Drowning in Images — Memory Management

Outlines best-practices and problems encountered managing bitmaps in an Android application

Transcript

1. dallasgutauckis
   DROWNING  IN  IMAGES  
   MEMORY  MANAGEMENT  
   

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2. github.com/dallasgutauckis
   Dallas  Gutauckis   dallas@gutauckis.com  
   h>p://dallasgutauckis.com  
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3. github.com/dallasgutauckis
   WHY  DO  I  NEED  TO  
   MANAGE  BITMAPS?  
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4. github.com/dallasgutauckis 4  
   FINITE  RESOURCES  
   

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5. github.com/dallasgutauckis
   TONS  OF  IMAGES  
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6. github.com/dallasgutauckis
   MEGAPIXELS  
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   (Lots of pixels -- not really big ones)
   
   

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7. github.com/dallasgutauckis
   CONVINCED  YET?  
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8. github.com/dallasgutauckis
   SO.  IT  CRASHES  
   SOMETIMES…  
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9. github.com/dallasgutauckis
   AND  YOU  GET  NEGATIVE  FEEDBACK  
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10. github.com/dallasgutauckis
    WHAT  SHOULD  I  DO?  
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11. github.com/dallasgutauckis
    IT'S  OBVIOUS  
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12. github.com/dallasgutauckis
    DOWNVOTE  THE  REVIEW  AND  
    MARK  IT  AS  SPAM  
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13. github.com/dallasgutauckis
    JUST  KIDDING  
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14. github.com/dallasgutauckis
    §  Use  a  download  manager  
    §  Don't  allow  mulRple  concurrent  downloads  of  the  same  image  
    §  Don't  download  on  the  UI  thread  
    §  Lists  (GridView,  ListView,  AdapterView)  
    §  Avoid  downloading  images  while  flinging  (use  ScrollListener)  
    §  Cache!  
    §  Bitmaps  stored  naRvely  vs.  on  applicaRon  heap  
    §  LruCache  (Least-­‐recently  used)  
    §  Override  sizeOf(String,  Bitmap)  
    §  Override  entryRemoved(boolean,  K,  V,  V)  
    §  OutOfMemoryError  
    §  Evict!  Recycle!  Resize!  
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15. github.com/dallasgutauckis
    §  RESAMPLE  
    §  Save  memory  when  determining  resample  factor,  just  decode  bounds  
     
    §  inSampleSize  to  tell  the  system  to  resample  
    §  Number  is  a  raRo  (1  pixel  for  every  X  original  pixels)  
    §  Factors  of  2  are  typically  more  performant  
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16. github.com/dallasgutauckis
    §  Avoid  the  ominous  "bitmap  is  recycled"  excepRon  
    §  Check  for  recycled  bitmaps  
    §  Bitmap#isRecycled();  
    §  ImageView#setImageBitmap(null);  
    §  Re-­‐download  
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    RuntimeException: trying to use a recycled bitmap
    android.graphics.Bitmap
    

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17. github.com/dallasgutauckis
    §  Trying  to  draw  recycled  bitmaps  
    §  Determining  the  size  of  a  Bitmap  by  decoding  the  enRre  Bitmap  
    §  Downloading  items  that  may  never  be  visible  
    §  LruCache  is  thread-­‐safe.  Synchronize!  
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18. github.com/dallasgutauckis
    §  I/O  Memory  Management  Talk  
    h>p://www.youtube.com/watch?v=_CruQY55HOk  
    §  Displaying  Bitmaps  Efficiently  
    h>p://developer.android.com/training/displaying-­‐bitmaps/index.html  
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