如何重置 ReactJS 文件输入

小开

最佳答案

I think you can just clear the input value like this :

e.target.value = null;

File input cannot be controlled, there is no React specific way to do that.

Edit For old browsers (<IE11), you can use one of the following techniques.

See http://jsbin.com/zurudemuma/1/edit?js,output (tested on IE10 & 9)

小开

What worked for me was setting a key attribute to the file input, then when I needed to reset it I update the key attribute value:

functionThatResetsTheFileInput() {
let randomString = Math.random().toString(36);


this.setState({
theInputKey: randomString
});
}


render() {
return(
<div>
<input type="file"
key={this.state.theInputKey || '' } />
<button onClick={this.functionThatResetsTheFileInput()} />
</div>
)
}

That forces React to render the input again from scratch.

小开

This work for me - ref={ref => this.fileInput = ref}

<input id="file_input_file" type="file" onChange={(e) => this._handleFileChange(e)} ref={ref=> this.fileInput = ref} />

then in my case once the file was uploaded to the server , I clear it by using the statement below

 this.fileInput.value = "";

小开

I know file input is always uncontrolled however the following code still works in my own porject, I can reset the input with no problems at all.

constructor(props) {
super(props);
this.state = {
selectedFile: undefined,
selectedFileName: undefined,
imageSrc: undefined,
value: ''
};


this.handleChange = this.handleChange.bind(this);
this.removeImage = this.removeImage.bind(this);
}


handleChange(event) {
if (event.target.files[0]) {
this.setState({
selectedFile: event.target.files[0],
selectedFileName: event.target.files[0].name,
imageSrc: window.URL.createObjectURL(event.target.files[0]),
value: event.target.value,
});
}
}


// Call this function to reset input
removeImage() {
this.setState({
selectedFile: undefined,
selectedFileName: undefined,
imageSrc: undefined,
value: ''
})
}


render() {
return (
<input type="file" value={this.state.value} onChange={this.handleChange} />
);
}

小开

Here is my solution using redux form

class FileInput extends React.Component {
constructor() {
super();


this.deleteImage = this.deleteImage.bind(this);
}


deleteImage() {
// Just setting input ref value to null did not work well with redux form
// At the same time just calling on change with nothing didn't do the trick
// just using onChange does the change in redux form but if you try selecting
// the same image again it doesn't show in the preview cause the onChange of the
// input is not called since for the input the value is not changing
// but for redux form would be.


this.fileInput.value = null;
this.props.input.onChange();
}


render() {
const { input: { onChange, value }, accept, disabled, error } = this.props;
const { edited } = this.state;


return (
<div className="file-input-expanded">
{/* ref and on change are key properties here */}
<input
className="hidden"
type="file"
onChange={e => onChange(e.target.files[0])}
multiple={false}
accept={accept}
capture
ref={(input) => { this.fileInput = input; }}
disabled={disabled}
/>
{!value ?
{/* Add button */}
<Button
className="btn-link action"
type="button"
text="Add Image"
onPress={() => this.fileInput.click()}
disabled={disabled}
/>
:
<div className="file-input-container">
<div className="flex-row">
{/* Image preview */}
<img src={window.URL.createObjectURL(value)} alt="outbound MMS" />
<div className="flex-col mg-l-20">
{/* This button does de replacing */}
<Button
type="button"
className="btn-link mg-b-10"
text="Change Image"
onPress={() => this.fileInput.click()}
disabled={disabled}
/>
{/* This button is the one that does de deleting */}
<Button
type="button"
className="btn-link delete"
text="Delete Image"
onPress={this.deleteImage}
disabled={disabled}
/>
</div>
</div>
{error &&
<div className="error-message"> {error}</div>
}
</div>
}
</div>
);
}
}


FileInput.propTypes = {
input: object.isRequired,
accept: string,
disabled: bool,
error: string
};


FileInput.defaultProps = {
accept: '*',
};


export default FileInput;

小开

You can also include this in your input element if you know you are not going to be using the built-in file input value at all.

<input value={""} ... />

This way the value is always reset to the empty string on render and you don't have to include it awkwardly in an onChange function.

小开

I do it by updating key inside my file input. This will force a re-render and previously selected file will go away.

<input type="file" key={this.state.inputKey} />

Changing the state inputKey will re-render the component. One way to change the inputKey will be to always set it to Date.now() on click of a button which is supposed to clear the field.

小开

With every click onClick you can reset the input, so that even with the same file onChange will be triggered.

<input onChange={this.onChange} onClick={e => (e.target.value = null)} type="file" />

小开

The following worked for me using React Hooks. This is done using what is known as a "controlled input". That means, the inputs are controlled by state, or their source of truth is state.

TL;DR Resetting the file input was a two-step process using both the useState() and useRef() hooks.

NOTE: I also included how I reset a text input in case anyone else was curious.

function CreatePost({ user }) {
const [content, setContent] = React.useState("");
const [image, setImage] = React.useState(null); //See Supporting Documentation #1
const imageInputRef = React.useRef(); //See Supporting Documentation #2


function handleSubmit(event) {
event.preventDefault(); //Stop the pesky default reload function
setContent(""); //Resets the value of the first input - See #1


//////START of File Input Reset
imageInputRef.current.value = "";//Resets the file name of the file input - See #2
setImage(null); //Resets the value of the file input - See #1
//////END of File Input Reset
}


return (
<div>
<form onSubmit={handleSubmit}>
<input
type="text"
placeholder="Add Post Content"
onChange={event => setContent(event.target.value)}
value={content} //Make this input's value, controlled by state
/>
<input
type="file"
onChange={event => setImage(event.target.files[0])} //See Supporting Doc #3
ref={imageInputRef} //Apply the ref to the input, now it's controlled - See #2
/>
<button type="submit">Submit Form</button>
</form>
</div>
)
};

Supporting Documentation:

useState Hook
- Returns a stateful value, and a function to update it.
useRef Hook
- If you pass a ref object to React, React will set its current property to the corresponding DOM node whenever that node changes.
Using files from web apps
- If the user selects just one file, it is then only necessary to consider the first file of the list.

小开

We can reset file input by using key = {this.state.fileInputKey} and initialsing fileInputKey to Date.now() in constructor state. On file upload success , we need to again assign fileInputKey: Date.now(), so it will have different value than previous and it create new file input component on next render()

We can also do this manually by clicking button to clear/reset file Input

Below is the working code :

import React from "react";
import { Button } from "reactstrap";


class FileUpload extends React.Component {
constructor(props) {
super(props);
this.state = {
selectedFile: null,
fileInputKey: Date.now(),
message: ""
};
this.handleClear = this.handleClear.bind(this);
this.onClickHandler = this.onClickHandler.bind(this);
this.onChangeHandler = this.onChangeHandler.bind(this);
}


onChangeHandler = event => {
this.setState({
selectedFile: event.target.files
});
};


onClickHandler = () => {
if (this.state.selectedFile === null) {
this.setState({
message: "Please select File"
});
return;
}
//axios POST req code to send file to server
{
/**
const data = new FormData()
data = this.state.selectedFile[0]
axios.post("http://localhost:8080/api/uploadFile/", data)
.then(res => {
if (res.status == 200) {
// upload success
}
})
.catch(err => {
//message upload failed
})
*/
}
//after upload to server processed


this.setState({
selectedFile: null,
fileInputKey: Date.now(),
message: "File Uploaded"
});
};


handleClear() {
this.setState({
selectedFile: null,
fileInputKey: Date.now(),
message: ""
});
}


render() {
return (
<div>
<input
type="file"
key={this.state.fileInputKey}
class="form-control"
onChange={this.onChangeHandler}
/>
<button
type="button"
class="btn btn-success btn-block"
onClick={this.onClickHandler}
>
Upload
</button>
<Button
type="button"
value="Clear"
data-test="clear"
onClick={this.handleClear}
>
{" "}
Clear{" "}
</Button>


<br />
<label>{this.state.message}</label>
</div>
);
}
}


export default FileUpload;

小开

In my case I had a functional component and after selecting a file it suppose to set the file name in the state so using any solution above was failing except the ref one which i fixed like this.

const fileUpload = props => {


const inputEl = useRef(null)
const onUpload = useCallback(e => {
uploadFile(fileDetails)
.then(res => {
inputEl.current.value = ''
})
.catch(err => {
inputEl.current.value = ''
})
})
    

return (
<input type='file' ref={inputEl} onChange={handleChange} />
<Button onClick={onUpload}>Upload</Button>
)
}

小开

import React, { useRef } from "react";


export default function App() {
const ref = useRef();


const reset = () => {
ref.current.value = "";
};


return (
<>
<input type="file" ref={ref} />
<button onClick={reset}>reset</button>
</>
);
}

小开

I recently got stumbled into this issue to reset the File type input field. I think it is still a milestone for most developers. So I thought I should share my solution.

Since we are listening to the onChange event to update the image file into some of our states, we will have our component rerendered once we set the state. In such case, we can specify the value of the input file as empty like value='' which will cause the input field to reset its value after each change of its value.

 <input
type="file"
value=''
onChange={onChangeFnc}
/>