android spinner显示空白项目没有显示错误

Question

我试图使用Spinner来显示来自SQLite的数据。没有错误但旋转器没有显示任何内容。任何人都可以解决这个问题。以下是我的代码 CategoryBO.java

package com.giao.ordersystem;

/**
 * Created by Long on 2/13/2016.

* /

public class CategoryBO {
    private String categoryName;
    public CategoryBO()
    {

    }
    public CategoryBO(String categoryName)
    {
        this.categoryName=categoryName;
    }
    public String getCategoryName()
    {
        return this.categoryName;
    }
    public void setCategoryName(String categoryName)
    {
        this.categoryName=categoryName;
    }
}

DishDAO.java

package com.giao.ordersystem;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import java.util.List;
import java.util.ArrayList;
/**
 * Created by Long on 2/13/2016.
 */
public class DishDAO {
    private static final String KEY_ROWID = "dishID";
    private static final String CATEGORYID = "categoryID";
    private static final String DISH_NAME = "dishName";
    private static final String DISH_PRICE = "dishPrice";
    private static final String DISH_DESCRIPTION = "dishDescription";
    private static final String DISH_AVAILABILITY="availability";
    private static final String DATABASE_TABLE = "Menu";
    private static DatabaseHelper databaseHelper;
    //
    public final Context context;
    private SQLiteDatabase database;

    public DishDAO(Context context) {
        this.context = context;
        // TODO Auto-generated constructor stub
    }

    public DishDAO open() throws SQLException {
        database = databaseHelper.getReadableDatabase();
        return this;
    }

    public void close() throws SQLException {
        this.close();
    }

    public long create(String categoryID, String dishName, String dishPrice, String dishDecription, String availability) throws SQLException {
        ContentValues cv = new ContentValues();
        cv.put(CATEGORYID, categoryID);
        cv.put(DISH_NAME, dishName);
        cv.put(DISH_PRICE, dishPrice);
        cv.put(DISH_DESCRIPTION, dishDecription);
        cv.put(DISH_AVAILABILITY,availability);
        return database.insert(DATABASE_TABLE, null, cv);
    }

    public List<DishBO> list() throws SQLException {
        String query = "SELECT * FROM Tables";
        Cursor cur = database.rawQuery(query, null);
        List<DishBO> list = new ArrayList<DishBO>();
        int iRow = cur.getColumnIndex(KEY_ROWID);
        for (cur.moveToFirst(); !cur.isAfterLast(); cur.moveToNext()) {
            DishBO record = new DishBO(Integer.parseInt(cur.getString(0)), Integer.parseInt(cur.getString(1)), cur.getString(2)
                    , Integer.parseInt(cur.getString(3)), cur.getString(4),Integer.parseInt(cur.getString(5)));
            list.add(record);
        }
        cur.close();
        return list;
    }

    public boolean remove(int dishID) throws SQLException {
        return database.delete(DATABASE_TABLE, KEY_ROWID + "=" + dishID, null) > 0;
    }

    public boolean removeAll() {
        return database.delete(DATABASE_TABLE, null, null) > 0;
    }

    public long update(String dishID, String categoryID, String dishName, String dishPrice, String dishDecription) throws SQLException
    {
        ContentValues cv = new ContentValues();
        if (categoryID != null)
            cv.put(CATEGORYID, categoryID);
        if (dishName != null)
            cv.put(DISH_NAME, dishName);
        if (dishPrice != null)
            cv.put(DISH_PRICE, dishPrice);
        if (dishDecription != null)
            cv.put(DISH_DESCRIPTION, dishDecription);
        return database.update(DATABASE_TABLE, cv, KEY_ROWID + "=?", new String[]{dishID});
    }
}

Menu_Event.Java

package com.giao.ordersystem;

import android.content.Context;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Spinner;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Long on 2/8/2016.
 */
public class Menu_Event {
    private Context context;
    private CategoryDAO categoryDAO;
    public Menu_Event()
    {}
    public Menu_Event(Context context)
    {
        this.context=context;
        categoryDAO = new CategoryDAO(context);
    }
    public void categoryListView_OnLoad(Spinner categorySpinner)
    {
        categoryDAO.open();
        List<String> categoryList = new ArrayList<String>();
        for(int i=0;i<categoryDAO.list().size();i++)
        {
            categoryList.add(categoryDAO.list().get(i).getCategoryName());
        }
        categoryDAO.close();
        ArrayAdapter<String> categoryAdapter =  new ArrayAdapter(context,android.R.layout.simple_spinner_item,categoryList);
        categoryAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        categorySpinner.setAdapter(categoryAdapter);
        categoryAdapter.notifyDataSetChanged();
    }
}

style.xml

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

<style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
</style>

<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />

<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

CategoryDAO

package com.giao.ordersystem;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import java.util.List;
import java.util.ArrayList;
/**
 * Created by Long on 2/12/2016.
 */
public class CategoryDAO{
    public static final String KEY_TableName="CategoryName";
    private static final String DATABASE_TABLE="Category";
    private static DatabaseHelper databaseHelper;
    //
    public final Context context;
    private SQLiteDatabase database;
    public CategoryDAO(Context context) {
        this.context=context;
        databaseHelper= new DatabaseHelper(context);
        // TODO Auto-generated constructor stub
    }
    public CategoryDAO open() throws SQLException
    {
        database=databaseHelper.getReadableDatabase();
        return this;
    }
    public void close() throws SQLException
    {
        databaseHelper.close();
    }
    public long create(String tableName) throws SQLException
    {
        ContentValues cv= new ContentValues();
        cv.put(KEY_TableName, tableName);
        return database.insert(DATABASE_TABLE,null ,cv);
    }
    public ArrayList<CategoryBO> list()
    {
        String query="SELECT * FROM Category";
        Cursor cur=database.rawQuery(query,null);
        ArrayList<CategoryBO> list = new ArrayList<CategoryBO>();
        int iRow= cur.getColumnIndex(KEY_TableName);
        for(cur.moveToFirst();!cur.isAfterLast();cur.moveToNext()) {
            CategoryBO record = new CategoryBO(cur.getString(0));
            list.add(record);        }
        cur.close();
        return list;
    }
    public boolean remove(int categoryName)
    {
        return database.delete(DATABASE_TABLE, KEY_TableName + "=" + categoryName, null) > 0;
    }
    public boolean removeAll()
    {
        return database.delete(DATABASE_TABLE, null, null) > 0;
    }

}