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@kmfish 2015-09-16T13:06:18.000000Z 字数 5875 阅读 3627

MultiTypeListViewAdapter Android ListView 多type的Adapter封装

Android ListView Adapter ViewType

MultiTypeListViewAdapter 是什么？

MultiTypeListViewAdapter，顾名思义。其封装了多type下的Adapter的编程模式，通过对每种type统一接口，利用多态的方式，将type的实现从Adapter中抽离出来。Adapter只需面向统一接口，所以可以提供一个通用实现，实现代码不再变动。而会变动的每个type对应的item实现，则由使用者自己去实现。对扩展开放，对修改封闭。

同时，由于每个type的item均被抽离出来了。相当于复用的粒度为每个type item，可以根据需要，动态地选择合适的item去添加到adapter中。提高了代码复用，每个人编写维护好自己的item即可，避免了多人合作时都去修改Adapter，容易造成冲突。

另外，由于ViewHolder 模式的规范，MultiTypeListViewAdapter也同时封装了ViewHolder模式。

常见的ListView Adapter 实现

先看一下常见的ListAdapter 实现，分为单个type和多type两种情况。

1、单Type的Adapter

  1. class ListAdapter extend BaseAdapter {
  2.     ...
  3.     private List<String> contents = new ArrayList();
  4.     ...
  5.     public View getView(int position, View convertView, ViewGroup parent) {
  6.             String item = getItem(position);
  7.             if(null == item) {
  8.                 throw new RuntimeException("list item is never null. pos:" + position);
  9.             } else {
  10.                 ViewHolder holder;
  11.                 if(null == convertView) {
  12.                     holder = createViewHolder(parent);
  13.                     convertView = holder.itemView;
  14.                     convertView.setTag(holder);
  15.                 } else {
  16.                     holder = (ViewHolder)convertView.getTag();
  17.                 }
  19.                 item.updateHolder(holder, position);
  20.                 return convertView;
  21.             }
  22.         }
  23.     }
  25.     private ViewHolder createViewHolder(ViewGroup parent) {
  26.         // create item view from layout xml
  27.         View itemView =  LayoutInflater.from(getContext()).inflate(R.layout.list_item1, parent, false);
  28.         ViewHolder holder = new ViewHolder(itemView);
  29.         return holder;
  30.     }
  32.     private void updateHolder(ViewHolder holder, String item) {
  33.         // update item view
  34.         holder.text.setText(item);
  35.     }
  37.     private class ViewHolder {
  38.         TextView text;
  40.         ViewHolder(View itemView) {
  41.             text = (TextView)itemView.findViewById(R.id.text);
  42.         }
  43.     }
  44.     ...
  45. }

应该是挺常见的写法吧，继续往下。

2、多type的adapter

  1. class ListAdapter extend BaseAdapter {
  2.     ...
  3.     private List<String> contents = new ArrayList();
  4.     ...
  5.     public int getItemViewType(int position) {
  6.         if (position % 2 == 0) {
  7.             return 0;
  8.         }
  10.         return 1;
  11.     }
  13.     public int getViewTypeCount() {
  14.         return 2;
  15.     }
  17.     public View getView(int position, View convertView, ViewGroup parent) {
  18.             String item = getItem(position);
  19.             if(null == item) {
  20.                 throw new RuntimeException("list item is never null. pos:" + position);
  21.             } else {
  22.                 ViewHolder holder;
  23.                 if(null == convertView) {
  24.                     if (getItemViewType(position) == 0) {
  25.                         holder = createViewHolder(parent);    
  26.                     } else if (getItemViewType(position) == 1) {
  27.                         holder = createViewHolder1(parent);
  28.                     }
  30.                     convertView = holder.itemView;
  31.                     convertView.setTag(holder);
  32.                 } else {
  33.                     holder = (ViewHolder)convertView.getTag();
  34.                 }
  36.                 if (getItemViewType(position) == 0) {
  37.                     item.updateHolder(holder, position);
  38.                 } else if (getItemViewType(position) == 1) {
  39.                     item.updateHolder1(holder, position);
  40.                 }
  42.                 return convertView;
  43.             }
  44.         }
  45.     }
  47.     private ViewHolder createViewHolder(ViewGroup parent) {
  48.         // create item view from layout xml
  49.         View itemView =  LayoutInflater.from(getContext()).inflate(R.layout.list_item1, parent, false);
  50.         ViewHolder holder = new ViewHolder(itemView);
  51.         return holder;
  52.     }
  54.     private ViewHolder createViewHolder1(ViewGroup parent) {
  55.         // create item view from layout xml
  56.         View itemView =  LayoutInflater.from(getContext()).inflate(R.layout.list_item2, parent, false);
  57.         ViewHolder holder = new ViewHolder(itemView);
  58.         return holder;
  59.     }
  61.     private void updateHolder(ViewHolder holder, String item) {
  62.         // update item view
  63.         holder.text.setText(item);
  64.     }
  66.     private void updateHolder1(ViewHolder1 holder, String item) {
  67.         // update item view
  68.         holder.text.setText(item);
  69.         holder.img.setImageResoure(R.drawable.img);
  70.     }
  72.     private class ViewHolder {
  73.         TextView text;
  75.         ViewHolder(View itemView) {
  76.             text = (TextView)itemView.findViewById(R.id.text);
  77.         }
  78.     }
  80.     private class ViewHolder1 {
  81.         TextView text;
  82.         ImageView img;
  84.         ViewHolder(View itemView) {
  85.             text = (TextView)itemView.findViewById(R.id.text);
  86.             img = (ImageView)itemView.findViewById(R.id.img);
  87.         }
  88.     }
  89.     ...
  90. }

看到这里，是否感觉这个Adapter的getView（）开始有些让人不舒服了呢。若type再进一步增加，难不成还得继续if/else下去，adapter变得又臭又长。估计往后下去，就再没人愿意维护了。而且，这个Adapter的这一堆代码还得到处重复写下去，每个有listView的地方，都得配套一个adapter。针对这个坑，我设计了MultiTypeListViewAdapter来解决。希望能帮助到有需要的程序猿们~

使用 MultiTypeListViewAdapter

  1. public class MainActivity extends AppCompatActivity {
  3.     private ListView listView;
  4.     private MultiTypeArrayAdapter adapter;
  6.     private static final int ITEM_TYPE_1 = 0;
  7.     private static final int ITEM_TYPE_2 = 1;
  9.     private static final int ITEM_TYPE_COUNT = 2;
  11.     @Override
  12.     protected void onCreate(Bundle savedInstanceState) {
  13.         super.onCreate(savedInstanceState);
  14.         setContentView(R.layout.activity_main);
  16.         listView = (ListView) findViewById(R.id.listview);
  17.         adapter = new MultiTypeArrayAdapter(ITEM_TYPE_COUNT);
  18.         listView.setAdapter(adapter);
  20.         setupAdapter();
  21.     }
  23.     private void setupAdapter() {
  24.         adapter.setTypeCount(ITEM_TYPE_COUNT);
  25.         LineListItem1 item1 = new LineListItem1(this, ITEM_TYPE_1, "line type 1");
  26.         LineListItem2 item2 = new LineListItem2(this, ITEM_TYPE_2, "line type 2");
  28.         adapter.setNotifyOnChange(false);
  29.         for (int i = 0, len = 50; i < len; i++) {
  30.             adapter.addItem( i  % 2 == 0 ? item1 : item2);
  31.         }
  32.         adapter.notifyDataSetChanged();
  33.     }
  35. }
  37. public class LineListItem1 extends BaseListItem {
  39.     private String line;
  41.     public LineListItem1(Context mContext, int viewType, String line) {
  42.         super(mContext, viewType);
  43.         this.line = line;
  44.     }
  46.     @Override
  47.     protected int onGetItemLayoutRes() {
  48.         return R.layout.list_item1;
  49.     }
  51.     @Override
  52.     protected ViewHolder onCreateViewHolder(View itemView) {
  53.         return new LineViewHolder(itemView);
  54.     }
  56.     @Override
  57.     public void updateHolder(ViewHolder holder, int pos) {
  58.         LineViewHolder h = (LineViewHolder) holder;
  59.         h.text.setText(line + "_" + pos);
  60.     }
  62.     private class LineViewHolder extends ViewHolder {
  64.         TextView text;
  66.         public LineViewHolder(View itemView) {
  67.             super(itemView);
  68.             text = (TextView) itemView.findViewById(R.id.line_text);
  69.         }
  70.     }
  71. }
  73. public class LineListItem2 extends BaseListItem {
  75.     private String line;
  77.     public LineListItem2(Context mContext, int viewType, String line) {
  78.         super(mContext, viewType);
  79.         this.line = line;
  80.     }
  82.     @Override
  83.     protected int onGetItemLayoutRes() {
  84.         return R.layout.list_item2;
  85.     }
  87.     @Override
  88.     protected ViewHolder onCreateViewHolder(View itemView) {
  89.         return new LineViewHolder2(itemView);
  90.     }
  92.     @Override
  93.     public void updateHolder(ViewHolder holder, int pos) {
  94.         LineViewHolder2 h = (LineViewHolder2) holder;
  95.         h.text.setText(line + "_" + pos);
  96.         h.img.setImageResource(R.drawable.icon_git);
  98.     }
  100.     private class LineViewHolder2 extends ViewHolder {
  101.         ImageView img;
  102.         TextView text;
  104.         public LineViewHolder2(View itemView) {
  105.             super(itemView);
  106.             img = (ImageView) itemView.findViewById(R.id.thumb);
  107.             text = (TextView) itemView.findViewById(R.id.name);
  108.         }
  109.     }
  110. }

可以看到，使用MultiTypeListViewAdapter之后，实现多type的Adapter变得相当简单了。再也不用面对一堆判断itemType的if/else了。每增加一种type，只需增加一种新的ListItem即可，再也不用去改动Adapter的代码了。

项目发布在github上了，MultiTypeListViewAdapter，欢迎fork和交流。

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