1. Memory Problems
In Android Programming
Trí Phạm – 2013
techcaotri@gmail.com

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. 2.1. Android Bitmaps (con’t)
• Decode bitmaps bugs on Android Gingerbread and
previous versions ( <= 2.3):
– https://code.google.com/p/android/issues/detail?id=8488
– If the native Bitmap allocation size plus the current
HeapSize (NOT the actually allocated size)
exceeds the limits, native Bitmap allocation will
always fail

12. 2.2. Bitmap cache
• Architecture

13. 2.2. Bitmap cache (con’t)
• Small tips:
– A better version:
• Honeycomb or later: android:largeHeap

14. 3. MEMORY LEAKING: DEMOS,
DETECTION METHODS AND
SOLUTIONS

15. 3.1. Garbage collection
• Basic algorithm: Mark and Sweep
• Does no compacting
• Memory leak ?

16. 3.2. Demo memory leak 1
• Demo 1
• Detection Method: Code Review and
Heuristics
• Solution

17. 3.3. Demo memory leak 2
• Demo 2
• Detection Method: MAT
• Solution

18. 3.4. Common ways to leak
• Context Leak
• Handler Leak or Inner Class leak Outer
• Solution

19. Q & A