[Solved] Why we need to implement certain methods when we extend classes in android? [closed]

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They are abstract classes/methods and need to be overridden. You can choose to override the functionality or just let it do what the parent classs is doing.

An abstract class is a class that is declared abstract—it may or may
not include abstract methods. Abstract classes cannot be instantiated,
but they can be subclassed.

An abstract method is a method that is declared without an
implementation (without braces, and followed by a semicolon), like
this:

abstract void moveTo(double deltaX, double deltaY);

If a class
includes abstract methods, then the class itself must be declared
abstract, as in:

public abstract class GraphicObject {
   // declare fields
   // declare nonabstract methods
   abstract void draw();
}

When an abstract class is subclassed, the subclass usually provides
implementations for all of the abstract methods in its parent class.
However, if it does not, then the subclass must also be declared
abstract.

solved Why we need to implement certain methods when we extend classes in android? [closed]