2 ================================================================================
4 Matt Styles wrote a tutorial on building SDL for Android with Visual Studio:
5 http://trederia.blogspot.de/2017/03/building-sdl2-for-android-with-visual.html
7 The rest of this README covers the Android gradle style build process.
9 If you are using the older ant build process, it is no longer officially
10 supported, but you can use the "android-project-ant" directory as a template.
13 ================================================================================
15 ================================================================================
17 Android SDK (version 19 or later)
18 https://developer.android.com/sdk/index.html
20 Android NDK r10e or later
21 https://developer.android.com/tools/sdk/ndk/index.html
23 Minimum API level supported by SDL: 14 (Android 4.0.1)
26 ================================================================================
28 ================================================================================
30 - Android applications are Java-based, optionally with parts written in C
31 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to
33 - This means that your application C code must be placed inside an Android
34 Java project, along with some C support code that communicates with Java
35 - This eventually produces a standard Android .apk package
37 The Android Java code implements an "Activity" and can be found in:
38 android-project/app/src/main/java/org/libsdl/app/SDLActivity.java
40 The Java code loads your game code, the SDL shared library, and
41 dispatches to native functions implemented in the SDL library:
42 src/core/android/SDL_android.c
45 ================================================================================
47 ================================================================================
49 For simple projects you can use the script located at build-scripts/androidbuild.sh
51 There's two ways of using it:
53 androidbuild.sh com.yourcompany.yourapp < sources.list
54 androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
56 sources.list should be a text file with a source file name in each line
57 Filenames should be specified relative to the current directory, for example if
58 you are in the build-scripts directory and want to create the testgles.c test, you'll
61 ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
63 One limitation of this script is that all sources provided will be aggregated into
64 a single directory, thus all your source files should have a unique name.
66 Once the project is complete the script will tell you where the debug APK is located.
67 If you want to create a signed release APK, you can use the project created by this
68 utility to generate it.
70 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
71 done in the build directory for the app!
74 For more complex projects, follow these instructions:
76 1. Copy the android-project directory wherever you want to keep your projects
77 and rename it to the name of your project.
78 2. Move or symlink this SDL directory into the "<project>/app/jni" directory
79 3. Edit "<project>/app/jni/src/Android.mk" to include your source files
80 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
82 If you want to use Android Studio (recommended), skip to the Android Studio section below.
84 5. Run './gradlew installDebug' in the project directory. This compiles the .java, creates an .apk with the native code embedded, and installs it on any connected Android device
86 Here's an explanation of the files in the Android project, so you can customize them:
89 build.gradle - build info including the application version and SDK
90 src/main/AndroidManifest.xml - package manifest. Among others, it contains the class name
91 of the main Activity and the package name of the application.
92 jni/ - directory holding native code
93 jni/Application.mk - Application JNI settings, including target platform and STL library
94 jni/Android.mk - Android makefile that can call recursively the Android.mk files in all subdirectories
95 jni/SDL/ - (symlink to) directory holding the SDL library files
96 jni/SDL/Android.mk - Android makefile for creating the SDL shared library
97 jni/src/ - directory holding your C/C++ source
98 jni/src/Android.mk - Android makefile that you should customize to include your source code and any library references
99 src/main/assets/ - directory holding asset files for your application
100 src/main/res/ - directory holding resources for your application
101 src/main/res/mipmap-* - directories holding icons for different phone hardware
102 src/main/res/values/strings.xml - strings used in your application, including the application name
103 src/main/java/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding to SDL. Be very careful changing this, as the SDL library relies on this implementation. You should instead subclass this for your application.
106 ================================================================================
107 Customizing your application name
108 ================================================================================
110 To customize your application name, edit AndroidManifest.xml and replace
111 "org.libsdl.app" with an identifier for your product package.
113 Then create a Java class extending SDLActivity and place it in a directory
114 under src matching your package, e.g.
116 src/com/gamemaker/game/MyGame.java
118 Here's an example of a minimal class file:
120 --- MyGame.java --------------------------
121 package com.gamemaker.game;
123 import org.libsdl.app.SDLActivity;
126 * A sample wrapper class that just calls SDLActivity
129 public class MyGame extends SDLActivity { }
131 ------------------------------------------
133 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
134 class, .e.g. "MyGame"
137 ================================================================================
138 Customizing your application icon
139 ================================================================================
141 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
142 the drawable directories under the res directory. There are several directories
143 for different screen sizes.
146 ================================================================================
148 ================================================================================
150 Any files you put in the "app/src/main/assets" directory of your project
151 directory will get bundled into the application package and you can load
152 them using the standard functions in SDL_rwops.h.
154 There are also a few Android specific functions that allow you to get other
155 useful paths for saving and loading data:
156 * SDL_AndroidGetInternalStoragePath()
157 * SDL_AndroidGetExternalStorageState()
158 * SDL_AndroidGetExternalStoragePath()
160 See SDL_system.h for more details on these functions.
162 The asset packaging system will, by default, compress certain file extensions.
163 SDL includes two asset file access mechanisms, the preferred one is the so
164 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
165 GC, but given this method does not work on compressed assets, there is also the
166 "Input Stream" method, which is automatically used as a fall back by SDL. You
167 may want to keep this fact in mind when building your APK, specially when large
169 For more information on which extensions get compressed by default and how to
170 disable this behaviour, see for example:
172 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
175 ================================================================================
176 Pause / Resume behaviour
177 ================================================================================
179 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
180 the event loop will block itself when the app is paused (ie, when the user
181 returns to the main Android dashboard). Blocking is better in terms of battery
182 use, and it allows your app to spring back to life instantaneously after resume
183 (versus polling for a resume message).
185 Upon resume, SDL will attempt to restore the GL context automatically.
186 In modern devices (Android 3.0 and up) this will most likely succeed and your
187 app can continue to operate as it was.
189 However, there's a chance (on older hardware, or on systems under heavy load),
190 where the GL context can not be restored. In that case you have to listen for
191 a specific message, (which is not yet implemented!) and restore your textures
192 manually or quit the app (which is actually the kind of behaviour you'll see
193 under iOS, if the OS can not restore your GL context it will just kill your app)
196 ================================================================================
197 Threads and the Java VM
198 ================================================================================
200 For a quick tour on how Linux native threads interoperate with the Java VM, take
201 a look here: https://developer.android.com/guide/practices/jni.html
203 If you want to use threads in your SDL app, it's strongly recommended that you
204 do so by creating them using SDL functions. This way, the required attach/detach
205 handling is managed by SDL automagically. If you have threads created by other
206 means and they make calls to SDL functions, make sure that you call
207 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
208 your thread automatically anyway (when you make an SDL call), but it'll never
212 ================================================================================
214 ================================================================================
216 You can use STL in your project by creating an Application.mk file in the jni
217 folder and adding the following line:
219 APP_STL := stlport_static
221 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
224 ================================================================================
225 Additional documentation
226 ================================================================================
228 The documentation in the NDK docs directory is very helpful in understanding the
229 build process and how to work with native code on the Android platform.
231 The best place to start is with docs/OVERVIEW.TXT
234 ================================================================================
236 ================================================================================
238 You can open your project directory with Android Studio and run it normally.
241 ================================================================================
243 ================================================================================
245 There are some good tips and tricks for getting the most out of the
246 emulator here: https://developer.android.com/tools/devices/emulator.html
248 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
250 Notice that this software emulator is incredibly slow and needs a lot of disk space.
251 Using a real device works better.
254 ================================================================================
256 ================================================================================
258 You can see if adb can see any devices with the following command:
262 You can see the output of log messages on the default device with:
266 You can push files to the device with:
268 adb push local_file remote_path_and_file
270 You can push files to the SD Card at /sdcard, for example:
272 adb push moose.dat /sdcard/moose.dat
274 You can see the files on the SD card with a shell command:
276 adb shell ls /sdcard/
278 You can start a command shell on the default device with:
282 You can remove the library files of your project (and not the SDL lib files) with:
286 You can do a build with the following command:
290 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
294 If your application crashes in native code, you can use addr2line to convert the
295 addresses in the stack trace to lines in your code.
297 For example, if your crash looks like this:
299 I/DEBUG ( 31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
300 I/DEBUG ( 31): r0 00000000 r1 00001000 r2 00000003 r3 400085d4
301 I/DEBUG ( 31): r4 400085d0 r5 40008000 r6 afd41504 r7 436c6a7c
302 I/DEBUG ( 31): r8 436c6b30 r9 435c6fb0 10 435c6f9c fp 4168d82c
303 I/DEBUG ( 31): ip 8346aff0 sp 436c6a60 lr afd1c8ff pc afd1c902 cpsr 60000030
304 I/DEBUG ( 31): #00 pc 0001c902 /system/lib/libc.so
305 I/DEBUG ( 31): #01 pc 0001ccf6 /system/lib/libc.so
306 I/DEBUG ( 31): #02 pc 000014bc /data/data/org.libsdl.app/lib/libmain.so
307 I/DEBUG ( 31): #03 pc 00001506 /data/data/org.libsdl.app/lib/libmain.so
309 You can see that there's a crash in the C library being called from the main code.
310 I run addr2line with the debug version of my code:
312 arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
314 and then paste in the number after "pc" in the call stack, from the line that I care about:
317 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
319 You can add logging to your code to help show what's happening:
321 #include <android/log.h>
323 __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
325 If you need to build without optimization turned on, you can create a file called
326 "Application.mk" in the jni directory, with the following line in it:
331 ================================================================================
333 ================================================================================
335 The best (and slowest) way to debug memory issues on Android is valgrind.
336 Valgrind has support for Android out of the box, just grab code using:
338 svn co svn://svn.valgrind.org/valgrind/trunk valgrind
340 ... and follow the instructions in the file README.android to build it.
342 One thing I needed to do on Mac OS X was change the path to the toolchain,
343 and add ranlib to the environment variables:
344 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
346 Once valgrind is built, you can create a wrapper script to launch your
347 application with it, changing org.libsdl.app to your package identifier:
349 --- start_valgrind_app -------------------
351 export TMPDIR=/data/data/org.libsdl.app
352 exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
353 ------------------------------------------
355 Then push it to the device:
357 adb push start_valgrind_app /data/local
359 and make it executable:
361 adb shell chmod 755 /data/local/start_valgrind_app
363 and tell Android to use the script to launch your application:
365 adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
367 If the setprop command says "could not set property", it's likely that
368 your package name is too long and you should make it shorter by changing
369 AndroidManifest.xml and the path to your class file in android-project/src
371 You can then launch your application normally and waaaaaaaiiittt for it.
372 You can monitor the startup process with the logcat command above, and
373 when it's done (or even while it's running) you can grab the valgrind
376 adb pull /sdcard/valgrind.log
378 When you're done instrumenting with valgrind, you can disable the wrapper:
380 adb shell setprop wrap.org.libsdl.app ""
383 ================================================================================
385 ================================================================================
387 If you are developing on a compatible Tegra-based tablet, NVidia provides
388 Tegra Graphics Debugger at their website. Because SDL2 dynamically loads EGL
389 and GLES libraries, you must follow their instructions for installing the
390 interposer library on a rooted device. The non-rooted instructions are not
391 compatible with applications that use SDL2 for video.
393 The Tegra Graphics Debugger is available from NVidia here:
394 https://developer.nvidia.com/tegra-graphics-debugger
397 ================================================================================
398 Why is API level 14 the minimum required?
399 ================================================================================
401 The latest NDK toolchain doesn't support targeting earlier than API level 14.
402 As of this writing, according to https://developer.android.com/about/dashboards/index.html
403 about 99% of the Android devices accessing Google Play support API level 14 or
404 higher (October 2017).
407 ================================================================================
408 A note regarding the use of the "dirty rectangles" rendering technique
409 ================================================================================
411 If your app uses a variation of the "dirty rectangles" rendering technique,
412 where you only update a portion of the screen on each frame, you may notice a
413 variety of visual glitches on Android, that are not present on other platforms.
414 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
415 contexts, in particular the use of the eglSwapBuffers function. As stated in the
416 documentation for the function "The contents of ancillary buffers are always
417 undefined after calling eglSwapBuffers".
418 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
419 is not possible for SDL as it requires EGL 1.4, available only on the API level
420 17+, so the only workaround available on this platform is to redraw the entire
423 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
426 ================================================================================
428 ================================================================================
430 - The number of buttons reported for each joystick is hardcoded to be 36, which
431 is the current maximum number of buttons Android can report.