G1 Development Environment and Applica4on Development. Adam C. Champion CSE 788X11 Prof. Dong Xuan

Transcription

1 G1 Development Environment and Applica4on Development Adam C. Champion CSE 788X11 Prof. Dong Xuan

2 Outline Introduc<on G1 development environment SeAng it up Hello Android example G1 applica<on development Mobile app dev rules Applica<on components GUI design and implementa<on

3 The Big Picture (1) The T Mobile G1 has many sensors you can easily program, e.g., Camera GPS, loca<on based services Accelerometer and orienta<on sensor (games) You can also program the G1 to Play music Work with online services, e.g., Google gdata Vibrate the phone when something happens

4 The Big Picture (2) Google has developed a set of Eclipse based tools and the Android SDK to program the G1 in Java Assump4on: you already know Java or can learn it very quickly All the apps on the G1 are wrixen in Java using this SDK, e.g., Amazon MP3, the Web browser, instant messenger,

5 Development Environment Setup (1) Development prerequisites: Download recent JDK from (version 6 preferable) Download Eclipse for Java Developers from Download the Android SDK from and unzip it to a directory (remember the directory!) setup =

6 Development Environment Setup (2) Within Eclipse, add ssl.google.com/ android/eclipse/ as a Soaware Update site (Help SoCware Update) Alterna<vely: use ssl.google.com/android/ eclipse/site.xml if an error occurs Download & install Google s Android Dev Tools plugin Restart Eclipse; go to Preferences (in Window menu, Eclipse menu on OS X), select Android, enter your SDK directory setup =

7 Development Environment Setup (3) You re in business!

8 Development Environment Tools (1) Android provides several dev tools: Hardware agnos<c mobile phone emulator Implements Dalvik, a Java VM op<mized for mobile devices Dalvik uses the Linux kernel to manage process isola<on, memory Dalvik Debug Monitor Service (DDMS) lets user monitor Dalvik threads, heap, log output, etc. Android Debug Bridge (ADB) provides interface between dev computer and G1 Android Asset Packaging Tool (AAPT) packages Android project files into an Android Package (.apk) file

9 Development Environment Tools (2) Google s Eclipse plugin seamlessly integrates all these tools Easy Android project management, edi<ng XML files/uis Automa<c AAPT compila<on to Android packages Eclipse runs your app on the emulator or your G1 phone if it s connected Debugging is straighlorward with the DDMS View

10 Example: Hello Android Eclipse demo on laptop If you plan to develop G1 apps, you should work through Google s simple Note Pad tutorial ( intro/tutorial.html) to get real hands on development experience

11 Key Mobile App Dev. Principles Mobile handsets are resource constrained devices: Short baxery life Small amount of memory, disk space Code must be fast users will only tolerate ms latency maximum and your apps must be responsive Avoid object crea<on, dynamic lookup, floats Launch resource intensive opera<ons in separate threads Always use UI elements to inform user of progress Save state and data whenever app could be interrupted (which is oaen!) Security: compartmentalize data within apps

12 Key Android Development Principles All of the above principles obviously apply to Android apps, with a few caveats: Android nondeterminis:cally kills processes when it s low on memory Android s nuclear op<on : if an app doesn t respond within 5 seconds, Android kills it

13 Android App Components Android apps have six building blocks : Ac4vity: app presenta<on layer (every screen in the app is an Ac<vity) Intent: instance of a message passing framework (abstracted, encapsulated ac<ons) Broadcast Receiver: global event listener that executes when the app broadcasts the corresponding Intent Content Provider: data store shared across apps Service: app s background worker, e.g., a fall down detector for seniors that watches for large accelera<ons No4fica4on: instance of a user no<fica<on framework (can make sound, vibrate phone, flash LED)

14 The AndroidManifest.xml file All of these components are bound together in the app s AndroidManifest.xml file Ac<vi<es and Services have <activity> and <service> tags, respec<vely The <intent filter> tag says what Intents launch which Ac<vi<es and Services Two permission related tags (for security) <uses permission> tag determines what permissions users must grant the app in order for it to work correctly, e.g., users must explicitly allow SMS and loca<on based services <permission> tags restrict access to app Eclipse provides a GUI to edit this file

15 Other App Resources Within a project s res directory, other app resources can be stored, e.g., Simple values (strings, colors, dimensions, arrays) Drawables (bitmaps and PNGs) Layouts for an Ac<vity s UI (best prac:ce MVC idiom) as well as UI styles and themes Anima<ons XML Raw resources, e.g., MP3 files Resources can be dynamically selected at run<me for different languages, screen orienta<ons, etc. Eclipse automa<cally generates the R.java file with all your app s resources, GUI layouts, etc. indexed by name

16 Android App Life Cycle Android apps have no control over their life cycles! Process classifica<on: Ac<ve Process (Ac<vity interac<ng with user, handling events) Visible Process (Ac<vity visible in background, not handling events e.g., a dialog box pops up) Started Service Process Background Process (invisible Ac<vity with no Services) Highest priority Empty Process (terminated process that Android caches for performance) Lowest priority (most likely to be killed)

17 Ac4vity Event Handling Android programming is event driven Ac<vity event handling methods are as follows: oncreate(): called at Ac<vity s birth, ini<alizes it onrestart(): called aaer oncreate() finishes, restores UI state onstart(): called when Ac<vity becomes visible onresume(): called when Ac<vity becomes ac<ve onsaveinstancestate(): called when Ac<vity becomes invisible, saves UI state changes onpause(): called when Ac<vity becomes inac<ve (save state here) onstop(): called when Ac<vity becomes invisible (save state here) ondestroy(): called at Ac<vity s death Your Ac<vi<es will need to implement some or all of these methods Source: R. Meier, Professional Android Applica:on Development

18 UI Design for Apps Good UI design is essen<al for your app to provide a pleasant user experience Android provides several means to build UIs and menus Android s UI terminology: Views are the basic class for visual interface controls (also known as widgets) ViewGroups extend the View class and can contain mul<ple Views, e.g., compound controls Ac<vi<es are the windows or screens shown to user Source: R. Meier, Professional Android Applica:on Development

19 Android Widget Views Android provides many standard Views, e.g., TextView: read only text label; EditText: editable text entry box ListView: displays values of items as TextViews in a list Spinner: combo box composite widget TextView showing currently selected item Dialog to select item from a ListView of items Button, CheckBox, RadioButton, See many more examples at android/reference/viewgallery.html

20 Android View Layouts Android provides 5 layouts ViewGroup extensions that control child widget posi<ons on screen FrameLayout: Pins each child View to top lea corner, each new View obscures the last LinearLayout: Adds each child View in a straight line, either horizontal or ver<cal RelativeLayout: Defines posi<ons of each child View rela<ve to other child views and screen boundaries TableLayout: Lays out Views in a grid of rows and columns AbsoluteLayout: Defines each child View s posi<on in absolute coordinates, can t dynamically adjust to new screen resolu<ons and orienta<ons Best prac:ce: define layouts and Views in XML with external resources as opposed to genera<ng them in code (c.f. Java Swing dev.) Google provides thorough documenta<on on layouts at

21 Modifying Views and Layouts You can easily modify Android s exis<ng Views and layouts by defining the new View or layout in XML and extending the respec<ve class, e.g., TextView and LinearLayout For modifica<ons, override the following event handling methods: ondraw() method to draw customized widgets onmeasure() method to determine how much space to use You must call setmeasureddimension() in the overridden onmeasure() to avoid throwing an excep<on onkeydown(), onkeyup(), ontrackballevent(), ontouchevent() methods handle pressing any device key, releasing a pressed key, moving trackball, interac<on with touch screen Make sure you before the method defini<on, call corresponding super.method() immediately Best prac:ce: make as many drawn objects class scoped as possible and create them in the constructor

22 Android s Menu System Android s menu system is ini<ated when you press the Menu buxon (obviously!) The menu system has not one but three types of menus: Icon menu: displays up to 6 items with or without icons, no checkboxes or radio buxons Expanded menu: If there are more than 6 items, a More entry appears in the menu Selec<ng More brings up the expanded menu, which can include checkboxes and radio buxons But you cannot force Android to display the expanded menu first Submenu When user selects a submenu in the icon menu, a dialog box pops up Checkboxes and radio buxons are allowed in this dialog Confused yet? There s yet another type of menu

23 Context Menus Context menus are View specific and are triggered by pressing trackball or screen for 3 seconds Example: at the home screen, press the screen for a few seconds You can move icons around, delete them You can add pictures, Google search, an analog clock, and music playlists to the home screen If you swipe the screen lea and right, you ll find a total of 3 screens on which you can insert these items

24 Implemen4ng Android Menus (1) Override Ac<vity s oncreateoptionsmenu(menu menu) method to create menu Use the menu.add(groupid, menuitemid, itemorder, itemtext) call to add a menu item Checkboxes: Invoke setcheckable(true) on the add() call above, i.e., add( ).setcheckable(true) Radio buxons: Add several menu items with the same groupid, then call menu.setgroupcheckable(groupid, true, true) Shortcut keys: Call setshortcut(a, b) on a MenuItem object, e.g., item, where a and b are the keys to use with a numeric keypad and full keyboard, respec<vely

25 Implemen4ng Android Menus (2) Condensed 4tles: Call item.settitlecondensed( ) to set icon menu text Icons: Call item.seticon(r.drawable.iconname) to set the icon that s displayed only in the icon menu Make sure you have the icon file stored in res/drawable directory (Eclipse automa<cally updates R.java so icon can be sta<cally accessed by name).png files are preferred, e.g., iconname.png Click listener: call item.setonmenuitemclicklistener() This is inefficient; you should override onoptionsitemselected() Intent: Call item.setintent() to trigger an Intent Caveat: item must not already be handled by the Ac<vity s onoptionsitemselected() method or a click listener Within oncreateoptionsmenu(), you can dynamically update menu You can also create submenus by calling menu.addsubmenu() No nested submenus allowed Call seticon(), setheadericon() on SubMenu to set icon, header icon

26 Implemen4ng Android Menus (3) Override onoptionsitemselected() to handle menu selec<ons Simply get the MenuItem s ID by calling getitemid() and run dispatcher control logic Create context menus in one of two ways: Override oncreatecontextmenu() for a given View Best prac:ce: Override oncreatecontextmenu() to create Ac<vity specific context menus and register the Views that use it by calling registerforcontextmenu() in oncreate() Context menus can be populated dynamically at run<me by specifying View data & asking if other Android apps support ac<ons for it, e.g., copy/paste text Override oncontextitemselected() to handle context menu selec<ons

27 Other Topics Please see Reto Meier s Professional Android Applica:on Development book for much more detail on advanced Android programming, e.g., loca<on based services Presently, there are certain things you can t program the G1 to do yet Record music as it is played Bluetooth connec<vity Google Talk instant messaging Video recording Accessing the underlying phone hardware Google may add some of this func<onality as well as a touchscreen keyboard in an upcoming firmware/sdk update that should be released in Q1 2009

28 Ques4ons or Comments? Thank you!

29 References Reto Meier, Professional Android Applica:on Development, Wiley, 2009 essen4al reading Online documenta<on at documentation