微信小程序canvas写字板效果及实例
写字板效果：书写文字，画板重置，导出图片，导出图片前判断是否书写内容
app.json：
添加一个路由："pages/canvas/canvas"
{ "pages":[ "pages/index/index", "pages/logs/logs", "pages/canvas/canvas" ], "window":{ "navigationBarBackgroundColor": "#ea6a46", "navigationBarTextStyle":"white", "navigationBarTitleText": "写字板", "backgroundTextStyle":"dark", "backgroundColor":"white", "enablePullDownRefresh":"true" } }
然后就是：
canvas.wxml:
<!--pages/canvas/canvas.wxml--> <canvas canvas-id="canvas" disable-scroll="true" bindtouchstart="canvasStart" bindtouchmove="canvasMove" bindtouchend="canvasEnd" touchcancel="canvasEnd" binderror="canvasIdErrorCallback"></canvas> <button type="default" bindtap="cleardraw">清除画布</button> <button type="default" bindtap="getimg">导出图片</button>
canvas.js:
// canvas 全局配置 var context = null;// 使用 wx.createContext 获取绘图上下文 context var isButtonDown = false; var arrx = []; var arry = []; var arrz = []; var canvasw = 0; var canvash = 0; //获取系统信息 wx.getSystemInfo({ success: function (res) { canvasw = res.windowWidth;//设备宽度 canvash = res.windowWidth*7/15; } }); //注册页面 Page({ canvasIdErrorCallback: function (e) { console.error(e.detail.errMsg) }, canvasStart: function (event){ isButtonDown = true; arrz.push(0); arrx.push(event.changedTouches[0].x); arry.push(event.changedTouches[0].y); //context.moveTo(event.changedTouches[0].x, event.changedTouches[0].y); }, canvasMove: function (event) { if (isButtonDown) { arrz.push(1); arrx.push(event.changedTouches[0].x); arry.push(event.changedTouches[0].y); // context.lineTo(event.changedTouches[0].x, event.changedTouches[0].y); // context.stroke(); // context.draw() }; for (var i = 0; i < arrx.length; i++) { if (arrz[i] == 0) { context.moveTo(arrx[i], arry[i]) } else { context.lineTo(arrx[i], arry[i]) }; }; context.clearRect(0, 0, canvasw, canvash); context.stroke(); context.draw(true); }, canvasEnd: function (event) { isButtonDown = false; }, cleardraw: function () { //清除画布 arrx = []; arry = []; arrz = []; context.clearRect(0, 0, canvasw, canvash); context.draw(true); }, getimg: function(){ if (arrx.length==0){ wx.showModal({ title: '提示', content: '签名内容不能为空！', showCancel: false }); return false; }; //生成图片 wx.canvasToTempFilePath({ canvasId: 'canvas', success: function (res) { console.log(res.tempFilePath); //存入服务器 wx.uploadFile({ url: 'a.php', //接口地址 filePath: res.tempFilePath, name: 'file', formData: { //HTTP 请求中其他额外的 form data 'user': 'test' }, success: function (res) { console.log(res); }, fail: function (res) { console.log(res); }, complete: function (res) { } }); } }) }, /** * 页面的初始数据 */ data: { src: "" }, /** * 生命周期函数--监听页面加载 */ onLoad: function (options) { // 使用 wx.createContext 获取绘图上下文 context context = wx.createCanvasContext('canvas'); context.beginPath() context.setStrokeStyle('#000000'); context.setLineWidth(4); context.setLineCap('round'); context.setLineJoin('round'); } })