1. Tips and Tricks to
attack memory
problem in Android
Programming
Phạm Cao Trí – tripc@vng.com.vn
Lead Engineer – Zalo team – Zing

2. Agenda
• 1. Memory problems: Why?
• 2. Android Bitmaps: A closer look and some tips
• 3. Memory leaking: Demos, Detection methods
and Solutions.

3. 1. Memory
problems: Why?

4. 1.1. Memory problem:
Why?
• Limited heap size: 16MB, 32MB, 64MB,..
• Usually in decoding or manipulating bitmaps.
• Painful in solving memory problem for low-end devices

5. 2. Android Bitmaps:
A closer look and
some tips

6. 2.1. Android Bitmaps
• Java object
• Decode in native via Skia library (SkBitmap)
• Allocation:
• Pre Honeycomb (< 3.0): Native heap but “report” size to Dalvik VM.
• Honeycomb and beyond (>= 3.0): VM/Java heap

7. 2.1. Android Bitmaps (con’t)
• BitmapFactory.java: decodeResource ->.. -> nativeDecodeAsset
• BitmapFactory.cpp: nativeDecodeAsset -> doDecode

8. 2.1. Android Bitmaps (con’t)
• Pixel allocation policy lies within Graphics.cpp:

9. 2.1. Android Bitmaps (con’t)
• Graphics.cpp: createBitmap -> Bitmap.java: Bitmap constructor
• Pre-Honeycomb (< 3.0):
• Honeycomb and beyond (>= 3.0):

10. 2.1. Android Bitmaps (con’t)
• Pre-Gingerbread GC (< 2.3):
• Stop all app’s threads – not stop all applications
• Full heap collection
• Pause times often > 100ms
• Gingerbread and beyond (>= 2.3):
• Mostly concurrent
• Partial collections
• Pause times usually < 5ms
• Garbage collection in Android does no compacting.

11. 2.2. Bitmap cache
• Architecture

12. 2.2. Bitmap cache (con’t)
• Small tips:
• A better version:
• Honeycomb or later: android:largeHeap

13. 3. Memory leaking:
Demos, Detection
methods and Solutions

14. 3.1. Garbage collection
• Basic algorithm: Mark and Sweep
• Does no compacting
• Memory leak ?

15. 3.2. Demo memory leak
• Demo
• Detection Method:
• Code Review, Log and Heuristics

16. 3.3. Demo memory leak
• Detection Method:
• MAT
• Solution

17. 3.4. Common ways to leak
• Context Leak
• Handler Leak or Inner Class leak Outer
• Solution