@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //画背景圆环
        int center = getWidth() / 2;

        float radius = center - roundWidth / 2;
        paint.setColor(roundColor);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(roundWidth); // 圆环的宽度
        paint.setAntiAlias(true);
        canvas.drawCircle(center,center,radius,paint);

        // 画进度百分比
        paint.setColor(textColor);
        paint.setStrokeWidth(0);
        paint.setTextSize(textSize);
        paint.setTypeface(Typeface.DEFAULT_BOLD);

        int percent = (int)(progress / (float)max * 100);
        String strPercent = percent + "%";
        Paint.FontMetricsInt fm = paint.getFontMetricsInt();
        if(percent != 0){
            canvas.drawText(strPercent, getWidth() / 2 - paint.measureText(strPercent) / 2 ,
                    getWidth() / 2  +(fm.bottom - fm.top)/2 - fm.bottom, paint);
        }


        // 画圆弧
        RectF oval = new RectF(center - radius, center - radius,
                center + radius, center + radius);
        paint.setColor(roundProgressColor);
        paint.setStrokeWidth(roundWidth);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeCap(Paint.Cap.ROUND);
        canvas.drawArc(oval, 0 , 360 * progress / max, false, paint);

    }

    public void setProgress(int progress){
        if(progress < 0 ){
            throw new IllegalArgumentException("进度Progress不能小于0");
        }
        if(progress > max){
            progress = max;
        }
        if(progress <= max){
            this.progress = progress;
            postInvalidate();
        }
    }