使用 FirebaseUI 将子集合中的数据放入第二个布局中
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【中文标题】使用 FirebaseUI 将子集合中的数据放入第二个布局中【英文标题】：Putting data from a subcollection in a second Layout with FirebaseUI 【发布时间】：2020-11-07 17:47:56 【问题描述】：我想在新的 RecyclerView 中打开 Firebase 子集合的数据。 Main Activity 有一个 RecyclerView，其中填充了来自第一个集合的数据，第二个 Activity 应通过单击其中一个项目打开。第二个 Activity 将具有第二个 RecyclerView。我的主要活动工作正常，我可以看到我的所有数据。但是当我点击其中一项时，我的应用程序崩溃了。
这是我的 MainActivity
private FirebaseFirestore db = FirebaseFirestore.getInstance();
private CollectionReference notebookRef = db.collection("Notebook");
private KisteAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FloatingActionButton buttonAddKiste = findViewById(R.id.button_add_kiste);
buttonAddKiste.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
startActivity(new Intent(MainActivity.this, NewKisteActivity.class));
);
setUpRecyclerView();
private void setUpRecyclerView()
Query query = notebookRef.orderBy("priority", Query.Direction.DESCENDING);
FirestoreRecyclerOptions<Kiste> options = new FirestoreRecyclerOptions.Builder<Kiste>()
.setQuery(query, Kiste.class)
.build();
adapter = new KisteAdapter(options);
final RecyclerView recyclerView = findViewById(R.id.recycler_view_kiste);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);
new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT |ItemTouchHelper.RIGHT)
@Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target)
return false;
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction)
adapter.deleteKiste(viewHolder.getAdapterPosition());
final DocumentReference docRef = adapter.getSnapshots().getSnapshot(viewHolder.getAdapterPosition()).getReference();
final Kiste kiste = adapter.getSnapshots().getSnapshot(viewHolder.getAdapterPosition()).toObject(Kiste.class);
Snackbar.make(recyclerView, "Item deleted", Snackbar.LENGTH_LONG)
.setAction("Undo", new View.OnClickListener()
@Override
public void onClick(View v)
docRef.set(kiste);
).show();
@Override
public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive)
new RecyclerViewSwipeDecorator.Builder(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
.addBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.colorAccent))
.addActionIcon(R.drawable.ic_delete_)
.create()
.decorate();
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
).attachToRecyclerView(recyclerView);
adapter.setOnKisteClickListen(new KisteAdapter.onItemClickListener()
@Override
public void onKisteClick(DocumentSnapshot documentSnapshot, int position)
final DocumentReference docRef = documentSnapshot.getReference();
final CollectionReference colRef = documentSnapshot.getReference().collection("A");
final Intent intent = new Intent(MainActivity.this,SecondaryActivity.class);
colRef.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>()
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots)
if (queryDocumentSnapshots.isEmpty())
colRef.add(new Item("DFB","SGRDG",5));
/*intent.putExtra("Document Reference",docRef.getId());
intent.putExtra("Collection Reference",colRef.getId());*/
startActivity(intent);
else
startActivity(intent);
);
);
@Override
protected void onStart()
super.onStart();
adapter.startListening();
@Override
protected void onStop()
super.onStop();
adapter.stopListening();
这是第一个 RecyclerView 得到的 Class Kiste
public class Kiste
private String title;
private int priority;
public Kiste()
public Kiste(String title, int priority)
this.title= title;
this.priority = priority;
public String getTitle()
return title;
public int getPriority()
return priority;
这是适配器
public class KisteAdapter extends FirestoreRecyclerAdapter<Kiste, KisteAdapter.KisteHolder>
private onItemClickListener listener;
public KisteAdapter(@NonNull FirestoreRecyclerOptions<Kiste> options)
super(options);
@Override
protected void onBindViewHolder(@NonNull KisteHolder holder, int position, @NonNull Kiste model)
holder.textViewTitle.setText(model.getTitle());
holder.textViewPriority.setText(String.valueOf(model.getPriority()));
@NonNull
@Override
public KisteHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.kiste_item,parent,false);
return new KisteHolder(v);
public void deleteKiste(int position)
getSnapshots().getSnapshot(position).getReference().delete();
class KisteHolder extends RecyclerView.ViewHolder
TextView textViewTitle;
TextView textViewPriority;
public KisteHolder(@NonNull View itemView)
super(itemView);
textViewTitle = itemView.findViewById(R.id.text_view_title);
textViewPriority = itemView.findViewById(R.id.text_view_priority);
itemView.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION && listener!= null)
listener.onKisteClick(getSnapshots().getSnapshot(position),position);
);
public interface onItemClickListener
void onKisteClick(DocumentSnapshot documentSnapshot, int position);
public void setOnKisteClickListen (onItemClickListener listener) this.listener = listener;
因为这对我有用，所以我尝试对子集合做同样的事情（因为我仍在测试它是否可以工作，所以我只使用了一个我知道存在的 DocumentPath），但正如我在上面所说的那样，应用程序不断崩溃。
这是第二个活动
public class SecondaryActivity extends AppCompatActivity
private FirebaseFirestore db = FirebaseFirestore.getInstance();
private CollectionReference colRef = db.collection("Notebook").document(
"JGBzWBwCASivfAjuF8xE").collection("A");
private ItemAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_secondary);
FloatingActionButton buttonAddItem = findViewById(R.id.button_add_item);
setupRecyclerView();
private void setupRecyclerView()
Query query2 = colRef.orderBy("priority", Query.Direction.DESCENDING);
FirestoreRecyclerOptions<Item> options = new FirestoreRecyclerOptions.Builder<Item>()
.setQuery(query2, Item.class)
.build();
adapter = new ItemAdapter(options);
final RecyclerView recyclerView = findViewById(R.id.recycler_view_item);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(adapter);
@Override
protected void onStart()
super.onStart();
adapter.startListening();
@Override
protected void onStop()
super.onStop();
adapter.stopListening();
类项：
public class Item
//private Bitmap imageItem;
private String itemName;
private String itemQuantity;
private int priority;
public Item()
public Item( String itemName, String itemQuantity, int priority)
//this.imageItem = imageViewItem;
this.itemName = itemName;
this.itemQuantity = itemQuantity;
this.priority = priority;
/*public Bitmap getImageItem()
return imageItem;
*/
public String getItemName()
return itemName;
public String getItemQuantity()
return itemQuantity;
public int getPriority()
return priority;
和适配器：
public class ItemAdapter extends FirestoreRecyclerAdapter<Item, ItemAdapter.ItemHolder>
public ItemAdapter(@NonNull FirestoreRecyclerOptions<Item> options)
super(options);
@Override
protected void onBindViewHolder(@NonNull ItemHolder holder, int position, @NonNull Item model)
//holder.imageViewItem.setImageBitmap(model.getImageItem());
holder.textViewTitle.setText(model.getItemName());
holder.textViewQuantity.setText(model.getItemQuantity());
holder.textViewPriority.setText(String.valueOf(model.getPriority()));
@NonNull
@Override
public ItemHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_item,parent,false);
return new ItemHolder(v);
class ItemHolder extends RecyclerView.ViewHolder
//ImageView imageViewItem;
TextView textViewTitle;
TextView textViewQuantity;
TextView textViewPriority;
public ItemHolder(@NonNull View itemView)
super(itemView);
//imageViewItem.findViewById(R.id.image_view_item);
textViewTitle.findViewById(R.id.text_view_item_name);
textViewQuantity.findViewById(R.id.text_view_item_quantity);
textViewPriority.findViewById(R.id.text_view_priority2);
如果有人能帮我找出问题所在，我将不胜感激。
【问题讨论】：
您在控制台中遇到的错误是什么？ java.lang.NullPointerException：尝试在 guellouzdaniels.android.wpf.hsh 的空对象引用上调用虚拟方法“android.view.View android.widget.TextView.findViewById(int)”。 abschlussaufgabe.ItemAdapter$ItemHolder.感谢您在控制台中指出错误，现在我们可以更轻松地查看问题所在，而无需阅读您的整个代码：D
您的 ItemAdapter 类的第 47 行出现错误。我无法确切看到它是哪一行，但我确定错误在您的 ViewHolder 中。
class ItemHolder extends RecyclerView.ViewHolder
//ImageView imageViewItem;
TextView textViewTitle;
TextView textViewQuantity;
TextView textViewPriority;
public ItemHolder(@NonNull View itemView)
super(itemView);
//imageViewItem.findViewById(R.id.image_view_item);
THESE LINES OF CODE -----------------------------------------------------------------
textViewTitle.findViewById(R.id.text_view_item_name);
textViewQuantity.findViewById(R.id.text_view_item_quantity);
textViewPriority.findViewById(R.id.text_view_priority2);
-------------------------------------------------------------------------------------
将它们替换为：
this.textViewTitle = (TextView) itemView.findViewById(R.id.text_view_item_name); // and so on...
你可以看看这个例子：
https://www.javatpoint.com/android-recyclerview-list-example
【讨论】：
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