vue 画二维码及长按保存

需求

想要做如下图的二维码带文字，且能够长按保存

前期准备

1. 一个canvas
2. 安装qrcode（命令：npm i qrcode）

画二维码及文字

初始化画布

<template><div><canvas ref="canvas" width="300" height="400"></canvas></div>
</template><script setup>
import { ref, onMounted } from 'vue';
const canvas = ref(null);
onMounted(() => {// 初始化画布let ctx = canvas.value.getContext('2d');
})
</script>

画文字

<template><div><canvas ref="canvas" width="300" height="400"></canvas></div>
</template><script setup>
import { ref, onMounted } from 'vue';
const canvas = ref(null);
onMounted(() => {// 初始化画布let ctx = canvas.value.getContext('2d');// 填充白色ctx.fillStyle = "#fff";ctx.fillRect(0, 0, 300, 400);// 画文字ctx.font = "14px Microsoft YaHei"ctx.textBaseline = "middle";ctx.textAlign = "center";ctx.fillStyle = "#333333";ctx.fillText("简单教程，简单编程", canvas.value.width / 2, 40);
})
</script>

画二维码

二维码需要使用qrcode转换

<template><div><canvas ref="canvas" width="300" height="400"></canvas></div>
</template><script setup>
import QRCode from 'qrcode';
import { ref, onMounted } from 'vue';
const canvas = ref(null);
onMounted(() => {// 初始化画布let ctx = canvas.value.getContext('2d');// 填充白色ctx.fillStyle = "#fff";ctx.fillRect(0, 0, 300, 400);// 画文字ctx.font = "14px Microsoft YaHei"ctx.textBaseline = "middle";ctx.textAlign = "center";ctx.fillStyle = "#333333";ctx.fillText("简单教程，简单编程", canvas.value.width / 2, 40);// 画二维码QRCode.toDataURL('I am a pony!', function (err, url) {let img = new Image()img.src = url;img.onload = function () {ctx.drawImage(img, 50, 50, 200, 200);}})
})
</script>

长按保存

通过监听触摸事件的时间判定长按

<template><div><div class="friend" @touchstart="gtouchstart()" @touchmove="gtouchmove()" @touchend="showDeleteButton()"><canvas ref="canvas" width="300" height="400"></canvas></div></div>
</template><script setup>
import QRCode from 'qrcode';
import { ref, onMounted } from 'vue';
const canvas = ref(null);
onMounted(() => {let ctx = canvas.value.getContext('2d');// 填充白色ctx.fillStyle = "#fff";ctx.fillRect(0, 0, 300, 400);// 画文字ctx.font = "14px Microsoft YaHei"ctx.textBaseline = "middle";ctx.textAlign = "center";ctx.fillStyle = "#333333";ctx.fillText("简单教程，简单编程", canvas.value.width / 2, 40);// 画二维码QRCode.toDataURL('I am a pony!', function (err, url) {let img = new Image()img.src = url;img.onload = function () {ctx.drawImage(img, 50, 50, 200, 200);}})
})
let timeOutEvent = null //定时器 
//长按事件设置定时器
let gtouchstart = () => {timeOutEvent = setTimeout(() => {longPress()}, 700)
}//手释放，如果在200毫秒内就释放，则取消长按事件，此时可以执行onclick应该执行的事件
let showDeleteButton = () => {clearTimeout(timeOutEvent); //清除定时器if (timeOutEvent != 0) {timeOutEvent = 0;}return false;
}
//如果手指有移动，则取消所有事件，此时说明用户只是要移动而不是长按
let gtouchmove = () => {clearTimeout(timeOutEvent); //清除定时器timeOutEvent = 0
}
//真正长按后应该执行的内容
let longPress = () => {timeOutEvent = 0;// 创建一个链接元素const link = document.createElement("a");// 将Canvas转换为数据URLconst dataURL = canvas.value.toDataURL();// 设置链接的href属性为数据URLlink.href = dataURL;// 设置链接的下载属性和文件名link.download = "canvas_image.png";// 模拟点击链接进行下载link.click();
}
</script><style scoped></style>