DOM Events

From Documentation


A DOM event (Event) is the DOM-level event that is usually triggered by the browser. It is usually listened by the implementation of a widget, rather than the client application.

Since ZK Client Engine can intercept most DOM events and encapsulate them into the widget events, it is suggested to listen the widget events, if possible, for better performance (by overriding the corresponding methods, such as Widget.doClick_(Event)). For more information, please refer to the previous section.

How to Listen and Unlisten

There are two different approaches to listen a DOM event: Widget.domListen_(DOMElement, String, Object) and jQuery (jq).

Use domListen_ and domUnlisten_

Widget.domListen_(DOMElement, String, Object) registers a DOM-level event listener. The registration should be done when a widget is bound to DOM elements, i.e., when Widget.bind_(Desktop, Skipper, Array) is called. It is important to un-register by the use of Widget.domUnlisten_(DOMElement, String, Object) when a widget is un-bound from DOM elements, i.e., when Widget.unbind_(Skipper, Array) is called. For example,

bind_: function () {
    this.$supers('bind_', arguments);
    this.domListen_(this.getNode(), "onChange");
},
unbind_: function () {
    this.domUnlisten_(this.node, "onChange");
    this.$supers('unbind_', arguments);
},
_doChange: function (evt) { //event listener
    //evt is an instance of jq.Event
},

Unlike jQuery's event listener (jq), Widget.domListen_(DOMElement, String, Object) will be ignored if the widget is under control of ZK Weaver (a WYSIWYG editor), i.e., in the so-called Design Mode. In most cases, a widget should not register any event listeners when it is under control of ZK Weaver to avoid any conflict.

Use jQuery

The use of jQuery (jq) is similar except using one of the event listening methods found in jQuery.

bind_: function () {
    this.$supers('bind_', arguments);
    jq(this.$n("form")).bind("reset", this.proxy(this._resetForm));
},
unbind_: function () {
    jq(this.$n("form")).unbind("reset", this.proxy(this._resetForm));
    this.$supers('unbind_', arguments);
},
_resetForm: function (evt) { //event listener
   this.doSomething(); //this refers to the widget since this.proxy is used
},

where we use Object.proxy(Function) to proxy a function such that this will refer to the widget when the method is called. Also notice that the event name used with jQuery does not start with on.

Version History

Last Update : 2022/01/18


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Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.