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.
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 Events
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
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()
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.
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 Events
It's possible to register any of the other tkinter event types with appJar widgets.
Just get the widget, then call the tkinter
bind() function, passing in the event name and function to call.
NB. The function you register must receive a single parameter, the event object.
# either grab the widget when it's created, and bind the event ent = app.addEntry("e1") ent.bind("<FocusOut>", function_name, add="+") # or do the above in one line app.addEntry("e1").bind("<FocusOut>", function_name, add="+") # or, if doing later on, get the widget from appJar and bind the event ent = app.getEntryWidget("e1") ent.bind("<FocusOut>", function_name, add="+") # or do the above in one line app.getEntryWidget("e1").bind("<FocusOut>", function_name, add="+")
We also 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:
from appJar import gui def keyPress(key): if key == "<Up>": app.increaseFont() elif key == "<Down>": app.decreaseFont() elif key == "<F1>": app.setFont(12) app = gui("Button Demo") app.addLabel("title", "Press the arrow keys to change the font") app.bindKey("<Up>", keyPress) app.bindKey("<Down>", keyPress) app.bindKey("<F1>", keyPress) app.go()
NB. You must use the full tkinter event format for events with these bindings, including the angle brackets
This is different to how menu shortcuts are defined.
Link the specified key to the specified function.
Link the specified keys to the specified function.
Unlink the specified key from any functions bound to it.
Unlink the specified keys from any functions bound to them.
Starting the GUI
If you want to call a function once the GUI starts, you can register it with the following call:
Set a function to call when the GUI starts up.
Stopping the GUI
Usually the user just presses the close icon to close and stop the GUI.
However, you might want to let them do it in other ways - maybe by pressing a button...
Will cuase the GUI to close and stop.
Confirming the user wants to quit/running clean up scripts on exit
You may want to add in a confirmation that the user really wants to stop the GUI.
Or, you may want to do some tidying up when the user stops the GUI, such as save a file.
If so, you can set a stopFunction to call, whenever the user tries to stop the GUI.
Set a function to call, before allowing the GUI to be stopped.
NB. This function must return
Falseto confirm if the GUI should stop.
So, if you're just doing some tidying up,
return True at the end of the function.
If you want to stop the user closing the GUI,
And, if you want to check if the user really wanted to stop the GUI:
def checkStop(): return app.yesNoBox("Confirm Exit", "Are you sure you want to exit the application?") app.setStopFunction(checkStop)
If you have a LOT of widgets (maybe a Table with hundreds of rows), stopping the GUI can take a while...
In which case, you should enable
fastStop on the GUI.
This will cause the GUI to exit more quickly, but lazily...
NB. this doesn't work from IDLE.