Question

Can any one tell me about
what is the Difference between validateProperties() and invalidateProperties() ?

Answer 1

invalidateProperties:

Marks a component so that its commitProperties() method gets called
during a later screen update.

Invalidation is a useful mechanism for eliminating duplicate work by
delaying processing of changes to a component until a later screen
update. For example, if you want to change the text color and size, it
would be wasteful to update the color immediately after you change it
and then update the size when it gets set. It is more efficient to
change both properties and then render the text with its new size and
color once.

Invalidation methods rarely get called. In general, setting a property
on a component automatically calls the appropriate invalidation
method.

validateProperties:

Used by layout logic to validate the properties of a component by
calling the commitProperties() method. In general, subclassers should
override the commitProperties() method and not this method.

Essentially, validate calls commitProperties directly while invalidate waits for the next frame to do it. Always use invalidate.