思路:取手指最后一段时间在屏幕上划动的平均速度v,让v按一个递减函数变化,直到不能移动或v<=0
/** * 这里只实现垂直滚动 */ var parent = document.getElementById(‘parent‘); var content = document.getElementById(‘content‘) var startY = 0; // 初始位置 var lastY = 0; // 上一次位置 /** * 用于缓动的变量 */ var lastMoveTime = 0; var lastMoveStart = 0; var stopInertiaMove = false; // 是否停止缓动 parent.addEventListener(‘touchstart‘, function(e) { lastY = startY = e.touches[0].pageY; /** * 缓动代码 */ lastMoveStart = lastY; lastMoveTime = e.timeStamp || Date.now(); stopInertiaMove = true; }); parent.addEventListener(‘touchmove‘, function(e) { var nowY = e.touches[0].pageY; var moveY = nowY - lastY; var contentTop = content.style.top.replace(‘px‘, ‘‘); // 设置top值移动content content.style.top = (parseInt(contentTop) + moveY) + ‘px‘; lastY = nowY; /** * 缓动代码 */ var nowTime = e.timeStamp || Date.now(); stopInertiaMove = true; if(nowTime - lastMoveTime > 300) { lastMoveTime = nowTime; lastMoveStart = nowY; } }); parent.addEventListener(‘touchend‘, function(e) { // do touchend var nowY = e.touches[0].pageY; var moveY = nowY - lastY; var contentTop = content.style.top.replace(‘px‘, ‘‘); var contentY = (parseInt(contentTop) + moveY); // 设置top值移动content content.style.top = contentY + ‘px‘; lastY = nowY; /** * 缓动代码 */ var nowTime = e.timeStamp || Date.now(); var v = (nowY - lastMoveStart) / (nowTime - lastMoveTime); //最后一段时间手指划动速度 stopInertiaMove = false; (function(v, startTime, contentY) { var dir = v > 0 ? -1 : 1; //加速度方向 var deceleration = dir*0.0006; var duration = v / deceleration; // 速度消减至0所需时间 var dist = v * duration / 2; //最终移动多少 function inertiaMove() { if(stopInertiaMove) return; var nowTime = e.timeStamp || Date.now(); var t = nowTime-startTime; var nowV = v + t*deceleration; // 速度方向变化表示速度达到0了 if(dir*nowV < 0) { return; } var moveY = (v + nowV)/2 * t; content.style.top = (contentY + moveY) + "px"; setTimeout(inertiaMove, 10); } inertiaMove(); })(v, nowTime, contentY); });
时间: 2024-10-30 16:08:54