从Firebase中的嵌套查询填充回收者视图
我正在尝试使用嵌套查询填充回收者视图。第一个查询转到groups_list节点，并获取该节点中的数据和唯一键。然后，它使用密钥将节点分组，并在该密钥下获取数据。这两个查询的结果都需要在“回收者”视图中更新。
简而言之，第一个查询获取一些数据和一个键，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者视图中进行更新。我为此使用了模型类和回收者视图适配器。
但是我在下面遇到了一个错误。
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
数据快照的日志如下...第一个...
第二个日志...
可能的解决方案1（传递给Recycler查看问题，否则可能会起作用）
这似乎是按正确的顺序获取数据，现在只需将其传递到“模型数组”列表中并设置适配器即可。
// 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-否则会起作用）
// 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您的答案有误，请参见下面的屏幕截图：
工作解决方案基于Prateek Jains的输入
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;
}
}
1 个答案:
答案 0 :(得分：6)
您必须将所需的数据添加到适配器正在用来渲染视图的列表中。完成后，您必须调用notifyDataSetChanged，以便适配器可以从更新后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) {
}
});
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