自定义适配器ViewHolder问题

Question

我正在尝试将自定义适配器用于列表。此列表有两种类型的行，但我只使用一种布局（将可见性设置为View.GONE时保留我不需要的项目）。但是，在尝试访问editbox样式行时，我不断收到类强制转换异常。我对自定义适配器的经验很少。非常感谢您的帮助：D

这是代码（我删除了setonclicklisteners以保持简短）：

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;
        }

logcat的：

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

在getView中尝试这个，检查convertView对象的类名（View Holder对象），如果它与ViewHolder的类名不匹配（在我的例子中是VisitsListViewHolder） - 将其设置为null，这样新的实例就是为视图持有者创建

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