Using Lists

This example shows how to use Lists from Jython.

Something has gone wrong loading this applet.

The complete source code for this example is included below.

from java import applet, awt
from java.awt.event import ItemEvent
from pawt import GridBag

class ListDemo(applet.Applet):
    def fillList(self, list, names):
        list.actionPerformed=self.action
        list.itemStateChanged=self.change

        for name in names:
            list.add(name)

    def init(self):
        self.spanish = awt.List(4, 1)
        self.fillList(self.spanish, ['uno', 'dos', 'tres', 'cuatro',
                            'cinco', 'seis', 'siete'])
        self.italian = awt.List()
        self.fillList(self.italian, ['uno', 'due', 'tre', 'quattro',
                            'cinque', 'sei', 'sette'])

        self.output = awt.TextArea(10, 40, editable=0)

        bag = GridBag(self)
        bag.add(self.output, fill='BOTH', weightx=1.0, weighty=1.0, gridheight=2)

        bag.addRow(self.spanish, fill='VERTICAL')
        bag.addRow(self.italian, fill='VERTICAL')

        self.language = {self.spanish:'Spanish', self.italian:'Italian'}

    def action(self, e):
        list = e.source
        text = 'Action event occurred on "%s" in %s.\n'
        self.output.append(text % (list.selectedItem, self.language[list]))

    def change(self, e):
        list = e.source
        if e.stateChange == ItemEvent.SELECTED:
            select = 'Select'
        else:
            select = 'Deselect'

        text = '%s event occurred on item #%d (%s) in %s.\n'
        params = (select, e.item, list.getItem(e.item), self.language[list])
        self.output.append(text % params)

This init method creates and fills lists of spanish and italian numbers. It uses a GridBag to layout the lists and a text widget in the applet. This GridBag is a wrapper placed on the awt.GridBagLayout and GridBagConstraints classes to make this very powerful layout method easier to use.

The action method is invoked whener a list item is double clicked. It uses Python's % operator on strings for convenient text formatting.

The change method is invoked when a list item is selected or deselected. It's primary difference from the Java implementation is to use a dictionary of languages instead of a case statement to determine the appropriate text to display. This is an example of the ease of use of standard data types (lists and dictionaries) from Python.