我在使用View Model时已在RecyclerView中实现了基本的ListAdapter。我得到的数据是通过调用API从networkManager到Viewmodel。即使我确实获得了数据，submitList也不起作用，因此没有数据膨胀。
UpcomingGroupFragment
really.new.data <- cbind(new.data[1:154], flatten(new.data[155]))
str(really.new.data)
#--------
'data.frame': 4 obs. of 714 variables:
$ ticker : chr "MS" "GS" "MPC" "ORCL"
$ tradeDate : chr "2019-03-01" "2019-03-01" "2019-03-01" "2019-03-01"
$ assetType : int 3 3 3 3
$ priorCls : num 42 196.7 62 52.1
$ pxAtmIv : num 42.6 198.4 62.5 52.6
$ mktCap : int 73261 73803 43158 217909
$ cVolu : int 24699 28845 9612 17659
#----------- snipped-----
Adapter类扩展了ListAdapter。
用于覆盖提交列表的链接：https://stackoverflow.com/a/50062174
代码如下：
GroupAdapter_new
public class UpcomingGroupFragment extends Fragment {
private UpcomingViewModel mViewModel;
private RecyclerView recyclerView;
private GroupAdapter_new adapter;
public static UpcomingGroupFragment newInstance() {
return new UpcomingGroupFragment();
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_chatgroups, container, false);
}
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
recyclerView = view.findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
adapter = new GroupAdapter_new();
recyclerView.setAdapter(adapter);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mViewModel = ViewModelProviders.of(this).get(UpcomingViewModel.class);
mViewModel.getMutableLiveData().observe(this, new Observer<List<ChatGroups_New>>() {
@Override
public void onChanged(@Nullable List<ChatGroups_New> chatGroups_news) {
adapter.submitList(chatGroups_news);
Log.e("Upcoming", String.valueOf(chatGroups_news.size()));
}
});
}
}
如果要查看我的ViewModel类，则：
UpcomingViewModel
public class GroupAdapter_new extends ListAdapter<ChatGroups_New,GroupAdapter_new.ViewHolder> {
public GroupAdapter_new() {
super(DIFF_CALLBACK);
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
Context context = parent.getContext();
int layoutID = R.layout.ongoing_group;
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(layoutID,parent,false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
ChatGroups_New currentGroup = getItem(position);
holder.text_flightarrival.setText(currentGroup.getFlightNameArrival());
}
class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(View itemView) {
super(itemView);
//... Finding ID's for various Views
}
}
/****ADDED THIS FROM CODE*****/
@Override
public void submitList(List<ChatGroups_New> list) {
super.submitList(list != null ? new ArrayList<ChatGroups_New>() : null);
}
/***********/
private static final DiffUtil.ItemCallback<ChatGroups_New> DIFF_CALLBACK =
new DiffUtil.ItemCallback<ChatGroups_New>() {
@Override
public boolean areItemsTheSame(ChatGroups_New oldItem, ChatGroups_New newItem) {
Log.e("areItemsTheSame", String.valueOf(oldItem.getMergedLogId() == newItem.getMergedLogId()));
return oldItem.getMergedLogId() == newItem.getMergedLogId();
}
@Override
public boolean areContentsTheSame(ChatGroups_New oldItem, ChatGroups_New newItem) {
if(oldItem.getFlightIcon().equals(newItem.getFlightIcon()) && oldItem.getFlightNameArrival().equals(newItem.getFlightNameArrival())){
if(oldItem.getGateValue().equals(newItem.getGateValue()) && oldItem.getEtaValue().equals(newItem.getEtaValue())){
if(oldItem.getAlertValue().equals(newItem.getAlertValue()) && oldItem.getTaskcompletedValue().equals(newItem.getTaskcompletedValue())){
Log.e("areContentsTheSame", "true");
return true;
}
}
}
return false;
}
};
}
最初，列表的大小为零，因此错误提示为
public class UpcomingViewModel extends AndroidViewModel
implements I_NetworkResponse {
private NetworkManager networkManager;
private SharedPrefService prefService;
private HashMap<String, String> header;
private final String TAG = "UpcomingViewModel";
private List<ChatGroups_New> upcomingList;
private MutableLiveData<List<ChatGroups_New>> mutableLiveData;
public UpcomingViewModel(@NonNull Application application) {
super(application);
prefService = SharedPrefService.getInstance(application);
networkManager = new NetworkManager(application,this);
upcomingList = new ArrayList<>();
mutableLiveData = new MutableLiveData<>();
mutableLiveData.setValue(upcomingList);
header = new HashMap<>();
header.put("authorizationcode",prefService.getStringValue(Keys.getPreferenceAuthKey()));
if(upcomingList.isEmpty()){
networkManager.Volley_JsonObjectRequest(Keys.getBaseUrl()+"AviLeap/flights/upcoming",
header,null,TAG,"AviLeap/flights/upcoming");
}
}
public MutableLiveData<List<ChatGroups_New>> getMutableLiveData() { return mutableLiveData; }
@Override
public void getNetworkSuccessResponse(String TAG, String successResponse, String TAGforApi) {
Log.e(TAGforApi,successResponse);
parseUpcomingFlight(successResponse, upcomingList);
mutableLiveData.setValue(upcomingList);
}
@Override
public void getNetworkFailResponse(String TAG, VolleyError failResponse, String TAGforApi) { }
@Override
protected void onCleared() {
super.onCleared();
networkManager.stopNetworkCallsWithTag(TAG);
}
private void parseUpcomingFlight(String successResponse, List<ChatGroups_New> upcomingList) {
try {
JSONObject rootObject = new JSONObject(successResponse);
if(rootObject.has("upcomingflights") && rootObject.opt("upcomingflights") instanceof JSONArray){
JSONArray flightsArray = rootObject.optJSONArray("upcomingflights");
for(int flightIndex = 0; flightIndex < flightsArray.length(); flightIndex++){
JSONObject flightObject = flightsArray.optJSONObject(flightIndex);
int mergedLogId = flightObject.optInt("logid");
upcomingList.add(new ChatGroups_New(mergedLogId));
Log.e("parseUpcomingFlight", String.valueOf(upcomingList.size()));//..... Log Point
}
}
}
catch (JSONException e) { e.printStackTrace(); }
}
}
以上日志显示数据正在添加到arraylist中，但没有更新。同样在所有这些日志之后，当我返回到片段时，也会收到以下错误。
AviLeap/flights/upcoming: //.... API CALL
2019-03-02 13:25:53.652 8477-8477/com.avileapconnect.com E/parseUpcomingFlight: 1 2019-03-02 13:25:53.652 8477-8477/com.avileapconnect.com E/parseUpcomingFlight: 2
2019-03-02 13:25:53.653 8477-8477/com.avileapconnect.com E/Upcoming: 2
要添加的另一件事是适配器的getItemCount正在正确更新。但即使在那之后，我仍然出错：
no adapter Attached, Skipping Layout
编辑：我通过注释掉用于覆盖SubmitList方法的代码来修复了该错误。我还在片段类的观察者方法中设置适配器