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)
Denis Bernard
Background information: http://android-developers.blogspot.fr/2010/09/one-screen-turn-deserves-another.html and http://developer.android.com/reference/android/hardware/SensorEvent.html
Right now, the Android accelerometer event handler feeds raw accelerometer data to the SDL Joystick driver. The result is that for landscape-only applications, the axis need to be swapped if running on a portrait device (like a phone), and vice-versa: running a portrait only app on a landscape device like a tablet.
The purpose of this patch is to perform coordinate remapping of the accelerometer data before feeding it to the SDL joystick driver so that the X axis of the joystick is always aligned with the X axis of the display, same for the Y axis.
This has been tested on applications that support screen orientation changes as well as applications with fixed screen orientations, both on phones and tablets.
Denis Bernard
This patch to Android.mk adds support for static linking of libSDL for Android applications. A patched readme with static build instructions is also provided.
It does not break existing build environments setup according to the README-android.txt since the static library version will not be built in not required.
The static build uses the Android NDK module system (see docs/IMPORT-MODULE.html in the NDK folder and step 5 in the instructions below).
Instructions:
1. Copy the android-project directory wherever you want to keep your projects
and rename it to the name of your project.
2. Create a symlink to SDL/src/main/android/SDL_android_main.c as
<project>/jni/src/SDL_android_main.c
3. Rename <project>/jni/src/Android_static.mk to <project>/jni/src/Android.mk
(overwrite the existing one)
4. Edit <project>/jni/src/Android.mk to include your source files
5. create and export an environment variable named NDK_MODULE_PATH that points
to the parent directory of this SDL directory. e.g.:
export NDK_MODULE_PATH="$PWD"/..
6. Edit <project>/src/org/libsdl/app/SDLActivity.java and remove the call to
System.loadLibrary("SDL2") line 42.
7. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
Although this requires an environment variable to be setup, it can be added once and for all to the main Android.mk of the project.
On Android available touch devices are now added with video initialization (like
the keyboard). This fixes SDL_GetNumTouchDevices() returning 0 before any touch
events happened although there is a touch screen available. The adding of touch
devices after a touch event was received is still active to allow connecting
devices later (if this is possible) and to provide a fallback if the new init
did not work somehow. For the implementation JNI was used and API level 9 is
required. There seems to be nothing in the Android NDK's input header (input.h)
to implement everything on C side without communication with Java side.
If the app is in landscape mode and the user presses the power button, a pause
is followed immediately by a surfaceChanged event because the lock screen
is shown in portrait mode. This triggers a "false" resume.
So, we just pause and resume following the onWindowFocusChanged events.
Also, wait for SDL_APP_WILLENTERBACKGROUND and SDL_APP_DIDENTERBACKGROUND before
blocking the event pump.
