update function don't work

[songotag]

Hello
,

I tried your code and the function : key.currentState.updateSpeed(120, animate: true,duration: Duration(milliseconds: 400));

return this error : The method 'updateSpeed' can't be unconditionally invoked because the receiver can be 'null'. Try making the call conditional (using '?.') or adding a null check to the target ('!').

[songotag]

I found the solution :

key.currentState?.updateSpeed(globals.Byte_Speed_1, animate: true, duration: Duration(milliseconds: 400));