Android：具有两种不同视图的EfficientAdapter

我使用基于SDK演示示例中的EfficientAdapter example的BaseAdapter扩展版本。Android：具有两种不同视图的EfficientAdapter

我的数据基本上是一个对象（ListPlaces），它包含一个ArrayList以及实际的位置列表，可通过listPlaces.getValues()访问。此ArrayList数据按范围排序，ArrayList由一些特殊项目（分隔符）组成，但没有数据，但separator标志设置为true。

现在，每当我EfficientAdapter得到一个数据对象，它是返回false为public boolean isEnabled(int position)和public View getView(int position, View convertView, ViewGroup parent)依靠，如果当前数据对象包括实时数据或只是一个分隔符虚拟膨胀两种不同布局的分隔符。

这很好，如果我每次膨胀布局。但是，每次膨胀布局并呼吁findViewById使得ListView几乎非常慢。

所以我试着用ViewHolder的方法使用EfficientAdapter。但是，由于我尝试访问两种不同的观点，这并不适用于开箱即用。因此，只要我的convertView != null（其他情况）通过我们的ViewHolder访问布局上的项目，并且当前一个View是分隔符时，它当然无法访问仅在“真实”项目布局上可用的TextView 。

所以我还逼我getView()膨胀布局不仅当convertView == null，还当上一listRow比当前的一个不同：if (convertView == null || (listRow != listRow_previous)) { [....] }

这似乎几乎现在的工作。或者至少它从一开始就不会崩溃。但它仍然崩溃，我不知道我要做什么不同。我试图去查看convertView.getID()和convertView.getResources()，但到目前为止这并没有真正的帮助。也许别人有一个想法，我可以检查我的当前convertView是否与列表项目布局或列表分隔符布局匹配。谢谢。

这是代码。凡曾经有一个[...]我拿出一些不太重要的代码，使其更容易阅读和理解：

private class EfficientAdapter extends BaseAdapter { 
    private LayoutInflater mInflater; 
    private ListPlaces listPlaces; 

    private ListRow listRow; 
    private ListRow listRow_previous; 


    public EfficientAdapter(Context context, ListPlaces listPlaces) { 
     // Cache the LayoutInflate to avoid asking for a new one each time. 
     mInflater = LayoutInflater.from(context); 

     // Data 
     this.listPlaces = listPlaces; 
    } 

    /** 
    * The number of items in the list is determined by the number of items 
    * in our ArrayList 
    * 
    * @see android.widget.ListAdapter#getCount() 
    */ 
    public int getCount() { 
     return listPlaces.getValues().size(); 
    } 

    /** 
    * Since the data comes from an array, just returning the index is 
    * sufficent to get at the data. If we were using a more complex data 
    * structure, we would return whatever object represents one row in the 
    * list. 
    * 
    * @see android.widget.ListAdapter#getItem(int) 
    */ 
    public Object getItem(int position) { 
     return position; 
    } 

    /** 
    * Use the array index as a unique id. 
    * 
    * @see android.widget.ListAdapter#getItemId(int) 
    */ 
    public long getItemId(int position) { 
     return position; 
    } 

    @Override 
    public boolean isEnabled(int position) { 
     // return false if item is a separator: 
     if(listPlaces.getValues().get(position).separator >= 0) 
      return false; 
     else 
      return true; 
    } 

    @Override 
    public boolean areAllItemsEnabled() { 
     return false;   
    } 



    /** 
    * Make a view to hold each row. 
    * 
    * @see android.widget.ListAdapter#getView(int, android.view.View, 
    *  android.view.ViewGroup) 
    */ 
    public View getView(int position, View convertView, ViewGroup parent) { 

     // Get the values for the current list element 
     ListPlacesValues curValues = listPlaces.getValues().get(position); 
     if (curValues.separator >= 0) 
      listRow = ListRow.SEPARATOR; 
     else 
      listRow = ListRow.ITEM; 
     Log.i(TAG,"Adapter: getView("+position+") " + listRow + " (" + listRow_previous + ") -> START"); 

     // A ViewHolder keeps references to children views to avoid unneccessary calls 
     // to findViewById() on each row. 
     ViewHolder holder; 

     // When convertView is not null, we can reuse it directly, there is no need 
     // to reinflate it. We only inflate a new View when the convertView supplied 
     // by ListView is null. 
     if (convertView == null || (listRow != listRow_previous)) { 
      Log.i(TAG, "--> (convertView == null) at position: " + position); 
      // Creates a ViewHolder and store references to the two children views 
      // we want to bind data to. 
      holder = new ViewHolder(); 

      if (listRow == ListRow.SEPARATOR) { 
       convertView = mInflater.inflate(R.layout.taxonomy_list_separator, null); 
       holder.separatorText = (TextView) convertView.findViewById(R.id.separatorText); 
       convertView.setTag(holder); 
       Log.i(TAG,"\tCREATE SEPARATOR: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); 

      } 
      else { 

       convertView = mInflater.inflate(R.layout.taxonomy_listitem, null); 
       holder.name = (TextView) convertView.findViewById(R.id.name); 
       holder.category = (TextView) convertView.findViewById(R.id.category); 
       // [...] 

       convertView.setTag(holder); 

       Log.i(TAG,"\tCREATE ITEM: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); 
      } 
     } else { 
      // Get the ViewHolder back to get fast access to the TextView 
      // and the ImageView. 
      Log.i(TAG,"\tconvertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); 

      holder = (ViewHolder) convertView.getTag(); 
      convertView.setAnimation(null); 
     } 

     /* Bind the data efficiently with the holder */ 
     if (listRow == ListRow.SEPARATOR) { 
      String separatorText; 
      switch (curValues.separator) { 
      case 0: separatorText="case 0"; break; 
      case 1: separatorText="case 1"; break; 
      case 2: separatorText="case 2"; break; 
      // [...] 
     default: separatorText="[ERROR]"; break; 
      } 
      holder.separatorText.setText(separatorText); 
     } 
     else { 
      // Set the name: 
      holder.name.setText(curValues.name); 
      // Set category 
      String cat = curValues.classification.toString(); 
      cat = cat.substring(1,cat.length()-1); // removing "[" and "]" 
      if (cat.length() > 35) { 
       cat = cat.substring(0, 35); 
       cat = cat + "..."; 
      } 
      holder.category.setText(cat); 

      // [...] (and many more TextViews and ImageViews to be set) 

     } 

     listRow_previous = listRow; 
     Log.i(TAG,"Adapter: getView("+position+") -> DONE"); 
     return convertView; 
    } 

    private class ViewHolder { 
     TextView name; 
     TextView category; 
     // [...] -> many more TextViews and ImageViews 

     TextView separatorText; 
    } 
}

在这里，我logcat的输出：

755  ListPlaces_Activity I onPostExecute: notifyDataSetChanged()                         
    755  ListPlaces_Activity I Adapter: getView(0) SEPARATOR (null) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 0                        
    755  ListPlaces_Activity I  CREATE SEPARATOR: convertView ID: 2131296317 Resource: [email protected]         
    755  ListPlaces_Activity I Adapter: getView(0) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 1                        
    755  ListPlaces_Activity I  CREATE ITEM: convertView ID: 2131296317 Resource: [email protected]          
    755  ListPlaces_Activity I Adapter: getView(1) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 2                        
    755  ListPlaces_Activity I  CREATE SEPARATOR: convertView ID: 2131296317 Resource: [email protected]         
    755  ListPlaces_Activity I Adapter: getView(2) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 3                        
    755  ListPlaces_Activity I  CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.R[email protected]          
    755  ListPlaces_Activity I Adapter: getView(3) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -> START                        
    755  ListPlaces_Activity I  convertView ID: 2131296317 Resource: [email protected]              
    755  ListPlaces_Activity I Adapter: getView(4) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -> START                        
    755  ListPlaces_Activity I  convertView ID: 2131296317 Resource: [email protected]              
    755  ListPlaces_Activity I Adapter: getView(5) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(6) ITEM (ITEM) -> START                        
    755  ListPlaces_Activity I  convertView ID: 2131296317 Resource: [email protected]              
    755  ListPlaces_Activity I Adapter: getView(6) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(0) SEPARATOR (ITEM) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 0                        
    755  ListPlaces_Activity I  CREATE SEPARATOR: convertView ID: 2131296317 Resource: [email protected]         
    755  ListPlaces_Activity I Adapter: getView(0) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 1                        
    755  ListPlaces_Activity I  CREATE ITEM: convertView ID: 2131296317 Resource: [email protected]          
    755  ListPlaces_Activity I Adapter: getView(1) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 2                        
    755  ListPlaces_Activity I  CREATE SEPARATOR: convertView ID: 2131296317 Resource: [email protected]         
    755  ListPlaces_Activity I Adapter: getView(2) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -> START                       
    755  ListPlaces_Activity I --> (convertView == null) at position: 3                        
    755  ListPlaces_Activity I  CREATE ITEM: convertView ID: 2131296317 Resource: [email protected]          
    755  ListPlaces_Activity I Adapter: getView(3) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -> START                        
    755  ListPlaces_Activity I  convertView ID: 2131296317 Resource: [email protected]              
    755  ListPlaces_Activity I Adapter: getView(4) -> DONE                           
    755  ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -> START                        
    755  ListPlaces_Activity I  convertView ID: 2131296317 Resource: [email protected]              
    755   AndroidRuntime D Shutting down VM                              
    755    dalvikvm W threadid=3: thread exiting with uncaught exception (group=0x4001aa28)                 
    755   AndroidRuntime E Uncaught handler: thread main exiting due to uncaught exception                  
    755   AndroidRuntime E java.lang.NullPointerException                          
    755   AndroidRuntime E  at com.tato.main.ListPlaces_Activity$EfficientAdapter.getView(ListPlaces_Activity.java:330)          
    755   AndroidRuntime E  at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:191)             
    755   AndroidRuntime E  at android.widget.AbsListView.obtainView(AbsListView.java:1255)                 
    755   AndroidRuntime E  at android.widget.ListView.makeAndAddView(ListView.java:1658)                 
    755   AndroidRuntime E  at android.widget.ListView.fillDown(ListView.java:637)                   
    755   AndroidRuntime E  at android.widget.ListView.fillFromTop(ListView.java:694)                  
    755   AndroidRuntime E  at android.widget.ListView.layoutChildren(ListView.java:1502)                 
    755   AndroidRuntime E  at android.widget.AbsListView.onLayout(AbsListView.java:1112)                 
    755   AndroidRuntime E  at android.view.View.layout(View.java:6569)                      
    755   AndroidRuntime E  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)               
    755   AndroidRuntime E  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998)               
    755   AndroidRuntime E  at android.widget.LinearLayout.onLayout(LinearLayout.java:918)                 
    755   AndroidRuntime E  at android.view.View.layout(View.java:6569)                      
    755   AndroidRuntime E  at android.widget.FrameLayout.onLayout(FrameLayout.java:333)                 
    755   AndroidRuntime E  at android.view.View.layout(View.java:6569)                      
    755   AndroidRuntime E  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119)               
    755   AndroidRuntime E  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998)               
    755   AndroidRuntime E  at android.widget.LinearLayout.onLayout(LinearLayout.java:918)                 
    755   AndroidRuntime E  at android.view.View.layout(View.java:6569)                      
    755   AndroidRuntime E  at android.widget.FrameLayout.onLayout(FrameLayout.java:333)                 
    755   AndroidRuntime E  at android.view.View.layout(View.java:6569)                      
    755   AndroidRuntime E  at android.view.ViewRoot.performTraversals(ViewRoot.java:979)                 
    755   AndroidRuntime E  at android.view.ViewRoot.handleMessage(ViewRoot.java:1613)                  
    755   AndroidRuntime E  at android.os.Handler.dispatchMessage(Handler.java:99)                   
    755   AndroidRuntime E  at android.os.Looper.loop(Looper.java:123)                      
    755   AndroidRuntime E  at android.app.ActivityThread.main(ActivityThread.java:4203)                 
    755   AndroidRuntime E  at java.lang.reflect.Method.invokeNative(Native Method)                   
    755   AndroidRuntime E  at java.lang.reflect.Method.invoke(Method.java:521)                    
    755   AndroidRuntime E  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)            
    755   AndroidRuntime E  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)                 
    755   AndroidRuntime E  at dalvik.system.NativeStart.main(Native Method)

来源

2009-11-02 znq

你可以添加一个注释来显示堆栈跟踪中的行300是哪里吗？如果它是'if（curValues.separator> = 0）'，你应该能够在列表的最后处理多达1的位置吗？ – rsp 2009-11-02 10:41:29

你忘了有几种方法需要覆盖：getViewTypeCount()和getItemViewType()。对于所有行都相同的列表，这些不是必需的，但它们对于您的方案非常重要。正确实施这些，Android将为您的标题和详细信息行维护单独的对象池。

或者，你可以看看：

杰夫·夏基的原始SeparatedListAdapter（GPL）
我updated rendition（GPL）
我MergeAdapter，其可用于这种情况下，以及（阿帕奇）

来源

2009-11-02 13:51:50 CommonsWare

感谢您的快速响应。提示getViewTypeCount（）和getItemViewType（）非常有用。我喜欢这个适配器的东西。也感谢您分享您和Jeff Sharkey的源代码。我上周已经看过它，但是由于我目前正在开发一个封闭源代码项目，所以我至少不能实现GPL示例。所以我决定开始自己的实施，现在终于有效了，这要感谢您的帮助。 Muchas格拉西亚斯！ – znq 2009-11-02 14:52:03

更新的演绎链接不再工作。找不到仍然有效的链接 – rtack 2014-09-10 06:36:54

感谢getViewTypeCount（）和getItemViewType（）的提示，它现在可以很好地工作。

这两种方法实现是非常简单的：

@Override 
public int getViewTypeCount() { 
    return 2; 
} 

@Override 
public int getItemViewType(int position) { 
if(listPlaces.getValues().get(position).separator >= 0) 
    return 0; 
else 
    return 1; 
}

由于commonsware在他的回答这样Android将保持不同的列表项，这也意味着你可以删除检查listRow_previous不同的对象池提到在我的示例中，只将if (convertView == null || (listRow != listRow_previous))更改为if (convertView == null)。

来源

2009-11-02 15:01:46 znq

Android：具有两种不同视图的EfficientAdapter

回答

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