Mixing
How to get child object's value inside a key from a list of data (using childeventlistener in firebase:...
Ok so I've been looking for related articles regarding this, I've made a few experiments but I can't understand why I can't still get the values of note, date_time and vaccine objects... I'm planning on putting them in a ListView and I already got the key from the list of data using ChildEventListener
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
and then I've tried using EventListener to get the values inside of it
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
DatabaseReference newRef = lastlastref.child(string);
newRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
note = snapshot.child("note").getValue(String.class);
vaccine = snapshot.child("vaccine").getValue(String.class);
timestamp = snapshot.child("date_time").getValue(String.class);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
arrayList.add(vaccine + "" + timestamp + "" + note);
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
But the app still crashes and logcat says "Can't pass null for argument 'pathString' in child()"
android firebase firebase-realtime-database edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
add a comment |
Ok so I've been looking for related articles regarding this, I've made a few experiments but I can't understand why I can't still get the values of note, date_time and vaccine objects... I'm planning on putting them in a ListView and I already got the key from the list of data using ChildEventListener
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
and then I've tried using EventListener to get the values inside of it
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
DatabaseReference newRef = lastlastref.child(string);
newRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
note = snapshot.child("note").getValue(String.class);
vaccine = snapshot.child("vaccine").getValue(String.class);
timestamp = snapshot.child("date_time").getValue(String.class);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
arrayList.add(vaccine + "" + timestamp + "" + note);
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
But the app still crashes and logcat says "Can't pass null for argument 'pathString' in child()"
android firebase firebase-realtime-database edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
This means thatbabyidisnull, which is not allowed in calls tochild(). You can easily verify the value ofbabyidby running the code in a debugger, and putting a breakpoint on the line withlastlastref = myRef.child(babyid)....
– Frank van Puffelen
Nov 20 '18 at 4:34
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03
add a comment |
Ok so I've been looking for related articles regarding this, I've made a few experiments but I can't understand why I can't still get the values of note, date_time and vaccine objects... I'm planning on putting them in a ListView and I already got the key from the list of data using ChildEventListener
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
and then I've tried using EventListener to get the values inside of it
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
DatabaseReference newRef = lastlastref.child(string);
newRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
note = snapshot.child("note").getValue(String.class);
vaccine = snapshot.child("vaccine").getValue(String.class);
timestamp = snapshot.child("date_time").getValue(String.class);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
arrayList.add(vaccine + "" + timestamp + "" + note);
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
But the app still crashes and logcat says "Can't pass null for argument 'pathString' in child()"
android firebase firebase-realtime-database edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
Ok so I've been looking for related articles regarding this, I've made a few experiments but I can't understand why I can't still get the values of note, date_time and vaccine objects... I'm planning on putting them in a ListView and I already got the key from the list of data using ChildEventListener
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
and then I've tried using EventListener to get the values inside of it
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String string = dataSnapshot.getValue(String.class);
DatabaseReference newRef = lastlastref.child(string);
newRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
note = snapshot.child("note").getValue(String.class);
vaccine = snapshot.child("vaccine").getValue(String.class);
timestamp = snapshot.child("date_time").getValue(String.class);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
arrayList.add(vaccine + "" + timestamp + "" + note);
adapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
But the app still crashes and logcat says "Can't pass null for argument 'pathString' in child()"
android firebase firebase-realtime-database android firebase firebase-realtime-database edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
edited Nov 20 '18 at 17:29
Frank van Puffelen
230k28376400
230k28376400
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
asked Nov 20 '18 at 4:18
Jackie ChanJackie Chan
86
86
This means thatbabyidisnull, which is not allowed in calls tochild(). You can easily verify the value ofbabyidby running the code in a debugger, and putting a breakpoint on the line withlastlastref = myRef.child(babyid)....
– Frank van Puffelen
Nov 20 '18 at 4:34
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03
add a comment |
This means thatbabyidisnull, which is not allowed in calls tochild(). You can easily verify the value ofbabyidby running the code in a debugger, and putting a breakpoint on the line withlastlastref = myRef.child(babyid)....
– Frank van Puffelen
Nov 20 '18 at 4:34
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03
This means that
babyid is null, which is not allowed in calls to child(). You can easily verify the value of babyid by running the code in a debugger, and putting a breakpoint on the line with lastlastref = myRef.child(babyid)....– Frank van Puffelen
Nov 20 '18 at 4:34
This means that
babyid is null, which is not allowed in calls to child(). You can easily verify the value of babyid by running the code in a debugger, and putting a breakpoint on the line with lastlastref = myRef.child(babyid)....– Frank van Puffelen
Nov 20 '18 at 4:34
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03
add a comment |
1 Answer
1
active
oldest
votes
You set up your reference to:
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
So each child node under this location is a JSON object like this:
{
"date_time": "November/16/2018...",
"note": "hhjj...",
"vaccine": "Measles"
}
But in your onChildAdded, you're trying to retrieve a single string value. Since the above JSON object is not a single string value, the getValue(String.class) returns null.
To get the values, you can call getValue() on the individual properties:
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String date_time = dataSnapshot.child("date_time").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String vaccine = dataSnapshot.child("vaccine").getValue(String.class);
}
You can also create a minimal class to wrap each record, and read that. The simplest version of that is:
public class ImmunizationRecord {
public String date_time;
public String note;
public String vaccine;
}
And the reading would then be done with:
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String record = dataSnapshot.getValue(ImmunizationRecord.class);
}
A small side note about the way you store date_time. This format will lead to problems as you progress, since it is not sortable. If you need to store time stamps, store them as milliseconds since the epoch, or in a string format that allows them to be sorted (e.g. 2018-11-16T11:29:00).
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
add a comment |
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1 Answer
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active
oldest
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1 Answer
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oldest
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oldest
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active
oldest
votes
You set up your reference to:
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
So each child node under this location is a JSON object like this:
{
"date_time": "November/16/2018...",
"note": "hhjj...",
"vaccine": "Measles"
}
But in your onChildAdded, you're trying to retrieve a single string value. Since the above JSON object is not a single string value, the getValue(String.class) returns null.
To get the values, you can call getValue() on the individual properties:
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String date_time = dataSnapshot.child("date_time").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String vaccine = dataSnapshot.child("vaccine").getValue(String.class);
}
You can also create a minimal class to wrap each record, and read that. The simplest version of that is:
public class ImmunizationRecord {
public String date_time;
public String note;
public String vaccine;
}
And the reading would then be done with:
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String record = dataSnapshot.getValue(ImmunizationRecord.class);
}
A small side note about the way you store date_time. This format will lead to problems as you progress, since it is not sortable. If you need to store time stamps, store them as milliseconds since the epoch, or in a string format that allows them to be sorted (e.g. 2018-11-16T11:29:00).
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
add a comment |
You set up your reference to:
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
So each child node under this location is a JSON object like this:
{
"date_time": "November/16/2018...",
"note": "hhjj...",
"vaccine": "Measles"
}
But in your onChildAdded, you're trying to retrieve a single string value. Since the above JSON object is not a single string value, the getValue(String.class) returns null.
To get the values, you can call getValue() on the individual properties:
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String date_time = dataSnapshot.child("date_time").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String vaccine = dataSnapshot.child("vaccine").getValue(String.class);
}
You can also create a minimal class to wrap each record, and read that. The simplest version of that is:
public class ImmunizationRecord {
public String date_time;
public String note;
public String vaccine;
}
And the reading would then be done with:
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String record = dataSnapshot.getValue(ImmunizationRecord.class);
}
A small side note about the way you store date_time. This format will lead to problems as you progress, since it is not sortable. If you need to store time stamps, store them as milliseconds since the epoch, or in a string format that allows them to be sorted (e.g. 2018-11-16T11:29:00).
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
add a comment |
You set up your reference to:
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
So each child node under this location is a JSON object like this:
{
"date_time": "November/16/2018...",
"note": "hhjj...",
"vaccine": "Measles"
}
But in your onChildAdded, you're trying to retrieve a single string value. Since the above JSON object is not a single string value, the getValue(String.class) returns null.
To get the values, you can call getValue() on the individual properties:
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String date_time = dataSnapshot.child("date_time").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String vaccine = dataSnapshot.child("vaccine").getValue(String.class);
}
You can also create a minimal class to wrap each record, and read that. The simplest version of that is:
public class ImmunizationRecord {
public String date_time;
public String note;
public String vaccine;
}
And the reading would then be done with:
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String record = dataSnapshot.getValue(ImmunizationRecord.class);
}
A small side note about the way you store date_time. This format will lead to problems as you progress, since it is not sortable. If you need to store time stamps, store them as milliseconds since the epoch, or in a string format that allows them to be sorted (e.g. 2018-11-16T11:29:00).
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
You set up your reference to:
lastlastref = myRef.child(babyid).child("baby_features").child("immunization_records");
So each child node under this location is a JSON object like this:
{
"date_time": "November/16/2018...",
"note": "hhjj...",
"vaccine": "Measles"
}
But in your onChildAdded, you're trying to retrieve a single string value. Since the above JSON object is not a single string value, the getValue(String.class) returns null.
To get the values, you can call getValue() on the individual properties:
lastlastref.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String date_time = dataSnapshot.child("date_time").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String vaccine = dataSnapshot.child("vaccine").getValue(String.class);
}
You can also create a minimal class to wrap each record, and read that. The simplest version of that is:
public class ImmunizationRecord {
public String date_time;
public String note;
public String vaccine;
}
And the reading would then be done with:
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String record = dataSnapshot.getValue(ImmunizationRecord.class);
}
A small side note about the way you store date_time. This format will lead to problems as you progress, since it is not sortable. If you need to store time stamps, store them as milliseconds since the epoch, or in a string format that allows them to be sorted (e.g. 2018-11-16T11:29:00).
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
answered Nov 20 '18 at 17:36
Frank van PuffelenFrank van Puffelen
230k28376400
230k28376400
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
add a comment |
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
Worked like a charm. Thanks a lot!
– Jackie Chan
Nov 21 '18 at 9:28
add a comment |
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This means that
babyidisnull, which is not allowed in calls tochild(). You can easily verify the value ofbabyidby running the code in a debugger, and putting a breakpoint on the line withlastlastref = myRef.child(babyid)....– Frank van Puffelen
Nov 20 '18 at 4:34
ok, fixed the null error but it still won't get the children object values... could my code be lacking something?
– Jackie Chan
Nov 20 '18 at 16:03