我已经实现了recyclerview，它一次加载10个任务。完成每项任务后，我将使用完成的按钮删除任务。它加载第11项如果我在一个条件下滚动到底部，则必须至少有一个未完成的任务存在于页面上。如果我清除所有10个项目，它只显示我加载动画并没有任何反应。我必须关闭应用程序并再次打开以再次加载任务。
我已经为页面实现了PaginationActivity，PaginationAdapter和滚动侦听器。它会在您到达页面末尾时从本地数据库加载数据，并且您需要加载更多任务。
PaginationActivity.java
public class PaginationActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
PaginationAdapter adapter;
LinearLayoutManager linearLayoutManager;
public static ArrayList<String> reasonsdata = new ArrayList<String>();
public static String rslt="";
public static String[] reasons;
public static boolean chk = true;
public static String payTypeSelected;
public static String reasonSelected;
public static HashMap<String, EditText> drivernotesMap = new HashMap<String, EditText>();
public static HashMap<String, EditText> paynoteMap = new HashMap<String, EditText>();
public static HashMap<String, String> paytypeMap = new HashMap<String, String>();
RecyclerView rv;
ProgressBar progressBar;
private static final int PAGE_START = 0;
private boolean isLoading = false;
private boolean isLastPage = false;
private int TOTAL_PAGES;
private int currentPage = PAGE_START;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.pagination_main);
fillspinner();
rv = (RecyclerView) findViewById(R.id.main_recycler);
progressBar = (ProgressBar) findViewById(R.id.main_progress);
adapter = new PaginationAdapter(this);
linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
rv.setLayoutManager(linearLayoutManager);
rv.setItemAnimator(new DefaultItemAnimator());
rv.setAdapter(adapter);
rv.addOnScrollListener(new PaginationScrollListener(linearLayoutManager) {
@Override
protected void loadMoreItems() {
isLoading = true;
currentPage += 1;
// mocking network delay for API call
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
loadNextPage();
}
}, 1000);
}
@Override
public int getTotalPageCount() {
return TOTAL_PAGES;
}
@Override
public boolean isLastPage() {
return isLastPage;
}
@Override
public boolean isLoading() {
return isLoading;
}
});
// mocking network delay for API call
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
loadFirstPage();
}
}, 1000);
}
private void fillspinner() {
reasonsdata.clear();
try
{
rslt="START";
CallReasons cr = new CallReasons();
cr.join();
cr.start();
while(rslt=="START") {
try {
Thread.sleep(10);
}catch(Exception ex) {
}
}
}
catch (Exception ex) {
ex.printStackTrace();
}
if(rslt == "Success"){
reasonsdata.add("<--- Select Reason --->");
for(int i =0; i< reasons.length;i++){
reasonsdata.add(reasons[i]);
}
}
}
public void loadFirstPage() {
Log.d(TAG, "loadFirstPage: ");
TOTAL_PAGES = Run.getTotalPages();
//List<Run> runs = Run.createRuns(adapter.getItemCount());
List<Run> runs = Run.createRuns(adapter.getMaxID());
progressBar.setVisibility(View.GONE);
adapter.addAll(runs);
if (currentPage <= TOTAL_PAGES) adapter.addLoadingFooter();
else isLastPage = true;
}
public void loadNextPage() {
Log.d(TAG, "loadNextPage: " + currentPage);
//List<Run> runs = Run.createRuns(adapter.getItemCount());
List<Run> runs = Run.createRuns(adapter.getMaxID());
adapter.removeLoadingFooter();
isLoading = false;
adapter.addAll(runs);
if (currentPage != TOTAL_PAGES) adapter.addLoadingFooter();
else isLastPage = true;
}
}
PaginationAdapter.java
public class PaginationAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private static final int ITEM = 0;
private static final int LOADING = 1;
private List<Run> runs = new ArrayList<>();
private Context context;
private boolean isLoadingAdded = false;
private String cash = "CASH";
private String cheque = "CHEQUE";
SQLiteDatabase db;
//PaginationActivity func_call;
public PaginationAdapter(Context context) {
this.context = context;
runs = new ArrayList<>();
//func_call = new PaginationActivity();
}
public List<Run> getRuns() {
return runs;
}
public void setRuns(List<Run> runs) {
this.runs = runs;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
RecyclerView.ViewHolder viewHolder = null;
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
switch (viewType) {
case ITEM:
viewHolder = getViewHolder(parent, inflater);
break;
case LOADING:
View v2 = inflater.inflate(R.layout.item_progress, parent, false);
viewHolder = new LoadingVH(v2);
//viewHolder = getViewHolder(parent, inflater);
//func_call.loadNextPage();
break;
}
return viewHolder;
}
@NonNull
private RecyclerView.ViewHolder getViewHolder(ViewGroup parent, LayoutInflater inflater) {
RecyclerView.ViewHolder viewHolder;
View v1 = inflater.inflate(R.layout.activity_main, parent, false);
viewHolder = new RunVH(v1);
return viewHolder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
final Run run = runs.get(position);
switch (getItemViewType(position)) {
case ITEM:
final RunVH runVH = (RunVH) holder;
//adding text areas to show data
//Completed task button
runVH.btnSave.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Toast.makeText(context, "Mark as Completed", Toast.LENGTH_LONG).show();
remove(run);
}
}
} catch (Exception ex) {
//pbbar.setVisibility(View.GONE);
ex.printStackTrace();
}
}
});
break;
case LOADING:
break;
}
}
@Override
public int getItemCount() {
return runs == null ? 0 : runs.size();
}
//@Override
public int getMaxID() {
if(runs == null || runs.size() == 0){
return 0;
}else{
Run test = runs.get(runs.size()-2);
int maxid = (int) test.getProperty(0);
return maxid;
}
}
@Override
public int getItemViewType(int position) {
return (position == runs.size() - 1 && isLoadingAdded) ? LOADING : ITEM;
}
public void add(Run run) {
runs.add(run);
notifyItemInserted(runs.size() - 1);
}
public void addAll(List<Run> runList) {
for (Run run : runList) {
add(run);
}
}
public void remove(Run run) {
int position = runs.indexOf(run);
if (position > -1) {
runs.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, runs.size());
}
/*if(runs.size() < 0){
clear();
func_call.loadNextPage();
}*/
}
public void clear() {
isLoadingAdded = false;
while (getItemCount() > 0) {
remove(getItem(0));
}
}
public boolean isEmpty() {
return getItemCount() == 0;
}
public void addLoadingFooter() {
isLoadingAdded = true;
add(new Run());
}
public void removeLoadingFooter() {
isLoadingAdded = false;
int position = runs.size() - 1;
Run item = getItem(position);
if (item != null) {
runs.remove(position);
notifyItemRemoved(position);
}
}
public Run getItem(int position) {
return runs.get(position);
}
protected class RunVH extends RecyclerView.ViewHolder {
private TextView textEsky;
private TextView textAdjusted;
private TextView textAddress;
private TextView textNew;
private TextView textTrusted;
private TextView textName;
private TextView textMobile;
private TextView textHome;
private TextView textWork;
private TextView payType;
private EditText textPayNote;
private EditText textDeliveryInst;
private EditText textDriverNotes;
private final Spinner reasons;
private RadioGroup rg;
private Button btnSave;
private CheckBox IsDriverData;
public RunVH(View itemView) {
super(itemView);
textEsky = (TextView) itemView.findViewById(R.id.idEsky);
textAdjusted = (TextView) itemView.findViewById(R.id.idAdjusted);
textAddress = (TextView) itemView.findViewById(R.id.idAddress);
textNew = (TextView) itemView.findViewById(R.id.idNew);
textTrusted = (TextView) itemView.findViewById(R.id.idTrusted);
textName = (TextView) itemView.findViewById(R.id.idName);
textMobile = (TextView) itemView.findViewById(R.id.idMobile);
textHome = (TextView) itemView.findViewById(R.id.idHome);
textWork = (TextView) itemView.findViewById(R.id.idWork);
payType = (TextView) itemView.findViewById(R.id.idPayType);
textPayNote = (EditText) itemView.findViewById(R.id.idPayNoteText);
textDeliveryInst = (EditText) itemView.findViewById(R.id.idDeliInsText);
textDriverNotes = (EditText) itemView.findViewById(R.id.idDriverNotesText);
IsDriverData = (CheckBox) itemView.findViewById(R.id.idCheckBox);
reasons = (Spinner) itemView.findViewById(R.id.idReason);
rg = (RadioGroup) itemView.findViewById(R.id.Radiogroup);
btnSave = (Button) itemView.findViewById(R.id.button);
}
}
protected class LoadingVH extends RecyclerView.ViewHolder {
public LoadingVH(View itemView) {
super(itemView);
}
}
}
PaginationScrollListener.java
public abstract class PaginationScrollListener extends RecyclerView.OnScrollListener {
LinearLayoutManager layoutManager;
public PaginationScrollListener(LinearLayoutManager layoutManager) {
this.layoutManager = layoutManager;
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visibleItemCount = layoutManager.getChildCount();
int totalItemCount = layoutManager.getItemCount();
int firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition();
if (!isLoading() && !isLastPage()) {
if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount
&& firstVisibleItemPosition >= 0) {
loadMoreItems();
}
}
}
protected abstract void loadMoreItems();
public abstract int getTotalPageCount();
public abstract boolean isLastPage();
public abstract boolean isLoading();
}
答案 0 :(得分：0)
我可能是错的，但在我看来，只有当您召回loadNextPage()时，RecyclerView才会收到滚动事件。删除ViewHolders不会导致滚动事件。
如果您在PaginationAdapter上注册AdapterDataObserver，则可以在没有任何任务时收听删除/添加事件并触发加载。对remove(Run)中注释掉的代码进行一些小的更改，你可能会做同样的事情：
if (runs.isEmpty()) {
func_call.loadNextPage();
}
编辑：
顺便问一下，您看到adapter = new PaginationAdapter(this);方法中您调用PaginationActivity.onCreate的位置了吗？这里的this是您的PaginationActivity，这意味着您可以将其分配到PaginationAdapter字段，如下所示：
/**
* @param context the activity this adapter will appear in
*/
public PaginationAdapter(Context context) {
this.context = context;
runs = new ArrayList<>();
func_call = (PaginationActivity)context;
}
这应该足以防止崩溃。为了更好地分离问题，您可能希望切换到基于AdapterDataObserver的逻辑（我认为这称为open/closed principle？可能？）。