A Simple Example
The
examples that we’re going to
demonstrate here, and throughout the rest of the book, are called
MIDlets. If you’ve programmed with Java applets or servlets
before, then you’ll likely recognize the similarities in the
“fill-in-the-method” program structure. This first
example, HelloMidlet.java, shown in Example 1-1, creates a text box and then prints the
archetypal “Hello World” in a text box.
Example 1-1. “Hello World”
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloMidlet extends MIDlet {
// The display for this MIDlet
private Display display;
// TextBox to display text
TextBox box = null;
public HelloMidlet( ) {
}
public void startApp( ) {
display = Display.getDisplay(this);
box = new TextBox("Simple Example", "Hello World", 20, 0);
display.setCurrent(box);
}
/**
* Pause is a no-op since there are no background activities or
* record stores that need to be closed.
*/
public void pauseApp( ) {
}
/**
* Destroy must cleanup everything not handled by the garbage
* collector. In this case there is nothing to cleanup.
*/
public void destroyApp(boolean unconditional) {
}
}This MIDlet consists of a public class definition that extends the
MIDlet class found in
javax.microedition.midlet
. This superclass forms
the base of all MIDlets in J2ME. Our HelloMidlet
class contains a constructor, as well as the
startApp()
, pauseApp( )
, and destroyApp( )
methods that have been inherited from
the MIDlet
class. Note that there is no ...