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Android for Java Developers
This document provides an overview and agenda for an Android training session. It discusses the Android stack including the Linux kernel, native libraries, Dalvik VM, and application framework. It also demonstrates how to create a basic "Hello World" Android app project in Eclipse and describes the anatomy of a typical Android app with both Java code and XML components.
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Android for Java Developers
- 1. Android for Java Developers Marko Gargenta marakana.com © 2011
- 2. About Marko Gargenta Developer of Android Bootcamp for Marakana. Instructor for 1,000s of developers on Android at Qualcomm, Cisco, Motorola, Texas Instruments, Sony- Ericsson, Sharp, NetGear, DoD and other great orgs. Author of Learning Android published by O’Reilly. Speaker at OSCON, ACM, IEEE, SDC, AnDevCon. Founder of SFAndroid.org © 2011
- 3. Agenda • The Stack • Hello World! • Main Building Blocks • Designing an Android App • Android User Interface • OperaEng System Features • Debugging and Tools • Summary © 2011
- 4. ANDROID STACK ©2011
- 5. The Stack ©2011
- 6. Linux Kernel Android runs on Linux. Applications Home Contacts Phone Browser Other Linux provides: Hardware abstraction layer Application Framework Memory management Activity Window Content View Process management Manager Manager Providers System Package Telephony Resource Location Notiication Networking Manager Manager Manager Manager Manager Libraries Users never see Linux sub system Surface Media SQLite Android Runtime Manager Framework Core Libs The adb shell command opens OpenGL FreeType WebKit Delvik Linux shell SGL SSL libc VM Display Camera Linux Kernel Flash Binder Driver Driver Driver Driver Keypad WiFi Audio Power Driver Driver Driver Mgmt © 2011
- 7. NaEve Libraries Pieces borrowed from other Applications open source projects: Home Contacts Phone Browser Other Bionic, a super fast and small Application Framework license-friendly libc library optimized Activity Manager Window Manager Content Providers View System for Android Package Telephony Resource Location Notiication Manager Manager Manager Manager Manager WebKit library for fast HTML Libraries rendering Surface Manager Media Framework SQLite Android Runtime Core Libs OpenGL FreeType WebKit OpenGL for graphics Delvik VM SGL SSL libc Media codecs offer support for major audio/video codecs Display Camera Linux Kernel Flash Binder Driver Driver Driver Driver Keypad WiFi Audio Power Driver Driver Driver Mgmt SQLite database Much more… © 2011
- 8. Dalvik Dalvik VM is Android implementation of Java VM Dalvik is optimized for mobile devices: • Battery consumption • CPU capabilities Key Dalvik differences: • Register-based versus stack-based VM • Dalvik runs .dex files • More efficient and compact implementation • Different set of Java libraries than JDK © 2011
- 9. ApplicaEon Framework The rich set of system services Applications wrapped in an intuitive Java API. Home Contacts Phone Browser Other This ecosystem that developers Application Framework can easily tap into is what makes Activity Window Content View writing apps for Android easy. Manager Manager Providers System Package Telephony Resource Location Notiication Manager Manager Manager Manager Manager Location, web, telephony, WiFi, Libraries Bluetooth, notifications, media, Surface Manager Media Framework SQLite Android Runtime camera, just to name a few. Core Libs OpenGL FreeType WebKit Delvik VM SGL SSL libc Display Camera Linux Kernel Flash Binder Driver Driver Driver Driver Keypad WiFi Audio Power Driver Driver Driver Mgmt © 2011
- 10. ApplicaEons Dalvik Executable + Resources = APK Must be signed (but debug key is okay for development) Many markets with different policies © 2011
- 11. Android and Java Android Java = Java SE – AWT/Swing + Android API © 2011
- 12. HELLO WORLD! ©2011
- 13. Android SDK -‐ What’s In The Box SDK Tools Docs Platforms Data Skins Images Samples Add-ons Google © 2011
- 14. Create New Project Use the Eclipse tool to create a new Android project. Here are some key constructs: Project Eclipse construct Target minimum to run App name whatever Package Java package AcEvity Java class © 2011
- 15. Anatomy of An App Java Code + XML and Other Resources + Manifest File = Android App © 2011
- 16. The Manifest File <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.marakana" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".HelloAndroid" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="5" /> </manifest> © 2011
- 17. The Layout Resource <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> </LinearLayout> © 2011
- 18. The Java File package com.marakana; import android.app.Activity; import android.os.Bundle; public class HelloAndroid extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); } } © 2011
- 19. Running on Emulator Emulator, not a simulator © 2011
- 20. MAIN BUILDING BLOCKS © 2011
- 21. Yamba Demo Let’s see a real-world medium complexity Android app in action: Yamba: Yet Another Micro Blogging App © 2011
- 22. AcEviEes Android Application An Activity represents a screen Main Activity Another Activity Another Activity or a window. Sort of. © 2011
- 23. AcEvity Lifecycle Activities have a well- defined lifecycle. The Android OS manages your activity by changing its state. You fill in the blanks. © 2011
- 24. Intents Intents represent events or actions. They are to Android apps what hyperlinks are to websites. Sort of. Intents can be implicit or explicit. © 2011
- 25. Services Services are code that runs in the background. They can be started and stopped. Services doesn’t have UI. © 2011
- 26. Service Lifecycle Service also has a lifecycle, but it’s much simpler than activity’s. An activity typically starts and stops a service to do some work for it in the background, such as play music, check for new tweets, etc. Services can be bound or unbound. © 2011
- 27. Remote Services © 2011
- 28. Content Providers Content Providers share content with applications across application boundaries. Examples of built-in Content Providers are: Contacts, MediaStore, Settings and more. © 2011
- 29. Content Provider Example © 2011
- 30. Broadcast Receivers An Intent-based publish-subscribe mechanism. Great for listening system events such as SMS messages. © 2011
- 31. Architecture of An App An Android application is a collection of many different building blocks. They are loosely coupled and can be reconfigured by the developer easily, or at least that’s the intention. Let’s look at 7 stages of Yamba next. © 2011
- 32. Yamba Part 1 © 2011
- 33. Yamba Part 2 © 2011
- 34. Yamba Part 3 © 2011
- 35. Yamba Part 4 © 2011
- 36. Yamba Part 5 © 2011
- 37. Yamba Part 6 © 2011
- 38. Yamba Part 7 © 2011
- 39. ANDROID USER INTERFACE © 2011
- 40. Two UI Approaches Procedural DeclaraAve You write Java code You write XML code Similar to Swing or AWT Similar to HTML of a web page You can mix and match both styles. Best practice: • Start with XML and declare most of UI • Switch to Java and implement the UI logic © 2011
- 41. XML-‐Based User Interface Use WYSIWYG tools to build powerful XML-based UI. Easily customize it from Java. Separate concerns. © 2011
- 42. Views and Layouts Layouts contain widgets and other layouts forming a “composite” pattern. © 2011
- 43. Linear Layout One of the most commonly used layouts. It lays its children next to each other, either horizontally or vertically. © 2011
- 44. RelaEve Layout Children of relative layout are placed in relationship to each other. This layout is efficient. © 2011
- 45. Table Layout Table layout puts its children into table rows and columns. It is similar to an HTML table. © 2011
- 46. Frame Layout Frame layout places its children on top of each other, like a deck of cards. It is useful for widgets such as tabs or as a placeholder for views added programmatically. © 2011
- 47. Common UI Components Android UI includes many common modern UI widgets, such as Buttons, Tabs, Progress Bars, Date and Time Pickers, etc. © 2011
- 48. SelecEon Components Some UI widgets may be linked to zillion pieces of data. Examples are ListView and Spinners (pull-downs). © 2011
- 49. Adapters Adapter Data Source To make sure they run smoothly, Android uses Adapters to connect them to their data sources. A typical data source is an Array or a Database. © 2011
- 50. Complex Components Certain high-level components are simply available just like Views. Adding a Map or a Video to your application is almost like adding a Button or a piece of text. © 2011
- 51. Menus and Dialogs © 2011
- 52. Graphics & AnimaEon Android has rich support for 2D graphics. You can draw & animate from XML. You can use OpenGL for 3D graphics. © 2011
- 53. MulEmedia AudioPlayer lets you simply specify the audio resource and play it. VideoView is a View that you can drop anywhere in your activity, point to a video file and play it. XML: <VideoView android:id="@+id/video" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_gravity="center” /> Java: player = (VideoView) findViewById(R.id.video); player.setVideoPath("/sdcard/samplevideo.3gp"); player.start(); © 2011
- 54. OPERATING SYSTEM FEATURES © 2011
- 55. File System The file system has three main mount points. One for system, one for the apps, and one for whatever. Each app has its own sandbox easily accessible to it. No one else can access its data. The sandbox is in /data/data/com.marakana/ SDCard is expected to always be there. It’s a good place for large files, such as movies and music. Everyone can access it. © 2011
- 56. Cloud to Device Push Big deal for many pull-based apps. Will make devices use less battery. © 2011
- 57. Preferences Your app can support complex preferences quite easily. You define your preferences in an XML file and the corresponding UI and data storage is done for free. © 2011
- 58. SQLite Database Android ships with SQLite3 SQLite is a • Zero configuration • Serverless • Single database file • Cross-Platform • Compact • Public Domain Database engine. May you do good and not evil May you find forgiveness for yourself and forgive others May you share freely, never taking more than you give. © 2011
- 59. DEBUGGING ANDROID APPS © 2011
- 60. LogCat The universal, most versatile way to track what is going on in your app. Can be viewed via command line or Eclipse. Logs can be generated both from SDK Java code, or low-level C code via Bionic libc extension. © 2011
- 61. Debugger Your standard debugger is included in SDK, with all the usual bells & whistles. © 2011
- 62. TraceView TraceView helps you profile you application and find bottlenecks. It shows execution of various calls through the entire stack. You can zoom into specific calls. © 2011
- 63. Hierarchy Viewer Hierarchy Viewer helps you analyze your User Interface. Base UI tends to be the most “expensive” part of your application, this tool is very useful. © 2011
- 64. Summary Android is open and complete system for mobile development. It is based on Java and augmented with XML, with lower levels written in C/C++. It takes about 3-5 days of intensive training to learn Android application development for someone who has basic Java (or similar) experience. Marko Gargenta, Marakana.com marko@marakana.com +1-415-647-7000 © 2011