Android-数据在微调器中分配，但选择时不显示微调器中的值

Problem我正在使用 Retrofit 从 mysql 获取一些产品类别。数据即将到来并在微调器中分配，但是当我选择一个项目时，它不会显示。在下拉菜单中，项目已分配，并且 setOnItemSelected 侦听器也正在工作。但所选项目未显示在微调器中。 我已经尝试了几乎所有与 stackoverflow 问题相关的内容，但都不起作用。请帮助我。提前致谢。

Code

这是订单活动

public class OrderActivity extends AppCompatActivity  {

Spinner sp_category,sp_product;
public static final String ROOT_URL = "http://10.0.2.2/sizzle/";
private List<Product> books;
List<String> prod_cat = new ArrayList<String>();
ArrayAdapter<String> adapter_prod_cat;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_order);

    //sp_product = (Spinner)findViewById(R.id.spinner_product);
    getBooks();
    sp_category = (Spinner)findViewById(R.id.spinner_category);
    sp_category.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            String category = parent.getSelectedItem().toString();
            Toast.makeText(getApplicationContext(),category,Toast.LENGTH_LONG).show();
        }

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

        }
    });
}


private void getBooks(){
    final ProgressDialog loading = ProgressDialog.show(this, "Fetching Data", "Please wait...", false, false);

    RestAdapter adapter = new RestAdapter.Builder()
            .setEndpoint(ROOT_URL)
            .build();

    ProductAPI api = adapter.create(ProductAPI.class);

    api.getProduct(new Callback<List<Product>>() {
        @Override
        public void success(List<Product> list, Response response) {
//Dismissing the loading progressbar
            loading.dismiss();
            books = list;
            for (int i = 0; i < books.size(); i++) {
                prod_cat.add(books.get(i).getProductCategory());
                System.out.println("added");
            }
            Set<String> citySet = new HashSet<String>(prod_cat);
            prod_cat.clear();
            prod_cat.addAll(citySet);
            prod_cat.add("Select Category");
            showListinSpinner();
        }

        @Override
        public void failure(RetrofitError error) {
            Toast.makeText(getApplicationContext(), error.toString(), Toast.LENGTH_LONG).show();
        }
    });
}

private void showListinSpinner(){
    //String array to store all the book names
    String[] items = new String[prod_cat.size()];

    //Traversing through the whole list to get all the names
    for(int i=0; i<prod_cat.size(); i++){
        //Storing names to string array
        items[i] = prod_cat.get(i);
    }

    //Spinner spinner = (Spinner) findViewById(R.id.spinner1);
    ArrayAdapter<String> adapter;
    adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, items);
    //setting adapter to spinner
    adapter.notifyDataSetChanged();
    sp_category.setAdapter(adapter);
    //Creating an array adapter for list view
}

}

这是布局文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res   /android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context="com.skipper.ash.ashtet.OrderActivity">
 <Spinner
    android:layout_width="300dp"
    android:layout_height="80dp"
    android:id="@+id/spinner_category"
    android:spinnerMode="dropdown"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="43dp"
    android:textAlignment="center"
    android:visibility="visible" />
</RelativeLayout>

在名为的布局文件夹中创建 xml 文件item_spinner并在其中写入下面的代码

<?xml version="1.0" encoding="utf-8"?>
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="15sp"
    android:textColor="#000000" >

并在创建适配器时更改代码。

adapter = new ArrayAdapter<String>(getApplicationContext(), 
                      R.layout.item_spinner, items);

也改变语句的顺序

sp_category.setAdapter(adapter);
adapter.notifyDataSetChanged();

首先将适配器设置为微调器，然后触发数据集更改事件。

希望它能帮助你。

EDIT

我观察了很多时间，如果我们将适配器设置为ListView or Spinner以编程方式使用ArrayAdapter和用途android.R.layout.simple_spinner_item_1或任何其他内置布局，然后它将项目的文本颜色设置为白色。我不明白为什么它默认将文本设置为白色。