从 Firebase 中的嵌套查询填充回收站视图
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【中文标题】从 Firebase 中的嵌套查询填充回收站视图【英文标题】：Populating Recycler View From Nested Queries in Firebase 【发布时间】：2019-08-10 15:18:32 【问题描述】：我正在尝试使用嵌套查询填充回收站视图。第一个查询转到 groups_list 节点并获取节点中的数据和唯一键。然后它使用该键进入组节点并获取该键下的数据。这两个查询的结果都需要在回收站视图中更新。
简而言之，第一个查询得到一些数据和一个键，该键用于进行第二个查询。这两个查询的结果都需要在回收站视图中更新。我为此使用了模型类和回收器视图适配器。
但我在下面遇到错误。
我的片段如下：
// Firebase
fbDatabaseRootNode = FirebaseDatabase.getInstance().getReference();
fbDatabaseRefGroupList = fbDatabaseRootNode.child("groups_list").child(current_user_id);
fbDatabaseRefGroups = fbDatabaseRootNode.child("groups");
fbDatabaseRefGroupList.addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
// Array to Get Group List
lGroupsList = new ArrayList<>();
if (dataSnapshot.exists())
// Clear Array to Get Group List
lGroupsList.clear();
for (DataSnapshot glSnapshot : dataSnapshot.getChildren())
// Use The Model To Format Array List and Pass It Into It
GroupsListModel g = glSnapshot.getValue(GroupsListModel.class);
// Array to Get Group List
lGroupsList.add(g);
String groupID = String.valueOf(glSnapshot.getKey());
fbDatabaseRefGroups.child(groupID).addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
if (dataSnapshot.exists())
for (DataSnapshot gSnapshot : dataSnapshot.getChildren())
// Use The Model To Format Array List and Pass It Into It
GroupsListModel g = gSnapshot.getValue(GroupsListModel.class);
// Array to Get Group List
lGroupsList.add(g);
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
aGroupList = new GroupsListAdapter(getContext(), lGroupsList);
rvGroupList.setAdapter(aGroupList);
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
System.out.println("The read failed: " + databaseError.getCode());
);
我的 Firebase 数据库结构看起来像
"groups" :
"-LaPfENd0G4pHlejrcd6" :
"group_creation_date" : 1553078221782,
"group_logo" : "0",
"group_member_count" : "0",
"group_name" : "dog lovers",
"group_tagline" : "we love dogs..."
,
"-LaPhG0YHnF3FG0Czxom" :
"group_creation_date" : 1553078751686,
"group_logo" : "0",
"group_member_count" : "0",
"group_name" : "hi",
"group_tagline" : "hello"
,
"groups_list" :
"F81wvGx9a7fXRrfVPQMhQtkM0wv2" :
"-LaPfENd0G4pHlejrcd6" :
"block_status" : "0",
"hide_status" : "0",
"notification_status" : "0",
"pin_sequence" : "0",
"report_status" : "0"
,
"-LaPhG0YHnF3FG0Czxom" :
"block_status" : "0",
"hide_status" : "0",
"notification_status" : "0",
"pin_sequence" : "0",
"report_status" : "0"
,
模型类是
public class GroupsListModel
private String block_status;
private String hide_status;
private String notification_status;
private String pin_sequence;
private String report_status;
private String group_name;
private Long group_creation_date;
private String group_logo;
private String group_member_count;
private String group_tagline;
public GroupsListModel()
public GroupsListModel(String block_status, String hide_status, String notification_status, String pin_sequence, String report_status, String group_name, Long group_creation_date, String group_logo, String group_member_count, String group_tagline)
this.block_status = block_status;
this.hide_status = hide_status;
this.notification_status = notification_status;
this.pin_sequence = pin_sequence;
this.report_status = report_status;
this.group_name = group_name;
this.group_creation_date = group_creation_date;
this.group_logo = group_logo;
this.group_member_count = group_member_count;
this.group_tagline = group_tagline;
public String getBlock_status()
return block_status;
public void setBlock_status(String block_status)
this.block_status = block_status;
public String getHide_status()
return hide_status;
public void setHide_status(String hide_status)
this.hide_status = hide_status;
public String getNotification_status()
return notification_status;
public void setNotification_status(String notification_status)
this.notification_status = notification_status;
public String getPin_sequence()
return pin_sequence;
public void setPin_sequence(String pin_sequence)
this.pin_sequence = pin_sequence;
public String getReport_status()
return report_status;
public void setReport_status(String report_status)
this.report_status = report_status;
public String getGroup_name()
return group_name;
public void setGroup_name(String group_name)
this.group_name = group_name;
public Long getGroup_creation_date()
return group_creation_date;
public void setGroup_creation_date(Long group_creation_date)
this.group_creation_date = group_creation_date;
public String getGroup_logo()
return group_logo;
public void setGroup_logo(String group_logo)
this.group_logo = group_logo;
public String getGroup_member_count()
return group_member_count;
public void setGroup_member_count(String group_member_count)
this.group_member_count = group_member_count;
public String getGroup_tagline()
return group_tagline;
public void setGroup_tagline(String group_tagline)
this.group_tagline = group_tagline;
错误是
Can't convert object of type java.lang.Long to type com.example.myproject
datasnapshots 的日志如下...第一个...
第二个的日志...
可能的解决方案 1（传递给 Recycler 查看问题否则有效）
这似乎是以正确的顺序获取数据，现在只需将其传递到模型数组列表并设置适配器
// Get The Data
fbDatabaseRefGroupList.addChildEventListener(new ChildEventListener()
@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
if (dataSnapshot.exists())
final String groupID = dataSnapshot.getKey();
final String blockStatus = (String) dataSnapshot.child("block_status").getValue();
final String hideStatus = (String) dataSnapshot.child("hide_status").getValue();
final String notificationStatus = (String) dataSnapshot.child("notification_status").getValue();
final String pinSequence = (String) dataSnapshot.child("pin_sequence").getValue();
final String reportStatus = (String) dataSnapshot.child("report_status").getValue();
fbDatabaseRefGroups.child(groupID).addListenerForSingleValueEvent(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
String groupName = (String) dataSnapshot.child("group_name").getValue();
String groupTagLine = (String) dataSnapshot.child("group_name").getValue();
String groupMemberCount = (String) dataSnapshot.child("group_name").getValue();
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
@Override
public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
@Override
public void onChildRemoved(@NonNull DataSnapshot dataSnapshot)
@Override
public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
可能的解决方案 2（列表合并是一个问题 - 否则有效）
// Firebase
fbDatabaseRootNode = FirebaseDatabase.getInstance().getReference();
fbDatabaseRefGroupList = fbDatabaseRootNode.child("groups_list").child(current_user_id);
fbDatabaseRefGroups = fbDatabaseRootNode.child("groups");
// Array to Get Group List
lGroupsListList = new ArrayList<>();
lGroupsList = new ArrayList<>();
lCombinedList = new ArrayList<>();
// Clear Array to Get Group List
lGroupsList.clear();
// Clear Array to Get Group List
lGroupsListList.clear();
// Clear Array to Get Group List
lCombinedList.clear();
ValueEventListener valueEventListener = new ValueEventListener()
@Override
public void onDataChange(DataSnapshot dataSnapshot)
for (DataSnapshot ds : dataSnapshot.getChildren())
// Use The Model To Format Array List and Pass It Into It
GroupsListModel g = ds.getValue(GroupsListModel.class);
// Array to Get Group List
lGroupsListList.add(g);
final String key = ds.getKey();
final String blockStatus = (String) ds.child("block_status").getValue();
DatabaseReference keyRef = fbDatabaseRootNode.child("groups").child(key);
ValueEventListener eventListener = new ValueEventListener()
@Override
public void onDataChange(DataSnapshot dataSnapshot)
// Use The Model To Format Array List and Pass It Into It
GroupsListModel g = dataSnapshot.getValue(GroupsListModel.class);
// Array to Get Group List
lGroupsList.add(g);
String groupName = (String) dataSnapshot.child("group_name").getValue();
Log.d(TAG, "groupdetails: " + key + "--" + groupName + "--" + blockStatus);
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
;
keyRef.addListenerForSingleValueEvent(eventListener);
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
;
aGroupList = new GroupsListAdapter(getContext(), lGroupsList);
rvGroupList.setAdapter(aGroupList);
fbDatabaseRefGroupList.addListenerForSingleValueEvent(valueEventListener);
@Prateek Jain 你的回答是错误的，请看下面的截图：
工作解决方案基于 Prateek Jains 输入
public class GroupsListFragment extends Fragment
private static final String TAG = "GroupsListFragment";
// Recycler View
private RecyclerView rvGroupList;
private GroupsListAdapter aGroupList;
private List<GroupsListModel> lGroupsListList;
private List<GroupsListModel> lGroupsList;
private List<GroupsListModel> lCombinedList;
// Firebase
private FirebaseAuth mAuth;
private DatabaseReference fbDatabaseRootNode;
private DatabaseReference fbDatabaseRefGroupList;
private DatabaseReference fbDatabaseRefGroups;
private String current_user_id;
private String groupID;
private List<String> lgroupIDs;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
View view = inflater.inflate(R.layout.fragment_groups_list, container, false);
mAuth = FirebaseAuth.getInstance();
current_user_id = mAuth.getCurrentUser().getUid();
// Init Recycler View
rvGroupList = view.findViewById(R.id.f_groups_list_groups_list);
rvGroupList.setHasFixedSize(true);
rvGroupList.setLayoutManager(new LinearLayoutManager(getActivity()));
// Firebase
fbDatabaseRootNode = FirebaseDatabase.getInstance().getReference();
fbDatabaseRefGroupList = fbDatabaseRootNode.child("groups_list").child(current_user_id);
fbDatabaseRefGroups = fbDatabaseRootNode.child("groups");
// Get The Data
fbDatabaseRefGroupList.addChildEventListener(new ChildEventListener()
@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
// Array to Get Group List
lGroupsList = new ArrayList<>();
if (dataSnapshot.exists())
// Clear Array to Get Group List
lGroupsList.clear();
final String groupID = dataSnapshot.getKey();
final String blockStatus = (String) dataSnapshot.child("block_status").getValue();
final String hideStatus = (String) dataSnapshot.child("hide_status").getValue();
final String notificationStatus = (String) dataSnapshot.child("notification_status").getValue();
final String pinSequence = (String) dataSnapshot.child("pin_sequence").getValue();
final String reportStatus = (String) dataSnapshot.child("report_status").getValue();
fbDatabaseRefGroups.child(groupID).addListenerForSingleValueEvent(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
Long groupCreationDate = (Long) dataSnapshot.child("group_creation_date").getValue();
String groupLogo = (String) dataSnapshot.child("group_logo").getValue();
String groupMemberCount = (String) dataSnapshot.child("group_member_count").getValue();
String groupName = (String) dataSnapshot.child("group_name").getValue();
String groupTagLine = (String) dataSnapshot.child("group_tagline").getValue();
lGroupsList.add(new GroupsListModel(blockStatus, hideStatus, notificationStatus, pinSequence,
reportStatus, groupName, groupCreationDate, groupLogo, groupMemberCount, groupTagLine));
aGroupList.notifyDataSetChanged();
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
aGroupList = new GroupsListAdapter(getContext(), lGroupsList);
rvGroupList.setAdapter(aGroupList);
@Override
public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
@Override
public void onChildRemoved(@NonNull DataSnapshot dataSnapshot)
@Override
public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
return view;
【问题讨论】：
我已经取得了一些进展，但还没有得到最终结果，请参阅***.com/questions/55259345/…' 【参考方案1】：您必须将所需的数据添加到适配器用于呈现视图的列表中。完成后，您必须调用 notifyDataSetChanged，以便适配器可以从更新的列表中重新加载其数据。
fbDatabaseRefGroups.child(groupID).addListenerForSingleValueEvent(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
String groupName = (String) dataSnapshot.child("group_name").getValue();
String groupTagLine = (String) dataSnapshot.child("group_name").getValue();
String groupMemberCount = (String) dataSnapshot.child("group_name").getValue();
lGroupsList.add(new GroupsListModel(groupName, groupMemberCount, groupTagLine));
aGroupList.notifyDataSetChanged();
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
);
【讨论】：
这是一个构造函数错误，能否请您发布您的 GroupListModel 类？ 你的 GroupListModel 接受 10 个参数，你必须将所有这些参数传递给它。以上是关于从 Firebase 中的嵌套查询填充回收站视图的主要内容，如果未能解决你的问题，请参考以下文章