实现横屏签字版可以利用uniapp中的canvas以及第三方的canvas插件实现。
步骤一:安装canvas插件
在uniapp中使用canvas需要下载并安装canvas插件,下载地址为:https://ext.dcloud.net.cn/plugin?id=127
下载完成后,在uniapp项目的根目录下,打开cmd或者终端并输入如下命令:
npm install canvas-uniapp -S
步骤二:创建canvas画布
在uniapp中,我们可以使用view标签来创建canvas画布,例如:
<view style="width: 100vw; height: 100vh;">
<canvas
canvas-id="canvas"
style="width: 100vw; height: 100vh;"
@touchstart="startDraw"
@touchmove="onDraw"
@touchend="endDraw"
></canvas>
</view>
在canvas标签中,指定了canvas-id为canvas,在js中可以通过uni.createSelectorQuery().select('#canvas')获取到canvas实例,进而进行绘图操作。在touchstart/touchmove/touchend事件中,分别触发开始绘制、绘制中、结束绘制的事件处理函数。
步骤三:编写绘图代码
绘图代码可根据需求自行编写,以下示例代码演示了如何使用canvas在横屏模式下进行画线:
let ctx = uni.createCanvasContext('canvas')
let painting = false
let lastX = 0
let lastY = 0
uni.onWindowResize(() => {
let systemInfo = uni.getSystemInfoSync()
ctx.canvas.width = systemInfo.screenHeight
ctx.canvas.height = systemInfo.screenWidth
})
function startDraw(e) {
painting = true
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function onDraw(e) {
if (!painting) return
ctx.beginPath()
ctx.moveTo(lastX, lastY)
ctx.lineTo(e.touches[0].x, e.touches[0].y)
ctx.stroke()
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function endDraw(e) {
painting = false
}
步骤四:在横屏模式下显示页面
为了在横屏模式下显示绘图页面,需要在manifest.json文件中进行配置:
{
"h5": {
"screenOrientation": "landscape"
},
"app-plus": {
"orientation": "landscape",
"softinputMode": "adjustResize"
}
}
示例1:在PDF中展示签名页面
我们可以利用uniapp创建的签名页面,在PDF中展示签名页面,并允许用户在该页面上进行签名操作。以下为示例代码:
const width = 595.28 // A4纸的宽
const height = 841.89 // A4纸的高
let ctx = uni.createCanvasContext('canvas')
let painting = false
let lastX = 0
let lastY = 0
uni.onWindowResize(() => {
let systemInfo = uni.getSystemInfoSync()
ctx.canvas.width = systemInfo.screenHeight
ctx.canvas.height = systemInfo.screenWidth
})
function startDraw(e) {
painting = true
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function onDraw(e) {
if (!painting) return
ctx.beginPath()
ctx.moveTo(lastX, lastY)
ctx.lineTo(e.touches[0].x, e.touches[0].y)
ctx.stroke()
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function endDraw(e) {
painting = false
}
function savePDF() {
uni.canvasToTempFilePath(
{
canvasId: 'canvas',
x: 0,
y: 0,
destWidth: width,
destHeight: height,
fileType: 'pdf',
quality: 1,
success: function (res) {
uni.saveFile({
tempFilePath: res.tempFilePath,
success: function (res) {
uni.openDocument({
filePath: res.savedFilePath,
fileType: 'pdf',
success: function () {
console.log('打开文档成功')
},
fail: function (err) {
console.log(err)
},
})
},
fail: function (err) {
console.log(err)
},
})
},
fail: function (err) {
console.log(err)
},
},
this
)
}
示例2:签字并保存图片至本地相册
我们可以利用uniapp创建的签名页面,让用户进行签名,并将签名保存至本地相册。以下为示例代码:
let ctx = uni.createCanvasContext('canvas')
let painting = false
let lastX = 0
let lastY = 0
uni.onWindowResize(() => {
let systemInfo = uni.getSystemInfoSync()
ctx.canvas.width = systemInfo.screenHeight
ctx.canvas.height = systemInfo.screenWidth
})
function startDraw(e) {
painting = true
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function onDraw(e) {
if (!painting) return
ctx.beginPath()
ctx.moveTo(lastX, lastY)
ctx.lineTo(e.touches[0].x, e.touches[0].y)
ctx.stroke()
lastX = e.touches[0].x
lastY = e.touches[0].y
}
function endDraw(e) {
painting = false
}
function saveImage() {
uni.canvasToTempFilePath(
{
canvasId: 'canvas',
success: function (res) {
uni.saveImageToPhotosAlbum({
filePath: res.tempFilePath,
success: function () {
console.log('保存图片成功')
},
fail: function (err) {
console.log(err)
},
})
},
fail: function (err) {
console.log(err)
},
},
this
)
}
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