Error inflating class com.github.gzuliyujiang.wheelpicker.widget.DateWheelLayout

[XuMengren]

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.github.gzuliyujiang.wheelview.widget.WheelView.setVisibleItemCount(int)' on a null object reference at com.github.gzuliyujiang.wheelpicker.widget.BaseWheelLayout.setVisibleItemCount(BaseWheelLayout.java:155)

使用的是demo的布局
<com.github.gzuliyujiang.wheelpicker.widget.DateWheelLayout
android:layout_width="120dp"
android:layout_height="150dp"
android:layout_gravity="center_horizontal"
app:wheel_dateMode="month_day"
app:wheel_dayLabel="日"
app:wheel_monthLabel="月" />

[XuMengren]

我就是想运行看看效果，发现运行不起来