Android UI Development

• A typical application will include
  • Acitivties (MainActivity as entry point)
  • Views (Screen layouts, ViewGroups)
  • Intents (multiple Activity screens

Layouts

• Defines the structure of a user interface in your app
• Can be nested
• When you compile your app, each XML layout file is compiled into a view source

View (Widget)

Properties

• background colour
• Text
• Font alignment
• Size
• Padding/margin
• etc.

Event Listener and Handlers

• Respond to various events such as click, long-click, focus change etc.

Set focus

• Set focus on a specific view requestFocus() or use XML tag <requestFocus />

Visibility

• You can hide or show views using setVisibility()

Linear Layout

• A view group that aligns all children in a single direction, vertically or horizontally
• All children of a LinearLayout are stacked one after the other
  • A vertical list will only have one child per row
  • A horizontal list will only be one row high

Orientation - vertical or horizontal?

Fill model - how will the child be filling the parent

Weight - assigns an "importance" value to view in terms how much space it would occupy on the screen

Relative Layout

• A ViewGroup that display child views in relative positions
• The position of each view can be specified as
  • Relative to sibling elements
  • In positions relative to the parent

Constraint Layout

• Similar to RelativeLayout
  • All views are laid out according to relationships with others