Android 如何通过单击菜单项获取下拉菜单项？

我在自定义ActionBar中实现下拉列表（如微调器）时遇到问题。我尝试了几种解决方案，包括getActionView（），但都不起作用：/

 Here is my code; @Override public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.planner_menu, menu);
MenuItem category_item = menu.findItem(R.id.CategoryAppointment);
    Spinner spinner =(Spinner) category_item.getActionView();

    String[] categories = new String[]{"meeting","training","puls","medicin","bloodsample"};
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_dropdown_item,categories);
    spinner.setAdapter(adapter);

spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
          parent.setSelection(position);

                switch (position) {
                    case 0:
                        String category = parent.getSelectedItem().toString();
                        Toast.makeText(parent.getContext(),
                                "OnItemSelectedListener : " + category, Toast.LENGTH_SHORT).show();
                        // Take string and compare it in database.
                        DB.getAllAppointmentsByCategory(category);
                        break;

                    case 1:
                        // Take string and compare it in database.
                        break;
                    case 2:
                        // Take string and compare it in database.
                        break;
                    case 3:
                        // Take string and compare it in database.
                        break;
                    case 4:
                        // Take string and compare it in database.
                        break;
                }
            }

@Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });

for (int j = 0; j < menu.size(); j++) {
    MenuItem item = menu.getItem(j);
    Log.d("TAG", "set flag for " + item.getTitle());
    item.setShowAsActionFlags(MenuItem.SHOW_AS_ACTION_ALWAYS);

}
return true;}

XML文件中的代码

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" tools:context=".Planning">

<item android:id="@+id/AllAppointments" android:title="All"
    android:orderInCategory="10"
    app:showAsAction="always|withText">
</item>
<item android:id="@+id/WeekAppointment"
    android:title="Week"
    android:orderInCategory="10"
    app:showAsAction="always|withText"
    >
</item>
<item android:id="@+id/CategoryAppointment"
    android:title="Cathegories"
    android:orderInCategory="10"
    app:showAsAction="always|withText"
    >
</item>

` 在item id->CategoryAppoition中，我想显示一个下拉菜单，用户可以在其中选择不同的类别，然后从数据库中列出数据。 在过去的几个小时里，我一直在研究这个问题，但似乎无法解决它。有人能给我解释一下我必须做什么以及我做错了什么吗

多谢各位

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" tools:context=".Planning">

<item android:id="@+id/AllAppointments" android:title="All"
    android:orderInCategory="10"
    app:showAsAction="always|withText">
</item>
<item android:id="@+id/WeekAppointment"
    android:title="Week"
    android:orderInCategory="10"
    app:showAsAction="always|withText"
    >
</item>
<item android:id="@+id/CategoryAppointment"
    android:title="Cathegories"
    android:orderInCategory="10"
    app:showAsAction="always|withText"
    >
</item>