Slides for the talk "Beginning Android Games" at Apps World 2012 by Mario Zechner @badlogicgames http://www.badlogicgames.com http://libgdx.badlogicgames.com

1. Beginning Android Games
Mario Zechner

2. Who am I?

3. Who am I?

4. Who am I?

5. Who am I?

6. Who am I?

7. Who am I?

8. Who am I?

9. Who am I?

10. Who am I?
@badlogicgames
http://www.badlogicgames.com/

11. What I‘ll Talk About
• Why Android?
• What‘s in a game?
• Android for game developers
• Frameworks & engines

12. Why Android?

13. Why Android?

14. Why Android?

15. Why Android?
… or how to not make an infographic …

16. Why Android?
A Gaming Machine For Everyone!

17. What‘s in a Game?

18. What‘s in a Game?
DESIGN

19. What‘s in a Game?

20. What‘s in a Game?

21. What‘s in a Game?

22. What‘s in a Game?

23. What‘s in a Game?

24. What‘s in a Game?

25. What‘s in a Game?
Technology

26. What‘s in a Game?
• Window & Life-Cycle Management
• File I/O
• Input Devices
• Audio
• Graphics
• Networking
• Social Media Integration
• Payment System
• Tools
• … you actually read all of this?

27. Android for Game Developers

28. Android for Game Developers
+ Tooling + Performance
+ API Access + Portability
- Performance - Tooling
- Portability - API Access

29. Android for Game Developers

30. Android for Game Developers

31. Android for Game Developers
• Store files in
– APK (read-only)
– Internal Storage (read/write, limited space)
– External Storage (read/write)
• SharedPreferences for simple settings
• GOTCHAS
– APK size limit (50mb)
– Asset file compression bug until Android 2.3
– No direct access via NDK in older Android versions

32. Android for Game Developers
• OnTouchListener and OnKeyListener on
View
• SensorManager for
compass, accelerometer, gyro, …
• USB/NFC since Android 3+
• GOTCHAS
– Horrible Touch API
– Multi-touch broken on many devices

33. Android for Game Developers
• SoundPool for sound effects
• MediaPlayer for streaming music
• OpenSL ES in C/C++
setVolumeControlStream(AudioManager.STREAM_MUSIC);
soundPool = new SoundPool(20, AudioManager.STREAM_MUSIC,
0);
• GOTCHAS
explosionId = soundPool.load(descriptor, 1);
soundPool.play(explosionId, 1, 1, 0, 0, 1);
– High latency (+100ms)
– Broken drivers mediaPlayer = new MediaPlayer()
mediaPlayer.setDataSource(descriptor.getFileDescriptor(),
descriptor.getStartOffset(), descriptor.getLength());
mediaPlayer.prepare();
mediaPlayer.setLooping(true);
mediaPlayer.start()

34. Android for Game Developers
Canvas OpenGL ES
canvas.drawRGB(255, 255, 255);
paint.setColor(Color.RED);
canvas.drawLine(0, 0, canvas.getWidth()-1, canvas.getHeight()-1, paint);
paint.setStyle(Style.STROKE);
paint.setColor(0xff00ff00);
canvas.drawCircle(canvas.getWidth()/2, canvas.getHeight()/2, 40, paint);
paint.setStyle(Style.FILL);
paint.setColor(0x770000ff);
canvas.drawRect(100, 100, 200, 200, paint);
+ Ease-of-Use + Performance
- Performance + 2D / 3D
- 2D-only - Ease-of-Use

35. Android for Game Developers
Canvas OpenGL ES
canvas.drawRGB(255, 255, 255);
paint.setColor(Color.RED);
canvas.drawLine(0, 0, canvas.getWidth()-1, canvas.getHeight()-1, paint);
paint.setStyle(Style.STROKE);
paint.setColor(0xff00ff00);
canvas.drawCircle(canvas.getWidth()/2, canvas.getHeight()/2, 40, paint);
paint.setStyle(Style.FILL);
paint.setColor(0x770000ff);
canvas.drawRect(100, 100, 200, 200, paint);
+ Ease-of-Use + Performance
- Performance + 2D / 3D
- 2D-only - Ease-of-Use
MY GOD, IT‘S FULL OF GOTCHAS

36. Android for Game Developers
Canvas OpenGL ES
canvas.drawRGB(255, 255, 255);
paint.setColor(Color.RED);
canvas.drawLine(0, 0, canvas.getWidth()-1, canvas.getHeight()-1, paint);
paint.setStyle(Style.STROKE);
paint.setColor(0xff00ff00);
canvas.drawCircle(canvas.getWidth()/2, canvas.getHeight()/2, 40, paint);
paint.setStyle(Style.FILL);
paint.setColor(0x770000ff);
canvas.drawRect(100, 100, 200, 200, paint);
+ Ease-of-Use + Performance
- Performance + 2D / 3D
- 2D-only - Ease-of-Use
MY GOD, IT‘S FULL OF GOTCHAS

37. Android for Game Developers
• Bugs in shader compilers
• Deviations from OpenGL ES specification
• Highly varying performance
• GPU dependent optimizations
• Texture compression formats
• …

38. Android for Game Developers
• And if you use Java …
• Garbage Collector pauses (+200ms)
• Varying maximum heap memory
• Direct ByteBuffers and Bitmaps counted
against Java heap
• Method call overhead

39. Android for Game Developers
• A lot better since 2.2, great since 4.0
• Concurrent GC
• JIT
• Tons of bug fixes
• GOTCHA

40. Android for Game Developers

41. Android for Game Developers
FRAGMENTATION

42. Android for Game Developers
Screen Sizes, Aspect Ratios, Resolutions

43. Android for Game Developers
• Pick target resolution/aspect ratio
• Stretch or Clip on other aspect ratios
• Ship multiple asset sizes
• We‘ve done this on the PC, we can do it on
Android!

44. Android for Game Developers

45. Android for Game Developers
• Device-specific driver bugs (audio, OpenGL ES)
• Android version-specific bugs
• Multiple test devices (3-4)
– PowerVR, Mali, Snapdragon, Tegra
– Low-end to high-end phones
– Tablet
• Or use a framework/engine!

46. Frameworks & Engines
Not exhaustive, visit
http://mobilegameengines.com/

47. Frameworks & Engines
$$$
Free
$$$
Free
$$$
Free
Free
$$$
Not exhaustive, visit
http://mobilegameengines.com/

48. WIP

49. • Java (lots of C/C++ under the hood)
• Develop on the desktop 90% of the time (no
slow deploys, no emulator madness)
• Abstraction layers
– Low-level: OpenGL ES, file i/o, input, audio, ...
– Mid-level: shaders, textures, linalg, …
– High-level: fonts, sprites, scene graph, …
• Pick and choose, see feature list
http://libgdx.badlogicgames.com/features.html

51. Spine, 2D skeletal animation editor
https://plus.google.com/100248578810918104811

52. Source & Releases
http://libgdx.badlogicgames.com/download.html
Docs
http://libgdx.badlogicgames.com/documentation.html
Forum
http://badlogicgames.com/forum/
Blog
http://www.badlogicgames.com
IRC
irc.freenode.org, #libgdx

53. Questions?
@badlogicgames
http://www.badlogicgames.com/