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📜  Angular7-事件绑定

📅  最后修改于: 2020-10-27 02:30:03             🧑  作者: Mango

在本章中，我们将讨论事件绑定在Angular 7中的工作方式。当用户以键盘移动，鼠标单击或鼠标悬停的形式与应用程序交互时，它将生成一个事件。需要处理这些事件以执行某种操作。这是事件绑定出现的地方。

让我们考虑一个例子，以更好地理解这一点。

app.component.html




   
Welcome to {{title}}.





 Months :
   







   
      Condition is valid.
   
   Condition is valid
   Condition is invalid

在app.component.html文件中，我们定义了一个按钮，并使用click事件向其中添加了一个函数。

以下是定义按钮并为其添加函数的语法。

(click) = "myClickFunction($event)"

该函数在以下位置定义： app.component.ts

import { Component } from '@angular/core';
@Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css']
})
export class AppComponent {
   title = 'Angular 7';
   
   // declared array of months.
   months = ["January", "February", "March", "April", "May","June", "July", 
      "August", "September", "October", "November", "December"];
   
   isavailable = true; //variable is set to true
   myClickFunction(event) {
      //just added console.log which will display the event details in browser on click of the button.
      alert("Button is clicked");
      console.log(event);
   }
}

单击按钮后，控件将转到函数myClickFunction ，将出现一个对话框，该对话框显示单击了Button ，如以下屏幕截图所示-

请点击

按钮的样式添加在add.component.css中-

button {
   background-color: #2B3BCF;
   border: none;
   color: white;
   padding: 10px 10px;
   text-align: center;
   text-decoration: none;
   display: inline-block;
   font-size: 20px;
}

现在让我们将onchange事件添加到下拉列表中。

以下代码行将帮助您将change事件添加到下拉列表中-

app.component.html




   
Welcome to {{title}}.





 Months :
   







   
      Condition is valid.
   
   Condition is valid
   Condition is invalid

该函数在app.component.ts文件中声明-

import { Component } from '@angular/core';
@Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css']
})
export class AppComponent {
   title = 'Angular 7';
   
   // declared array of months.
   months = ["January", "Feburary", "March", "April", "May", "June", "July", 
      "August", "September", "October", "November", "December"];
   
   isavailable = true; //variable is set to true
   myClickFunction(event) {
      //just added console.log which will display the event 
      details in browser on click of the button.
      alert("Button is clicked");
      console.log(event);
   }
   changemonths(event) {
      console.log("Changed month from the Dropdown");
      console.log(event);
   }
}

从下拉列表中选择月份，您会看到控制台消息“事件从下拉列表中更改了月份”以及事件。

落下

当下拉菜单中的值更改时，让我们在app.component.ts中添加警报消息，如下所示-

import { Component } from '@angular/core';
@Component({ 
   selector: 'app-root', 
   templateUrl: './app.component.html', 
   styleUrls: ['./app.component.css'] 
}) 
export class AppComponent { 
   title = 'Angular 7'; 
   
   // declared array of months. 
   months = ["January", "February", "March", "April", "May", "June", "July", 
      "August", "September", "October", "November", "December"]; 
   
   isavailable = true; //variable is set to true 
   myClickFunction(event) { 
      //just added console.log which will display the event 
      details in browser on click of the button. 
      alert("Button is clicked"); console.log(event); 
   } 
   changemonths(event) { 
      alert("Changed month from the Dropdown");
   } 
}

更改下拉列表中的值时，将出现一个对话框，并显示以下消息：

“从下拉菜单更改月份”。

健康）状况