[Android]Nothing is displayed in RecyclerView

Phenomenon

When I try to read the data in the database and display it in RecyclerView, nothing is displayed. When I set a breakpoint and examined it, there was no problem up to the point where the data was read.

Cause

The return value of the method getItemCount () implemented in the RecyclerView.Adapter class was 0.

When deciding the layout of RecyclerView, getItemCount () is used to get the number of items, so if this returns 0, nothing will be displayed.

（https://qiita.com/takahirom/items/7978d1cf514d67097456）

If you override this method in Android Studio, it will initially return 0, so don't forget to change it.

@Override
public int getItemCount() {

    return c;  //Enter the number of items in c
}