An event is just calling a function - you want an event to be generated every time the user does something, such as clicking a button, dragging a scale, or pressing a key...
Button has an event automatically linked to it - whenever you press it, a function gets called. The other widgets don't.
Types of Event
appJar currently has four basic types of event you can register:
.set XXX ChangeFunction(title, function)call a function whenever the widget changes
.set XXX SubmitFunction(title, function)call a function when the widget is submitted
.set XXX OverFunction(title, functions)call function(s) when the mouse enters/leaves the widget
.set XXX DragFunction(title, functions)call function(s) when the mouse is dragged in/out of the widget
Change & Submit Functions
These do similar things, so probably shouldn't both exist, but have evolved from a single
.set XXX Function() which is now deprecated.
.set XXX ChangeFunction(title, function)
Bind the specified function to the named widget:
- Scales, OptionBoxes, SpinBoxes, ListBoxes, RadioButtons & CheckBoxes, Entries & TextAreas, and Properties - the function will be called each time the widget is changed.
- Buttons, Labels & Images - it is not available.
- Other widgets - it will set the command property for the underlying tkinter widget; this may or may not do anything...
.set XXX SubmitFunction(title, function)
Creates a submit option for some widgets:
- Labels & Images - it binds a function to the
<Left-Mouse-Button>, making the widget clickable.
- Entries & Buttons - it binds a function to the
- TextAreas - it's not available
- Other widgets - it does the same as
- Labels & Images - it binds a function to the
WARNING - it's possible to generate a RuntimeError. If you've got two widgets changing the same variable, say a Scale and a SpinBox, and you want a change in one widget to cause an update in the other, you might inadvertently end up stuck in a recursive loop, until the stack overflows.
In this case, make sure you set the optional parameter
callFunction = False when you call the
set XXX Function() of a widget.
from appJar import gui def songChanged(rb): print(app.getRadioButton(rb)) def reset(btn): # set back to the default, but don't call the change function app.setRadioButton("song", "Killer Queen", callFunction=False) app=gui() app.addRadioButton("song", "Killer Queen") app.addRadioButton("song", "Paradise City") app.setRadioButtonChangeFunction("song", songChanged) app.addButton("Reset", reset) app.go()
Set functions to call whenever the mouse enters (goes over) or leaves the specified widget.
.set XXX OverFunction(name, [inFunction, outFunction])
The first function is called when the mouse first enters the widget.
The second function is called when the mouse leaves the widget.
If you only want a function to be called when the mouse leaves the widget, pass an array like:
from appJar import gui def enter(wdgt): print("IN", wdgt) def leave(wdgt): print("OUT", wdgt) app=gui() app.addLabel("l1", "Testing...") app.setLabelOverFunction("l1", [enter, leave]) app.go()
Additional function, specific to images, to change the specified image, while the mouse is over it.
Set functions to call when the mouse button is clicked and dragged on a Label, then released.
.set XXX DragFunction(name, [startDragFunction, stopDragFunction])
The named Label will be the only one that can start a drag event.
The first function will be called when the mouse is initially clicked on the Label.
The second function will be called when the mouse is released, this can happen anywhere.
The same rules for passing functions apply as above.
Registering Other Event Types
It's possible to register any of the standard event types with appJar widgets
app.getEntryWidget("widget_name").bind("<FocusOut>", function_name, add="+")
As well as changing widgets, we sometimes want keys to trigger events.
The classic example is the
<Enter> key, we often want to be able to hit the
<Enter> key to submit a form...
Link a function to the
Unlink a function from the
You may also want to bind other keys to events.
Link the specified key to the specified function.
Unlink the specified key from any functions bound to it.
Stopping the GUI
Usually the user just presses the close icon to stop the GUI.
However, you might want to let them do it in other ways - maybe by pressing a button...
To stop the GUI, simply call
If you want to add a feature to confirm the user really wants to exit, or to save some data, then you'll need a stop function.
Set a function to call, before allowing the GUI to be stopped.
This function should return True/False to confirm if the GUI should stop.
def checkStop(): return app.yesNoBox("Confirm Exit", "Are you sure you want to exit the application?") app.setStopFunction(checkStop)