Once you've defined the root element, you can add additional layout objects or widgets as child elements to gradually build a View hierarchy that defines your layout.

Using Android's XML vocabulary, you can quickly design UI layouts and the screen elements they contain, in the same way you create web pages in HTML - with a series of nested elements.Įach layout file must contain exactly one root element, which must be a View or ViewGroup object. Tip: To debug your layout at runtime, use the For example, you can declare your app's default layouts in XML, and then The Android framework gives you the flexibility to use either or both of these methods toīuild your app's UI. Using XML files also makes it easy to provide different layouts forĭifferent screen sizes and orientations (discussed further in Supporting Different Screen Sizes). YourĪpp can create View and ViewGroup objects (and manipulate their properties) programmatically.ĭeclaring your UI in XML allows you to separate the presentation of your app from the code thatĬontrols its behavior. Instantiate layout elements at runtime.To build your XML layout using a drag-and-drop interface. You can also use Android Studio's Layout Editor Vocabulary that corresponds to the View classes and subclasses, such as those for widgets and Provide a different layout structure, such as LinearLayout or ViewGroup objects are usually called 'layouts' can be one of many types that The View objects are usually called 'widgets' and can be one of many Illustration of a view hierarchy, which defines a Invisible container that defines the layout structure for View and otherįigure 1. A layout defines the structure for a user interface in your app, such as in an activity.Īll elements in the layout are built using a hierarchy of View andĭraws something the user can see and interact with.

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