当我运行该活动时，它会向我显示我想要的项目以及一张无效的卡片视图（当我从tostring()删除holder.setTitle("product name:"+model.getName().toString());时，我正竭尽全力解决此问题，但我没有找到解决方案。
这是我的课程 Client_order：
public class Client_order extends AppCompatActivity {
FragmentManager fragmentManager;
Fragment Settingsfrag,Orderfrag,panierfrag;
TextView delorder;
Order model2;
Button submit;
DatabaseReference ref,ref1,ref2;
private Toolbar hometoolbar;
private ImageView settingsbtn, orderIV, imageView7,imageView10;
private RecyclerView orderrv;
private FirebaseAuth mAuth;
private FirebaseUser currentUser;
private DatabaseReference mDatabase;
private String user_id;
Spinner spinnerorder;
private String name;
private String email;
private String phone;
TextView tvName;
Orderviewholder holder1;
private FirebaseRecyclerAdapter<Order, Orderviewholder> orderAdapter;
DatabaseReference dborder,dbpanier;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_client_order);
tvName = findViewById(R.id.tvName);
hometoolbar = findViewById(R.id.hometoolbarorder);
hometoolbar.setTitle("ordre");
hometoolbar.setTitleTextColor(Color.WHITE);
settingsbtn = findViewById(R.id.settingsbtn);
orderIV = findViewById(R.id.orderIV);
imageView7 = findViewById(R.id.imageView7);
fragmentManager=getSupportFragmentManager();
Orderfrag=fragmentManager.findFragmentById(R.id.orderfrag);
Settingsfrag=fragmentManager.findFragmentById(R.id.settingsfrag);
mAuth = FirebaseAuth.getInstance();
currentUser = mAuth.getCurrentUser();
mDatabase = FirebaseDatabase.getInstance().getReference();
if (currentUser == null) {
Intent intent=new Intent(Client_order.this,Login.class);
startActivity(intent);
} else {
if (!mAuth.getCurrentUser().isEmailVerified()) {
Toast.makeText(getApplicationContext(), "Please verify your email address", Toast.LENGTH_LONG).show();
Intent startActivity = new Intent(this, Login.class);
startActivity(startActivity);
finish();
} else {
user_id = currentUser.getUid();
}
}
Toast.makeText(getApplicationContext(),user_id, Toast.LENGTH_LONG).show();
panierfrag=fragmentManager.findFragmentById(R.id.panierfrag);
submit=findViewById(R.id.submit);
submit.setVisibility(View.VISIBLE);
fragmentManager.beginTransaction()
.hide(panierfrag)
.show(Orderfrag)
.hide(Settingsfrag)
.commit();
imageView7.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(Client_order.this,Client_panier.class);
startActivity(intent);
}
});
settingsbtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
fragmentManager.beginTransaction()
.hide(panierfrag)
.hide(Orderfrag)
.show(Settingsfrag)
.commit();
}
});
orderIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
fragmentManager.beginTransaction()
.hide(panierfrag)
.show(Orderfrag)
.hide(Settingsfrag)
.commit();
}
});
dborder = FirebaseDatabase.getInstance().getReference().child("order");
dborder.keepSynced(true);
orderrv = (RecyclerView) findViewById(R.id.orderrv);
DatabaseReference personsRef = FirebaseDatabase.getInstance().getReference().child("order").child(user_id.toString());
Query personsQuery = personsRef.orderByKey();
orderrv.hasFixedSize();
orderrv.setLayoutManager(new LinearLayoutManager(this));
FirebaseRecyclerOptions personsOptions = new FirebaseRecyclerOptions.Builder<Order>().setQuery(personsQuery, Order.class).build();
orderAdapter=new FirebaseRecyclerAdapter<Order, Orderviewholder>(personsOptions) {
@Override
protected void onBindViewHolder(@NotNull Orderviewholder holder, int position, @NotNull Order model) {
holder.setTitle("product name:"+model.getName().toString());
holder1=holder;
imageView10=holder.mView.findViewById(R.id.imageVieworder);
Picasso.get().load(model.getImage()).into(imageView10, new Callback() {
@Override
public void onSuccess() {
ProgressBar progressbar3;
progressbar3=holder1.mView.findViewById(R.id.progressBar4);
progressbar3.setVisibility(View.INVISIBLE);
}
@Override
public void onError(Exception e) {
}
});
holder.setdesc(model.getDesc().toString());
holder.setprice(model.getPrice());
holder.setquantity(model.getQuantity());
TextView status;
status=holder.mView.findViewById(R.id.statusorder);
status.setText(model.getStatus());
status.setVisibility(View.VISIBLE);
delorder=holder.mView.findViewById(R.id.orderDelbtn);
delorder.setText("done");
holder.mView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
delorder.setVisibility(View.VISIBLE);
}
});
model2=model;
delorder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
dborder.child(currentUser.getUid()).child(model2.getId()).removeValue().addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NotNull Task<Void> task) {
if (task.isSuccessful()) {
Toast.makeText(Client_order.this, "order deleted successfully", Toast.LENGTH_LONG).show();
}
}
});
}
});
submit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
ref=FirebaseDatabase.getInstance().getReference().child("order").child(user_id.toString());
ref2=FirebaseDatabase.getInstance().getReference().child("order").child(user_id.toString()).child("submitted");
ref1=FirebaseDatabase.getInstance().getReference().child("order").child("admin");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NotNull DataSnapshot dataSnapshot) {
for (DataSnapshot orderSnapshot: dataSnapshot.getChildren()) {
Order category = orderSnapshot.getValue(Order.class);
//if (category!=null){
ref1.child(category.getId()).setValue(category);
Toast.makeText(Client_order.this,"product successfully submitted", Toast.LENGTH_LONG).show();
ref2.child(category.getId()).setValue(category);
ref.child(category.getId()).removeValue();
// }
}
}
@Override
public void onCancelled(@NotNull DatabaseError databaseError) {
}
});
}
});
}
@NotNull
@Override
public Orderviewholder onCreateViewHolder(@NotNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.product_list_itemorder, parent, false);
return new Orderviewholder(view);
}
};
orderrv.setAdapter(orderAdapter);
}
@Override
protected void onStart() {
super.onStart();
orderAdapter.startListening();
}
@Override
protected void onStop() {
super.onStop();
orderAdapter.stopListening();
}
public static class Orderviewholder extends RecyclerView.ViewHolder{
View mView;
public Orderviewholder(View itemView){
super(itemView);
mView = itemView;
}
public void setTitle(String title){
TextView post_title = (TextView)mView.findViewById(R.id.order_name);
post_title.setText(title);
}
public void setdesc(String desc) {
TextView post_title = (TextView) mView.findViewById(R.id.order_description);
post_title.setText(desc);
}
public void setprice(int price) {
TextView post_title = (TextView) mView.findViewById(R.id.order_price);
post_title.setText(Integer.toString(price)+" dhs");
}
public void setquantity(int quantity) {
TextView post_title = (TextView) mView.findViewById(R.id.order_quantity);
post_title.setText(Integer.toString(quantity));
}
}
}
它向我显示此错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
at com.omar.lazywork.Client_order$4.onBindViewHolder(Client_order.java:207)
at com.omar.lazywork.Client_order$4.onBindViewHolder(Client_order.java:204)