小程序为何这么火_微信小程序canvas写字板效果及

微信小程序canvas写字板效果及实例       这篇文章主要介绍了微信小程序canvas写字板效果及实例的相关资料,需要的朋友可以参考下

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 id="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');