What is GlobalKey and how it works?

person shubham sharmafolder_openFlutterlocal_offeraccess_time September 20, 2023

GlobalKey is a special key in Flutter that provides a way to uniquely identify a widget across the entire application. It allows you to reference and interact with a specific widget from anywhere in your code.

Here’s how GlobalKey works:

  1. Unique Identifier:
    • GlobalKey is a unique identifier that you can assign to a widget. This key is used to distinguish one instance of a widget from another, even if they are of the same type.
  2. Scope Across the Application:
    • Unlike regular Key objects, which are only unique within the context of a single widget subtree, a GlobalKey is unique across the entire application.
  3. Accessing Widgets from Anywhere:
    • Once a widget is associated with a GlobalKey, you can use that key to reference the widget from anywhere in your code, regardless of its location in the widget tree.
  4. Manipulating Widgets:
    • With a GlobalKey, you can perform operations on the widget it’s associated with, such as changing its properties, triggering its methods, or even removing it from the widget tree.
  5. Use Cases:
    • Form Submission: GlobalKey can be used in forms to access and validate form fields before submission.
    • Scrolling and Focus: It’s often used in conjunction with ScrollController and FocusNode to manage scrolling behavior or focus traversal across different parts of the UI.
    • Managing State in Parent Widgets: It can be used by a parent widget to interact with or retrieve the state of its child widget.
    • Integration with Native Code: GlobalKey can be used to integrate Flutter widgets with native code, allowing you to perform platform-specific operations.
  6. Creation and Association:
    • You typically create a GlobalKey and associate it with a widget using the GlobalKey() constructor, like this:GlobalKey<FormState> formKey = GlobalKey<FormState>(); You then pass this key to the widget’s key property.
  7. Finding Widgets with GlobalKey:
    • You can use the currentContext property of a GlobalKey to get the BuildContext associated with the widget. From there, you can use BuildContext‘s methods, like findRenderObject(), to locate the widget in the widget tree.
  8. Performance Considerations:
    • While GlobalKey provides powerful capabilities, it should be used judiciously. Overuse of GlobalKey can lead to complex code and potentially impact performance, so it’s best reserved for cases where it’s truly necessary.
  9. Lifecycle Management:
    • It’s important to manage the lifecycle of a GlobalKey properly. For example, if a widget associated with a GlobalKey is disposed, you should also dispose the key to avoid memory leaks.

In summary, GlobalKey is a powerful tool in Flutter that allows you to uniquely identify and interact with widgets across the entire application. It’s particularly useful for scenarios where you need to access widgets from different parts of your codebase. However, it should be used thoughtfully to maintain code readability and performance.

warningComments are closed.