我刚接触Android，正在与一群大学的朋友建立和应用。我们遇到的问题是，当通过从服务器获取数据来填充要显示的元素列表时，数据会加载并添加到列表中，但是recyclerView从不显示它（即使从我的自定义Adapter调用NotifyDataSetChanged之后）。回到我们使用硬编码数据测试应用程序时，这从未发生。
奇怪的是，关闭显示然后重新打开后，元素列表会显示在recyclerView上（当我重新打开屏幕时，将调用自定义适配器的onBindViewHolder）。此外，如果我替换片段包含一个带有另一个的recyclerView，然后返回到它，数据被加载到列表中，但未显示。
我想知道的是为什么会发生这种情况，我该怎么做才能解决（通过解决这个问题，我的意思是在启动片段时向recyclerView填充正确的项目，并在向其中添加更多元素时更新recyclerView清单）
我们正在使用自定义adpater和Retrofit从服务器获取数据。
这是代码
包含recyclerView的片段
public class EventViewListFragment extends Fragment implements EventListAdapter.ClickListener{
private RestClient restClient;
private Builder builder;
private String token ;
private boolean userScrolled = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
private LinearLayoutManager mLayoutManager;
private RecyclerView recyclerView;
private EventListAdapter eventListAdapter;
private Button btnNewEvent;
FloatingActionButton suggestFAB;
private int currentPage=1;
public EventViewListFragment(){
restClient = new RestClient();
}
@Override
public void onCreate(Bundle savedInstanceState) {
System.out.println("Se llamo al onCreate de EventViewListFragment");
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
System.out.println("se llamo al onCreateView de EvENT List Fragment");
// Inflate the layout for this fragment
View layout =inflater.inflate(R.layout.fragment_events_list, container, false);
setUpElements(layout);
addListeners();
return layout;
}
private void setUpElements(View layout)
{
recyclerView = (RecyclerView) layout.findViewById(R.id.eventList);
eventListAdapter = new EventListAdapter(getActivity());
eventListAdapter.setClickListener(this);
eventListAdapter.setData(getInitialData());
recyclerView.setAdapter(eventListAdapter);
mLayoutManager=new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(mLayoutManager);
suggestFAB = (FloatingActionButton) layout.findViewById(R.id.suggestFAB);
builder = new Builder();
}
private void addListeners()
{
addNewEventListener();
addScrollBottomListener();
}
private void addNewEventListener()
{
/*btnNewEvent.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view)
{
EventsActivity.getInstance().toNewEventForm();
}
});*/
suggestFAB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
EventsActivity.getInstance().toNewEventForm();
currentPage=1;
}
});
}
public List<Event> getInitialData()
{
List<Event> data=new ArrayList<>();
data = getEvents(data);
return data;
}
@Override
public void itemClicked(View view, int position) {
EventsActivity.getInstance().toEventPage(eventListAdapter.getItemAtPos(position));
currentPage=1;
}
private void addScrollBottomListener() {
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
userScrolled = true;
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx,
int dy) {
super.onScrolled(recyclerView, dx, dy);
// Here get the child count, item count and visibleitems
// from layout manager
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
if (userScrolled && (visibleItemCount + pastVisiblesItems) == totalItemCount) {
userScrolled = false;
addNewElementsToList();
}
}
});
}
private void addNewElementsToList()
{
Toast.makeText(getActivity(), "Cargando Mas Elementos", Toast.LENGTH_SHORT).show();
eventListAdapter.setData(getEvents(eventListAdapter.getData()));
}
private List<Event> getEvents(final List<Event> eventsList)
{
System.out.println("Asignando CALL");
Call<JsonElement> eventPage = restClient.getConsumerService().getEvents(token, "", currentPage, 10);
System.out.println("Enquequeing");
eventPage.enqueue(new Callback<JsonElement>() {
@Override
public void onResponse(Response<JsonElement> response) {
JsonObject responseBody = response.body().getAsJsonObject();
if (responseBody.has("events")) {
JsonArray jsonArray = responseBody.getAsJsonArray("events");
System.out.println(jsonArray.size());
for (int i = 0; i < jsonArray.size(); i++) {
JsonObject storedObject = jsonArray.get(i).getAsJsonObject();
Event current = new Event();
current.setEventId(storedObject.get("id").getAsInt());
current.setName(storedObject.get("title").getAsString());
Calendar startCal = new GregorianCalendar();
startCal.setTimeInMillis((storedObject.get("starts_at").getAsLong()) * 1000);
current.setStartDateTime(startCal);
Calendar endCal = new GregorianCalendar();
endCal.setTimeInMillis((storedObject.get("ends_at").getAsLong()) * 1000);
current.setFinishDateTime(endCal);
current.setImgUrl(storedObject.get("image").getAsString());
eventsList.add(current);
}
} else {
if (responseBody.has("error")) {
System.out.println("ERROR");
wan.wanmarcos.models.Error error = builder.buildError(responseBody.get("error").getAsJsonObject());
Toast.makeText(getActivity(), "Error : " + error.toString(), Toast.LENGTH_SHORT).show();
} else {
}
}
}
@Override
public void onFailure(Throwable t) {
}
});
eventListAdapter.notifyDataSetChanged();
currentPage++;
return eventsList;
}
}
RecyclerView的自定义适配器
public class EventListAdapter extends RecyclerView.Adapter<EventListAdapter.EventListViewHolder>{
private LayoutInflater inflater;
private List<Event> data = Collections.emptyList();
private Context context;
private ClickListener clickListener;
public EventListAdapter(Context context){
inflater = LayoutInflater.from(context);
this.context=context;
}
@Override
public EventListViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.event_list_item, parent, false);
EventListViewHolder holder = new EventListViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(EventListViewHolder holder, int position) {
System.out.println("se llamo al onBindViewHolder de ELA");
Event current = getData().get(position);
holder.title.setText(current.getName());
Picasso.with(context)
.load(current.getImgUrl())
.into(holder.img);
String startDateAndTime = current.CalendarToString(current.getStartDateTime())+" - "+current.CalendarToString(current.getFinishDateTime());
holder.dateAndTime.setText(startDateAndTime);
}
public void setClickListener(ClickListener clickListener){
this.clickListener=clickListener;
}
@Override
public int getItemCount() {
return getData().size();
}
public List<Event> getData() {
return data;
}
public void setData(List<Event> data) {
this.data = data;
}
class EventListViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
TextView title;
TextView dateAndTime;
ImageView img;
public EventListViewHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
title = (TextView) itemView.findViewById(R.id.eventListTitle);
img = (ImageView) itemView.findViewById(R.id.eventListImage);
dateAndTime =(TextView) itemView.findViewById(R.id.eventListDateAndTime);
}
@Override
public void onClick(View v) {
if(clickListener!=null)
{
clickListener.itemClicked(v,getPosition());
}
}
}
public Event getItemAtPos(int pos)
{
return getData().get(pos);
}
public interface ClickListener{
public void itemClicked(View view,int position);
}
}
Fragment XML File
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
android:id="@+id/main_content"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="wan.wanmarcos.fragments.EventViewListFragment">
<android.support.v7.widget.RecyclerView
android:id="@+id/eventList"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
>
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
<android.support.design.widget.FloatingActionButton
android:id="@+id/suggestFAB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
app:layout_anchorGravity="bottom|right|end"
android:layout_margin="16dp"
android:clickable="true"
android:src="@mipmap/ic_add_white_48dp" />
</android.support.design.widget.CoordinatorLayout>
eventsList在你Activity和data你的适配器是两个不同的集合。您正在填充前者，但没有填充后者。Intializedata与new ArrayList<>替代Collections.emptyList();，然后在适配器中添加了一个方法，调用中的addAll，这样的：
public void addAll(final List<Event> new events) {
final int currentCount = data.size();
synchronized(data) {
data.addAll(events);
}
if (Looper.getMainLooper() == Looper.myLooper()) {
notifyItemRangeInserted(currentCount, events.size());
} else {
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
notifyItemRangeInserted(currentCount, events.size());
}
});
}
}
if else检查您是从ui线程还是从其他线程调用addAll，并notifyItemRangeInserted以安全的方式调用。在调用Activitywhen时onResponse，完全填满后eventsList，只需调用eventListAdapter.addAll(eventsList)
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我来说两句