet { Button button1; public void init() { button1 = new Button("Ok"); add(button1); } public boolean action(Event e, Object arg) { if (e.target instanceof Button) { System.out.println("Button: " + arg); } return false; } public boolean handleEvent(Event e) { if ((e.id == Event.MOUSE_DOWN) || (e.target instanceof Button)) { System.out.println("This might have been a button event: "); } return true; } public boolean mouseDown(Event e, int x, int y) { System.out.println("Mouse works: (" + x +","+y+") "); return false; } }

I wanted to test the idea of handleEvent() passing to the enclosing environment. ... and what does enclosing environment mean?

(no texts at this time)

The given code (in and out of button)always returned :

This might have been a button event:

* so ignored action, MouseDown - expected since return true in handleEvent

When changed all returns to true, still always returned :

This might have been a button event: (still expected no diff)

When changed handleEvent to false, still always returned :

This might have been a button event: (this was not expected - what happened to action? )

* Discussion

When changed handleEvent to the following, worked as expected (reasonable - spefically "handles " Event )

public boolean handleEvent(Event e) { if (e.id == Event.MOUSE_DOWN){ mouseDown(e, e.x, e.y);} else if (e.target instanceof Button){ action(e, e.arg); } return true; }

When changed handleEvent to the following, worked only when hit button. Here it would provide Mouse works (x,y) stuff . Made no difference if return true or false. Nothing otherwise

public boolean handleEvent(Event e) { if (e.target instanceof Button) mouseDown(e, e.x, e.y); return false; }

Discussion:

Events and HandleEvent - Core2: page 292, 293 and API

handleEvent:

return true: the event is handled - don't propogate

return false: the event is not handled - propogate to parent in the window hierarchy

return super.handleEvent(evt): the event is not handled - propogate to the parent in the inheritance hierarchy

What is meant by the window hierarchy? generic handleEvent passes to Applet

Remeber that previously I had said that it gives it to the enclosing environment. If a button is instantiated and then added to an applet (or a subclass of applet), then the enclosing environment is applet (or the subclass of applet). The example after this discussion will show how this works.

Conclusion: handleEvent can handle all events in a Container; consider it as a kind of "director"... it is looked at first

How does action() fit in:

public boolean action(Event evt, Object arg) {

... }

(Teach Yourself: pg 255): "Testing for an action by a UI component is a form of event management. UI components produce the special kind of event called an action.

If one uses action(), the method handles only ACTION_EVENTS Nutshell: page 183, discusses Events and Event Types. Note that only Components: Button, Checkbox, Choice, List, MenuItem, and TextField are ACTION_EVENTS

Examples of how to deal with action() in Teach, pg. 255-257

Note: "Although you can handle UI actions in the body of the action() method, it is much more common simply to define a handler method and call that method from action() instead." misleading sentence

This is NOT talking about the handleEvent(). It is talking about making specific methods to handle specific Components.

Core2, pg. 226, "when a button is clicked, the action() method is the one that is triggered."

As we saw in the first example, handleEvent() "overrides" the action(),

so these sentences are true only if there is no handleEvent method there

Nutshell: All Java GUI Components, pg. 108; Handling GUI Events, pg. 114,

Core2, page 292, Teach Yourself, page 233

Almost forgot: when I did do

return super.handleEvent(e);

in the first example, all worked as should. Before the return, I placed

System.out.println("My super is: " + super.getClass().getName());

and got

My super is myButton

Now, example tried with subclassing:

import java.awt.*; import java.util.*; import java.io.*; public class subButton extends Button { public subButton(String label){ super(label);} // without constructor get error public boolean action(Event e, Object arg) { if (e.target instanceof Button) { System.out.println("Button: " + arg); } return true; } } And its enclosing environment: import java.awt.*; import java.util.*; import java.io.*; import java.applet.Applet; import subButton; public class testButton extends Applet { subButton button1, button2; public void init() { button1 = new subButton("Ok"); button2 = new subButton("notOK"); add(button1); add(button2); } public boolean handleEvent(Event e) { if (e.target instanceof subButton) mouseDown(e, e.x, e.y); return false; } public boolean mouseDown(Event e, int x, int y) { System.out.println("Mouse works: (" + x +","+y+") "); return true; } }

This only does the action of the button. If I change the action return to false, it does both the buttons action and the handleEvent.

In applet, what if there are a lot of buttons; theoretically ask: should Button do the action or Applet?