uni-halo/.agents/bak-skills/uniappx-project/references/components/built-in/canvas.md

canvas

Instructions

画布

属性说明

注意事项：

Syntax

• 使用 <canvas />（或 <canvas></canvas>，当需要包裹子节点时）。
• 遇到平台差异时，建议使用条件编译（#ifdef / #endif）显式处理。

Properties

属性名	类型	默认值	说明	平台差异说明
type	String		指定 canvas 类型，支持 2d 和 webgl	微信小程序2.7.0+ 、抖音小程序1.78.0+、支付宝小程序2.7.0+
canvas-id	String		canvas 组件的唯一标识符
disable-scroll	Boolean	false	当在 canvas 中移动时且有绑定手势事件时，禁止屏幕滚动以及下拉刷新	抖音小程序与飞书小程序不支持
hidpi	Boolean	true	是否启用高清处理	H5 (HBuilder X 3.4.0+)、App-vue (HBuilder X 3.4.0+)

Events

事件名	类型	默认值	说明	平台差异说明
@touchstart	EventHandle		手指触摸动作开始	抖音小程序1.78.0+、小红书小程序
@touchmove	EventHandle		手指触摸后移动	抖音小程序1.78.0+、小红书小程序
@touchend	EventHandle		手指触摸动作结束	抖音小程序1.78.0+、小红书小程序
@touchcancel	EventHandle		手指触摸动作被打断，如来电提醒，弹窗	抖音小程序1.78.0+
@longtap	EventHandle		手指长按 500ms 之后触发，触发了长按事件后进行移动不会触发屏幕的滚动	抖音小程序与飞书小程序不支持
@error	EventHandle		当发生错误时触发 error 事件，detail = {errMsg: 'something wrong'}	抖音小程序与飞书小程序不支持

Platform Compatibility

See official docs for platform support table: https://doc.dcloud.net.cn/uni-app-x/component/canvas.html

Examples

Example (Example 1)

<template>
	<view>
		<canvas style="width: 300px; height: 200px;" canvas-id="firstCanvas" id="firstCanvas"></canvas>
		<canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas" id="secondCanvas"></canvas>
		<canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas" id="secondCanvas" @error="canvasIdErrorCallback"></canvas>
	</view>
</template>

Example (Example 2)

<template>
	<view>
		<canvas style="width: 300px; height: 200px;" canvas-id="firstCanvas" id="firstCanvas"></canvas>
		<canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas" id="secondCanvas"></canvas>
		<canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas" id="secondCanvas" @error="canvasIdErrorCallback"></canvas>
	</view>
</template>

Example (Example 3)

<script>
export default {
	onReady: function (e) {
		var context = uni.createCanvasContext('firstCanvas')
		context.setStrokeStyle("#00ff00")
		context.setLineWidth(5)
		context.rect(0, 0, 200, 200)
		context.stroke()
		context.setStrokeStyle("#ff0000")
		context.setLineWidth(2)
		context.moveTo(160, 100)
		context.arc(100, 100, 60, 0, 2 * Math.PI, true)
		context.moveTo(140, 100)
		context.arc(100, 100, 40, 0, Math.PI, false)
		context.moveTo(85, 80)
		context.arc(80, 80, 5, 0, 2 * Math.PI, true)
		context.moveTo(125, 80)
		context.arc(120, 80, 5, 0, 2 * Math.PI, true)
		context.stroke()
		context.draw()
	},
	methods: {
		canvasIdErrorCallback: function (e) {
			console.error(e.detail.errMsg)
		}
	}
}
</script>

Reference: Official Documentation