如果没有正确的堆栈跟踪，我只能假设
我做过一些事情，当arraylist.day==calendar.dayofmonth时，它会以编程方式滚动到arraylist位置，但当我开始活动时，我遇到了这样的错误："尝试在null对象引用上调用虚拟方法'boolean java.lang.String.equals(java.lang.Object('"。
有人能帮帮我吗？
Planning.java：
public void setUpRecyclerView(){
recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
}
private void setUpFirebase(){
db = FirebaseFirestore.getInstance();
}
private void loadDataFromFirebase(){
if(eventsArrayList.size()>0){
eventsArrayList.clear();}
db.collection("Planning").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
@Override
public void onComplete(@NonNull Task<QuerySnapshot> task) {
for(DocumentSnapshot querySnapshot: task.getResult()){
Events Nom = new Events(querySnapshot.getString("Nom"),querySnapshot.getString("Lieu"),querySnapshot.getString("Heure"),querySnapshot.getString("Minute"),querySnapshot.getString("Day"));
eventsArrayList.add(Nom);
}
tvLoad.setVisibility(View.GONE);
progressBar.setVisibility(View.GONE);
adapter = new MyRecyclerViewAdapter(Planning.this, eventsArrayList);
recyclerView.setAdapter(adapter);
recyclerView.setItemAnimator(new DefaultItemAnimator());
}
}
public void ScrollTo(int position){
recyclerView.scrollToPosition(position);
}
}
RecyclerViewAdapter:
@Override
public void onBindViewHolder(@NonNull MyRecyclerViewHolder holder, int position) {
Calendar cal = Calendar.getInstance();
holder.tvLieu.setVisibility(View.VISIBLE);
holder.tvDate.setVisibility(View.VISIBLE);
holder.cardView.setCardBackgroundColor(Color.WHITE);
LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) holder.tvNom.getLayoutParams();
params.gravity = Gravity.START;
holder.tvNom.setLayoutParams(params);
if(eventsArrayList.get(position).getDay().equals(String.valueOf(cal.get(Calendar.DAY_OF_MONTH)))) { planning.ScrollTo(position); }
holder.tvNom.setText(eventsArrayList.get(position).getNom());
holder.tvLieu.setText(eventsArrayList.get(position).getLieu());
holder.tvDate.setText(eventsArrayList.get(position).getHeure() + "h" + eventsArrayList.get(position).getMinute());
if(eventsArrayList.get(position).getHeure().equals("")){
holder.tvDate.setVisibility(View.GONE);
holder.tvLieu.setVisibility(View.GONE);
params.gravity = Gravity.CENTER;
holder.tvNom.setLayoutParams(params);
holder.cardView.setCardBackgroundColor(Color.parseColor("#227c97"));
}
}
eventsArrayList.get(position).getHeure()或eventsArrayList.get(position).getDay()返回了null。
如果你认为它在eventsArrayList.get(position).getHeure()崩溃，你可以尝试TextUtils.isEmpty，它也会检查null：
if(TextUtils.isEmpty(eventsArrayList.get(position).getHeure())){
holder.tvDate.setVisibility(View.GONE);
holder.tvLieu.setVisibility(View.GONE);
params.gravity = Gravity.CENTER;
holder.tvNom.setLayoutParams(params);
holder.cardView.setCardBackgroundColor(Color.parseColor("#227c97"));
} else {
// also you should update tvDate, tvLieu, tvNom and cardView
// or you would get weird behaviour when the view holder is being recycled
}
如果你认为它在eventsArrayList.get(position).getDay()崩溃，你可以使用TextUtils.equals：
if (TextUtils.equals(eventsArrayList.get(position).getDay(), String.valueOf(cal.get(Calendar.DAY_OF_MONTH)))
最重要的是，我不建议在onBindViewHolder中使用RecyclerView.scrollTo，这是一种糟糕的做法，您应该在其他地方执行此操作。也许是因为你试图匹配一个条件，而它可以为其他位置返回null，所以发生了NPE。