onDraw中画弧这个地方不理解

老师，关于画弧那个方法，我查阅了api，了解到各个参数的含义，但在结合代码（代码中问号处）时看不懂

    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (this.reset) {
            canvas.drawColor(0xFFFFFFFF);
            this.reset = false;
        }

        this.width = this.getMeasuredWidth();
        this.height = this.getMeasuredHeight();
        this.radius = this.getMeasuredWidth() / 2 - this.pathWidth;
        //画笔颜色
        this.pathPaint.setColor(this.PATHCOLOR);
        //设置画笔宽度
        this.pathPaint.setStrokeWidth((float) this.pathWidth);
        //添加浮雕效果
        this.pathPaint.setMaskFilter(this.emboss);
        // 在中心的地方画个半径为r的圆
        //#用粗为35的画笔画了一个半径为radius，圆心为(自身宽/2,自身高/2)的圆形（圆1）
        canvas.drawCircle((float) (this.width / 2), (float) (this.height / 2), (float) this.radius, this.pathPaint);
        this.pathPaint.setStrokeWidth(0.5F);
        this.pathPaint.setColor(this.pathBorderColor);
        //#用粗为0.5的画笔画了一个半径为radius+pathWidth/2+0.5，圆心为(自身宽/2,自身高/2)的圆形（圆2）
        canvas.drawCircle((float) (this.width / 2), (float) (this.height / 2), (float) (this.radius + this.pathWidth / 2) + 0.5F, this.pathPaint);
        //#圆3
        canvas.drawCircle((float) (this.width / 2), (float) (this.height / 2), (float) (this.radius - this.pathWidth / 2) - 0.5F, this.pathPaint);
//        SweepGradient sweepGradient = new SweepGradient((float)(this.width / 2), (float)(this.height / 2), this.arcColors, (float[])null);
        this.fillArcPaint.setShader(sweepGradient);
        this.fillArcPaint.setMaskFilter(this.mBlur);
        this.fillArcPaint.setStrokeCap(Paint.Cap.ROUND);
        this.fillArcPaint.setStrokeWidth((float) this.pathWidth);
        this.oval.set((float) (this.width / 2 - this.radius),//left
                (float) (this.height / 2 - this.radius), //top
                (float) (this.width / 2 + this.radius), //right
                (float) (this.height / 2 + this.radius));//bottom
                //？
        canvas.drawArc(this.oval, -90.0F, (float) this.progress / (float) this.max * 360.0F, false, this.fillArcPaint);
    }