创建ViewHolders的列表视图与不同的项目布局 [英] Creating ViewHolders for ListViews with different item layouts

问题描述

我有不同的布局，为不同的项目一个ListView。有些项目是分隔符。有些项目是不同的，因为他们持有不同类型的数据，等等。

I have a ListView with different layouts for different items. Some items are separators. Some items are different because they hold different kinds of data, etc.

我想实现ViewHolders加快getView的过程，但我不太清楚如何去做。不同的布局有不同的数据块（这使得命名困难）和不同数量的意见我想使用。

I want to implement ViewHolders to speed up the getView process, but I'm not quite sure how to go about it. Different layouts have different pieces of data (which makes naming difficult) and different numbers of Views I want to use.

我应该如何去这样做？

我能想出的最好的办法是建立一个通用的ViewHolder以X项目，其中X是一个项目布局最多人浏览的数量。对于少数意见的其他意见，我就用了ViewHolder这些变量的小节。所以说我有2的布局我用2个不同的项目。其中有3个TextViews和其他有1.我将创建一个ViewHolder 3 TextView的变量，并且只使用其中1为我的其他项目。我的问题是这样可以得到真正丑陋的外观和感觉真的哈克;特别是当某个项目的布局可以具有许多观许多不同类型的

The best idea I can come up with is to create a generic ViewHolder with X items where X is the number of Views in an item layout with the highest number of them. For the other views with a small number of Views, I'll just use a subsection of those variables in the ViewHolder. So say I have 2 layouts I use for 2 different items. One has 3 TextViews and the other has 1. I would create a ViewHolder with 3 TextView variables and only use 1 of them for my other item. My problem is that this can get really ugly looking and feels really hacky; especially when an item layout may have many Views of many different types.

下面是一个非常基本的getView：

Here is a very basic getView:

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    MyHolder holder;

    View v = convertView;
    if (v == null) {
        LayoutInflater vi = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = vi.inflate(R.layout.layout_mylistlist_item, parent, false);

        holder = new MyHolder();
        holder.text = (TextView) v.findViewById(R.id.mylist_itemname);
        v.setTag(holder);
    }
    else {
        holder = (MyHolder)v.getTag();
    }

    MyListItem myItem = m_items.get(position);

    // set up the list item
    if (myItem != null) {
        // set item text
        if (holder.text != null) {
            holder.text.setText(myItem.getItemName());
        }
    }

    // return the created view
    return v;
}

假如我有不同类型的行布局，我可以有一个ViewHolder每种类型行。不过，我会宣布什么类型的持有人是在顶部？我会不会宣布针对每种类型的支架，然后使用一个用于排我的类型。

Suppose I had different types of row layouts, I could have a ViewHolder for each type of row. But what type would I declare "holder" to be at the top? Or would I declare a holder for each type and then use the one for the type of row I'm on.

推荐答案

ListView中有一个内置式的管理制度。在您的适配器，你有几个类型的项目，每一个都有自己的观点和布局。通过重写<一href="http://developer.android.com/reference/android/widget/Adapter.html#getItemViewType%28int%29">getItemViewType返回给定位置的数据类型，ListView中被garunteed通过在正确convertview该类型的数据。然后，在getView方法简单地检查数据类型和使用switch语句来处理每种类型的不同。

ListView has a built in type management system. In your adapter, you have several types of items, each with their own view and layout. By overriding getItemViewType to return the data type of a given position, ListView is garunteed to pass in the correct convertview for that type of data. Then, in your getView method simply check the datatype and use a switch statement to handle each type differently.

每个布局类型应该有自己的viewholder命名清晰和易于maintainence的。命名ViewHolders一些相关的每个数据类型把一切都直。

Each Layout type should have its own viewholder for naming clarity and ease of maintainence. Name the ViewHolders something related to each data type to keep everything straight.

尝试一切重叠成一个ViewHolder是不值得的。

Trying to overlap everything into one ViewHolder is just not worth the effort.

修改的 示例

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    int viewType = this.getItemViewType(position);

    switch(viewType)
    {
       case TYPE1:

        Type1Holder holder1; 

         View v = convertView; 
         if (v == null) { 
             LayoutInflater vi = (LayoutInflater)getContext().getSystemService     (Context.LAYOUT_INFLATER_SERVICE); 
             v = vi.inflate(R.layout.layout_mylistlist_item_type_1, parent, false); 

             holder1 = new Type1Holder (); 
             holder1.text = (TextView) v.findViewById(R.id.mylist_itemname); 
             v.setTag(holder1); 
         } 
         else { 
             holder1 = (Type1Holder)v.getTag(); 
         } 

         MyListItem myItem = m_items.get(position); 

         // set up the list item 
         if (myItem != null) { 
             // set item text 
             if (holder1.text != null) { 
                 holder1.text.setText(myItem.getItemName()); 
             } 
         } 

         // return the created view 
         return v; 


     case TYPE2:
            Type2Holder holder2; 

         View v = convertView; 
         if (v == null) { 
             LayoutInflater vi = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
             v = vi.inflate(R.layout.layout_mylistlist_item_type_2, parent, false); 

             holder2 = new Type2Holder (); 
             holder2.text = (TextView) v.findViewById(R.id.mylist_itemname); 
             holder2.icon = (ImageView) v.findViewById(R.id.mylist_itemicon); 
             v.setTag(holder1); 
         } 
         else { 
             holder2 = (Type2Holder)v.getTag(); 
         } 

         MyListItem myItem = m_items.get(position); 

         // set up the list item 
         if (myItem != null) { 
             // set item text 
             if (holder2.text != null) { 
                 holder2.text.setText(myItem.getItemName()); 
             } 

             if(holder2.icon != null)
                 holder2.icon.setDrawable(R.drawable.icon1);
         } 


         // return the created view 
         return v; 


       default:
           //Throw exception, unknown data type
    }
} 

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