鸿蒙HarmonyOS开发实例：【简单时钟】

简单时钟

介绍

本示例通过使用[@ohos.display]接口以及Canvas组件来实现一个简单的时钟应用。

效果预览

主页

使用说明

1.界面通过setInterval实现周期性实时刷新时间，使用Canvas绘制时钟，指针旋转角度通过计算得出。

例如："2 Math.PI / 60 second"是秒针旋转的角度。

鸿蒙开发应用知识已更新gitee.com/li-shizhen-skin/harmony-os/blob/master/README.md参考前往。

具体实现

鸿蒙学习文档前往mau123789是v添加即可

• 本示例展示简单时钟的方法主要封装在Index中，源码参考:[Index.ets] 。

/*

 * Copyright (c) 2022 Huawei Device Co., Ltd.

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

import display from '@ohos.display'

import Logger from '../model/Logger'



const HOURS: Array<string> = ['3', '4', '5', '6', '7', '8', '9', '10', '11', '12', '1', '2']

const HEIGHT_ADD: number = 150 // 表盘下面需要绘制时间，canvas高度是宽度加150

const TAG: string = 'Index'



@Entry

@Component

struct Clock {

  private settings: RenderingContextSettings = new RenderingContextSettings(true)

  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)

  @State canvasWidth: number = 300 // 300是表盘默认大小

  private radius: number = 150 // 默认表盘半径

  private intervalId: number = 0

  updateTime = () => {

    this.context.clearRect(0, 0, this.canvasWidth, this.canvasWidth + HEIGHT_ADD)

    let nowTime = new Date()

    let hour = nowTime.getHours()

    let minute = nowTime.getMinutes()

    let second = nowTime.getSeconds()

    let time = `${this.fillTime(hour)}:${this.fillTime(minute)}:${this.fillTime(second)}`

    this.drawBackGround()

    this.drawHour(hour, minute)

    this.drawMinute(minute)

    this.drawSecond(second)

    this.drawDot()

    this.drawTime(time)

    this.context.translate(-this.radius, -this.radius)

  }



  fillTime(time: number) {

    return time < 10 ? `0${time}` : `${time}`

  }



  aboutToAppear() {

    this.getSize()

  }



  // 获取设备宽高计算表盘大小

  async getSize() {

    let mDisplay = await display.getDefaultDisplay()

    Logger.info(TAG, `getDefaultDisplay mDisplay = ${JSON.stringify(mDisplay)}`)

    this.canvasWidth = px2vp(mDisplay.width > mDisplay.height ? mDisplay.height * 0.6 : mDisplay.width * 0.6)

    this.radius = this.canvasWidth / 2

  }



  drawBackGround() {



    // 绘制背景

    let grad = this.context.createRadialGradient(this.radius, this.radius, this.radius - 32, this.radius,

      this.radius, this.radius)

    grad.addColorStop(0.0, 'white')

    grad.addColorStop(0.9, '#eee')

    grad.addColorStop(1.0, 'white')

    this.context.fillStyle = grad

    this.context.fillRect(0, 0, this.canvasWidth, this.canvasWidth)



    // 绘制外圈圆

    this.context.translate(this.radius, this.radius)

    this.context.lineWidth = 6

    this.context.beginPath()

    this.context.strokeStyle = '#fff'

    this.context.arc(0, 0, this.radius - 5, 0, 2 * Math.PI, false)

    this.context.stroke()



    // 绘制时间文字

    this.context.font = '30px'

    this.context.textAlign = "center"

    this.context.textBaseline = "middle"

    this.context.fillStyle = '#000'

    this.context.save()

    HOURS.forEach((num, index) => {

      let rad = 2 * Math.PI / 12 * index

      let x = Math.cos(rad) * (this.radius - 38)

      let y = Math.sin(rad) * (this.radius - 38)

      this.context.fillText(num, x, y)

    })

    this.context.restore()



    // 绘制刻度

    for (let i = 0; i < 60; i++) {

      let rad = 2 * Math.PI / 60 * i

      let x = Math.cos(rad) * (this.radius - 12)

      let y = Math.sin(rad) * (this.radius - 12)

      this.context.beginPath()

      this.context.moveTo(x, y)

      if (i % 5 == 0) {

        let x1 = Math.cos(rad) * (this.radius - 20)

        let y1 = Math.sin(rad) * (this.radius - 20)

        this.context.strokeStyle = '#000'

        this.context.lineWidth = 2

        this.context.lineTo(x1, y1)

      } else {

        let x1 = Math.cos(rad) * (this.radius - 18)

        let y1 = Math.sin(rad) * (this.radius - 18)

        this.context.strokeStyle = '#ccc'

        this.context.lineWidth = 1

        this.context.lineTo(x1, y1)

      }

      this.context.stroke()

    }

    this.context.restore()

  }



  // 绘制时针

  drawHour(hour: number, minute: number) {

    this.context.save()

    this.context.beginPath()

    this.context.lineWidth = 8

    this.context.lineCap = 'round'

    let rad = 2 * Math.PI / 12 * hour

    let mrad = 2 * Math.PI / 12 / 60 * minute

    this.context.rotate(rad + mrad)

    this.context.moveTo(0, 10)

    this.context.strokeStyle = '#000'

    this.context.lineTo(0, -this.radius / 2)

    this.context.stroke()

    this.context.restore()

  }



  // 绘制分针

  drawMinute(minute: number) {

    this.context.save()

    this.context.beginPath()

    this.context.lineWidth = 5

    this.context.lineCap = 'round'

    let rad = 2 * Math.PI / 60 * minute

    this.context.rotate(rad)

    this.context.moveTo(0, 10)

    this.context.strokeStyle = '#000'

    this.context.lineTo(0, -this.radius + 40)

    this.context.stroke()

    this.context.restore()

  }



  // 绘制秒针

  drawSecond(second: number) {

    this.context.save()

    this.context.beginPath()

    this.context.lineWidth = 2

    this.context.lineCap = 'round'

    let rad = 2 * Math.PI / 60 * second

    this.context.rotate(rad)

    this.context.moveTo(0, 10)

    this.context.strokeStyle = '#05f'

    this.context.lineTo(0, -this.radius + 21)

    this.context.stroke()

    this.context.restore()

  }



  // 绘制中心点

  drawDot() {

    this.context.save()

    this.context.beginPath()

    this.context.fillStyle = '#05f'

    this.context.arc(0, 0, 4, 0, 2 * Math.PI, false)

    this.context.fill()

    this.context.restore()

  }



  // 绘制表盘下面时间文本

  drawTime(time: string) {

    this.context.save()

    this.context.beginPath()

    this.context.font = '90px'

    this.context.textAlign = "center"

    this.context.textBaseline = "middle"

    this.context.fillStyle = '#000'

    this.context.fillText(time, 0, this.radius + 80)

    this.context.restore()

  }



  build() {

    Stack({ alignContent: Alignment.Center }) {

      Canvas(this.context)

        .padding({ top: 76 })

        .width(this.canvasWidth)

        .height(this.canvasWidth + HEIGHT_ADD)

        .onReady(() => {

          this.updateTime()

          this.intervalId = setInterval(this.updateTime, 1000)

        })

    }

    .width('100%')

    .height('100%')

  }



  onPageHide() {

    clearInterval(this.intervalId)

  }



  aboutToDisappear(){

    clearInterval(this.intervalId)

  }

}

• 设置表盘大小：通过Index中的display.getDefaultDisplay()方法来获取设备宽高计算表盘大小；
• 获取当前时间：调用updateTime函数，执行new Date().getHours()、new Date().getMinutes()、new Date().getSeconds()获取当前时间。
• 绘制表盘内容：通过[CanvasRenderingContext2D] 来画表盘背景、时针、分针、秒针、圆心以及表盘下方文本；
• 启动时钟：添加setInterval定时器，每隔1s执行一次updateTime函数。