Google Web Toolkit (Beta)
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# Creating Custom Widgets

GWT makes it easy to create custom widgets entirely in the Java language.

## Composites

Composites are by far the most effective way to create new widgets. You can easily combine groups of existing widgets into a composite that is itself a reusable widget. Composite is a specialized widget that can contain another component (typically, a panel) but behaves as if it were its contained widget. Using Composite is preferable to attempting to create complex widgets by subclassing Panel because a composite usually wants to control which methods are publicly accessible without exposing those methods that it would inherit from its panel superclass. This is an example of how to create a composite.

## From Scratch in Java code

It is also possible to create a widget from scratch, although it is trickier since you have to write code at a lower level. Many of the basic widgets are written this way, such as Button and TextBox. Please refer to the implementations of these widgets to understand how to create your own.

## Using JavaScript

When implementing a custom widget that derives directly from the Widget base class, you may also write some of the widget's methods using JavaScript. This should generally be done only as a last resort, as it becomes necessary to consider the cross-browser implications of the native methods that you write, and also becomes more difficult to debug. For an example of this pattern in practice, see the TextBox widget and its underlying implementation.