Question

有谁能告诉我在哪里实例化像ArrayList这样的单例类对象？

我正在尝试使用onCreate()方法进行实例化 但未实例化。谁能告诉我在哪里分配它？

public class SharedVariables extends Application 
{
public static ArrayList<ArrayList<Map<String,String>>>  ArrayOfImageUrlDicts;
public static ArrayList<ArrayList<Map<String,String>>> ArrayOfImageNameDicts;

@Override
public void onCreate()
{
    super.onCreate();
    ArrayOfImageUrlDicts  = new ArrayList<ArrayList<Map<String,String>>>(); 
    ArrayOfImageNameDicts = new ArrayList<ArrayList<Map<String,String>>>();
}
}

Answer 1

这实际上不是真正的Singelton（see Wikipedia for an accurate Description of Singeltons），而是一个普通的静态变量。如果你想使用更多的静态变量，你可以考虑使用它，因为它使事情变得更加美好。但是，要回答您的具体问题，您可以使用静态块来初始化这些变量，也可以在变换后直接初始化它们。

public class SharedVariables extends Application 
{
   public static ArrayList<ArrayList<Map<String,String>>>  ArrayOfImageUrlDicts = new ArrayList<ArrayList<Map<String,String>>>();
   public static ArrayList<ArrayList<Map<String,String>>> ArrayOfImageNameDicts = new ArrayList<ArrayList<Map<String,String>>>();

   @Override
   public void onCreate()
   {
      super.onCreate();
   }
}

或

public class SharedVariables extends Application 
{
   public static ArrayList<ArrayList<Map<String,String>>>  ArrayOfImageUrlDicts;
   public static ArrayList<ArrayList<Map<String,String>>> ArrayOfImageNameDicts;
   static 
   {
      ArrayOfImageUrlDicts = new ArrayList<ArrayList<Map<String,String>>>();
      ArrayOfImageNameDicts = = new ArrayList<ArrayList<Map<String,String>>>();
   }
   @Override
   public void onCreate()
   {
      super.onCreate();
   }
}

Answer 2

public class SharedVariables extends Application 
{

ModelSingleTonclass obj;

public static ArrayList<ArrayList<Map<String,String>>>  ArrayOfImageUrlDicts;
public static ArrayList<ArrayList<Map<String,String>>> ArrayOfImageNameDicts;

@Override
public void onCreate()
{
    super.onCreate();

obj=ModelSingleTonclass.getInstance();

    ArrayOfImageUrlDicts  = new ArrayList<ArrayList<Map<String,String>>>(); 
    ArrayOfImageNameDicts = new ArrayList<ArrayList<Map<String,String>>>();
}
}

在Android中实例化单例类对象

2 个答案: