@Spinner
One, Spinner overview
1.
Spinner features: Spinner is a drop-down list box. When you click Spinner, a drop-down list will pop up for the user to choose, and only one item in the list can be displayed when it is displayed. The Spinner inheritance relationship is as follows: 
According to the inheritance relationship, Spinner is a subclass of ViewGroup's insight and can also be used as a container.
2. Link to official documentation of XML attributes and methods supported by Spinner
| Serial number | Attributes | effect |
|---|---|---|
| 01 | dropDownHorizontalOffset setdropDownHorizontalOffset (int) | Set the pull-down horizontal offset |
| 02 | dropDownVerticalOffset | Set drop-down selector |
| 03 | dropdownVerticalOffset | Set the drop-down vertical offset |
| 04 | dropdownWidth | Set the width of the drop-down list |
| 05 | gravity setGravity（int） | Alignment |
| 06 | PopupBackgroud setPopupBackgroundRouse(int) | Set drop-down background |
| 07 | prompt setPrompt() | Set the prompt text of the drop-down list |
| 08 | spinnerMode | List box mode |
| 09 | entries | Set the data source for the drop-down list box |
| 10 | setAdapter | Set the drop-down list box and data source association |
| 11 | getPrompt | Get reminder text |
| 12 | setOnItemClickListence() | Click the event listener to register options for the drop-down list |
| 13 | setOnItemSelectedListener() | Register an option event listener for the drop-down list box |
Second, ArrayAdaper
overview: two major functions: one is to read the list items defined in the resource file, and the other is to use the array or List collection items,
methods:
| method | effect |
|---|---|
| public ArrayAdapter（Context context，int resource，Listobjects） | Constructor, create an ArrayAdapter object in the current interface |
| public ArrayAdapter(Context,context,int resource,T[] objects | Construction method, according to the specified list item display style and array data, create an ArrayAdapter object in the current interface |
public static ArraryAdapter <CharSequen>cecreateFromResouce(Context context,int textArrayResld,int textViewResld) createFromResouce(Context context,int textArrayResld,int textViewResld) |
Create an ArrayAdapter object in the current interface through array resource and list item display style |
| Public void | Set the display style of the drop-down list items |
