我怎样才能消除从ListView的onItemClick / getView和行类型的依赖？ [英] How can I eliminate the dependency from of a ListView's onItemClick/getView and its row types?

问题描述

作为一个简单的例子，假设有一个的ListView ，可以包含两个子类别和书名。如果点击书名，一个新的活动应该开始显示封面图片。如果点击一个子类，显示的书籍和类别的新列表。

As a simplified example, consider a ListView that can contain both sub-categories and book titles. If a book title is clicked, a new activity should start that shows the cover image. If a sub-category is clicked, a new list of books and categories is displayed.

A 行接口定义如下。

A Row interface is defined as follows.

interface Row {
   void onClick();
   void draw(View v);
}

我想知道如何prevent从的ListView 的 ArrayAdapter ，以及依赖从 onItemClickListener 的实施者上的行实施者（例如，图书和类别）。

I would like to know how to prevent a dependency from the ListView's ArrayAdapter as well as from the implementer of onItemClickListener on the Row implementers (e.g.,Book and Category).

其中的力量推动这个要求就是不要重复自己（DRY）原则： ArrayAdapter 的实现并不需要在新行类型改变出台。

One of the forces driving this requirement is the "don't repeat yourself" (DRY) principle: the ArrayAdapter implementation does not need to change when new row types are introduced.

推荐答案

请原谅我的鸡划伤UML的，但在这里就是我如何做到这一点。

Forgive my chicken-scratched "UML" below, but here's how I do it.

class ListAdapter extends ArrayAdapter<Row<?>> {
...
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = listViewRowViewRecycler.getView(convertView);
        rowProvider.get().getRow(position).draw(view);
        return view;
    }
}

OnItemClickListener 的实施者有一个方法是这样的：

The implementer of OnItemClickListener has a method like this:

void onItemClick(AdapterView<?> adapterView, View view, int rowIndex, long rowId)
{
   rowProvider.onItemClick(rowIndex);
}

然后 RowProvider 有这样的方法：

void onItemClick(int rowIndex) {
    rowList.get(rowIndex).onClick();
}

然后行接口与签名无效的onClick（），有类别和图书 行提供必要的行为。的实现

Then the Row interface has a method with signature void onClick() and there are Category and Book implementations of Row that provide the necessary behavior.

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