need to solve this Attempt to invoke virtual method on a null object reference im used firebase realtime
49
What is a NullPointerException, and how do I fix it?
94683
Implement a pure virtual method in Objective-C
150853
An object reference is required to access non-static member
69180
onActivityResult() called prematurely
45196
Calling class method through NULL class pointer
66856
Method does not exist or incorrect signature?
60930
How to call asynchronous method from synchronous method in C#?
29404
What does "Incompatible types: void cannot be converted to ..." mean?
35590
How to fix NullPointerException in Java?
127599
Odd situation for "cannot reference this before supertype constructor has been called"
37988
System.NullPointerException: Attempt to de-reference a null object:
126921
Nonstatic method cannot be reference from a Static context
108938
Dealing with Scope in Object methods containing 'this' keyword called by Event Listeners
2831
Undefined reference to vtable
123381
How do I use IValidatableObject?
48221
Solving "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection" InvalidOperationException
2116
IllegalArgumentException or NullPointerException for a null parameter?