GenericTypeIndicator

Due to the way that Java implements generics (type-erasure), it is necessary to use a slightly more complicated method to properly resolve types for generic collections at runtime. To solve this problem, Firebase Database accepts subclasses of this class in calls to getValue (getValue(GenericTypeIndicator), getValue(GenericTypeIndicator)) and returns a properly-typed generic collection.

As an example, you might do something like this to get a list of Message instances from a DataSnapshot:

     class Message {
         private String author;
         private String text;

         private Message() {}

         public Message(String author, String text) {
             this.author = author;
             this.text = text;
         }

         public String getAuthor() {
             return author;
         }

         public String getText() {
             return text;
         }
     }

     // Later ...

     GenericTypeIndicator<List<Message>> t = new GenericTypeIndicator<List<
     Message>>()
 {};
     List<Message> messages = snapshot.getValue(t);