Android 自定义ListView适配器getView()在第二项上失败
我正在编写一个自定义的Android 自定义ListView适配器getView()在第二项上失败,android,listview,android-listview,android-arrayadapter,android-adapter,Android,Listview,Android Listview,Android Arrayadapter,Android Adapter,我正在编写一个自定义的ListView适配器来提供一个项目列表,每个组之间都有一个“header”项目(特别是一个带有年份标题的日历)。我根据在线信息()编写了自定义类,以包含其他SO帖子() 我想我拥有了我想要的一切(由于结构的不同,有两个独立的布局文件),但是当适配器被使用时,getView()中的convertView参数在第二次使用时决不会像我所期望的那样为空,适配器尝试对“事件”项使用非空的“header”视图,我得到一个typecast异常。下面是我的适配器代码的全部内容。我在这里遗
ListView
适配器来提供一个项目列表,每个组之间都有一个“header”项目(特别是一个带有年份标题的日历)。我根据在线信息()编写了自定义类,以包含其他SO帖子()
我想我拥有了我想要的一切(由于结构的不同,有两个独立的布局文件),但是当适配器被使用时,getView()
中的convertView
参数在第二次使用时决不会像我所期望的那样为空,适配器尝试对“事件”项使用非空的“header”视图,我得到一个typecast异常。下面是我的适配器代码的全部内容。我在这里遗漏了什么——这在概念上似乎非常简单
public class CalendarListAdapter extends BaseAdapter {
private final String TAG = this.getClass().getSimpleName();
private List<CalendarItem> items;
private final Context context;
private final int ITEM_HEADER = 0;
private final int ITEM_EVENT = 1;
private LayoutInflater layoutInflater;
public CalendarListAdapter(Context context, List<CalendarItem> items) {
this.items = items;
this.context = context;
layoutInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return items.size();
}
@Override
public Object getItem(int position) {
return items.get(position);
}
public void addItem(final CalendarItem item) {
items.add(item);
notifyDataSetChanged();
}
@Override
public long getItemId(int position) {
return position;
}
public void setItems(List<CalendarItem> items) {
this.items = items;
notifyDataSetChanged();
}
@Override
public int getItemViewType(int position) {
CalendarItem item = items.get(position);
if (item instanceof CalendarHeader)
return ITEM_HEADER;
else
return ITEM_EVENT;
}
@Override
public int getViewTypeCount() {
return 2;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
Log.i(TAG, "getView " + position + " " + convertView);
HeaderViewHolder headerViewHolder;
EventViewHolder eventViewHolder;
CalendarItem item = items.get(position);
Log.i(TAG, "Item at position " + position + " is " + item);
int rowType = getItemViewType(position);
if (rowType == ITEM_HEADER) {
CalendarHeader header = (CalendarHeader)item;
if (convertView != null)
headerViewHolder = (HeaderViewHolder) convertView.getTag();
else {
convertView = layoutInflater.inflate(R.layout.item_calendar_header, null);
headerViewHolder = new HeaderViewHolder();
headerViewHolder.headerTextView = (TextView)convertView.findViewById(R.id.calendar_header_textview);
convertView.setTag(headerViewHolder);
}
// Set data in view holder for header
headerViewHolder.headerTextView.setText(header.getTitle());
} else {
CalendarEvent event = (CalendarEvent)item;
if (convertView != null)
eventViewHolder = (EventViewHolder) convertView.getTag();
else {
convertView = layoutInflater.inflate(R.layout.item_calendar_event, null);
eventViewHolder = new EventViewHolder();
eventViewHolder.dateView = (TextView)convertView.findViewById(R.id.row_date_textview);
eventViewHolder.daysTextView = (TextView)convertView.findViewById(R.id.row_days_textview);
eventViewHolder.itemTextView = (TextView)convertView.findViewById(R.id.row_item_textview);
convertView.setTag(eventViewHolder);
}
// Set data in view holder for event
DateTime dateOfEvent = new DateTime(event.getTimestamp());
DateTimeFormatter formatter = DateTimeFormat.forPattern("MMM dd")
.withLocale(Locale.US);
String text = formatter.print(dateOfEvent);
eventViewHolder.dateView.setText(text);
DateTime today = new DateTime();
int daysBetween = Days.daysBetween(today.toLocalDate(),
dateOfEvent.toLocalDate()).getDays();
eventViewHolder.daysTextView.setText(String.format("%d %s", daysBetween,
context.getResources().getString(R.string.days)));
eventViewHolder.itemTextView.setText(event.getTitle());
}
return convertView;
}
static class HeaderViewHolder {
protected TextView headerTextView;
}
static class EventViewHolder {
protected TextView dateView;
protected TextView daysTextView;
protected TextView itemTextView;
}
}
适配器的定义:
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
...
calendarListAdapter = new CalendarListAdapter(getActivity(), items);
calendarListView.setAdapter(calendarListAdapter);
...
return view;
}
items = new ArrayList<CalendarItem>();
Set<String> keys = calendarMap.keySet();
for (String key : keys) {
// Add the header for each year we have data for. This will be a simple
// TextView layout
items.add(new CalendarHeader(key));
// Add the individual events for the year
List<CalendarEvent> events = calendarMap.get(key);
for (CalendarEvent event : events)
items.add(new CalendarEvent(event.getTitle(), event.getTimestamp()));
}
calendarListAdapter.setItems(items);
适配器的用法:
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
...
calendarListAdapter = new CalendarListAdapter(getActivity(), items);
calendarListView.setAdapter(calendarListAdapter);
...
return view;
}
items = new ArrayList<CalendarItem>();
Set<String> keys = calendarMap.keySet();
for (String key : keys) {
// Add the header for each year we have data for. This will be a simple
// TextView layout
items.add(new CalendarHeader(key));
// Add the individual events for the year
List<CalendarEvent> events = calendarMap.get(key);
for (CalendarEvent event : events)
items.add(new CalendarEvent(event.getTitle(), event.getTimestamp()));
}
calendarListAdapter.setItems(items);
以及发送到适配器的某些数据的快照:
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
...
calendarListAdapter = new CalendarListAdapter(getActivity(), items);
calendarListView.setAdapter(calendarListAdapter);
...
return view;
}
items = new ArrayList<CalendarItem>();
Set<String> keys = calendarMap.keySet();
for (String key : keys) {
// Add the header for each year we have data for. This will be a simple
// TextView layout
items.add(new CalendarHeader(key));
// Add the individual events for the year
List<CalendarEvent> events = calendarMap.get(key);
for (CalendarEvent event : events)
items.add(new CalendarEvent(event.getTitle(), event.getTimestamp()));
}
calendarListAdapter.setItems(items);
我认为问题不在于这个类,而在于这个类的使用。请同时发布使用您的类的代码。
(我想发表评论,但我没有足够的声誉。)你们有什么课程?CalendarItem哪个是超类?CalendarHeader和CalendarEvent?是否继承自
CalendarHeader
?在if(rowType==ITEM_标题)中,您将convertView设置为HeaderViewWholder,并在位置1处尝试将HeaderViewWholder转换为添加到原始帖子中的EventViewHolderClass。