动画原理——用户交互：移动物体
书籍名称：HTML5-Animation-with-JavaScript
书籍源码：https://github.com/lamberta/html5-animation1
1.物体内外的事件
判断物体内外的条件是判断鼠标位置和物体中心的位置。
01-mouse-events.html
<!doctype html> <html> <head> <meta charset="utf-8"> <title>Mouse Events</title> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <textarea id="log"></textarea> <aside>Move and press mouse inside and outside of circle.</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'), mouse = utils.captureMouse(canvas), log = document.getElementById('log'), ball = new Ball(); ball.x = canvas.width / 2; ball.y = canvas.height / 2; ball.draw(context); canvas.addEventListener('mousedown', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { log.value = "in ball: mousedown"; } else { log.value = "canvas: mousedown"; } }, false); canvas.addEventListener('mousemove', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { log.value = "in ball: mousemove"; } else { log.value = "canvas: mousemove"; } }, false); canvas.addEventListener('mouseup', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { log.value = "in ball: mouseup"; } else { log.value = "canvas: mouseup"; } }, false); }; </script> </body> </html>
手机事件
02-touch-events.html
<!doctype html> <html> <head> <meta charset="utf-8"> <title>Touch Events</title> <meta name="viewport" content="width=device-width,initial-scale=1.0,user-scalable=no"> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <textarea id="log"></textarea> <aside>Press and move touch inside and outside of circle (touch-capable device required).</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'), touch = utils.captureTouch(canvas), log = document.getElementById('log'), ball = new Ball(); ball.x = canvas.width / 2; ball.y = canvas.height / 2; ball.draw(context); canvas.addEventListener('touchstart', function (event) { event.preventDefault(); if (utils.containsPoint(ball.getBounds(), touch.x, touch.y)) { log.value = "in ball: touchstart"; } else { log.value = "canvas: touchstart"; } }, false); canvas.addEventListener('touchend', function (event) { event.preventDefault(); log.value = "canvas: touchend"; }, false); canvas.addEventListener('touchmove', function (event) { event.preventDefault(); if (utils.containsPoint(ball.getBounds(), touch.x, touch.y)) { log.value = "in ball: touchmove"; } else { log.value = "canvas: touchmove"; } }, false); }; </script> </body> </html>
2.拖动
将鼠标的位置设置给物体的位置
03-mouse-move-drag.html
View Code
3.将拖动交互和运动效果合并
04-drag-and-move-1.html
<!doctype html> <html> <head> <meta charset="utf-8"> <title>Drag and Move 1</title> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <aside>Press and drag circle with mouse.</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'), mouse = utils.captureMouse(canvas), ball = new Ball(), vx = Math.random() * 10 - 5, vy = -10, bounce = -0.7, gravity = 0.2, isMouseDown = false; ball.x = canvas.width / 2; ball.y = canvas.height / 2; canvas.addEventListener('mousedown', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { isMouseDown = true; canvas.addEventListener('mouseup', onMouseUp, false); canvas.addEventListener('mousemove', onMouseMove, false); } }, false); function onMouseUp () { isMouseDown = false; canvas.removeEventListener('mouseup', onMouseUp, false); canvas.removeEventListener('mousemove', onMouseMove, false); } function onMouseMove (event) { ball.x = mouse.x; ball.y = mouse.y; } function checkBoundaries () { var left = 0, right = canvas.width, top = 0, bottom = canvas.height; vy += gravity; ball.x += vx; ball.y += vy; //boundary detect and bounce if (ball.x + ball.radius > right) { ball.x = right - ball.radius; vx *= bounce; } else if (ball.x - ball.radius < left) { ball.x = left + ball.radius; vx *= bounce; } if (ball.y + ball.radius > bottom) { ball.y = bottom - ball.radius; vy *= bounce; } else if (ball.y - ball.radius < top) { ball.y = top + ball.radius; vy *= bounce; } } (function drawFrame () { window.requestAnimationFrame(drawFrame, canvas); context.clearRect(0, 0, canvas.width, canvas.height); if (!isMouseDown) { checkBoundaries(); } ball.draw(context); }()); }; </script> </body> </html>
05-drag-and-move-2.html
解决每次拖动速度不清零的问题
<!doctype html> <html> <head> <meta charset="utf-8"> <title>Drag and Move 2</title> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <aside>Press and drag circle with mouse.</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'), mouse = utils.captureMouse(canvas), ball = new Ball(), vx = Math.random() * 10 - 5, vy = -10, bounce = -0.7, gravity = 0.2, isMouseDown = false; ball.x = canvas.width / 2; ball.y = canvas.height / 2; canvas.addEventListener('mousedown', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { isMouseDown = true; vx = vy = 0; canvas.addEventListener('mouseup', onMouseUp, false); canvas.addEventListener('mousemove', onMouseMove, false); } }, false); function onMouseUp () { isMouseDown = false; canvas.removeEventListener('mouseup', onMouseUp, false); canvas.removeEventListener('mousemove', onMouseMove, false); } function onMouseMove (event) { ball.x = mouse.x; ball.y = mouse.y; } function checkBoundaries () { var left = 0, right = canvas.width, top = 0, bottom = canvas.height; vy += gravity; ball.x += vx; ball.y += vy; //boundary detect and bounce if (ball.x + ball.radius > right) { ball.x = right - ball.radius; vx *= bounce; } else if (ball.x - ball.radius < left) { ball.x = left + ball.radius; vx *= bounce; } if (ball.y + ball.radius > bottom) { ball.y = bottom - ball.radius; vy *= bounce; } else if (ball.y - ball.radius < top) { ball.y = top + ball.radius; vy *= bounce; } } (function drawFrame () { window.requestAnimationFrame(drawFrame, canvas); context.clearRect(0, 0, canvas.width, canvas.height); if (!isMouseDown) { checkBoundaries(); } ball.draw(context); }()); }; </script> </body> </html>
4.抛
存储物体的位置，两帧中两个物体的位移即为物体的初始速度。
<!doctype html> <html> <head> <meta charset="utf-8"> <title>Throwing</title> <link rel="stylesheet" href="../include/style.css"> </head> <body> <header> Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a> </header> <canvas id="canvas" width="400" height="400"></canvas> <aside>Press, drag, and throw circle with mouse.</aside> <script src="../include/utils.js"></script> <script src="./classes/ball.js"></script> <script> window.onload = function () { var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'), mouse = utils.captureMouse(canvas), ball = new Ball(), vx = Math.random() * 10 - 5, vy = -10, bounce = -0.7, gravity = 0.2, isMouseDown = false, oldX, oldY; ball.x = canvas.width / 2; ball.y = canvas.height / 2; canvas.addEventListener('mousedown', function () { if (utils.containsPoint(ball.getBounds(), mouse.x, mouse.y)) { isMouseDown = true; oldX = ball.x; oldY = ball.y; canvas.addEventListener('mouseup', onMouseUp, false); canvas.addEventListener('mousemove', onMouseMove, false); } }, false); function onMouseUp () { isMouseDown = false; canvas.removeEventListener('mouseup', onMouseUp, false); canvas.removeEventListener('mousemove', onMouseMove, false); } function onMouseMove (event) { ball.x = mouse.x; ball.y = mouse.y; } function trackVelocity () { vx = ball.x - oldX; vy = ball.y - oldY; oldX = ball.x; oldY = ball.y; } function checkBoundaries () { var left = 0, right = canvas.width, top = 0, bottom = canvas.height; vy += gravity; ball.x += vx; ball.y += vy; //boundary detect and bounce if (ball.x + ball.radius > right) { ball.x = right - ball.radius; vx *= bounce; } else if (ball.x - ball.radius < left) { ball.x = left + ball.radius; vx *= bounce; } if (ball.y + ball.radius > bottom) { ball.y = bottom - ball.radius; vy *= bounce; } else if (ball.y - ball.radius < top) { ball.y = top + ball.radius; vy *= bounce; } } (function drawFrame () { window.requestAnimationFrame(drawFrame, canvas); context.clearRect(0, 0, canvas.width, canvas.height); if (isMouseDown) { trackVelocity(); } else { checkBoundaries(); } ball.draw(context); }()); }; </script> </body> </html>
06-throwing.html