docs/README-android.md
author Sam Lantinga <slouken@libsdl.org>
Mon, 23 Oct 2017 15:23:43 -0700
changeset 11647 5816b27073a4
parent 11432 04dd43a2c83a
child 11649 fe6769530709
permissions -rw-r--r--
Switched to new style gradle Android application build process
     1 Android
     2 ================================================================================
     3 
     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
     6 
     7 The rest of this README covers the traditional style build process.
     8 
     9 
    10 ================================================================================
    11  Requirements
    12 ================================================================================
    13 
    14 Android SDK (version 16 or later)
    15 https://developer.android.com/sdk/index.html
    16 
    17 Android NDK r7 or later
    18 https://developer.android.com/tools/sdk/ndk/index.html
    19 
    20 Minimum API level supported by SDL: 10 (Android 2.3.3)
    21 Joystick support is available for API level >= 12 devices.
    22 
    23 
    24 ================================================================================
    25  How the port works
    26 ================================================================================
    27 
    28 - Android applications are Java-based, optionally with parts written in C
    29 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to 
    30   the SDL library
    31 - This means that your application C code must be placed inside an Android 
    32   Java project, along with some C support code that communicates with Java
    33 - This eventually produces a standard Android .apk package
    34 
    35 The Android Java code implements an "Activity" and can be found in:
    36 android-project/app/src/main/java/org/libsdl/app/SDLActivity.java
    37 
    38 The Java code loads your game code, the SDL shared library, and
    39 dispatches to native functions implemented in the SDL library:
    40 src/core/android/SDL_android.c
    41 
    42 
    43 ================================================================================
    44  Building an app
    45 ================================================================================
    46 
    47 For simple projects you can use the script located at build-scripts/androidbuild.sh
    48 
    49 There's two ways of using it:
    50 
    51     androidbuild.sh com.yourcompany.yourapp < sources.list
    52     androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
    53 
    54 sources.list should be a text file with a source file name in each line
    55 Filenames should be specified relative to the current directory, for example if
    56 you are in the build-scripts directory and want to create the testgles.c test, you'll
    57 run:
    58 
    59     ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
    60 
    61 One limitation of this script is that all sources provided will be aggregated into
    62 a single directory, thus all your source files should have a unique name.
    63 
    64 Once the project is complete the script will tell you where the debug APK is located.
    65 If you want to create a signed release APK, you can use the project created by this
    66 utility to generate it.
    67 
    68 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
    69 done in the build directory for the app!
    70 
    71 
    72 For more complex projects, follow these instructions:
    73     
    74 1. Copy the android-project directory wherever you want to keep your projects
    75    and rename it to the name of your project.
    76 2. Move or symlink this SDL directory into the "<project>/app/jni" directory
    77 3. Edit "<project>/app/jni/src/Android.mk" to include your source files
    78 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
    79 
    80 If you want to use Android Studio (recommended), skip to the Android Studio section below.
    81 
    82 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
    83 
    84 Here's an explanation of the files in the Android project, so you can customize them:
    85 
    86     android-project/app
    87         build.gradle            - build info including the application version and SDK
    88         src/main/AndroidManifest.xml	- package manifest. Among others, it contains the class name
    89         			  of the main Activity and the package name of the application.
    90         jni/			- directory holding native code
    91         jni/Application.mk	- Application JNI settings, including target platform and STL library
    92         jni/Android.mk		- Android makefile that can call recursively the Android.mk files in all subdirectories
    93         jni/SDL/		- (symlink to) directory holding the SDL library files
    94         jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
    95         jni/src/		- directory holding your C/C++ source
    96         jni/src/Android.mk	- Android makefile that you should customize to include your source code and any library references
    97         src/main/assets/	- directory holding asset files for your application
    98         src/main/res/		- directory holding resources for your application
    99         src/main/res/mipmap-*	- directories holding icons for different phone hardware
   100         src/main/res/values/strings.xml	- strings used in your application, including the application name
   101         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.
   102 
   103 
   104 ================================================================================
   105  Customizing your application name
   106 ================================================================================
   107 
   108 To customize your application name, edit AndroidManifest.xml and replace
   109 "org.libsdl.app" with an identifier for your product package.
   110 
   111 Then create a Java class extending SDLActivity and place it in a directory
   112 under src matching your package, e.g.
   113 
   114     src/com/gamemaker/game/MyGame.java
   115 
   116 Here's an example of a minimal class file:
   117 
   118     --- MyGame.java --------------------------
   119     package com.gamemaker.game;
   120     
   121     import org.libsdl.app.SDLActivity; 
   122     
   123     /**
   124      * A sample wrapper class that just calls SDLActivity 
   125      */ 
   126     
   127     public class MyGame extends SDLActivity { }
   128     
   129     ------------------------------------------
   130 
   131 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   132 class, .e.g. "MyGame"
   133 
   134 
   135 ================================================================================
   136  Customizing your application icon
   137 ================================================================================
   138 
   139 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   140 the drawable directories under the res directory. There are several directories
   141 for different screen sizes.
   142 
   143 
   144 ================================================================================
   145  Loading assets
   146 ================================================================================
   147 
   148 Any files you put in the "app/src/main/assets" directory of your project
   149 directory will get bundled into the application package and you can load
   150 them using the standard functions in SDL_rwops.h.
   151 
   152 There are also a few Android specific functions that allow you to get other
   153 useful paths for saving and loading data:
   154 * SDL_AndroidGetInternalStoragePath()
   155 * SDL_AndroidGetExternalStorageState()
   156 * SDL_AndroidGetExternalStoragePath()
   157 
   158 See SDL_system.h for more details on these functions.
   159 
   160 The asset packaging system will, by default, compress certain file extensions.
   161 SDL includes two asset file access mechanisms, the preferred one is the so
   162 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   163 GC, but given this method does not work on compressed assets, there is also the
   164 "Input Stream" method, which is automatically used as a fall back by SDL. You
   165 may want to keep this fact in mind when building your APK, specially when large
   166 files are involved.
   167 For more information on which extensions get compressed by default and how to
   168 disable this behaviour, see for example:
   169     
   170 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   171 
   172 
   173 ================================================================================
   174  Pause / Resume behaviour
   175 ================================================================================
   176 
   177 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   178 the event loop will block itself when the app is paused (ie, when the user
   179 returns to the main Android dashboard). Blocking is better in terms of battery
   180 use, and it allows your app to spring back to life instantaneously after resume
   181 (versus polling for a resume message).
   182 
   183 Upon resume, SDL will attempt to restore the GL context automatically.
   184 In modern devices (Android 3.0 and up) this will most likely succeed and your
   185 app can continue to operate as it was.
   186 
   187 However, there's a chance (on older hardware, or on systems under heavy load),
   188 where the GL context can not be restored. In that case you have to listen for
   189 a specific message, (which is not yet implemented!) and restore your textures
   190 manually or quit the app (which is actually the kind of behaviour you'll see
   191 under iOS, if the OS can not restore your GL context it will just kill your app)
   192 
   193 
   194 ================================================================================
   195  Threads and the Java VM
   196 ================================================================================
   197 
   198 For a quick tour on how Linux native threads interoperate with the Java VM, take
   199 a look here: https://developer.android.com/guide/practices/jni.html
   200 
   201 If you want to use threads in your SDL app, it's strongly recommended that you
   202 do so by creating them using SDL functions. This way, the required attach/detach
   203 handling is managed by SDL automagically. If you have threads created by other
   204 means and they make calls to SDL functions, make sure that you call
   205 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
   206 your thread automatically anyway (when you make an SDL call), but it'll never
   207 detach it.
   208 
   209 
   210 ================================================================================
   211  Using STL
   212 ================================================================================
   213 
   214 You can use STL in your project by creating an Application.mk file in the jni
   215 folder and adding the following line:
   216 
   217     APP_STL := stlport_static
   218 
   219 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   220 
   221 
   222 ================================================================================
   223  Additional documentation
   224 ================================================================================
   225 
   226 The documentation in the NDK docs directory is very helpful in understanding the
   227 build process and how to work with native code on the Android platform.
   228 
   229 The best place to start is with docs/OVERVIEW.TXT
   230 
   231 
   232 ================================================================================
   233  Using Android Studio
   234 ================================================================================
   235 
   236 You can open your project directory with Android Studio and run it normally.
   237 
   238 
   239 ================================================================================
   240  Using the emulator
   241 ================================================================================
   242 
   243 There are some good tips and tricks for getting the most out of the
   244 emulator here: https://developer.android.com/tools/devices/emulator.html
   245 
   246 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   247 
   248 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   249 Using a real device works better.
   250 
   251 
   252 ================================================================================
   253  Troubleshooting
   254 ================================================================================
   255 
   256 You can see if adb can see any devices with the following command:
   257 
   258     adb devices
   259 
   260 You can see the output of log messages on the default device with:
   261 
   262     adb logcat
   263 
   264 You can push files to the device with:
   265 
   266     adb push local_file remote_path_and_file
   267 
   268 You can push files to the SD Card at /sdcard, for example:
   269 
   270     adb push moose.dat /sdcard/moose.dat
   271 
   272 You can see the files on the SD card with a shell command:
   273 
   274     adb shell ls /sdcard/
   275 
   276 You can start a command shell on the default device with:
   277 
   278     adb shell
   279 
   280 You can remove the library files of your project (and not the SDL lib files) with:
   281 
   282     ndk-build clean
   283 
   284 You can do a build with the following command:
   285 
   286     ndk-build
   287 
   288 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   289 
   290     ndk-build V=1
   291 
   292 If your application crashes in native code, you can use addr2line to convert the
   293 addresses in the stack trace to lines in your code.
   294 
   295 For example, if your crash looks like this:
   296 
   297     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   298     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   299     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   300     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   301     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   302     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   303     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   304     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   305     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   306 
   307 You can see that there's a crash in the C library being called from the main code.
   308 I run addr2line with the debug version of my code:
   309 
   310     arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   311 
   312 and then paste in the number after "pc" in the call stack, from the line that I care about:
   313 000014bc
   314 
   315 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   316 
   317 You can add logging to your code to help show what's happening:
   318 
   319     #include <android/log.h>
   320     
   321     __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   322 
   323 If you need to build without optimization turned on, you can create a file called
   324 "Application.mk" in the jni directory, with the following line in it:
   325 
   326     APP_OPTIM := debug
   327 
   328 
   329 ================================================================================
   330  Memory debugging
   331 ================================================================================
   332 
   333 The best (and slowest) way to debug memory issues on Android is valgrind.
   334 Valgrind has support for Android out of the box, just grab code using:
   335 
   336     svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   337 
   338 ... and follow the instructions in the file README.android to build it.
   339 
   340 One thing I needed to do on Mac OS X was change the path to the toolchain,
   341 and add ranlib to the environment variables:
   342 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   343 
   344 Once valgrind is built, you can create a wrapper script to launch your
   345 application with it, changing org.libsdl.app to your package identifier:
   346 
   347     --- start_valgrind_app -------------------
   348     #!/system/bin/sh
   349     export TMPDIR=/data/data/org.libsdl.app
   350     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   351     ------------------------------------------
   352 
   353 Then push it to the device:
   354 
   355     adb push start_valgrind_app /data/local
   356 
   357 and make it executable:
   358 
   359     adb shell chmod 755 /data/local/start_valgrind_app
   360 
   361 and tell Android to use the script to launch your application:
   362 
   363     adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   364 
   365 If the setprop command says "could not set property", it's likely that
   366 your package name is too long and you should make it shorter by changing
   367 AndroidManifest.xml and the path to your class file in android-project/src
   368 
   369 You can then launch your application normally and waaaaaaaiiittt for it.
   370 You can monitor the startup process with the logcat command above, and
   371 when it's done (or even while it's running) you can grab the valgrind
   372 output file:
   373 
   374     adb pull /sdcard/valgrind.log
   375 
   376 When you're done instrumenting with valgrind, you can disable the wrapper:
   377 
   378     adb shell setprop wrap.org.libsdl.app ""
   379 
   380 
   381 ================================================================================
   382  Graphics debugging
   383 ================================================================================
   384 
   385 If you are developing on a compatible Tegra-based tablet, NVidia provides
   386 Tegra Graphics Debugger at their website. Because SDL2 dynamically loads EGL
   387 and GLES libraries, you must follow their instructions for installing the
   388 interposer library on a rooted device. The non-rooted instructions are not
   389 compatible with applications that use SDL2 for video.
   390 
   391 The Tegra Graphics Debugger is available from NVidia here:
   392 https://developer.nvidia.com/tegra-graphics-debugger
   393 
   394 
   395 ================================================================================
   396  Why is API level 10 the minimum required?
   397 ================================================================================
   398 
   399 API level 10 is the minimum required level at runtime (that is, on the device) 
   400 because SDL requires some functionality for running not
   401 available on older devices. Since the incorporation of joystick support into SDL,
   402 the minimum SDK required to *build* SDL is version 16. Devices running API levels
   403 10-11 are still supported, only with the joystick functionality disabled.
   404 
   405 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
   406 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
   407 has since then been obsoleted, with the recommendation to developers to bump the
   408 required API level to 10.
   409 As of this writing, according to https://developer.android.com/about/dashboards/index.html
   410 about 90% of the Android devices accessing Google Play support API level 10 or
   411 higher (March 2013).
   412 
   413 
   414 ================================================================================
   415  A note regarding the use of the "dirty rectangles" rendering technique
   416 ================================================================================
   417 
   418 If your app uses a variation of the "dirty rectangles" rendering technique,
   419 where you only update a portion of the screen on each frame, you may notice a
   420 variety of visual glitches on Android, that are not present on other platforms.
   421 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   422 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   423 documentation for the function "The contents of ancillary buffers are always 
   424 undefined after calling eglSwapBuffers".
   425 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   426 is not possible for SDL as it requires EGL 1.4, available only on the API level
   427 17+, so the only workaround available on this platform is to redraw the entire
   428 screen each frame.
   429 
   430 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   431 
   432 
   433 ================================================================================
   434  Known issues
   435 ================================================================================
   436 
   437 - The number of buttons reported for each joystick is hardcoded to be 36, which
   438 is the current maximum number of buttons Android can report.
   439