自定義適配器ViewHolder問題

Question

我試圖使用自定義適配器的列表。此列表有兩種類型的行，但我只使用一種佈局（將可見性不需要的項目保留爲View.GONE）。但是，當我試圖訪問編輯框風格的行時，我不斷收到一個類轉換異常。我對自定義適配器的使用經驗不多。你的幫助是非常讚賞：d

下面的代碼（我刪除了setonclicklisteners儘量簡短）：

public class SubEventListAdapter extends ArrayAdapter<MobileSubEvent> 
{ 

    private ArrayList<MobileSubEvent> _items; 
    private Context _context; 

    public SubEventListAdapter(Context context, ArrayList<MobileSubEvent> items) 
     { 
      super(context, R.layout.view_select_event_item3, items); 
      this._items = items; 
      this._context = context; 
     } 

    static class ViewHolder 
     { 
      TextView text; 
      ImageButton imagebutton; 
      ImageView check; 
      EditText editText; 
      Button button; 
     } 

    @Override 
    public int getCount() 
     { 
      return this._items.size(); 
     } 


    @Override 
    public View getView(final int position, View convertView, ViewGroup parent) 
     { 
      View v = convertView; 
      final ViewHolder viewHolder; 
      final MobileSubEvent event = _items.get(position); 

      if (v == null) 
       { 
        LayoutInflater _inflater = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
        v = _inflater.inflate(R.layout.view_select_event_item3, null); 
        viewHolder = new ViewHolder(); 
        viewHolder.imagebutton = (ImageButton) v.findViewById(R.id.ibNext); 
        viewHolder.text = (TextView) v.findViewById(R.id.EVENT); 
        viewHolder.check = (ImageView) v.findViewById(R.id.ivCheck); 
        viewHolder.button = (Button) v.findViewById(R.id.bScanOrSign); 
        viewHolder.editText = (EditText) v.findViewById(R.id.etInput); 

          v.setTag(viewHolder); 

       } else 
       { 
        v = convertView; 
        viewHolder = (ViewHolder) v.getTag(); //here is where the class cast exception occurs 
       } 


      if (viewHolder.text != null) 
       viewHolder.text.setText(this._items.get(position).get_description()); 
      v.setTag(this._items.get(position)); 

    ... 


    return v; 
     } 

的logcat：

view_select_event_item3：

<?xml version="1.0" encoding="utf-8"?> 

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:background="@android:color/transparent" 
    android:padding="5dip" > 

    <ImageView 
     android:id="@+id/ivCheck" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_gravity="center_vertical" 
     android:background="@drawable/check" 
     android:focusable="false" 
     android:visibility="invisible" /> 

    <TextView 
     android:id="@+id/EVENT" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_toRightOf="@id/ivCheck" 
     android:background="@android:color/transparent" 
     android:padding="5dp" 
     android:text="Sample text" 
     android:textSize="20sp" 
     android:textStyle="bold" 
     android:visibility="visible" 
     /> 

    <EditText 
     android:id="@+id/etInput" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:minWidth="130dp" 
     android:maxWidth="165dp" 
     android:layout_toRightOf="@id/ivCheck" 
     android:background="@android:drawable/editbox_background" 
     android:padding="5dp" 
     android:hint="Hint text" 
     android:singleLine="true" 
     android:text="" 
     android:textSize="20sp" 
     android:visibility="invisible" 
     /> 

    <Button 
     android:id="@+id/bScanOrSign" 
     android:layout_width="62dp" 
     android:layout_height="32dp" 
     android:layout_gravity="center_vertical" 
     android:layout_toLeftOf="@id/ibNext" 
     android:text="Scan" 
     android:visibility="invisible" 
     /> 

    <ImageButton 
     android:id="@+id/ibNext" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentRight="true" 
     android:layout_gravity="right|center_vertical" 
     android:background="@drawable/right" 
     android:visibility="invisible" /> 

</RelativeLayout> 

Answer 1

嘗試這在getView中檢查convertView對象的類名（View Holder對象），如果它不匹配類名y我們的ViewHolder（在我的情況下它是VisitsListViewHolder） - 將其設置爲空，因此爲視圖持有者創建新實例

if(convertView != null) 
    { 
    String className = convertView.getTag().getClass().getName(); 
    if(!className.equalsIgnoreCase("VisitsListViewHolder")) 
    { 
     convertView = null; 
    } 
    }