Flutter globalkey currentstate null

by

Flutter GlobalKey currentState is Null

When working with Flutter, a GlobalKey is a unique identifier for widgets. It allows you to reference and interact with widgets from outside their own build methods.

Understanding GlobalKey and currentState

A GlobalKey can be used to maintain a reference to a widget’s State object, which provides access to the widget’s properties, methods, and state variables.

However, GlobalKey’s currentState property can be null in certain cases. Let’s explore some scenarios where this can happen.

Scenario 1: GlobalKey not associated with a widget

If a GlobalKey is not associated with any widget at any given moment, its currentState property will be null. For example:

    
      GlobalKey<MyWidgetState> myGlobalKey = GlobalKey(); // Creating a GlobalKey
      myGlobalKey.currentState; // Returns null

Scenario 2: GlobalKey current state accessed before widget build

If the currentState property is accessed before the widget associated with the GlobalKey has been built, it will return null. This is because the State object is created during the widget build process. For instance:

    
      GlobalKey<MyWidgetState> myGlobalKey = GlobalKey(); // Creating a GlobalKey
      MyWidget(key: myGlobalKey); // Creating the widget associated with the GlobalKey
      
      // Trying to access currentState before widget build
      myGlobalKey.currentState; // Returns null

Scenario 3: GlobalKey current state accessed in different build context

If the currentState property is accessed in a different build context than the one in which the GlobalKey was created, it will return null. The build context determines the position of the widget in the widget tree. Example:

    
      GlobalKey<MyWidgetState> myGlobalKey = GlobalKey(); // Creating a GlobalKey

      Widget build(BuildContext context) {
        // Trying to access currentState from different build context
        myGlobalKey.currentState; // Returns null
        // ...
      }

Using GlobalKey and accessing currentState

To ensure the currentState property of a GlobalKey is not null, you should follow these guidelines:

  • Assign the GlobalKey to the widget’s key parameter when defining the widget.
  • Access the currentState property after the associated widget has been built.
  • Access the currentState property from the same build context in which the GlobalKey was created.

Here’s an example:

    
      GlobalKey<MyWidgetState> myGlobalKey = GlobalKey(); // Creating a GlobalKey

      Widget build(BuildContext context) {
        return MyWidget(key: myGlobalKey);
      }

      void someFunction() {
        // Accessing currentState after widget build
        myGlobalKey.currentState.doSomething();
      }

By following these guidelines, you can successfully access the currentState property of a GlobalKey without encountering null values.

Leave a comment