CODEWITHSUNDEEP
androidfirebasefirebase-realtime-database
Kirenov Penguinovitsh
Kirenov Penguinovitsh

Reputation: 55

Using addChildEventListener on Firebase database query android

I'm using addChildEventListener for my chat application

Query chatRoot = Qref
            .child("Messages")
            .orderByChild("lobbykey")
            .equalTo(lobbykey);`

This is the query that I am using works fine to my knowledge, just a bit of idea on what I'm trying to do. I also have a constructor class for my list to place objects:

public ChatParameters(String userUID, String message, String imageURL, String sender, String lobbykey, String msgkey) {
    this.UserUID = userUID;
    this.sender = sender;
    this.message = message;
    this.imageURL = imageURL;
    this.lobbykey = lobbykey;
    this.msgkey = msgkey;
}

The onchildadded listener works fine. When I tried it with just Toast, it make text works fine. But when i add the Chatparameters.class to get all the values it crashes

public void onChildAdded(DataSnapshot dataSnapshot, String s) {
  for (DataSnapshot chatSnapshot: dataSnapshot.getChildren()){
    ChatParameters chatParameters = chat.getValue(ChatParameters.class); //i get the error here.
  }
}

this is the error logcat, it's refering to ChatParameters chatParameters = chat.getValue(ChatParameters.class);

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.woofy_nocco.testapp.ChatParameters
    at com.google.android.gms.internal.zzelw.zzb(Unknown Source)
    at com.google.android.gms.internal.zzelw.zza(Unknown Source)
    at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
    at com.example.woofy_nocco.testapp.Chatroom$1.onChildAdded(Chatroom.java:78)
    at com.google.android.gms.internal.zzecw.zza(Unknown Source)
    at com.google.android.gms.internal.zzeia.zzbyc(Unknown Source)
    at com.google.android.gms.internal.zzeig.run(Unknown Source)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)

this is what my database structure looks like

database.png

Upvotes: 1

Views: 188

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 598728

The onChildAdded method of your ChildEventListener is invoked on individual child nodes already. So most likely you don't need to loop over dataSnapshot.getChildren() in there:

public void onChildAdded(DataSnapshot dataSnapshot, String s) {
    ChatParameters chatParameters = dataSnapshot.getValue(ChatParameters.class);
}

Explanation of the problem: By looping over dataSnapshot.getChildren() the chatSnapshot will end up referring to individual properties of the chat message. So if your ChatParameters consists if a text property and a message property, the chatSnapshot will be point to that text or message property, and chatSnapshot.getValue() will be a string. Since a String can't be converted to your ChatParameters class, the SDK throws an exception.

Upvotes: 1

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