Making
a button is quite simple: you just call the
Buttonconstructor with the label you want on the button. (You can also use the
default constructor if you want a button with no label, but this is not very
useful.) Usually you’ll want to create a handle for the button so you can
refer to it later.
The
Button
is a component, like its own little window, that will automatically get
repainted as part of an update. This means that you don’t explicitly
paint a button or any other kind of control; you simply place them on the form
and let them automatically take care of painting themselves. So to place a
button on a form you override
init( )
instead
of overriding
paint( )
:
//: Button1.java
// Putting buttons on an applet
import java.awt.*;
import java.applet.*;
public class Button1 extends Applet {
Button
b1 = new Button("Button 1"),
b2 = new Button("Button 2");
public void init() {
add(b1);
add(b2);
}
} ///:~
It’s
not enough to create the
Button
(or any other control). You must also call the
Applet
add( )
method to cause the button to be placed on the applet’s form. This seems
a lot simpler than it is, because the call to
add( )
actually decides, implicitly, where to place the control on the form.
Controlling the layout of a form is examined shortly.
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