HarmonyOS Next鸿蒙开发：图形验证码

做项目过程中往往需要增加图形验证码，那么鸿蒙里面也提供了画笔进行写字，也就生成了一个图形验证码图形，具体代码如下：

图形验证码工具类，在时间过程中，getCode函数需要请求后端服务获取验证码，在生成图形，本案例为了演示就直接随机生成。

@Component
export default struct ImageCode {
  //用来配置CanvasRenderingContext2D对象的参数，包括是否开启抗锯齿，true表明开启抗锯齿。
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  //用来创建CanvasRenderingContext2D对象，通过在canvas中调用CanvasRenderingContext2D对象来绘制。
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  //指定canvas要绘制的图形的宽（可使用@Prop装饰器装饰，由调用此组件的父组件传递）
  @State canvas_width: number = 100;
  //指定canvas要绘制的图形的高
  @State canvas_height: number = 40;
  //用于接收图形验证码的文本值
  @State showCode: string = ''
  sCode: string = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,l,m,n,p,q,r,s,t,u,v,w,x,y,z,1,2,3,4,5,6,7,8,9";
  aCode: string[] = this.sCode.split(",");
  aLength: number = this.aCode.length;

  build() {
    Row() {
      //在canvas中调用CanvasRenderingContext2D对象。
      Canvas(this.context)
        .width(this.canvas_width)
        .height(this.canvas_height)
        .backgroundColor('#00000')
        .onReady(() => {
          //在这里绘制图形
           this.drawImgCode(this.context,this.canvas_width,this.canvas_height)
          console.log(this.showCode)
        })
        .onClick(() => {
           this.drawImgCode(this.context,this.canvas_width,this.canvas_height)
          console.log(this.showCode)
        })
    }
    .width('100%')
    .height('100%')
  }


  getCode():string{
    let showCode: string = ''
    for (let i = 0; i < 4; i++) { //这里的for循环可以控制验证码位数
      const j = Math.floor(Math.random() * this.aLength); //获取到随机的索引值
      const txt = this.aCode[j]; //得到随机的一个内容
      showCode += txt.toLowerCase(); //转小写
    }
    return showCode
  }

  drawImgCode(context: CanvasRenderingContext2D, canvas_width: number = 100, canvas_height: number = 40) {
    context.clearRect(0, 0, canvas_width, canvas_height)
    this.showCode = this.getCode()
    let strarr = Array.from(this.showCode)
    for (let i = 0; i < 4; i++) { //这里的for循环可以控制验证码位数


      const deg = Math.random() - 0.5; //产生一个随机弧度
      const txt = strarr[i]

      const x = 10 + i * 20; //文字在canvas上的x坐标
      const y = canvas_height / 2 + Math.random() * 8; //文字在canvas上的y坐标
      context.font = "25vp sans-serif";
      context.translate(x, y);
      context.rotate(deg);
      context.fillStyle = this.getColor();
      //画字母
      context.fillText(txt, 0, 0);
      context.rotate(-deg);
      context.translate(-x, -y);
    }
    for (let i = 0; i <= 5; i++) { //验证码上显示线条
      context.strokeStyle = this.getColor();
      context.beginPath();
      context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height);
      context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height);
      context.stroke();
    }
    for (let i = 0; i <= 20; i++) { //验证码上的小点
      context.strokeStyle = this.getColor(); //随机生成
      context.beginPath();
      const x = Math.random() * canvas_width;
      const y = Math.random() * canvas_height;
      context.moveTo(x, y);
      context.lineTo(x + 1, y + 1);
      context.stroke();
    }

  }
  getColor() {
    const r = Math.floor(Math.random() * 256);
    const g = Math.floor(Math.random() * 256);
    const b = Math.floor(Math.random() * 256);
    return "rgb(" + r + "," + g + "," + b + ")";
  }



}

页面代码

import ImageCode from './ImageCode'

@Entry
@Component
struct ImageCodeDemo {
  build() {
    Row() {
      TextInput({placeholder:'请输入验证码'})
        .layoutWeight(1)
      ImageCode()
        .width(100)
        .height(40)
    }
    .height('100%')
    .width('100%')
  }
}