事件是在类发生的时候触发的。 例如，当一个按钮被点击或元素被渲染之前/之后。
ext js提供了用于在ext js文件中编写事件和自定义事件的侦听器属性。
在ext js中编写侦听器
我们将通过在面板中添加listen属性来将监听器添加到上一个程序中，如下所示:
<!doctype html>
<html>
<head>
<link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/classic/theme-neptune/resources/theme-neptune-all.css" rel="stylesheet" />
<script type="text/javascript" src="/attachements/w3c/ext-all.js"></script>
<script type="text/javascript">
ext.onready(function(){
ext.create('ext.button', {
renderto: ext.getelementbyid('helloworldpanel'),
text: 'my button',
listeners: {
click: function() {
ext.messagebox.alert('alert box', 'button is clicked');
}
}
});
});
</script>
</head>
<body>
<p> please click the button to see event listener </p>
<div id = 'helloworldpanel' /> <!-- panel will be rendered here-- >
</body>
</html>
这会产生以下结果:
这样我们可以在listeners属性中写多个事件。
同一个侦听器中的多个事件
<!doctype html>
<html>
<head>
<link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/classic/theme-neptune/resources/theme-neptune-all.css" rel="stylesheet" />
<script type="text/javascript" src="/attachements/w3c/ext-all.js"></script>
<script type="text/javascript">
ext.onready(function(){
ext.get('tag2').hide()
ext.create('ext.button', {
renderto: ext.getelementbyid('helloworldpanel'),
text: 'my button',
listeners: {
click: function() {
this.hide();
},
hide: function() {
ext.get('tag1').hide();
ext.get('tag2').show();
}
}
});
});
</script>
</head>
<body>
<div id = "tag1">please click the button to see event listener.</div>
<div id = "tag2">the button was clicked and now it is hidden.</div>
<div id = 'helloworldpanel' /> <!-- panel will be rendered here-- >
</body>
</html>
在前面的写事件的方法中，我们在创建元素时在侦听器中写入事件。
其他方式是附加事件在as:
<!doctype html>
<html>
<head>
<link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/classic/theme-neptune/resources/theme-neptune-all.css" rel="stylesheet" />
<script type="text/javascript" src="/attachements/w3c/ext-all.js"></script>
<script type="text/javascript">
ext.onready(function(){
var button = ext.create('ext.button', {
renderto: ext.getelementbyid('helloworldpanel'),
text: 'my button'
});
// this way we can attach event to the button after the button is created.
button.on('click', function() {
ext.messagebox.alert('alert box', 'button is clicked');
});
});
</script>
</head>
<body>
<p> please click the button to see event listener </p>
<div id = 'helloworldpanel' /> <!-- panel will be rendered here-- >
</body>
</html>
我们可以在ext js中编写自定义事件，并使用fireevent方法触发事件，下面的示例解释了如何编写自定义事件。
<!doctype html>
<html>
<head>
<link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/classic/theme-neptune/resources/theme-neptune-all.css" rel="stylesheet" />
<script type="text/javascript" src="/attachements/w3c/ext-all.js"></script>
<script type="text/javascript">
ext.onready(function(){
var button = ext.create('ext.button', {
renderto: ext.getelementbyid('helloworldpanel'),
text: 'my button',
listeners: {
myevent: function(button) {
ext.messagebox.alert('alert box', 'my custom event is called');
}
}
});
ext.defer(function() {
button.fireevent('myevent');
}, 5000);
});
</script>
</head>
<body>
<p> the event will be called after 5 seconds when the page is loaded. </p>
<div id = 'helloworldpanel' /> <!-- panel will be rendered here-- >
</body>
</html>
一旦页面被加载并且文档准备就绪，ui页面与按钮将出现，并且我们在5秒后触发事件文档准备就绪，警报框将在5秒后出现。
这里我们写了自定义事件\'myevent\'，我们将事件触发为button.fireevent（eventname）;
这些是在ext js中编写事件的三种方式。
