Question

我使用JSON和数据库来获取一些值并将它们设置为listviews。 JSON个对象没问题但是当我尝试从数据库（游标对象）获取值并将它们设置为ArrayList时，它会给出NullPointerException。

ArrayList<String> stringName,stringAddress,stringCapacity;
...
...
...
cursor_restnames = db.getRestNames("Ankara");

if (cursor_restnames.moveToFirst()) {
    for (cursor_restnames.moveToFirst(); !cursor_restnames.isAfterLast(); cursor_restnames.moveToNext()) {
        System.out.println("aaaaa "+cursor_restnames.getString(cursor_restnames.getColumnIndex("name")).toString()); // I can see the cursor object in logcat which is "aspava".
        stringName.add(cursor_restnames.getString(cursor_restnames.getColumnIndex("name")).toString()); // I got error here which is NullPointerException but as I mentioned it is not null, it has "aspava" string.
    }

    cursor_restnames.close();
}

我的DBadapter有 getRestNames 功能，即

public Cursor getRestNames(String city) {
      Cursor myCursor = db.rawQuery("select name from rest where city='"+city+"'", null);

       if (myCursor != null) {  
            myCursor.moveToFirst();  
       }  

       return myCursor;  
  }

如果这些代码段无效，我可以写下整个项目。感谢您的帮助，如果我的英语有任何错误，我很抱歉。

Answer 1

你是否初步确定了你的Arraylist

stringName = new Arraylist（）;

Answer 2

您应该初始化数组列表，因为这样您的对象值为null

 ArrayList<String> stringName = new ArrayList<String>();

我的光标不为空，但我无法将它们设置为ArrayList.NullPointerException错误

2 个答案: