[英]How to get nested collection from Firebase Firestore on Android?
[英]How to Get Nested Children From Firebase
我需要从 firebase 中获取嵌套的孩子(见图)。 我想展示一个仅来自特定用户的回收站视图。 以下是我到目前为止所拥有的,但这给了我所有的孩子。
DatabaseReference notificationInviteRef = FirebaseDatabase.getInstance().getReference().child(Strings.InvitesReference);
notificationInviteRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot1) {
ArrayList<Model_Notifications_Invite> model_notification_invites = new ArrayList<>();
for (DataSnapshot snapshot2:snapshot1.getChildren()) {
Model_Notifications_Invite invites = snapshot2.getValue(Model_Notifications_Invite.class);
model_notifications_invites.add(invites);
}
myNotificationsAdapter.updateNotificationsList(model_notifications_invites);
}
@Override
public void onCancelled(DatabaseError databaseError) {
//throw databaseError.toException();
}
});
如果我理解正确,您的数据结构中有两个未知级别,这意味着您的onDataChange
中需要两个嵌套循环:每个级别一个。
DatabaseReference notificationInviteRef = FirebaseDatabase.getInstance().getReference().child(Strings.InvitesReference);
notificationInviteRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot1) {
ArrayList<Model_Notifications_Invite> model_notification_invites = new ArrayList<>();
for (DataSnapshot snapshot2:snapshot1.getChildren()) {
for (DataSnapshot snapshot3:snapshot2.getChildren()) {
Model_Notifications_Invite invites = snapshot3.getValue(Model_Notifications_Invite.class);
model_notifications_invites.add(invites);
}
}
myNotificationsAdapter.updateNotificationsList(model_notifications_invites);
}
@Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // 👈 never ignore errors
}
});
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