android:efficientadapter具有两种不同的视图

v1uwarro  于 2021-07-05  发布在  Java
关注(0)|答案(2)|浏览(319)

我使用的是baseadapter的扩展版本,它基于sdk演示示例中的efficientadapter示例。
我的数据基本上是一个对象( ListPlaces )它有一个 ArrayList 实际位置列表,可通过 listPlaces.getValues() . 此arraylist数据按范围和 ArrayList 由一些特殊项目(分隔符)组成,没有数据,但是 separator 标志设置为 true .
现在每当我 EfficientAdapter 获取数据对象,该对象是它返回的分隔符 false 为了 public boolean isEnabled(int position) 以及 public View getView(int position, View convertView, ViewGroup parent) 根据当前数据对象是由真实数据组成还是只是分隔符虚拟对象,对两种不同的布局进行充气。
如果我每次都膨胀布局的话,效果会很好。但是,每次都会膨胀布局并调用 findViewById 使 ListView 几乎慢得无法形容。
所以我试着用efficientadapter ViewHolder 接近。但这并不是开箱即用的,因为我尝试访问两种不同的视图。所以每当我 convertView != null (else情况)通过我们的 ViewHolder 当前面的视图是一个分隔符时,访问textview当然不起作用,它只在“real”items布局上可用。
所以我也强迫自己 getView() 不仅在 convertView == null ,但当前一个listrow与当前listrow不同时: if (convertView == null || (listRow != listRow_previous)) { [....] } 现在看来差不多可以了。或者至少它不会从一开始就崩溃。但它仍然崩溃,我不知道我要做什么不同。我试着调查 convertView.getID() 以及 convertView.getResources() ,但到目前为止这并没有什么帮助。也许有人知道我该怎么检查我的电流 convertView 与列表项布局或列表分隔符布局匹配。谢谢。
这是密码。在有[…]的地方,我拿出一些不太重要的代码,以便更容易阅读和理解:

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;
  }
}

这里是我的logcat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: android.content.res.Resources@437613e0                                  
  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: android.content.res.Resources@437613e0                                       
  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: android.content.res.Resources@437613e0                                  
  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.Resources@437613e0                                       
  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: android.content.res.Resources@437613e0                                                    
  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: android.content.res.Resources@437613e0                                                    
  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: android.content.res.Resources@437613e0                                                    
  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: android.content.res.Resources@437613e0                                  
  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: android.content.res.Resources@437613e0                                       
  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: android.content.res.Resources@437613e0                                  
  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.Resources@437613e0                                       
  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: android.content.res.Resources@437613e0                                                    
  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: android.content.res.Resources@437613e0                                                    
  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)
2ic8powd

2ic8powd1#

您忘记了几个需要重写的方法:getviewtypecount()和getitemviewtype()。所有行都相同的列表不需要这些,但它们对于您的场景非常重要。正确地实现这些,android将为您的header和detail行维护单独的对象池。
或者,你可以看看:
jeff sharkey最初的separatedlistadapter(gpl)
我更新的格式副本(gpl)
我的mergeadapter,也可以用于此场景(apache)

ddarikpa

ddarikpa2#

多亏了getviewtypecount()和getitemviewtype()的提示,它现在可以完美地工作了。
实现这两种方法非常简单:

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

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

正如commonware在他的回答中提到的那样,android将为不同的列表项维护不同的对象池,这也意味着您可以删除对 listRow_previous 在我的例子中 if (convertView == null || (listRow != listRow_previous))if (convertView == null) 只是。

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