Fixed bug 2156 - Android: Accelerometer values fed to joystick driver are inverted for the X axis and wrong for Z
authorSam Lantinga <slouken@libsdl.org>
Sun, 20 Oct 2013 23:52:02 -0700
changeset 7864 fdada7e3b3e7
parent 7863 c6b33210e610
child 7865 f2a42ca4ddf0
Fixed bug 2156 - Android: Accelerometer values fed to joystick driver are inverted for the X axis and wrong for Z Denis Bernard Background information: http://developer.android.com/reference/android/hardware/SensorEvent.html#values Steps to reproduce: compile testjoystick.c as an android app (change screen size according to your device). While running the app, also run: adb logcat -c; adb logcat -s 'SDL:*' 'SDL/APP:*' When tilting the device left/right, the joystick moves in the opposite direction of what one would expect. Or at least, the behaviour is not consistent with the Y axis. Also when the device sits on a table (obviously not moving), the Z axis value oscillates between -32000 and +32000 (by overflow): I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32511 I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32575 I/SDL/APP ( 1994): Joystick 0 axis 2 value: 32383 I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32386 I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32450 I/SDL/APP ( 1994): Joystick 0 axis 2 value: -32578 This is caused by the accelerometer yielding a constant value around 9.81 for Z and feeding something like 0.9 to 1.1 to the joystick driver, resulting in the overflow. Proposed fix in SDLActivity.java (swap X and subtract G from Z reading)
android-project/src/org/libsdl/app/SDLActivity.java
--- a/android-project/src/org/libsdl/app/SDLActivity.java	Sun Oct 20 23:23:25 2013 -0700
+++ b/android-project/src/org/libsdl/app/SDLActivity.java	Sun Oct 20 23:52:02 2013 -0700
@@ -642,9 +642,9 @@
                     y = event.values[1];
                     break;
             }
-            SDLActivity.onNativeAccel(x / SensorManager.GRAVITY_EARTH,
+            SDLActivity.onNativeAccel(-x / SensorManager.GRAVITY_EARTH,
                                       y / SensorManager.GRAVITY_EARTH,
-                                      event.values[2] / SensorManager.GRAVITY_EARTH);
+                                      event.values[2] / SensorManager.GRAVITY_EARTH - 1);
         }
     }