自定义事件和监听器（Custom Events and Listeners）

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2023-12-01

当事情发生在课堂上时，事件会被触发。例如，在单击按钮时或在呈现元素之前/之后。

写事件的方法

使用侦听器的内置事件
Attaching events later
自定义活动

使用监听器的内置事件

Ext JS提供了侦听器属性，用于在Ext JS文件中编写事件和自定义事件。

Writing listener in Ext JS

我们将通过向面板添加listen属性来在前一个程序中添加监听器。

<!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 = "https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/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>

这样我们也可以在listeners属性中编写多个事件。

Multiple Events in the Same Listener

<!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 = "https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/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>

稍后附加事件

在前面编写事件的方法中，我们在创建元素时在侦听器中编写了事件。另一种方式是附加事件。

<!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 = "https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/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>

自定义事件

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。以下示例说明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 = "https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/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>

加载页面并准备文档后，将显示带有按钮的UI页面，当我们在5秒后触发事件时，文档就绪。警告框将在5秒后出现。

在这里，我们编写了自定义事件'myEvent'，我们将事件发送为button.fireEvent（eventName）;