访问它创建了一个对象中的调用活动的方法 [英] accessing a calling activity's method from within an object it created

问题描述

MYI不明白为什么我得到一个编译错误此：

MyI don't understand why I get a compile error for this:

   public class Main_screen extends ListActivity {

       List<Object> completeList;
       private My_ArrayAdapter adapter;


    public void onCreate(Bundle icicle) {
       super.onCreate(icicle);
       completeList = getCompleteList();
       adapter = new My_ArrayAdapter(this, completeList);
       setListAdapter(adapter);
       }

    public void doSth() {
                ...
        }
    }

和在My_ArryAdapter：

and in My_ArryAdapter:

 public class My_ArrayAdapter extends ArrayAdapter<Object> {

        private final List<Object> list;
        private final Activity context;


        public My_ArrayAdapter(Activity context, List<Object> list) {
           this.context = context;
           this.list = list;

        }

        public void tryIt() {
           context.doSth();   // <-------- THIS DOES NOT WORK, this method can not be called
        }
    }

请解释一下，是有什么我根本没有理解。我只是路过的背景下进入一个ArrayAdapter实例创建。而从这个实例中，我想acccess调用者的方法。

Please explain, is there something fundamental I have not understood. I am just passing the context into the ArrayAdapter instance I create. And from within this instance I would like to acccess the caller's method.

为什么shoudl这是不可能的？

Why shoudl this not be possible?

非常感谢！

推荐答案

试试这个：

public void tryIt() {
           ((Main_screen)context).doSth();  
        }

上下文是活动现在也没有doSth（），但Main_screen了，所以你应该转换为该类

context is Activity and it hasn't doSth(), but Main_screen has, so you should cast to this class

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