android的图形的绘制，主要用到Canvas。
google官网上已经给出了Canvas的用法，https://developer.android.google.cn/guide/topics/graphics/2d-graphics.html

• Canvas类具有画图的能力，如果你想画图，要具备四个部件。
  1.Bitmap控制像素
  2.Canvas控制绘图请求
  3.一些绘图的方法， Rect, Path, text, Bitmap等
  4.一个画笔，可以自定义colors和styles

• Canvas的常用操作

• Paint 代表了Canvas上的画笔、画刷、颜料等等；
  Paint类常用方法:

• 画笔初始化

 mPaint2 = new Paint();
  mPaint2.setColor(Color.RED);
  mPaint2.setStyle(Paint.Style.FILL);
  mPaint2.setAntiAlias(true);```
1.画点

mPaint2.setStrokeWidth(10);
canvas.drawPoint(100, 100, mPaint2);
canvas.drawPoints(new float[]{100, 120, 120, 120, 140, 120},mPaint2);```
2.画直线，绘制直线需要两个点，初始点和结束点，同样绘制直线也可以绘制一条或者绘制一组：

 canvas.drawLine(100,150,200,150,mPaint2);
canvas.drawLines(new float[]{100,170,220,170,100,190,300,190},mPaint2);```
3.绘制矩形，确定一个矩形最少需要四个数据，就是对角线的两个点的坐标值

canvas.drawRect(100,210,300,300,mPaint2); //第一种，两点确定一个矩形
Rect rect=new Rect(400,210,600,300); //将矩形封装为rect ,Rect是int(整形)的
canvas.drawRect(rect,mPaint2);
RectF rectF=new RectF(700,210,900,300); //RectF是float(单精度浮点型)的
canvas.drawRect(rectF,mPaint2);```
4.绘制圆角矩形

 RectF rectF1=new RectF(100,350,500,400);
 canvas.drawRoundRect(rectF1,30,30,mPaint2);
 canvas.drawRoundRect(60,350,800,400,mPaint2);   //API>=21```

  5.绘制椭圆

RectF rectF2=new RectF(100,450,500,550);
canvas.drawOval(rectF2,mPaint2);
canvas.drawOval(600,500,800,600,mPaint2); //API>=21```
6.绘制圆，绘制圆形有四个参数，前两个是圆心坐标，第三个是半径，最后一个是画笔

canvas.drawCircle(700,700,100,mPaint2);```
7.绘制圆弧
- 第一种
public void drawArc(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter, @NonNull Paint paint){}
   
- 第二种
public void drawArc(float left, float top, float right, float bottom, float startAngle,float sweepAngle, boolean useCenter, @NonNull Paint paint) {}

startAngle  - 开始角度
sweepAngle  - 扫过角度
useCenter   - 是否使用中心

RectF rectF3=new RectF(100,850,300,900);
canvas.drawRect(rectF3,mPaint1);
canvas.drawArc(rectF3,0,90,false,mPaint2);
RectF rectF4=new RectF(400,850,600,900);
canvas.drawRect(rectF4,mPaint1);
canvas.drawArc(rectF4,0,90,true,mPaint2);```

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