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javascript - HTML Canvas 和 JavaScript - 悬停时缩放对象

转载 作者：太空宇宙 更新时间：2023-11-04 15:42:09 25 4
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下面的脚本绘制 4 个弯曲的矩形，并检测它们是否悬停在或单击 mouseup和mousemove事件监听器。当其中一个矩形悬停时，我希望它在一秒钟内稍微增长 - 当光标移离矩形时它应该收缩回来。

我遇到的问题是，我能想到的唯一方法是在 if (this.selected) { 中编写一个函数。子句为持续一秒的动画中的每一帧绘制矩形的新版本，但该子句位于绘制矩形本身的新版本的函数内部!那么，我怎样才能在curvedRect.prototype.makeCurvedRect之外编写一个函数呢？仅当光标位于其中一个矩形上时才运行？任何帮助将不胜感激。

var c=document.getElementById('game'),
		canvasX=c.offsetLeft,
		canvasY=c.offsetTop,
		ctx=c.getContext('2d');

var curvedRect = function(id, x, y, w, h) {
	this.id = id;
	this.x = x;
	this.y = y;
	this.w = w;
	this.h = h;
	this.selected = false;
}

curvedRect.prototype.makeCurvedRect = function() {
	ctx.beginPath();
	ctx.lineWidth='8';
	ctx.strokeStyle='white';
	ctx.moveTo(this.x+10, this.y);
	ctx.lineTo(this.x+this.w-10, this.y);
	ctx.quadraticCurveTo(this.x+this.w, this.y, this.x+this.w, this.y+10);
	ctx.lineTo(this.x+this.w, this.y+this.h-10);
	ctx.quadraticCurveTo(this.x+this.w, this.y+this.h, this.x+this.w-10, this.y+this.h);
	ctx.lineTo(this.x+10, this.y+this.h);
	ctx.quadraticCurveTo(this.x, this.y+this.h, this.x, this.y+this.h-10);
	ctx.lineTo(this.x, this.y+10);
	ctx.quadraticCurveTo(this.x, this.y, this.x+10, this.y);
	ctx.stroke();
	if (this.selected) {
        // BM67 edit By Blindman67 removed annoying alert and replaced it with console.log 
        // As I did not want to add elsewhere to the code to declare hoverMessageShown is safely declared here to stop the console repeating the message.
        if(window["hoverMessageShown"] === undefined){
           window["hoverMessageShown"] = true; 
  		   console.log('When hovered over, I would like this box to grow slightly over a short period of time (say a second). When the mouse is removed I would like it to shrink back.')
        }
        // BM67 end.
	}
}

curvedRect.prototype.hitTest = function(x, y) {
	return (x >= this.x) && (x <= (this.w+this.x)) && (y >= this.y) && (y <= (this.h+this.y));
}

var Paint = function(element) {
	this.element = element;
	this.shapes = [];
}

Paint.prototype.addShape = function(shape) {
	this.shapes.push(shape);
}

Paint.prototype.render = function() {
	this.element.w = this.element.w;
	for (var i=0; i<this.shapes.length; i++) {
		this.shapes[i].makeCurvedRect();
	}
}

Paint.prototype.setSelected = function(shape) {
	for (var i=0; i<this.shapes.length; i++) {
		this.shapes[i].selected = this.shapes[i] == shape;
	}
	this.render();
}

Paint.prototype.select = function(x, y) {
	for (var i=this.shapes.length-1; i >= 0; i--) {
		if (this.shapes[i].hitTest(x, y)) {
			return this.shapes[i];
		}
	}
	return null
}

var paint = new Paint(c);
var img1 = new curvedRect('1', 200, 55, 150, 150);
var img2 = new curvedRect('2', 375, 55, 150, 150);
var img3 = new curvedRect('3', 200, 230, 150, 150);
var img4 = new curvedRect('4', 375, 230, 150, 150);

paint.addShape(img1);
paint.addShape(img2);
paint.addShape(img3);
paint.addShape(img4);

paint.render();

function mouseUp(event) {
	var x = event.x - canvasX;
	var y = event.y - canvasY;
	var shape = paint.select(x, y);
	if (shape) {
		alert(shape.id);
	}
	// console.log('selected shape: ', shape);
}

function mouseMove(event) {
	var x = event.x - canvasX;
	var y = event.y - canvasY;
	var shape = paint.select(x, y);

	paint.setSelected(shape);
}

c.addEventListener('mouseup', mouseUp);
c.addEventListener('mousemove', mouseMove);
canvas {
  display: block;
  margin: 1em auto;
  border: 1px solid black;
  background: #FF9900;
}
<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>uTalk Demo</title>
	<link rel='stylesheet' type='text/css' href='game.css' media='screen'></style>
</head>
<body>
	<canvas id="game" width = "750" height = "500"></canvas>
</body>
</html>

最佳答案

将 makeCurvedRect 方法更改为如下所示:

var c=document.getElementById('game'),
		canvasX=c.offsetLeft,
		canvasY=c.offsetTop,
		ctx=c.getContext('2d');

var curvedRect = function(id, x, y, w, h) {
	this.id = id;
	this.x = x;
	this.y = y;
	this.w = w;
	this.h = h;
	this.selected = false;
}

curvedRect.prototype.makeCurvedRect = function() { 
    var delta = this.selected?10:0 ;
    var x = this.x - delta;
    var y = this.y - delta;
    var w  = this.w + (2*delta);
    var h = this.h + (2*delta);
	ctx.beginPath();
	ctx.lineWidth='8';
	ctx.strokeStyle='white';
	ctx.moveTo(x+10, y);
	ctx.lineTo(x+ w -10, y);
	ctx.quadraticCurveTo(x + w,  y,x + w,y + 10);
	ctx.lineTo( x + w,  y + h-10);
	ctx.quadraticCurveTo( x + w, y + h,  x +  w - 10,  y + h);
	ctx.lineTo(x + 10,y + h);
	ctx.quadraticCurveTo( x,  y + h, x,  y+h-10);
	ctx.lineTo(x, y+10);
	ctx.quadraticCurveTo(x, y, x+10, y);
	ctx.stroke();
	 
}

curvedRect.prototype.hitTest = function(x, y) {
	return (x >= this.x) && (x <= (this.w+this.x)) && (y >= this.y) && (y <= (this.h+this.y));
}

var Paint = function(element) {
	this.element = element;
	this.shapes = [];
}

Paint.prototype.addShape = function(shape) {
	this.shapes.push(shape);
}

Paint.prototype.render = function() {
	this.element.width = this.element.width;
	for (var i=0; i<this.shapes.length; i++) {
		this.shapes[i].makeCurvedRect();
	}
}

Paint.prototype.setSelected = function(shape) {
	for (var i=0; i<this.shapes.length; i++) {
		this.shapes[i].selected = this.shapes[i] == shape;
	}
	this.render();
}

Paint.prototype.select = function(x, y) {
	for (var i=this.shapes.length-1; i >= 0; i--) {
		if (this.shapes[i].hitTest(x, y)) {
			return this.shapes[i];
		}
	}
	return null
}

var paint = new Paint(c);
var img1 = new curvedRect('1', 200, 55, 150, 150);
var img2 = new curvedRect('2', 375, 55, 150, 150);
var img3 = new curvedRect('3', 200, 230, 150, 150);
var img4 = new curvedRect('4', 375, 230, 150, 150);

paint.addShape(img1);
paint.addShape(img2);
paint.addShape(img3);
paint.addShape(img4);

paint.render();

function mouseUp(event) {
	var x = event.x - canvasX;
	var y = event.y - canvasY;
	var shape = paint.select(x, y);
	if (shape) {
		alert(shape.id);
	}
	// console.log('selected shape: ', shape);
}

function mouseMove(event) {
	var x = event.x - canvasX;
	var y = event.y - canvasY;
	var shape = paint.select(x, y);

	paint.setSelected(shape);
}

c.addEventListener('mouseup', mouseUp);
c.addEventListener('mousemove', mouseMove);
canvas {
  display: block;
  margin: 1em auto;
  border: 1px solid black;
  background: #FF9900;
}
<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>uTalk Demo</title>
	<link rel='stylesheet' type='text/css' href='game.css' media='screen'></style>
</head>
<body>
	<canvas id="game" width = "750" height = "500"></canvas>
</body>
</html>

关于javascript - HTML Canvas 和 JavaScript - 悬停时缩放对象，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43788062/

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