如何消除ListView的onItemClick / getView及其行类型的依赖关系？ [英] How can I eliminate the dependency from of a ListView's onItemClick/getView and its row types?

问题描述

作为一个简化的例子，考虑一个可以包含子类别和书籍标题的 ListView 。如果一个书名被点击，一个新的活动应该开始显示封面图像。如果点击了子类别，则会显示新的图书和类别列表。

行界面是定义如下。

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

我想知道如何防止从 ListView 的 ArrayAdapter 以及 onItemClickListener 的实现者行实现者（例如书和类别）。 p>

驱动这个要求的力量之一是不要重复自己（DRY）原则： ArrayAdapter 实现

解决方案

在下面原谅我的划痕的UML，但这里是如何我这样做

  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）; 
返回视图; 
} 
} 
  

实现者 OnItemClickListener 有一个这样的方法：

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

然后 RowProvider 一个这样的方法：

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

然后行接口有一个方法，具有签名 void onClick（），还有类别和 Book 执行行，提供必要的行为。

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 Row interface is defined as follows.

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

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).

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.

解决方案

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;
    }
}

The implementer of OnItemClickListener has a method like this:

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

Then RowProvider has a method like this:

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

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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