AngularJS 仿微信图片手势缩放的实例
前言：
最近，公司做一个混合应用项目，涉及到一个图片缩放功能，类似微信那样支持touch事件。
亲测，实现方案很不错，所以放出来，和大家分享一下，希望有人能用得到。
核心思想就是用到了CSS3的transform属性， 不多说，我们看代码：
'use strict'; /** * @ngInject */ module.exports = function () { var _directive = { restrict : 'A', scope : false, link : _link }; function _link(scope, element, attrs) { var elWidth, elHeight; // mode : 'pinch' or 'swipe' var mode = ''; // distance between two touche points (mode : 'pinch') var distance = 0; var initialDistance = 0; // image scaling var scale = 1; var relativeScale = 1; var initialScale = 1; var maxScale = parseInt(attrs.maxScale, 10); if (isNaN(maxScale) || maxScale <= 1) { maxScale = 3; } // position of the upper left corner of the element var positionX = 0; var positionY = 0; var initialPositionX = 0; var initialPositionY = 0; // central origin (mode : 'pinch') var originX = 0; var originY = 0; // start coordinate and amount of movement (mode : 'swipe') var startX = 0; var startY = 0; var moveX = 0; var moveY = 0; var image = new Image(); image.onload = function() { elWidth = element[0].clientWidth; elHeight = element[0].clientHeight; element.css({ '-webkit-transform-origin' : '0 0', 'transform-origin' : '0 0' }); element.on('touchstart', touchstartHandler); element.on('touchmove', touchmoveHandler); element.on('touchend', touchendHandler); }; if (attrs.ngSrc) { image.src = attrs.ngSrc; } else { image.src = attrs.src; } /** * @param {object} evt */ function touchstartHandler(evt) { var touches = evt.originalEvent ? evt.originalEvent.touches : evt.touches; startX = touches[0].clientX; startY = touches[0].clientY; initialPositionX = positionX; initialPositionY = positionY; moveX = 0; moveY = 0; } /** * @param {object} evt */ function touchmoveHandler(evt) { var touches = evt.originalEvent ? evt.originalEvent.touches : evt.touches; if (mode === '') { if (touches.length === 1 && scale > 1) { mode = 'swipe'; } else if (touches.length === 2) { mode = 'pinch'; initialScale = scale; initialDistance = getDistance(touches); originX = touches[0].clientX - parseInt((touches[0].clientX - touches[1].clientX) / 2, 10) - element[0].offsetLeft - initialPositionX; originY = touches[0].clientY - parseInt((touches[0].clientY - touches[1].clientY) / 2, 10) - element[0].offsetTop - initialPositionY; } } if (mode === 'swipe') { evt.preventDefault(); moveX = touches[0].clientX - startX; moveY = touches[0].clientY - startY; positionX = initialPositionX + moveX; positionY = initialPositionY + moveY; transformElement(); } else if (mode === 'pinch') { evt.preventDefault(); distance = getDistance(touches); relativeScale = distance / initialDistance; scale = relativeScale * initialScale; positionX = originX * (1 - relativeScale) + initialPositionX + moveX; positionY = originY * (1 - relativeScale) + initialPositionY + moveY; transformElement(); } } /** * @param {object} evt */ function touchendHandler(evt) { var touches = evt.originalEvent ? evt.originalEvent.touches : evt.touches; if (mode === '' || touches.length > 0) { return; } if (scale < 1) { scale = 1; positionX = 0; positionY = 0; } else if (scale > maxScale) { scale = maxScale; relativeScale = scale / initialScale; positionX = originX * (1 - relativeScale) + initialPositionX + moveX; positionY = originY * (1 - relativeScale) + initialPositionY + moveY; } else { if (positionX > 0) { positionX = 0; } else if (positionX < elWidth * (1 - scale)) { positionX = elWidth * (1 - scale); } if (positionY > 0) { positionY = 0; } else if (positionY < elHeight * (1 - scale)) { positionY = elHeight * (1 - scale); } } transformElement(0.1); mode = ''; } /** * @param {Array} touches * @return {number} */ function getDistance(touches) { var d = Math.sqrt(Math.pow(touches[0].clientX - touches[1].clientX, 2) + Math.pow(touches[0].clientY - touches[1].clientY, 2)); return parseInt(d, 10); } /** * @param {number} [duration] */ function transformElement(duration) { var transition = duration ? 'all cubic-bezier(0,0,.5,1) ' + duration + 's' : ''; var matrixArray = [scale, 0, 0, scale, positionX, positionY]; var matrix = 'matrix(' + matrixArray.join(',') + ')'; element.css({ '-webkit-transition' : transition, transition : transition, '-webkit-transform' : matrix + ' translate3d(0,0,0)', transform : matrix }); } } return _directive; };
上面代码中我们新建了一个directive，方便多个地方重用。
当我们建立好directive时候，该如何使用呢？
<img src="https://www.jb51.net/assets/images/floorplan.jpeg" ng-pinch-zoom>
我们只需要在img文件上设定一个属性即可，是不是很简单呢？