java - 1mm 网格显示不正确 (Android)

Question

我正在尝试创建一个网格，显示每 1mm 的线条和每 10mm 的粗线条，并具有以下代码：

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

    float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_MM, 1,
            getResources().getDisplayMetrics());

    float currentH = 0;
    float currentW = 0;

    int countX = 0;
    int countY = 0;

    DisplayMetrics metrics = getResources().getDisplayMetrics();

    while (currentW < metrics.widthPixels) {
        if(countX % 10 == 0){
            this.paint.setStrokeWidth(0.5f);
            this.paint.setColor(getResources().getColor(R.color.GridGreenTens));
        } else {
            this.paint.setStrokeWidth(0.1f);
            this.paint.setColor(getResources().getColor(R.color.GridGreen));
        }
        canvas.drawLine(currentW, 0, currentW, metrics.heightPixels, paint);
        countX++;
        currentW += px;
    }
    while (currentH < metrics.heightPixels) {
        if(countY % 10 == 0){
            this.paint.setStrokeWidth(0.5f);
            this.paint.setColor(getResources().getColor(R.color.GridGreenTens));
        } else {
            this.paint.setStrokeWidth(0.1f);
            this.paint.setColor(getResources().getColor(R.color.GridGreen));
        }
        canvas.drawLine(0, currentH, metrics.widthPixels, currentH, paint);
        countY++;
        currentH += px;
    }
}

我的问题是它显示如下：

如您所见，粗线 (o.5f) 出现的频率比应有的要高得多。任何帮助将不胜感激。