Android初识贝塞尔曲线，安卓移动开发实验报告

private Paint getPaintByColor(int color) {

Paint paint = new Paint();

paint.setAntiAlias(true);

paint.setDither(true);

paint.setColor(color);

paint.setStyle(Paint.Style.STROKE);

return paint;

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

//获取点的坐标

centerY = getMeasuredHeight()/2;

startX = getMeasuredWidth()/2 - 250;

endX = getMeasuredWidth()/2 + 250;

eventX = getMeasuredWidth()/2;

eventY = getMeasuredHeight()/2 - 250;

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

}

@Override

protected void onDraw(Canvas canvas) {

//画三个点

mPointPaint.setColor(Color.GRAY);

canvas.drawCircle(startX,centerY,8,mPointPaint);

canvas.drawCircle(endX,centerY,8,mPointPaint);

canvas.drawCircle(eventX,eventY,8,mPointPaint);

//连线

Path path = new Path();

path.moveTo(startX,centerY);

path.lineTo(eventX,eventY);

path.lineTo(endX,centerY);

mPointPaint.setStrokeWidth(5);

canvas.drawPath(path,mPointPaint);

//绘制二阶贝塞尔曲线

Path bPath = new Path();

bPath.moveTo(startX,centerY);

bPath.quadTo(eventX,eventY,endX,centerY);

mPointPaint.setColor(Color.BLUE);

canvas.drawPath(bPath,mPointPaint);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

switch (event.getAction()){

case MotionEvent.ACTION_DOWN:

case MotionEvent.ACTION_MOVE:

case MotionEvent.ACTION_POINTER_UP:

{

eventX = (int) event.getX();

eventY = (int) event.getY();

}

break;

}

invalidate();

//如果你发现你的 onTouchEvent 无法捕获 MOVE 事件，就是因为这个方法返回的是 false导致的

System.out.println("super.onTouchEvent(event) -> " + super.onTouchEvent(event));

return true;

}

}

三阶贝塞尔曲线

========

效果展示

---

源码展示

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package com.wust.mybeisaier;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Path;

import android.util.AttributeSet;

import android.view.MotionEvent;

import android.view.View;

import androidx.annotation.Nullable;

/**

• ClassName: selfBeiSaiEr
  

• Description:
  

• date: 2021/7/16 14:30
  

• @author yiqi
  

• @QQ 1820762465

*/

public class selfBeiSaiEr extends View {

private int centerY;

private int startX;

private int endX;

private int eventX_left;

private int eventX_right;

private int eventY_left;

private int eventY_right;

private Paint mPointPaint;

public selfBeiSaiEr(Context context) {

super(context);

}

public selfBeiSaiEr(Context context, @Nullable AttributeSet attrs) {

super(context, attrs);

initPaint();

}

public selfBeiSaiEr(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

initPaint();

}

private void initPaint() {

mPointPaint = getPaintByColor(Color.GRA

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Y);

}

private Paint getPaintByColor(int color) {

Paint paint = new Paint();

paint.setAntiAlias(true);

paint.setDither(true);

paint.setColor(color);

paint.setStyle(Paint.Style.STROKE);

return paint;

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

centerY = getMeasuredHeight()/2;

startX = getMeasuredWidth()/2 - 250;

endX = getMeasuredWidth()/2 + 250;

eventX_left = startX;

eventX_right = endX;

eventY_left = getMeasuredHeight()/2 - 250;

eventY_right = eventY_left;

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

}

@Override

protected void onDraw(Canvas canvas) {

//画四个点

mPointPaint.setColor(Color.GRAY);

canvas.drawCircle(startX,centerY,8,mPointPaint);

canvas.drawCircle(endX,centerY,8,mPointPaint);

canvas.drawCircle(eventX_left,eventY_left,8,mPointPaint);

canvas.drawCircle(eventX_right,eventY_right,8,mPointPaint);

//连线

Path path = new Path();

path.moveTo(startX,centerY);

path.lineTo(eventX_left,eventY_left);

path.lineTo(eventX_right,eventY_right);

path.lineTo(endX,centerY);

mPointPaint.setStrokeWidth(5);

canvas.drawPath(path,mPointPaint);

//绘制三阶贝塞尔曲线

Path bPath = new Path();

bPath.moveTo(startX,centerY);

bPath.cubicTo(eventX_left,eventY_left,eventX_right,eventY_right,endX,centerY);

mPointPaint.setColor(Color.BLUE);

canvas.drawPath(bPath,mPointPaint);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

switch (event.getAction()){

case MotionEvent.ACTION_DOWN:

case MotionEvent.ACTION_MOVE:

case MotionEvent.ACTION_POINTER_UP:

{

//为了方便，这里我就只让他控制左边点就好了

eventX_left = (int) event.getX();

eventY_left = (int) event.getY();

}

break;