I've recently started learning ExtJS, and have trouble understanding how to handle Events. I have no experience of any previous versions of ExtJS.
From reading various manuals, guides and documentation pages, I've figured out how to use it, but I'm not clear on how it works. I've found several tutorials for older versions of ExtJS, but I'm not sure how applicable they are in ExtJS 4.
I'm specifically looking on the "final word" on things like
For example, this question leads me to believe that an event handler can receive quite a few arguments. I've seen other tutorials where there are just two arguments to the handler. What changes?
Let's start by describing DOM elements' event handling.
First of all you wouldn't want to work with DOM node directly. Instead you probably would want to utilize Ext.Element
interface. For the purpose of assigning event handlers, Element.addListener
and Element.on
(these are equivalent) were created. So, for example, if we have html:
<div id="test_node"></div>
and we want add click
event handler.
Let's retrieve Element
:
var el = Ext.get('test_node');
Now let's check docs for click
event. It's handler may have three parameters:
click( Ext.EventObject e, HTMLElement t, Object eOpts )
Knowing all this stuff we can assign handler:
// event name event handler
el.on( 'click' , function(e, t, eOpts){
// handling event here
});
Widgets event handling is pretty much similar to DOM nodes event handling.
First of all, widgets event handling is realized by utilizing Ext.util.Observable
mixin. In order to handle events properly your widget must containg Ext.util.Observable
as a mixin. All built-in widgets (like Panel, Form, Tree, Grid, ...) has Ext.util.Observable
as a mixin by default.
For widgets there are two ways of assigning handlers. The first one - is to use on method (or addListener
). Let's for example create Button
widget and assign click
event to it. First of all you should check event's docs for handler's arguments:
click( Ext.button.Button this, Event e, Object eOpts )
Now let's use on
:
var myButton = Ext.create('Ext.button.Button', {
text: 'Test button'
});
myButton.on('click', function(btn, e, eOpts) {
// event handling here
console.log(btn, e, eOpts);
});
The second way is to use widget's listeners config:
var myButton = Ext.create('Ext.button.Button', {
text: 'Test button',
listeners : {
click: function(btn, e, eOpts) {
// event handling here
console.log(btn, e, eOpts);
}
}
});
Notice that Button
widget is a special kind of widgets. Click event can be assigned to this widget by using handler
config:
var myButton = Ext.create('Ext.button.Button', {
text: 'Test button',
handler : function(btn, e, eOpts) {
// event handling here
console.log(btn, e, eOpts);
}
});
First of all you need to register an event using addEvents method:
myButton.addEvents('myspecialevent1', 'myspecialevent2', 'myspecialevent3', /* ... */);
Using the addEvents
method is optional. As comments to this method say there is no need to use this method but it provides place for events documentation.
To fire your event use fireEvent method:
myButton.fireEvent('myspecialevent1', arg1, arg2, arg3, /* ... */);
arg1, arg2, arg3, /* ... */
will be passed into handler. Now we can handle your event:
myButton.on('myspecialevent1', function(arg1, arg2, arg3, /* ... */) {
// event handling here
console.log(arg1, arg2, arg3, /* ... */);
});
It's worth mentioning that the best place for inserting addEvents method call is widget's initComponent
method when you are defining new widget:
Ext.define('MyCustomButton', {
extend: 'Ext.button.Button',
// ... other configs,
initComponent: function(){
this.addEvents('myspecialevent1', 'myspecialevent2', 'myspecialevent3', /* ... */);
// ...
this.callParent(arguments);
}
});
var myButton = Ext.create('MyCustomButton', { /* configs */ });
To prevent bubbling you can return false
or use Ext.EventObject.preventDefault()
. In order to prevent browser's default action use Ext.EventObject.stopPropagation()
.
For example let's assign click event handler to our button. And if not left button was clicked prevent default browser action:
myButton.on('click', function(btn, e){
if (e.button !== 0)
e.preventDefault();
});