docs/README-android.md
author Ryan C. Gordon <icculus@icculus.org>
Wed, 18 Oct 2017 23:49:46 -0400
changeset 11634 ced7925b7a95
parent 11432 04dd43a2c83a
permissions -rw-r--r--
Check correct variable for malloc() results.
     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 old style build process.
     8 
     9 ================================================================================
    10  Requirements
    11 ================================================================================
    12 
    13 Android SDK (version 16 or later)
    14 https://developer.android.com/sdk/index.html
    15 
    16 Android NDK r7 or later
    17 https://developer.android.com/tools/sdk/ndk/index.html
    18 
    19 Minimum API level supported by SDL: 10 (Android 2.3.3)
    20 Joystick support is available for API level >= 12 devices.
    21 
    22 ================================================================================
    23  How the port works
    24 ================================================================================
    25 
    26 - Android applications are Java-based, optionally with parts written in C
    27 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to 
    28   the SDL library
    29 - This means that your application C code must be placed inside an Android 
    30   Java project, along with some C support code that communicates with Java
    31 - This eventually produces a standard Android .apk package
    32 
    33 The Android Java code implements an "Activity" and can be found in:
    34 android-project/src/org/libsdl/app/SDLActivity.java
    35 
    36 The Java code loads your game code, the SDL shared library, and
    37 dispatches to native functions implemented in the SDL library:
    38 src/core/android/SDL_android.c
    39 
    40 Your project must include some glue code that starts your main() routine:
    41 src/main/android/SDL_android_main.c
    42 
    43 
    44 ================================================================================
    45  Building an app
    46 ================================================================================
    47 
    48 For simple projects you can use the script located at build-scripts/androidbuild.sh
    49 
    50 There's two ways of using it:
    51 
    52     androidbuild.sh com.yourcompany.yourapp < sources.list
    53     androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
    54 
    55 sources.list should be a text file with a source file name in each line
    56 Filenames should be specified relative to the current directory, for example if
    57 you are in the build-scripts directory and want to create the testgles.c test, you'll
    58 run:
    59 
    60     ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
    61 
    62 One limitation of this script is that all sources provided will be aggregated into
    63 a single directory, thus all your source files should have a unique name.
    64 
    65 Once the project is complete the script will tell you where the debug APK is located.
    66 If you want to create a signed release APK, you can use the project created by this
    67 utility to generate it.
    68 
    69 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
    70 done in the build directory for the app!
    71 
    72 
    73 For more complex projects, follow these instructions:
    74     
    75 1. Copy the android-project directory wherever you want to keep your projects
    76    and rename it to the name of your project.
    77 2. Move or symlink this SDL directory into the "<project>/jni" directory
    78 3. Edit "<project>/jni/src/Android.mk" to include your source files
    79 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
    80 
    81 If you want to use the Eclipse IDE, skip to the Eclipse section below.
    82 
    83 5. Create "<project>/local.properties" and use that to point to the Android SDK directory, by writing a line with the following form:
    84 
    85        sdk.dir=PATH_TO_ANDROID_SDK
    86 
    87 6. Run 'ant debug' in android/project. This compiles the .java and eventually 
    88    creates a .apk with the native code embedded
    89 7. 'ant debug install' will push the apk to the device or emulator (if connected)
    90 
    91 Here's an explanation of the files in the Android project, so you can customize them:
    92 
    93     android-project/
    94         AndroidManifest.xml	- package manifest. Among others, it contains the class name
    95         			  of the main Activity and the package name of the application.
    96         build.properties	- empty
    97         build.xml		- build description file, used by ant. The actual application name
    98         			  is specified here.
    99         default.properties	- holds the target ABI for the application, android-10 and up
   100         project.properties	- holds the target ABI for the application, android-10 and up
   101         local.properties	- holds the SDK path, you should change this to the path to your SDK
   102         jni/			- directory holding native code
   103         jni/Android.mk		- Android makefile that can call recursively the Android.mk files
   104         			  in all subdirectories
   105         jni/SDL/		- (symlink to) directory holding the SDL library files
   106         jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
   107         jni/src/		- directory holding your C/C++ source
   108         jni/src/Android.mk	- Android makefile that you should customize to include your 
   109                                   source code and any library references
   110         res/			- directory holding resources for your application
   111         res/drawable-*		- directories holding icons for different phone hardware. Could be
   112         			  one dir called "drawable".
   113         res/layout/main.xml	- Usually contains a file main.xml, which declares the screen layout.
   114         			  We don't need it because we use the SDL video output.
   115         res/values/strings.xml	- strings used in your application, including the application name
   116         			  shown on the phone.
   117         src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
   118         			  to SDL.  Be very careful changing this, as the SDL library relies
   119         			  on this implementation.
   120 
   121 
   122 ================================================================================
   123  Build an app with static linking of libSDL
   124 ================================================================================
   125 
   126 This build uses the Android NDK module system.
   127 
   128 Instructions:
   129 1. Copy the android-project directory wherever you want to keep your projects
   130    and rename it to the name of your project.
   131 2. Rename "<project>/jni/src/Android_static.mk" to "<project>/jni/src/Android.mk"
   132    (overwrite the existing one)
   133 3. Edit "<project>/jni/src/Android.mk" to include your source files
   134 4. create and export an environment variable named NDK_MODULE_PATH that points
   135    to the parent directory of this SDL directory. e.g.:
   136 
   137        export NDK_MODULE_PATH="$PWD"/..
   138 
   139 5. Edit "<project>/src/org/libsdl/app/SDLActivity.java" and remove the call to
   140    System.loadLibrary("SDL2").
   141 6. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
   142 
   143 
   144 ================================================================================
   145  Customizing your application name
   146 ================================================================================
   147 
   148 To customize your application name, edit AndroidManifest.xml and replace
   149 "org.libsdl.app" with an identifier for your product package.
   150 
   151 Then create a Java class extending SDLActivity and place it in a directory
   152 under src matching your package, e.g.
   153 
   154     src/com/gamemaker/game/MyGame.java
   155 
   156 Here's an example of a minimal class file:
   157 
   158     --- MyGame.java --------------------------
   159     package com.gamemaker.game;
   160     
   161     import org.libsdl.app.SDLActivity; 
   162     
   163     /**
   164      * A sample wrapper class that just calls SDLActivity 
   165      */ 
   166     
   167     public class MyGame extends SDLActivity { }
   168     
   169     ------------------------------------------
   170 
   171 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   172 class, .e.g. "MyGame"
   173 
   174 ================================================================================
   175  Customizing your application icon
   176 ================================================================================
   177 
   178 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   179 the drawable directories under the res directory. There are four directories for
   180 different screen sizes. These can be replaced with one dir called "drawable",
   181 containing an icon file "ic_launcher.png" with dimensions 48x48 or 72x72.
   182 
   183 You may need to change the name of your icon in AndroidManifest.xml to match
   184 this icon filename.
   185 
   186 ================================================================================
   187  Loading assets
   188 ================================================================================
   189 
   190 Any files you put in the "assets" directory of your android-project directory
   191 will get bundled into the application package and you can load them using the
   192 standard functions in SDL_rwops.h.
   193 
   194 There are also a few Android specific functions that allow you to get other
   195 useful paths for saving and loading data:
   196 * SDL_AndroidGetInternalStoragePath()
   197 * SDL_AndroidGetExternalStorageState()
   198 * SDL_AndroidGetExternalStoragePath()
   199 
   200 See SDL_system.h for more details on these functions.
   201 
   202 The asset packaging system will, by default, compress certain file extensions.
   203 SDL includes two asset file access mechanisms, the preferred one is the so
   204 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   205 GC, but given this method does not work on compressed assets, there is also the
   206 "Input Stream" method, which is automatically used as a fall back by SDL. You
   207 may want to keep this fact in mind when building your APK, specially when large
   208 files are involved.
   209 For more information on which extensions get compressed by default and how to
   210 disable this behaviour, see for example:
   211     
   212 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   213 
   214 ================================================================================
   215  Pause / Resume behaviour
   216 ================================================================================
   217 
   218 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   219 the event loop will block itself when the app is paused (ie, when the user
   220 returns to the main Android dashboard). Blocking is better in terms of battery
   221 use, and it allows your app to spring back to life instantaneously after resume
   222 (versus polling for a resume message).
   223 
   224 Upon resume, SDL will attempt to restore the GL context automatically.
   225 In modern devices (Android 3.0 and up) this will most likely succeed and your
   226 app can continue to operate as it was.
   227 
   228 However, there's a chance (on older hardware, or on systems under heavy load),
   229 where the GL context can not be restored. In that case you have to listen for
   230 a specific message, (which is not yet implemented!) and restore your textures
   231 manually or quit the app (which is actually the kind of behaviour you'll see
   232 under iOS, if the OS can not restore your GL context it will just kill your app)
   233 
   234 ================================================================================
   235  Threads and the Java VM
   236 ================================================================================
   237 
   238 For a quick tour on how Linux native threads interoperate with the Java VM, take
   239 a look here: https://developer.android.com/guide/practices/jni.html
   240 
   241 If you want to use threads in your SDL app, it's strongly recommended that you
   242 do so by creating them using SDL functions. This way, the required attach/detach
   243 handling is managed by SDL automagically. If you have threads created by other
   244 means and they make calls to SDL functions, make sure that you call
   245 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
   246 your thread automatically anyway (when you make an SDL call), but it'll never
   247 detach it.
   248 
   249 ================================================================================
   250  Using STL
   251 ================================================================================
   252 
   253 You can use STL in your project by creating an Application.mk file in the jni
   254 folder and adding the following line:
   255 
   256     APP_STL := stlport_static
   257 
   258 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   259 
   260 ================================================================================
   261  Additional documentation
   262 ================================================================================
   263 
   264 The documentation in the NDK docs directory is very helpful in understanding the
   265 build process and how to work with native code on the Android platform.
   266 
   267 The best place to start is with docs/OVERVIEW.TXT
   268 
   269 
   270 ================================================================================
   271  Using Eclipse
   272 ================================================================================
   273 
   274 First make sure that you've installed Eclipse and the Android extensions as described here:
   275 	https://developer.android.com/tools/sdk/eclipse-adt.html
   276 
   277 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   278  * File -> New -> Other
   279  * Select the Android -> Android Project wizard and click Next
   280  * Enter the name you'd like your project to have
   281  * Select "Create project from existing source" and browse for your project directory
   282  * Make sure the Build Target is set to Android 3.1 (API 12)
   283  * Click Finish
   284 
   285 
   286 ================================================================================
   287  Using the emulator
   288 ================================================================================
   289 
   290 There are some good tips and tricks for getting the most out of the
   291 emulator here: https://developer.android.com/tools/devices/emulator.html
   292 
   293 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   294 
   295 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   296 Using a real device works better.
   297 
   298 ================================================================================
   299  Troubleshooting
   300 ================================================================================
   301 
   302 You can create and run an emulator from the Eclipse IDE:
   303  * Window -> Android SDK and AVD Manager
   304 
   305 You can see if adb can see any devices with the following command:
   306 
   307     adb devices
   308 
   309 You can see the output of log messages on the default device with:
   310 
   311     adb logcat
   312 
   313 You can push files to the device with:
   314 
   315     adb push local_file remote_path_and_file
   316 
   317 You can push files to the SD Card at /sdcard, for example:
   318 
   319     adb push moose.dat /sdcard/moose.dat
   320 
   321 You can see the files on the SD card with a shell command:
   322 
   323     adb shell ls /sdcard/
   324 
   325 You can start a command shell on the default device with:
   326 
   327     adb shell
   328 
   329 You can remove the library files of your project (and not the SDL lib files) with:
   330 
   331     ndk-build clean
   332 
   333 You can do a build with the following command:
   334 
   335     ndk-build
   336 
   337 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   338 
   339     ndk-build V=1
   340 
   341 If your application crashes in native code, you can use addr2line to convert the
   342 addresses in the stack trace to lines in your code.
   343 
   344 For example, if your crash looks like this:
   345 
   346     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   347     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   348     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   349     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   350     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   351     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   352     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   353     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   354     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   355 
   356 You can see that there's a crash in the C library being called from the main code.
   357 I run addr2line with the debug version of my code:
   358 
   359     arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   360 
   361 and then paste in the number after "pc" in the call stack, from the line that I care about:
   362 000014bc
   363 
   364 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   365 
   366 You can add logging to your code to help show what's happening:
   367 
   368     #include <android/log.h>
   369     
   370     __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   371 
   372 If you need to build without optimization turned on, you can create a file called
   373 "Application.mk" in the jni directory, with the following line in it:
   374 
   375     APP_OPTIM := debug
   376 
   377 
   378 ================================================================================
   379  Memory debugging
   380 ================================================================================
   381 
   382 The best (and slowest) way to debug memory issues on Android is valgrind.
   383 Valgrind has support for Android out of the box, just grab code using:
   384 
   385     svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   386 
   387 ... and follow the instructions in the file README.android to build it.
   388 
   389 One thing I needed to do on Mac OS X was change the path to the toolchain,
   390 and add ranlib to the environment variables:
   391 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   392 
   393 Once valgrind is built, you can create a wrapper script to launch your
   394 application with it, changing org.libsdl.app to your package identifier:
   395 
   396     --- start_valgrind_app -------------------
   397     #!/system/bin/sh
   398     export TMPDIR=/data/data/org.libsdl.app
   399     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   400     ------------------------------------------
   401 
   402 Then push it to the device:
   403 
   404     adb push start_valgrind_app /data/local
   405 
   406 and make it executable:
   407 
   408     adb shell chmod 755 /data/local/start_valgrind_app
   409 
   410 and tell Android to use the script to launch your application:
   411 
   412     adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   413 
   414 If the setprop command says "could not set property", it's likely that
   415 your package name is too long and you should make it shorter by changing
   416 AndroidManifest.xml and the path to your class file in android-project/src
   417 
   418 You can then launch your application normally and waaaaaaaiiittt for it.
   419 You can monitor the startup process with the logcat command above, and
   420 when it's done (or even while it's running) you can grab the valgrind
   421 output file:
   422 
   423     adb pull /sdcard/valgrind.log
   424 
   425 When you're done instrumenting with valgrind, you can disable the wrapper:
   426 
   427     adb shell setprop wrap.org.libsdl.app ""
   428 
   429 ================================================================================
   430  Graphics debugging
   431 ================================================================================
   432 
   433 If you are developing on a compatible Tegra-based tablet, NVidia provides
   434 Tegra Graphics Debugger at their website.  Because SDL2 dynamically loads EGL
   435 and GLES libraries, you must follow their instructions for installing the
   436 interposer library on a rooted device.  The non-rooted instructions are not
   437 compatible with applications that use SDL2 for video.
   438 
   439 The Tegra Graphics Debugger is available from NVidia here:
   440 https://developer.nvidia.com/tegra-graphics-debugger
   441 
   442 ================================================================================
   443  Why is API level 10 the minimum required?
   444 ================================================================================
   445 
   446 API level 10 is the minimum required level at runtime (that is, on the device) 
   447 because SDL requires some functionality for running not
   448 available on older devices. Since the incorporation of joystick support into SDL,
   449 the minimum SDK required to *build* SDL is version 12. Devices running API levels
   450 10-11 are still supported, only with the joystick functionality disabled.
   451 
   452 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
   453 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
   454 has since then been obsoleted, with the recommendation to developers to bump the
   455 required API level to 10.
   456 As of this writing, according to https://developer.android.com/about/dashboards/index.html
   457 about 90% of the Android devices accessing Google Play support API level 10 or
   458 higher (March 2013).
   459 
   460 ================================================================================
   461  A note regarding the use of the "dirty rectangles" rendering technique
   462 ================================================================================
   463 
   464 If your app uses a variation of the "dirty rectangles" rendering technique,
   465 where you only update a portion of the screen on each frame, you may notice a
   466 variety of visual glitches on Android, that are not present on other platforms.
   467 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   468 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   469 documentation for the function "The contents of ancillary buffers are always 
   470 undefined after calling eglSwapBuffers".
   471 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   472 is not possible for SDL as it requires EGL 1.4, available only on the API level
   473 17+, so the only workaround available on this platform is to redraw the entire
   474 screen each frame.
   475 
   476 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   477 
   478 ================================================================================
   479  Known issues
   480 ================================================================================
   481 
   482 - The number of buttons reported for each joystick is hardcoded to be 36, which
   483 is the current maximum number of buttons Android can report.
   484