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Bug 2370 - Accelerometer axes return weird/random values
Summary: Accelerometer axes return weird/random values
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: joystick (show other bugs)
Version: 2.0.1
Hardware: ARM Android (All)
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-01-27 19:04 UTC by Jairo Luiz
Modified: 2014-01-27 21:02 UTC (History)
2 users (show)

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Description Jairo Luiz 2014-01-27 19:04:43 UTC 
I found a bug when a try to read the accelerometer axes on android devices.
The values are a weird/random value for the first axis and 0 for ther others.

I search in the code and found a bug in this line:
https://hg.libsdl.org/SDL/file/af040fdf47e4/src/joystick/android/SDL_sysjoystick.c#l500

The "Android_JNI_GetAccelerometerValues" returns a boolean, indicating if the "values" array are been updated.
But you don't use this boolean. So, in the next lines, you try to read values from a uninitialized array, generating weird/unpredictable results.

I made this change in my project and that solved the problem for now:
https://bitbucket.org/tangerinagames/love-android-sdl2/commits/f4754554774fc92fb5acddab6aee322a670d5ba5?at=accelerometer

Thanks.
Comment 1 Gabriel Jacobo 2014-01-27 20:59:51 UTC 
Fixed, thanks! https://hg.libsdl.org/SDL/rev/47f67902b179
Comment 2 Jairo Luiz 2014-01-27 21:02:37 UTC 
Great!