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MDAD 3 - Android - System, Platform and Application Types
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- 2. Bibliography 1. Wallace Jackson,Android Apps for Absolute Beginners, Apress, 2017 2. Peter Späth, Learn Kotlin for Android Development, Apress 2019 3. Android Application Fundamentals, http://developer.android.com/guide/topics/f undamentals.html 2
- 3. Google Android Platform Developedby Google Based upon Linux Virtual Machine (Dalvik) & ART Open Source 3
- 4. Android Platform • Android –OS – Platform • Application types – Activities – Services – Content providers – Intents – Broadcast Revceivers 4
- 5. NOT only aOS • Radio Firmware – Phone system • GSM/CDMA / UMTS • Linux – Kernel 3.x • Android 4 and newer – Optimised forARM – X86 (Intel), MIPS • User Space Libraries – Bionic – SQLite – WebKit • Application platform 5
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- 7. Kernel • OS • Notvisible • Extended Machine – Hardware abstraction • Contains drivers • Manages – Processor – Peripherals • Audio • Video • GPS • WiFi – Input/Output – Network stack 7
- 8. Kernel - Optimizations •Memory Management – No swap – On demand application closing system • Power management – WAIT_LOCK • Specific IPC – Binder • AIDL • Synchronous call between processes 8
- 9. User Space Libraries •Programming libraries – Link between the kernel and programs – Screen display • printf (…) • scanf (…) – Network access • socket (…) • Bionic – Libc for Android 9
- 10. User Space Libraries •SQlite • WebKit • Surfaces • FreeType • Media Framework • OpenGL|ES • SSL • … 10
- 11. Dalvik - AndroidRuntime • Virtual Machine(Java) – Java 1.5 SE • Most of it • Missing – AWT / Swing – Imprimare – Alte componente speciale – Optimised for mobile • Small memory • Fast garbage collection – Different file format • .class -> .dex • JIT Compiler 11
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- 13. ART - AndroidRuntime • Environment for compiler and executer – Dalvik – Different file format • .dex -> .elf and odex • AOT • Includes a memory allocator 13
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- 18. Android Libraries • ForDalvik – Not user space libraries! • Written in Java/Kotlin • Access to the device’s functions – Phone – Messages – Sensors • Services – Window Manager – Audio Manager 18
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- 20. Features • Application API •Dalvik • Browser • Graphics – 2D optimised – 3D – OpenGL ES 1.0 • SQLite – Data base • Multimedia Support – Audio / Video • GSM/CDMA • Connectivity – Bluetooth – WiFi – GPRS / EDGE / 3G • Sensors – Photo camera – GPS / AGPS – Magnetometer – Accelerometer • Development platform – Command line – Android Studio 20
- 21. Programming • Dalvik (Application) –in Java/Kotlin – High speed – Access to many libraries • AJAX – In the browser (WebKit) – Slow – JavaScript • Native Development Kit (NDK) – C/C++ – Limited number of libraries – High speed – JNI Support – Not recommended for standard applications • C/C++ (directly for the system) 21
- 22. Application Security • Implementedin the kernel – Linux policy • Ext3 file system • Users can write only in their folder – Every application runs with its own user • Determined by the digital signature! • Group permissions – May write in • /data/name.package.application / • /SDCard/ – Works for any application type • Dalvik / AJAX / NDK / C/C++ 22
- 23. Application Security • Implementedin the Android Libraries – Permissions • Declared in the Manifest • Access device’s functions – Network – Phone / messages – Photo – GPS • Access to another application’s components – Permissions imposed by that application – User will be asked – at install (Android < 6) – at usage (Android >= 6) – Works only for Dalvik / ART applications 23
- 24. Programs (Dalvik) • Thereis no main() • Formed of components – Activities – Services – Intents – Content Providers – Broadcast Receivers • Components can run separately 24
- 25. Application (Dalvik) • APKFile – JAR uncompressed • Components – .dex File • Resources – Images – XML Files • Manifest – File with information – Digital signature • For development • For production – Authentic – Self signed 25
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- 27. Task (UI Application) •Runs in one process – usually! – There are exceptions • Stack of activities • Root activity – Add • Display • push – Remove • Hide • pop – Activities from other applications 27
- 28. Task (UI Application) •Runs in one process – usually! – There are exceptions • Stack of activities • Root activity – Add • Display • push – Remove • Hide • pop – Activities from other applications 28
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- 30. Funcții importante • ClassActivity – void onCreate (…); – void onStart (…); – void onRestart (…); – void onResume (…); – void onPause (…); – void onStop (…); – void onDestroy (…); • Must call parent functions – super.onCreate (…); – … 30
- 31. Activity • Window • Longerthan the process – Serializing – Partially controlled by the programmer • Not for a lot of processing 31
- 32. Services • Android Component •Specially for processing • Runs in background • process – Low priority – More stable (in time) 32
- 33. Service implementation • Extendsclass Service – Simple Service • void onCreate (); • void onStart (Intent intent, int startID); • void onDestroy (); – Using AIDL • void onBind (Intent intent); • void onUnbind(); 33
- 34. Content Providers /Broadcast Receivers • Content providers – Offer information – Link with SQLite – Based on URLs • Broadcast receivers – Observers – Public events • SCREEN_ON • SCREEN_OFF • BATTER_STATUS_CHANGED 34
- 35. Simulator vs. RealPhone • Simulator – Real • Boots Linux – Several versions • 2.3.3 • 4.0 • 4.1.2 – Runs separately • Real Phone – USB Debugging • Applications/Developmen t 35
- 36. Application template • AndroidManifest.xml •build.xml • default.properties • Bin – compiled files • res – drawable – layout – values • assets – resources – gen – Resources IDs (automatically generated) • Src – source files 36
- 37. Conclusions • Android Platform –Linux OS – Set of libraries for Android • Programming ways – Dalvik/ART – Java/Kotlin – AJAX – Web – NDK – C/C++ • Android Applications are a set of components – Activities – Services – Intents – Content Providers – Broadcast Receivers – There is no main() • Real emulator • Task – UI Applications – Set of Activities • Survive the process 37
- 38. Keywords • Operating System –Kernel – User Space Library • Linux – Process • Dalvik – Activity – Service – Content Provider – Intent – Broadcast Receiver • ART • Emulator • Security • Kernel (file system) • User Mode (Dalvik/ART) • Task – Activities Stack • Application State – Running – Paused – Stopped – Destroyed – Event • method call 38
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