顶点数在<5时没有正多角星,顶点数>5时正多角星不唯一,本文只绘制最具代表性的一种
代码如下:
public class CanvasStar extends View{
public CanvasStar(Context context) {
super(context);
}
public CanvasStar(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CanvasStar(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public CanvasStar(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint=new Paint();
paint.setAntiAlias(true);
drawStar(canvas,paint,Color.RED,getHeight()/12,3,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.RED,getHeight()/12,3,true);
canvas.translate(-getHeight()/6,0);
canvas.translate(0,getHeight()/6);
drawStar(canvas,paint,Color.YELLOW,getHeight()/12,4,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.YELLOW,getHeight()/12,4,true);
canvas.translate(-getHeight()/6,0);
canvas.translate(0,getHeight()/6);
drawStar(canvas,paint,Color.GREEN,getHeight()/12,5,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.GREEN,getHeight()/12,5,true);
canvas.translate(-getHeight()/6,0);
canvas.translate(0,getHeight()/6);
drawStar(canvas,paint,Color.CYAN,getHeight()/12,6,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.CYAN,getHeight()/12,6,true);
canvas.translate(-getHeight()/6,0);
canvas.translate(0,getHeight()/6);
drawStar(canvas,paint,Color.BLUE,getHeight()/12,7,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.BLUE,getHeight()/12,7,true);
canvas.translate(-getHeight()/6,0);
canvas.translate(0,getHeight()/6);
drawStar(canvas,paint,Color.BLACK,getHeight()/12,8,false);
canvas.translate(getHeight()/6,0);
drawStar(canvas,paint,Color.BLACK,getHeight()/12,8,true);
canvas.translate(0,getHeight()/6);
}
/**
* 绘制彩色多边形或星形
* @param canvas Canvas画布
* @param paint Paint画笔
* @param color 颜色
* @param radius 外接圆半径
* @param count 外顶点数
* @param isStar 是否为星形
*/
private void drawStar(Canvas canvas, Paint paint, @ColorInt int color, float radius,int count,boolean isStar){
canvas.translate(radius,radius);
if ((!isStar) && count < 3){
canvas.translate(-radius,-radius);
return;
}
if (isStar && count < 5){
canvas.translate(-radius,-radius);
return;
}
canvas.rotate(-90);
if (paint == null){
paint = new Paint();
}else{
paint.reset();
}
Path path = new Path();
float inerRadius = count%2==0?
(radius*(cos(360/count/2)-sin(360/count/2)*sin(90-360/count)/cos(90-360/count)))
:(radius*sin(360/count/4)/sin(180-360/count/2-360/count/4));
for (int i=0;i
效果如下: