如何绘制一个仪表盘

public class Dashboard extends View {    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);    private static final int ANGLE = 120;    private static final float RADIUS = Util.dp2px(150);    private static final float LENGTH = Util.dp2px(120);    private static final int count = 20;    private PathMeasure pathMeasure;    Path dash = new Path();    PathDashPathEffect effect;
    Path arc = new Path();
    public Dashboard(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }
    {        paint.setStyle(Paint.Style.STROKE);        paint.setStrokeWidth(Util.dp2px(2));        dash.addRect(0, 0, Util.dp2px(2), Util.dp2px(10), Path.Direction.CW);

    }
    float pos[] = new float[2];    float tan[] = new float[2];
    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        super.onSizeChanged(w, h, oldw, oldh);
        arc = new Path();        arc.addArc(getWidth()/2-RADIUS, getHeight()/2-RADIUS, getWidth()/2+RADIUS, getHeight()/2+RADIUS, 90+ANGLE/2, 360-ANGLE);
        pathMeasure = new PathMeasure(arc, false);        float length = pathMeasure.getLength();        float advance = length/(count);//-Util.dp2px(0);        effect = new PathDashPathEffect(dash, advance, 0, PathDashPathEffect.Style.ROTATE);    }
    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        // 画刻度        canvas.drawPath(arc, paint);//        canvas.drawArc(getWidth()/2-RADIUS, getHeight()/2-RADIUS, getWidth()/2+RADIUS, getHeight()/2+RADIUS, 90+ANGLE/2, 360-ANGLE, false, paint);        paint.setPathEffect(effect);
        canvas.drawPath(arc, paint);//        canvas.drawArc(getWidth()/2-RADIUS, getHeight()/2-RADIUS, getWidth()/2+RADIUS, getHeight()/2+RADIUS, 90+ANGLE/2, 360-ANGLE, false, paint);        paint.setPathEffect(null);
        // 画指针//        boolean success = pathMeasure.getPosTan(2900, pos, tan);//        if (success)//            canvas.drawLine(getWidth()/2, getHeight()/2, pos[0], pos[1], paint);
        int markValue = getMark();        canvas.drawLine(getWidth()/2, getHeight()/2,                (float) Math.cos(Math.toRadians(getAngleFromMark(markValue)))*LENGTH + getWidth()/2,                (float) Math.sin(Math.toRadians(getAngleFromMark(markValue)))*LENGTH + getHeight()/2,                paint);
        postDelayed(this::invalidate, 1000);    }
    int mark = 0;    int getMark(){        mark++;        if (mark > 20) mark = 0;        return mark;    }
    int getAngleFromMark(int mark){        return (int) (90 + (float) ANGLE / 2 + (float)(360-ANGLE)/count*mark);    }}