这篇文章运用简单易懂的例子给大家介绍鸿蒙自定义组件之鸿蒙画板的概述，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。

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初识鸿蒙OS 2.0

华为的鸿蒙OS 2.0是目前唯一个有希望和安卓、IOS对抗的全新生态系统。9月10日，在东莞正式发布。华为喊出了“HarmonyOS 2.0 连接无限可能”的口号，将是未来十年很有竞争力的优秀操作系统。

自定义Component

这里我编写一个简易的画板。

1.新建一个类DrawComponment 继承自Componment；
2.实现Component.TouchEventListener，用于对touch事件生成相应的path；
3.实现Component.DrawTask，用于把path画到屏幕上；

代码

DrawComponment

package com.quqx.draw;

import ohos.agp.components.Component;
import ohos.agp.render.Canvas;
import ohos.agp.render.Paint;
import ohos.agp.render.Path;
import ohos.agp.utils.Color;
import ohos.agp.utils.Point;
import ohos.app.Context;
import ohos.hiviewdfx.HiLog;
import ohos.hiviewdfx.HiLogLabel;
import ohos.media.image.PixelMap;
import ohos.multimodalinput.event.MmiPoint;
import ohos.multimodalinput.event.TouchEvent;

public class DrawComponment extends Component implements Component.DrawTask, Component.TouchEventListener {
  private static final String TAG = "DrawComponment";
  PixelMap mPixelMap;
  Canvas mCanvas;
  Path mPath = new Path();
  Paint mPaint;
  Point mPrePoint = new Point();
  Point mPreCtrlPoint = new Point();

  public DrawComponment(Context context) {
    super(context);
    //初始化paint
    mPaint = new Paint();
    mPaint.setColor(Color.WHITE);
    mPaint.setStrokeWidth(5f);
    mPaint.setStyle(Paint.Style.STROKE_STYLE);
    //添加绘制任务
    addDrawTask(this::onDraw);
    //设置TouchEvent监听
    setTouchEventListener(this::onTouchEvent);
  }

  @Override
  public void onDraw(Component component, Canvas canvas) {
    canvas.drawPath(mPath, mPaint);
  }


  @Override
  public boolean onTouchEvent(Component component, TouchEvent touchEvent) {
    switch (touchEvent.getAction()) {
      case TouchEvent.PRIMARY_POINT_DOWN: {
        //鸿蒙Log工具
        HiLog.debug(new HiLogLabel(0, 0, TAG), "TouchEvent.PRIMARY_POINT_DOWN");
        //获取点信息
        MmiPoint point = touchEvent.getPointerPosition(touchEvent.getIndex());
        mPath.reset();
        mPath.moveTo(point.getX(), point.getY());
        mPrePoint.position[0] = point.getX();
        mPrePoint.position[1] = point.getY();
        mPreCtrlPoint.position[0] = point.getX();
        mPreCtrlPoint.position[1] = point.getY();
        //PRIMARY_POINT_DOWN 一定要返回true
        return true;
      }
      case TouchEvent.PRIMARY_POINT_UP:

        break;
      case TouchEvent.POINT_MOVE: {
        HiLog.debug(new HiLogLabel(0, 0, TAG), "TouchEvent.POINT_MOVE");
        MmiPoint point = touchEvent.getPointerPosition(touchEvent.getIndex());
        Point currCtrlPoint = new Point((point.getX() + mPrePoint.position[0]) / 2,
            (point.getY() + mPrePoint.position[1]) / 2);
        //绘制三阶贝塞尔曲线
        mPath.cubicTo(mPrePoint, mPreCtrlPoint, currCtrlPoint);
        mPreCtrlPoint.position[0] = currCtrlPoint.position[0];
        mPreCtrlPoint.position[1] = currCtrlPoint.position[1];
        mPrePoint.position[0] = point.getX();
        mPrePoint.position[1] = point.getY();
        //更新显示
        invalidate();
        break;
      }

    }
    return false;
  }
}

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