如何在Angular 2中使用输入标签文件类型重置所选文件?

本文介绍了如何在Angular 2中使用输入标签文件类型重置所选文件?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

这是我的输入标签的样子:

This is how my input tag looks like:

<input type="file" placeholder="File Name" name="filename" (change)="onChange($event)">
<button>Reset</button>

我想在Angular 2中重置所选文件.非常感谢您的帮助.让我知道您是否需要更多详细信息.

I want to reset the selected file in Angular 2. Help would be greatly appreciated. Let me know if you need more details.

P.S.

我可以从$event参数获取文件详细信息，并将其保存在typescript变量中，但是此变量未绑定到输入标签.

I could get file details from $event parameters and save it in a typescript variable, but this variable is not bound to the input tag.

推荐答案

您可以使用ViewChild访问组件中的输入.首先，您需要在输入中添加#someValue以便可以在组件中读取它:

You can use ViewChild to access the input in your component. First, you need to add #someValue to your input so you can read it in the component:

<input #myInput type="file" placeholder="File Name" name="filename" (change)="onChange($event)">

然后在您的组件中，需要从@angular/core导入ViewChild:

Then in your component you need to import ViewChild from @angular/core:

import { ViewChild } from '@angular/core';

然后使用ViewChild来访问模板的输入:

Then you use ViewChild to access the input from template:

@ViewChild('myInput')
myInputVariable: ElementRef;

现在您可以使用myInputVariable重置所选文件，因为它是对#myInput输入的引用，例如创建方法reset()，该方法将在按钮的click事件上调用:

Now you can use myInputVariable to reset the selected file because it's a reference to input with #myInput, for example create method reset() that will be called on click event of your button:

reset() {
    console.log(this.myInputVariable.nativeElement.files);
    this.myInputVariable.nativeElement.value = "";
    console.log(this.myInputVariable.nativeElement.files);
}

第一个console.log将打印您选择的文件，第二个console.log将打印一个空数组，因为this.myInputVariable.nativeElement.value = "";从输入中删除所选文件.我们必须使用this.myInputVariable.nativeElement.value = "";来重置输入的值，因为输入的FileList属性是 readonly ，因此不可能仅从数组中删除项目.在这里工作柱塞.

First console.log will print the file you selected, second console.log will print an empty array because this.myInputVariable.nativeElement.value = ""; deletes selected file(s) from the input. We have to use this.myInputVariable.nativeElement.value = ""; to reset the value of the input because input's FileList attribute is readonly, so it is impossible to just remove item from array. Here's working Plunker.

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NativeElement