安卓绘制五角星

package com.example.test;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.View;
/**
 * 
 *  假设五角星外接圆半径为1,有一个角朝上,以五角星中心为原点:
	
		外点
 		x=Rcos(72°*k)  y=Rsin(72°*k)   k=0,1,2,3,4
		
 		内点
 		r=Rsin(18)/sin(180-36-18)
 		x=rcos(72°*k+36°)  y=rsin(72°*k+36°)   k=0,1,2,3,4
	 
 * @author Young
 *
 */
public class FiveView extends View {

	public FiveView(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
	}

	public FiveView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
	}

	public FiveView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		// TODO Auto-generated constructor stub
	}

	@SuppressLint("NewApi")
	public FiveView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
		super(context, attrs, defStyleAttr, defStyleRes);
		// TODO Auto-generated constructor stub
	}


 

	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		
		int width=getWidth();
		int r=width/2;
		canvas.translate(r, r );
		 
	 
		Path path=new Path();
	
		path.moveTo(0, -r);//A
		
		path.lineTo(  r* sin(36), r*cos(36));//C
		
		path.lineTo( -r*sin(72), -r*cos(72) );//E
		
		path.lineTo(  r*sin(72), -r*cos(72)  );//B
		
		path.lineTo(  -r*sin(36), r*cos(36)  );//D
		
		path.close(); 
		
		Paint paint=new Paint();
		paint.setAntiAlias(true);
		paint.setColor(Color.YELLOW);
		paint.setStyle(Style.STROKE);
		paint.setStrokeWidth(5);
		canvas.drawPath(path, paint);
		
		addCoordinateAndMark(canvas);

		
		ff2(canvas);
	}

	private void addCoordinateAndMark(Canvas canvas) {
		// TODO Auto-generated method stub
		int width=getWidth();
		int r=width/2;
		
		Paint paint=new Paint();
		paint.setAntiAlias(true);
		paint.setColor(Color.BLACK);
		paint.setStrokeWidth(5);
		canvas.drawLine(-r	, 0, r, 0, paint);
		canvas.drawLine(0, -r, 0, r, paint);
		
		paint.setColor(Color.BLUE);
		paint.setTextSize(30); 
		
		r=(int) (r*0.9);
		canvas.drawText("A", 0, -r, paint);
		canvas.drawText("B", r*sin(72), -r*cos(72), paint);
		canvas.drawText("C", r*sin(36), r*cos(36), paint);
		canvas.drawText("D",-r*sin(36), r*cos(36)  , paint);
		canvas.drawText("E", -r*sin(72), -r*cos(72), paint);
		
	}

	/***
	 * 外点 </br>
 		x=Rcos(72°*k) </br>
 		 y=Rsin(72°*k) </br>
 		   k=0,1,2,3,4 </br>
		</br></br>
 		内点 </br>
 		r=Rsin(18)/sin(180-36-18) </br>
 		x=rcos(72°*k+36°)</br>
 		  y=rsin(72°*k+36°) </br>
 		    k=0,1,2,3,4 </br>
	 
	 * @param canvas
	 */
	private void ff2(Canvas canvas) {
		canvas.rotate(-18);
 
		float r=getWidth()/2 ;
		
		
		Paint paint=new Paint();
		paint.setAntiAlias(true);
		paint.setColor(Color.MAGENTA);
		paint.setStyle(Style.STROKE);
		paint.setStrokeWidth(5);
		
		Path path=new Path();
		path.moveTo(r*cos(72*0), r*sin(72*0));
		for (int i = 1; i <5 ; i++) {
			canvas.drawText(""+i,r*cos(72*i), r*sin(72*i), paint);
			path.lineTo(r*cos(72*i), r*sin(72*i));
		}
		path.close();
		
		
		canvas.drawPath(path, paint);
		
		r=r*sin(18)/sin(180-36-18);
		paint.setColor(Color.CYAN);
		path=new Path();
		path.moveTo(r*cos(72*0+36), r*sin(72*0+36));
		for (int i = 1; i <5 ; i++) {
			canvas.drawText(""+i,r*cos(72*i+36), r*sin(72*i+36), paint);
			path.lineTo(r*cos(72*i+36), r*sin(72*i+36));
		}
		path.close();
		canvas.drawPath(path, paint);
	}
	
	float cos(int num){
		return (float) Math.cos(num*Math.PI/180);
	}
 
	float sin(int num){
		return (float) Math.sin(num*Math.PI/180);
	}
}