a single screen; can invoke functionality from other applications.
long-running operations in background; has no UI.
retrieves/stores data; system uses it to manage a shared set of app data
responds to system-wide messages (normal or ordered) ; very lightweight
messages that link app components together (explicit or implicit)
declare features, components, and version compatibility. Sets app permissions.
Activity Created -> Activity Running -> returns to app or gets destroyed.
event-driven notifications; even app can link to it!
display app info on homescreen; keep users engaged!
cloud to device messages
the server "pushes" messages (data) to app.
defined by XML layout files, a hierarchy of View & ViewGroup
comprised by res folder, esp. R.java. Qualifiers of these allow different device configs.
supporting multiple screens
Think web style layout. Provide density assets and size layouts
devices have these to make more fluid experience with environment (accelerometer, gyroscope, etc.)
multitasking, regular updates, and offline availability granted.
make tasks, tweaks, setting changes, and UI accessible.
in conjunction with Activity lifecycle; Set up feedback mechanisms and consult an app designer to ensure this.