Peter Wolf (Application architect)

Platform Architecutre

• Linux Kernel
  • _{threading, low-level memory management, drivers, security features (permissions, process isolation, IPC), application sandbox, system partition, netwroking}
• Hardware Abstration Layer
  • _{gigher level Java API framework fod device hardware (camera, Bluetooth, ...)}
• Android Runtime
  • _{virtual machine(s), AOT & JIT compilation, GC, debugging, profilling, diagnostic, crash reporting}
• Native C/C++ Libraries
  • _{application building blocks}
• System apps
  • _{default apps can be replaced}

 Application Components

• Intents & Intent Filters
  • _{to start an activity, to start a service, to deliver a broadcast}
• Activities
  • _{a screen with which users can interact; has a window to draw its interface – typically full screen}
• Services
• Content Providers
• Application Widgets

Activities

• Main activity – started by launcher, defined by intent filter
• Within a task activities are contained in back stack
• User interface = hierarchy of views
• Layout = android.view.ViewGroup
  • _{linear, grid, relative}
• onCreate
  • _{create views, bind data, restore state}
• onResume
  • _{in foreground, user input}
• onPause
  • _{commit unsaved changes, stop animations}

Saving Activity State

• onSaveInstanceState
  • _{default implementation does some job, use only for state of the UI, not to persist data}
• onRestoreInstanceState

Services

• Invoked via Intents
• Started Service
  • _{startService(), usually single operation, returns no results, stops itself in the end (by calling stopSelf()), can be stopped from outside by calling stopService(), i.e. upload/download file}
• Bound Service
  • _{bindService(), client-server interface, runs while it is bound, stops when all components unbind it (by calling unbindService())}
• Notifications to user via toasts or status bar

Content Providers

• Manage access to structured data
• Access via android.content.ContentResolver
• Share data with other applications
• Provide custom search suggestions
• Defined by URI
  • _{content://user_dictionary/words}
• API to retrieve data
• API to insert, update, or delete data
• Custom APIs

Application Widgets

• Mini application views that can be embedded in other application (home screen)

User Interface

• Composed of Views and ViewGroups
• Forms layout
• Standard controls
  • Input controls
    • _{button, text field, checkbox, radio button, toggle button, picker, spinner}
  • Input events (gestures)
    • _{click, long click, focus change, touch, context menu}
  • Menus
  • Settings
  • Dialogs
  • Notifications
  • Search
• Custom components

Best Practices

• Support multiple screens
• Support tablets and handsets
• Material Design
  • _{https://material.google.com/}