Each command button has
associated with it a method that is triggered when the user selects that
button. breezypythongui provides a default event handler method that does nothing. However, an application normally
supplies its own event handler method as an argument when a button is added to
the window. The programmer must
then define this method in the application windowÕs class. Here is the code for associating an
event handler method with the command button in the tax calculator program:
def __init__(self):
.
.
# Add the
command button
self.addButton(text = "Compute",
row = 3, column = 0,
columnspan = 2, command
= self.computeTax)
# The event handler method for the button
def computeTax(self):
"""Obtains
the data from the input fields and uses
them to compute the tax, which is sent to the
output field."""
income
= self.incomeField.getNumber()
numDependents = self.depField.getNumber()
exemptionAmount = self.exeField.getNumber()
tax
= (income - numDependents * exemptionAmount)
* .15
self.taxField.setNumber(tax)
If an application needs
more than one command button, each button is added to the window in the __init__ method. The programmer should then define a
separate event handler method for each button.