MIDP Programming - Java 2 Micro Edition Application Development - page 49

The TextBox Class
Beneath Alert , List , and Form , there is only one further subclass of Screen : the TextBox . The
TextBox allows the user to enter multi-line text on a separate screen. The constructor parameters and
the constraint constants are identical to those of TextField .
As for the currency list, you can also add a new screen enabling the user to enter a transfer reason if
desired. Similar to the CurrencyList , you implement a new class handling the commands related to
the new screen. However, this time it is derived from the TextBox . Again, you implement the
CommandListener interface:
public class TransferReason extends TextBox implements
CommandListener {
In the TextBox , you provide two commands, okCommand for applying the entered text and
clearCommand for clearing the text:
static final Command okCommand = new Command ("OK", Command.BACK, 1);
static final Command clearCommand = new Command ("Clear",
Command.SCREEN, 2);
Again, you store a reference back to the TeleTransfer MIDlet in the TransferReason
TextBox :
TeleTransfer teleTransfer;
The constructor gets the reference back to TeleTransfer MIDlet and stores it in the variable
declared previously. You also add the commands to the TextBox , and register it as
CommandListener :
public TransferReason (TeleTransfer teleTransfer) {
super ("Transfer Reason", "", 50, TextField.ANY);
this.teleTransfer = teleTransfer;
addCommand (okCommand);
addCommand (clearCommand);
setCommandListener(this);
}
Your commandAction() implementation clears the text or returns to the main screen, depending on
the Command selected:
public void commandAction (Command c, Displayable d) {
if (c == clearCommand) {
setString ("");
}
else if (c == okCommand) {