android的圖形的繪制，主要用到Canvas。
google官網上已經給出了Canvas的用法，https://developer.android.google.cn/guide/topics/graphics/2d-graphics.html

• Canvas類具有畫圖的能力，如果你想畫圖，要具備四個部件。
  1.Bitmap控制像素
  2.Canvas控制繪圖請求
  3.一些繪圖的方法， Rect, Path, text, Bitmap等
  4.一個畫筆，可以自定義colors和styles

• Canvas的常用操作

• Paint 代表了Canvas上的畫筆、畫刷、顏料等等；
  Paint類常用方法:

• 畫筆初始化

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

mPaint2.setStrokeWidth(10);
canvas.drawPoint(100, 100, mPaint2);
canvas.drawPoints(new float[]{100, 120, 120, 120, 140, 120},mPaint2);```
2.畫直線，繪制直線需要兩個點，初始點和結束點，同樣繪制直線也可以繪制一條或者繪制一組：

 canvas.drawLine(100,150,200,150,mPaint2);
canvas.drawLines(new float[]{100,170,220,170,100,190,300,190},mPaint2);```
3.繪制矩形，確定一個矩形最少需要四個數據，就是對角線的兩個點的坐標值

canvas.drawRect(100,210,300,300,mPaint2); //第一種，兩點確定一個矩形
Rect rect=new Rect(400,210,600,300); //將矩形封裝為rect ,Rect是int(整形)的
canvas.drawRect(rect,mPaint2);
RectF rectF=new RectF(700,210,900,300); //RectF是float(單精度浮點型)的
canvas.drawRect(rectF,mPaint2);```
4.繪制圓角矩形

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

  5.繪制橢圓

RectF rectF2=new RectF(100,450,500,550);
canvas.drawOval(rectF2,mPaint2);
canvas.drawOval(600,500,800,600,mPaint2); //API>=21```
6.繪制圓，繪制圓形有四個參數，前兩個是圓心坐標，第三個是半徑，最后一個是畫筆

canvas.drawCircle(700,700,100,mPaint2);```
7.繪制圓弧
- 第一種
public void drawArc(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter, @NonNull Paint paint){}
   
- 第二種
public void drawArc(float left, float top, float right, float bottom, float startAngle,float sweepAngle, boolean useCenter, @NonNull Paint paint) {}

startAngle  - 開始角度
sweepAngle  - 掃過角度
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);```

微信圖片_20170323095301.png