javascript - 在 p5.js 中单击按钮更改图像

Question

我有一个充满单元格的二维数组。我希望此单元格在按下按钮时更新图像。我想将值传递给构造函数，但出了点问题，它现在无法正常工作。我的想法是传递给构造函数图像值 this.img = img，然后在 show_cell 函数中将图像值更改为 this.img 值。当我按下按钮时，它开始运行，我将图像添加到构造函数并显示网格。这些都不起作用。请帮忙，这让我很头疼。

Answer 1

您必须在 draw() 中绘制网格.注意，draw()是不断被系统调用并重新绘制整个窗口，是应用循环。在 draw 开始时，您必须设置背景颜色 ( background() )，然后绘制整个场景。

当按下按钮时设置一个状态变量(show_grid):

let show_grid = false;
function a(){
    show_grid = true;
}

根据变量的状态绘制网格:

function draw() {

    background(255);

    if (show_grid) {
        grid.display();
    }

    fill(255);
    stroke(0);
    let fps = frameRate();
    text("FPS: " + fps.toFixed(0), 10, height - 10);
}

如果您想在单击按钮时更改图像，那么您必须使用变量(例如current_img`)来绘制单元格:

class Cell {
    constructor (column, row, size) {
        this.x = column;
        this.y = row;
        this.w = size;
    }
    show_cell () {
        image(current_img, this.x * this.w , this.y * this.w , this.w , this.w );
    }
}

单击按钮时，必须更改 current_image:

function a(){
    show_grid = true;
    current_img = img1;
}

function b(){
    show_grid = true;
    current_img = img2;
}

看例子:

var grid;
var current_img;
var img1;
var img2;
function preload(){
  img1 = loadImage('https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/fish64.png');
  img2 = loadImage('https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/ball64.png');
}

function setup() {
    const background_btn1 = select('#BgCategory1-btn1');
    background_btn1.mousePressed(a);
    const background_btn2 = select('#BgCategory1-btn2');
    background_btn2.mousePressed(b);
    let cnv = createCanvas(1000, 1000);
    cnv.parent('canvas-holder');
    grid = new Grid(40);
    current_img = img1;
} 

function draw() {
    background(128);
  
    if (show_grid) {
        grid.display();
    }

    fill(255);
    stroke(0);
    let fps = frameRate();
    text("FPS: " + fps.toFixed(0), 10, 30);
}

let show_grid = false;

function a(){
    show_grid = true;
    current_img = img1;
}

function b(){
    show_grid = true;
    current_img = img2;
}

class Grid {
    constructor (cellSize) {
      this.cellSize = cellSize;
      this.numberOfColumns = floor(width / this.cellSize);
      this.numberOfRows = floor(height / this.cellSize);

      this.cells = new Array(this.numberOfColumns);
      for (var column = 0; column < this.numberOfColumns; column ++) {
          this.cells[column] = new Array(this.numberOfRows);
      }

      for (var column = 0; column < this.numberOfColumns; column ++) {
          for (var row = 0; row < this.numberOfRows; row++) {
              this.cells[column][row] = new Cell(column, row, cellSize)  
          }
      }
    }

    display () {
        for (var column = 0; column < this.numberOfColumns; column ++) {
            for (var row = 0; row < this.numberOfRows; row++) {
                this.cells[column][row].show_cell();
            }
        }
    }
}

class Cell {
    constructor (column, row, size) {
        this.x = column;
        this.y = row;
        this.w = size;
    }
    show_cell () {
        image(current_img, this.x * this.w , this.y * this.w , this.w , this.w );
    }
}

#BgCategory1-btn1 { position: absolute; top: 0; left: 0; }
#BgCategory1-btn2 { position: absolute; top: 0; left: 10%; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.9.0/p5.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.9.0/addons/p5.dom.js"></script>
<button id= "BgCategory1-btn1" >image 1</button>
<button id= "BgCategory1-btn2" >image 2</button>
<div id = "canvas-holder"></div>