ReactJS 中的图像模式，带有幻灯片，使用 JavaScript

Question

I am trying to use this image lightbox in a React app:

https://www.w3schools.com/howto/howto_js_lightbox.asp

This is the code sandbox link what have tried

https://codesandbox.io/s/reactjs-practice-vbxwt

The image modal works fine for me. But it seems to be not working when I try to implement a slider.I want implement the slider for eachlist. I am getting the image data from a backend.

Here is how I am getting all the image data:

{
    "results": [{
        "data": [{
            "id": "f06f2cdf-1bb8-4388-a655-4e916a2703ce",
            "visitRequirementList": [{
                "imageName": "dining pic 1",
                "imagePath": "visitImageDirectory/0297b1ef-644b-45fc-9760-4e5693f54ac0.png",
            }, {
                "imageName": "dining pic 2",
                "imagePath": "visitImageDirectory/1b4915c1-733a-4bdb-a8d7-59ce3a095d44.png",
            }]
        }, {
            "id": "ce059d7a-d3d4-462c-a90f-62be13f24a29",
            "visitRequirementList": [{
                "imageName": "bedroom pic 1",
                "imagePath": "visitImageDirectory/64960b86-f9bf-4de9-816f-f27487245c53.png",
            }]
        }]
    }],
    "message": "data Found",
    "status": "success"
}

This is my render method for showing the images:

import React, { Component } from 'react';

export default class extends Component {
    state = {
        showModal: false,
        caption: '',
        modalSrc: '',
        ioImageListing: [],

        // ...rest of the state
    };
    componentDidMount() {
        this.getAllProjectRequirementImageList();
    }
    getAllProjectRequirementImageList = () => {
        axios.get(this.state.apiUrl+'/api/v1/visitRequirement/getAllByProjectId', {
            params: {   projectId: this.state.projectId }
        }).then((response) => {
            console.log("get with list ImageData",response.data.data);
            this.setState({ ioImageListing: response.data.data  });
        }).catch((error)=>{  console.log("error",error); this.setState({ ioImageListing: []  });   });
    }



    render() {
        return (
            <div>
                <div style={{}}>
                    {this.state.ioImageListing.map((io, key) =>
                        <Grid container spacing={24}>
                            {io.visitRequirementList.map((pic, key) => [
                                <Grid style={{position: 'relative'}} item xs={3} key={key}>
                                <span key={key}>
                                    <img
                                        src={this.state.apiUrl + '/api/v1/visitImageRequirementInfo/getImageByImagePathId?imagePath=' + pic.imagePath}
                                        onClick={() => {
                                            this.setState({
                                                showModal: true,
                                                caption: `${pic.imageName}`,
                                                slideIndex: `${io.visitRequirementList.length}`,
                                                modalSrc: `${this.state.apiUrl}/api/v1/visitImageRequirementInfo/getImageByImagePathId?imagePath=${pic.imagePath}`,
                                                count: `${key}`
                                            });
                                        }}
                                    />
                                </span>
                                </Grid>
                            ])}
                        </Grid>
                    )}
                </div>
                <div id="myModal" className="modal" style={{display: this.state.showModal ? 'block' : 'none'}}>
                    <div>
                        <span className="close" onClick={() => this.setState({showModal: false})}>&times;</span>
                        <div className="mySlides"><img className="modal-content" id="img01" src={this.state.modalSrc}/>
                        </div>
                        <a className="prev" onClick={() => {
                            this.plusSlides(-1)
                        }}>&#10094;</a>
                        <a className="next" onClick={() => {
                            this.plusSlides(1)
                        }}>&#10095;</a>
                    </div>
                </div>
            </div>
        );
    }
}

And this is the function I wrote for showing the slider:

    plusSlides = (n) => {
        var slideIndex=parseFloat(this.state.count);
        slideIndex=slideIndex+n
        this.setState({ count: slideIndex  });

        this.showSlides(slideIndex, n);
    }

  showSlides(slideIndex,n) {
        var i;
        var slides = document.getElementsByClassName("mySlides");
        if (n > slides.length) {slideIndex = 1}
        if (n < 1) {slideIndex = slides.length}
        for (i = 1; i < slides.length; i++) {
            slides[i].style.display = "none";
        }
        slides[slideIndex-1].style.display = "block";
    }

When the image modal opens, I am tring to turn it into a slide on click on my next and previous buttons. What i am doing wrong?

Answer 1

First of all, you are not using React in a correct way. The function showSlides uses DOM manipulation directly. Always avoid manipulating DOM directly instead update the state to desired value and let React handle the DOM for you.

Having said that, let me explain how your slider will work in a reactive way by just updating the state . So far you have managed to make the modal work. The slider logic will be as follows ( codesandbox link ):

Your imageListData is a list of list. For clarity I will be referring the outer list as section

1 - On clicking any image, update the state with following data:

showModal // to toggle the visibility of modal
caption // caption for current image
modalSrc // current image source
sectionIndex // current index of outer list
imageIndex // index of current image
currentSectionLength // outer list, i.e. section length

2 - On clicking the Next or Previous button, we will only update the state mentioned in step 1 and the slider will work. The only thing to think about is the logic to update the state with correct values. I will try to explain it through comments. All the logic is in plusSlides function.

plusSlides = n => {
    const { ioImageListing, imageIndex, sectionIndex, currentSectionLength } = this.state; // extract all the current values from the state

    const nextIndex = imageIndex + n; // add or subtract 1 to get nextIndex. This is temporary. We will use this to determine next image on the slider.
    const numberOfSections = ioImageListing.length; // count of number of outer list.

    if (nextIndex < 0 && sectionIndex === 0) {
      // this means we are at the 1st image of 1st section. Hence no more left navigation, and the function returns. No more execution.
      alert("NO MORE LEFT IMAGE");
      return;
    }

    if (sectionIndex === numberOfSections - 1 && nextIndex > ioImageListing[numberOfSections - 1].visitRequirementList.length - 1) {
      // this condition says we are at the last image of last section. Hence no more right navigation, and the function returns. No more execution.
      alert("NO MORE RIGHT IMAGE");
      return;
    }

    let nextImage, nextImageIndex, nextSectionIndex, nextSectionLength; // these variables will hold the value for next image to be shown determined by the following logic

    if (nextIndex >= 0 && nextIndex < currentSectionLength) {
      // if the nextIndex is >=0 and less than the length of currentSectionLength, it means our next/previous image is in the same section. So we only need to update nextImage data whereas section data remains same
      nextImage = ioImageListing[sectionIndex].visitRequirementList[nextIndex];
      nextImageIndex = nextIndex;
      nextSectionIndex = sectionIndex;
      nextSectionLength = currentSectionLength;
    } else if (nextIndex < 0) {
      // if the nextIndex is less than 0, it means our previous image is in the previous section and it has to be the last image of previous section. So we update both nextImage data and section data accordingly.
      nextImage = ioImageListing[sectionIndex - 1].visitRequirementList[ioImageListing[sectionIndex - 1].visitRequirementList.length - 1];
      nextImageIndex = ioImageListing[sectionIndex - 1].visitRequirementList.length - 1;
      nextSectionIndex = sectionIndex - 1;
      nextSectionLength = ioImageListing[sectionIndex - 1].visitRequirementList.length
    } else {
      // atlast if the nextIndex >= currentSectionLength, it means our next image is in the next section and it has to be the first image of next section. So we update both nextImage data and section data accordingly.
      nextImage = ioImageListing[sectionIndex + 1].visitRequirementList[0];
      nextImageIndex = 0;
      nextSectionIndex = sectionIndex + 1;
      nextSectionLength = ioImageListing[sectionIndex + 1].visitRequirementList.length;
    }

    // finally we update the state with current next values, and the slider works as expected.
    this.setState({
      caption: nextImage.imageName,
      modalSrc: nextImage.imagePath,
      imageIndex:nextImageIndex,
      sectionIndex: nextSectionIndex,
      currentSectionLength:nextSectionLength
    });
  }

I hope it helps. Let me know if there is any doubt. The working code is available in the link

Answer 2

You need to save images in an array: Save those images into state then change the img inside of "mySlides" to be like this:

/** -- snip -- **/
// Inside of "mySlides" div
<img 
    className="modal-content" 
    id="img01" 
    src={this.state.images[this.state.count]}
/>