LayoutInflater

LayoutInflater is a component of the Android framework that converts XML layout resources into a hierarchy of View objects. It reads a layout file and creates the corresponding View instances in memory, which can then be inserted into a window or reused as part of a UI. The inflater uses information from the XML, including view classes, attributes, and theming, to instantiate and configure the views.

LayoutInflater is typically obtained via LayoutInflater.from(context) or Activity.getLayoutInflater(). It provides several inflate methods, with the most common being inflate(int resource, ViewGroup root, boolean attachToRoot). When attachToRoot is true, the inflated hierarchy is attached to the specified root; when false, the inflated root is returned and the root’s layout parameters are provided by the root (but no attachment occurs). Other overloads include inflate(int resource) and inflate(XmlPullParser, ViewGroup root, boolean attachToRoot).

Common usage includes activities calling setContentView(layoutResId), which inflates and attaches a layout, fragments inflating a view in onCreateView, and adapters inflating item layouts for each row. The root parameter helps apply proper LayoutParams to the inflated views, especially in lists and complex hierarchies.

LayoutInflater can be customized via a LayoutInflater.Factory or Factory2, allowing interception or substitution of view creation during inflation, which is useful for theming or replacing specific widgets.

Performance considerations include avoiding unnecessary inflation, reusing views in adapters, and using view binding or data binding to access views efficiently. Proper use of the root parameter and attachToRoot flag helps ensure correct layout behavior and parameter application.