我在使用recyclelerview中的偏移量解析数据时遇到问题。此刻，我能够显示前30个项目的偏移0.然后我检测到滚动到达列表项目的末尾，然后再次服务电话，但这次我无法向上滚动查看我以前的项目，每次有一组30个新项目，但没有以前的项目。我可以使用任何第三部分lib来解决这个问题吗？
private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount,firstVisibleInListview;
private RecyclerView unitListView;
LinearLayoutManager mLayoutManager;
private NumberOfUnitsAdapter unitsAdapter;
private List<UnitsModel> unitsModelList;
private SessionManager sessionManager;
public static final String KEY_TOKEN = "token";
private String token;
int offSet = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_number_of_units);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
sessionManager = new SessionManager(getApplicationContext());
unitListView = (RecyclerView) findViewById(R.id.unitlist);
unitsModelList = new ArrayList<>();
unitListView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(this);
unitListView.setLayoutManager( mLayoutManager );
unitListView.setItemAnimator(new DefaultItemAnimator());
unitsAdapter = new NumberOfUnitsAdapter(getApplicationContext(),unitsModelList,unitListView);
unitListView.setAdapter(unitsAdapter);
unitListView.addOnScrollListener(new RecyclerView.OnScrollListener()
{
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
unitListView.getLayoutManager().canScrollVertically();
if(dy> 0)
{
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
if (loading)
{
if ( (visibleItemCount + pastVisiblesItems) >= totalItemCount)
{
loading = false;
Log.v("...", "Last Item Wow !");
Toast.makeText(getApplicationContext(), "Last Station Agaya hai Bahi",
Toast.LENGTH_LONG).show();
//Do pagination.. i.e. fetch new data
callUnitAPI();
loading = true;
}
}
}
}
});
callUnitAPI();
}
private void callUnitAPI() {
Map<String, String> jsonParams = new HashMap<>();
HashMap<String, String> user = sessionManager.getUserDetails();
token = user.get(SessionManager.TOKEN);
jsonParams.put(KEY_TOKEN, token);
String url = createGetWithParams(Constant.BASE_URL+UNITS_API+offSet,jsonParams);
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
private String unitName ,unitNumber;
private int unitId,unitBedroom,unitBathroom,unitBuildArea,unitPlotArea;
private float unitPrice;
@Override
public void onResponse(JSONObject response) {
unitsModelList.clear();
if (response.length() > 0) {
try {
JSONArray ownersData = response.getJSONArray("units");
for (int i = 0; i < ownersData.length(); i++) {
JSONObject jsonObj = ownersData.getJSONObject(i);
unitName = jsonObj.getString("Jhon");
unitNumber = jsonObj.getString("unitq");
unitId = Integer.parseInt(jsonObj.getString("iden"));
unitPlotArea = Integer.parseInt(jsonObj.getString("plan"));
unitBuildArea = Integer.parseInt(jsonObj.getString("build"));
unitBedroom = Integer.parseInt(jsonObj.getString("bed"));
unitBathroom = Integer.parseInt(jsonObj.getString("bath"));
unitPrice = BigDecimal.valueOf(jsonObj.getDouble("pro")).floatValue();
UnitsModel numUnitModel = new UnitsModel();
numUnitModel.setUnitName(unitName);
numUnitModel.setUnitNumber(unitNumber);
numUnitModel.setUnitId(unitId);
numUnitModel.setUnitPlotArea(unitArea);
numUnitModel.setUnitBuildArea(uniBArea);
numUnitModel.setUnitBedroom(unitBedroom);
numUnitModel.setUnitBathroom(unitBathroom);
numUnitModel.setUnitPrice(unitPrice);
unitsModelList.add(numUnitModel);
if(unitId >= offSet)
offSet = unitId;
}
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
unitsAdapter.addUnitsModels(unitsModelList);
unitsAdapter.notifyDataSetChanged();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError response) {
NetworkResponse networkResponse = response.networkResponse;
if (networkResponse != null && networkResponse.statusCode == 401) {
Toast.makeText(getApplicationContext(), "Token Expire", Toast.LENGTH_LONG).show();
}
}
});
AppController.getInstance().addToRequestQueue(request);
}
以下是适配器已更新
public class NumberOfUnitsAdapter extends RecyclerView.Adapter {
private final int VIEW_ITEM = 1;
private final int VIEW_PROG = 0;
private Activity activity;
private List<UnitsModel> unitsModelList;
private OnLoadMoreListener onLoadMoreListener;
Context mContext;
public NumberOfUnitsAdapter( Context mContext, List<UnitsModel> unitsModelList,RecyclerView recyclerView) {
this.mContext = mContext;
this.unitsModelList = unitsModelList;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
RecyclerView.ViewHolder vh;
if (viewType == VIEW_ITEM) {
View v = LayoutInflater.from(parent.getContext()).inflate(
R.layout.numberofunits_items, parent, false);
vh = new NumberOfUnitsHolder(v);
} else {
View v = LayoutInflater.from(parent.getContext()).inflate(
R.layout.progress_item, parent, false);
vh = new ProgressViewHolder(v);
}
return vh;
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
UnitsModel unitsModel= unitsModelList.get(position);
if (holder instanceof NumberOfUnitsHolder) {
NumberOfUnitsHolder vholder = (NumberOfUnitsHolder) holder;
vholder.unitName.setText(unitsModel.getUnitNumber());
vholder.manageBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Bundle bundle = new Bundle();
bundle.putString("UNIT_NAME", unitsModelList.get(position).getUnitName());
bundle.putString("UNIT_NUMB", unitsModelList.get(position).getUnitNumber());
bundle.putFloat("UNIT_PRICE", unitsModelList.get(position).getUnitPrice());
bundle.putInt("UNIT_PLOT", unitsModelList.get(position).getUnitPlotArea());
bundle.putInt("UNIT_BUILD", unitsModelList.get(position).getUnitBuildArea());
bundle.putInt("UNIT_BATH", unitsModelList.get(position).getUnitBathroom());
bundle.putInt("UNIT_BED", unitsModelList.get(position).getUnitBedroom());
bundle.putInt("UNIT_ID", unitsModelList.get(position).getUnitId());
Intent itemClick = new Intent(mContext, NumOfUnitDetail.class);
itemClick.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
itemClick.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
itemClick.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
itemClick.putExtras(bundle);
mContext.startActivity(itemClick);
}
});
}
else {
((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
}
}
@Override
public int getItemCount() {
return unitsModelList.size();
}
@Override
public int getItemViewType(int position) {
return unitsModelList.get(position) != null ? VIEW_ITEM : VIEW_PROG;
}
public void addUnitsModels(List<UnitsModel> unitsModelList) {
this.unitsModelList.addAll(unitsModelList);
}
public class NumberOfUnitsHolder extends RecyclerView.ViewHolder {
public final View mView;
public final TextView unitName;
public final Button historyBtn;
public final Button manageBtn;
public NumOwnerModel mItem;
public NumberOfUnitsHolder(View view) {
super(view);
mView = view;
unitName = (TextView)view.findViewById(R.id.unitNo);
historyBtn= (Button) view.findViewById(R.id.historyBtn);
manageBtn = (Button) view.findViewById(R.id.manageBtn);
}
}
public static class ProgressViewHolder extends RecyclerView.ViewHolder {
public ProgressBar progressBar;
public ProgressViewHolder(View v) {
super(v);
progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
}
}
}
答案 0 :(得分：2)
当您执行callUnitAPI时，您正在设置一个带有新列表的新适配器。
相反，您应该附加到现有适配器中的旧列表并执行notifyDataSetChanged。
例如，在unitsAdapter添加方法：
public void addUnitsModels(ArrayList<UnitsModel> list){
this.unitsModeList.addAll(list);
}
在callUnitApi()
unitsAdapter.addUnitsModels(unitsModelList);
unitsAdapter.notifyDataSetChanged();
而不是创建和设置新的适配器。 此外，不是使用类变量将项添加到列表并每次清除，而是在响应回调中创建临时列表。
//unitsModelList.clear();
ArrayList<>temp = new ArrayList<UnitsModel>();
// setting object and adding to list
unitsAdapter.addUnitsModels(temp);
unitsAdapter.notifyDataSetChanged();