FrameLayout

A FrameLayout is a layout container in Android development that is designed to stack child views on top of each other. When you add multiple child views to a FrameLayout, they are all drawn at the top-left corner of the FrameLayout by default. You can then control the positioning of these child views within the FrameLayout by using layout parameters, such as gravity.

The primary use case for FrameLayout is for implementing features where you want to display multiple elements that can overlap, such as a background image with overlaid text or buttons. It is also commonly used as a container for fragments, allowing for dynamic content replacement within a specific area of the screen. For example, you might use a FrameLayout to hold a placeholder for a fragment, and then later swap out that fragment to display different content without affecting other parts of the UI.

When positioning child views within a FrameLayout, you can use attributes like android:layout_gravity. For instance, setting android:layout_gravity to "center" will center that specific child view within the FrameLayout. Similarly, "top", "bottom", "left", and "right" can be used to align views to the edges. Multiple gravity attributes can be combined, for example, "bottom|right" would align the view to the bottom-right corner. Due to its simple stacking nature, FrameLayout is generally the most performant layout when you only need to stack views.