docs/README-android.md
author Philipp Wiesemann <philipp.wiesemann@arcor.de>
Sun, 26 Mar 2017 21:00:19 +0200
changeset 10945 1300a3135d61
parent 10891 c079cd0dc02d
permissions -rw-r--r--
Removed newlines from error messages.
     1 Android
     2 ================================================================================
     3 
     4 Requirements:
     5 
     6 Android SDK (version 12 or later)
     7 https://developer.android.com/sdk/index.html
     8 
     9 Android NDK r7 or later
    10 https://developer.android.com/tools/sdk/ndk/index.html
    11 
    12 Minimum API level supported by SDL: 10 (Android 2.3.3)
    13 Joystick support is available for API level >=12 devices.
    14 
    15 ================================================================================
    16  How the port works
    17 ================================================================================
    18 
    19 - Android applications are Java-based, optionally with parts written in C
    20 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to 
    21   the SDL library
    22 - This means that your application C code must be placed inside an Android 
    23   Java project, along with some C support code that communicates with Java
    24 - This eventually produces a standard Android .apk package
    25 
    26 The Android Java code implements an "Activity" and can be found in:
    27 android-project/src/org/libsdl/app/SDLActivity.java
    28 
    29 The Java code loads your game code, the SDL shared library, and
    30 dispatches to native functions implemented in the SDL library:
    31 src/core/android/SDL_android.c
    32 
    33 Your project must include some glue code that starts your main() routine:
    34 src/main/android/SDL_android_main.c
    35 
    36 
    37 ================================================================================
    38  Building an app
    39 ================================================================================
    40 
    41 For simple projects you can use the script located at build-scripts/androidbuild.sh
    42 
    43 There's two ways of using it:
    44 
    45     androidbuild.sh com.yourcompany.yourapp < sources.list
    46     androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
    47 
    48 sources.list should be a text file with a source file name in each line
    49 Filenames should be specified relative to the current directory, for example if
    50 you are in the build-scripts directory and want to create the testgles.c test, you'll
    51 run:
    52 
    53     ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
    54 
    55 One limitation of this script is that all sources provided will be aggregated into
    56 a single directory, thus all your source files should have a unique name.
    57 
    58 Once the project is complete the script will tell you where the debug APK is located.
    59 If you want to create a signed release APK, you can use the project created by this
    60 utility to generate it.
    61 
    62 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
    63 done in the build directory for the app!
    64 
    65 
    66 For more complex projects, follow these instructions:
    67     
    68 1. Copy the android-project directory wherever you want to keep your projects
    69    and rename it to the name of your project.
    70 2. Move or symlink this SDL directory into the "<project>/jni" directory
    71 3. Edit "<project>/jni/src/Android.mk" to include your source files
    72 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
    73 
    74 If you want to use the Eclipse IDE, skip to the Eclipse section below.
    75 
    76 5. Create "<project>/local.properties" and use that to point to the Android SDK directory, by writing a line with the following form:
    77 
    78        sdk.dir=PATH_TO_ANDROID_SDK
    79 
    80 6. Run 'ant debug' in android/project. This compiles the .java and eventually 
    81    creates a .apk with the native code embedded
    82 7. 'ant debug install' will push the apk to the device or emulator (if connected)
    83 
    84 Here's an explanation of the files in the Android project, so you can customize them:
    85 
    86     android-project/
    87         AndroidManifest.xml	- package manifest. Among others, it contains the class name
    88         			  of the main Activity and the package name of the application.
    89         build.properties	- empty
    90         build.xml		- build description file, used by ant. The actual application name
    91         			  is specified here.
    92         default.properties	- holds the target ABI for the application, android-10 and up
    93         project.properties	- holds the target ABI for the application, android-10 and up
    94         local.properties	- holds the SDK path, you should change this to the path to your SDK
    95         jni/			- directory holding native code
    96         jni/Android.mk		- Android makefile that can call recursively the Android.mk files
    97         			  in all subdirectories
    98         jni/SDL/		- (symlink to) directory holding the SDL library files
    99         jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
   100         jni/src/		- directory holding your C/C++ source
   101         jni/src/Android.mk	- Android makefile that you should customize to include your 
   102                                   source code and any library references
   103         res/			- directory holding resources for your application
   104         res/drawable-*		- directories holding icons for different phone hardware. Could be
   105         			  one dir called "drawable".
   106         res/layout/main.xml	- Usually contains a file main.xml, which declares the screen layout.
   107         			  We don't need it because we use the SDL video output.
   108         res/values/strings.xml	- strings used in your application, including the application name
   109         			  shown on the phone.
   110         src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
   111         			  to SDL.  Be very careful changing this, as the SDL library relies
   112         			  on this implementation.
   113 
   114 
   115 ================================================================================
   116  Build an app with static linking of libSDL
   117 ================================================================================
   118 
   119 This build uses the Android NDK module system.
   120 
   121 Instructions:
   122 1. Copy the android-project directory wherever you want to keep your projects
   123    and rename it to the name of your project.
   124 2. Rename "<project>/jni/src/Android_static.mk" to "<project>/jni/src/Android.mk"
   125    (overwrite the existing one)
   126 3. Edit "<project>/jni/src/Android.mk" to include your source files
   127 4. create and export an environment variable named NDK_MODULE_PATH that points
   128    to the parent directory of this SDL directory. e.g.:
   129 
   130        export NDK_MODULE_PATH="$PWD"/..
   131 
   132 5. Edit "<project>/src/org/libsdl/app/SDLActivity.java" and remove the call to
   133    System.loadLibrary("SDL2").
   134 6. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
   135 
   136 
   137 ================================================================================
   138  Customizing your application name
   139 ================================================================================
   140 
   141 To customize your application name, edit AndroidManifest.xml and replace
   142 "org.libsdl.app" with an identifier for your product package.
   143 
   144 Then create a Java class extending SDLActivity and place it in a directory
   145 under src matching your package, e.g.
   146 
   147     src/com/gamemaker/game/MyGame.java
   148 
   149 Here's an example of a minimal class file:
   150 
   151     --- MyGame.java --------------------------
   152     package com.gamemaker.game;
   153     
   154     import org.libsdl.app.SDLActivity; 
   155     
   156     /**
   157      * A sample wrapper class that just calls SDLActivity 
   158      */ 
   159     
   160     public class MyGame extends SDLActivity { }
   161     
   162     ------------------------------------------
   163 
   164 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   165 class, .e.g. "MyGame"
   166 
   167 ================================================================================
   168  Customizing your application icon
   169 ================================================================================
   170 
   171 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   172 the drawable directories under the res directory. There are four directories for
   173 different screen sizes. These can be replaced with one dir called "drawable",
   174 containing an icon file "ic_launcher.png" with dimensions 48x48 or 72x72.
   175 
   176 You may need to change the name of your icon in AndroidManifest.xml to match
   177 this icon filename.
   178 
   179 ================================================================================
   180  Loading assets
   181 ================================================================================
   182 
   183 Any files you put in the "assets" directory of your android-project directory
   184 will get bundled into the application package and you can load them using the
   185 standard functions in SDL_rwops.h.
   186 
   187 There are also a few Android specific functions that allow you to get other
   188 useful paths for saving and loading data:
   189 * SDL_AndroidGetInternalStoragePath()
   190 * SDL_AndroidGetExternalStorageState()
   191 * SDL_AndroidGetExternalStoragePath()
   192 
   193 See SDL_system.h for more details on these functions.
   194 
   195 The asset packaging system will, by default, compress certain file extensions.
   196 SDL includes two asset file access mechanisms, the preferred one is the so
   197 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   198 GC, but given this method does not work on compressed assets, there is also the
   199 "Input Stream" method, which is automatically used as a fall back by SDL. You
   200 may want to keep this fact in mind when building your APK, specially when large
   201 files are involved.
   202 For more information on which extensions get compressed by default and how to
   203 disable this behaviour, see for example:
   204     
   205 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   206 
   207 ================================================================================
   208  Pause / Resume behaviour
   209 ================================================================================
   210 
   211 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   212 the event loop will block itself when the app is paused (ie, when the user
   213 returns to the main Android dashboard). Blocking is better in terms of battery
   214 use, and it allows your app to spring back to life instantaneously after resume
   215 (versus polling for a resume message).
   216 
   217 Upon resume, SDL will attempt to restore the GL context automatically.
   218 In modern devices (Android 3.0 and up) this will most likely succeed and your
   219 app can continue to operate as it was.
   220 
   221 However, there's a chance (on older hardware, or on systems under heavy load),
   222 where the GL context can not be restored. In that case you have to listen for
   223 a specific message, (which is not yet implemented!) and restore your textures
   224 manually or quit the app (which is actually the kind of behaviour you'll see
   225 under iOS, if the OS can not restore your GL context it will just kill your app)
   226 
   227 ================================================================================
   228  Threads and the Java VM
   229 ================================================================================
   230 
   231 For a quick tour on how Linux native threads interoperate with the Java VM, take
   232 a look here: https://developer.android.com/guide/practices/jni.html
   233 
   234 If you want to use threads in your SDL app, it's strongly recommended that you
   235 do so by creating them using SDL functions. This way, the required attach/detach
   236 handling is managed by SDL automagically. If you have threads created by other
   237 means and they make calls to SDL functions, make sure that you call
   238 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
   239 your thread automatically anyway (when you make an SDL call), but it'll never
   240 detach it.
   241 
   242 ================================================================================
   243  Using STL
   244 ================================================================================
   245 
   246 You can use STL in your project by creating an Application.mk file in the jni
   247 folder and adding the following line:
   248 
   249     APP_STL := stlport_static
   250 
   251 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   252 
   253 ================================================================================
   254  Additional documentation
   255 ================================================================================
   256 
   257 The documentation in the NDK docs directory is very helpful in understanding the
   258 build process and how to work with native code on the Android platform.
   259 
   260 The best place to start is with docs/OVERVIEW.TXT
   261 
   262 
   263 ================================================================================
   264  Using Eclipse
   265 ================================================================================
   266 
   267 First make sure that you've installed Eclipse and the Android extensions as described here:
   268 	https://developer.android.com/tools/sdk/eclipse-adt.html
   269 
   270 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   271  * File -> New -> Other
   272  * Select the Android -> Android Project wizard and click Next
   273  * Enter the name you'd like your project to have
   274  * Select "Create project from existing source" and browse for your project directory
   275  * Make sure the Build Target is set to Android 3.1 (API 12)
   276  * Click Finish
   277 
   278 
   279 ================================================================================
   280  Using the emulator
   281 ================================================================================
   282 
   283 There are some good tips and tricks for getting the most out of the
   284 emulator here: https://developer.android.com/tools/devices/emulator.html
   285 
   286 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   287 
   288 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   289 Using a real device works better.
   290 
   291 ================================================================================
   292  Troubleshooting
   293 ================================================================================
   294 
   295 You can create and run an emulator from the Eclipse IDE:
   296  * Window -> Android SDK and AVD Manager
   297 
   298 You can see if adb can see any devices with the following command:
   299 
   300     adb devices
   301 
   302 You can see the output of log messages on the default device with:
   303 
   304     adb logcat
   305 
   306 You can push files to the device with:
   307 
   308     adb push local_file remote_path_and_file
   309 
   310 You can push files to the SD Card at /sdcard, for example:
   311 
   312     adb push moose.dat /sdcard/moose.dat
   313 
   314 You can see the files on the SD card with a shell command:
   315 
   316     adb shell ls /sdcard/
   317 
   318 You can start a command shell on the default device with:
   319 
   320     adb shell
   321 
   322 You can remove the library files of your project (and not the SDL lib files) with:
   323 
   324     ndk-build clean
   325 
   326 You can do a build with the following command:
   327 
   328     ndk-build
   329 
   330 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   331 
   332     ndk-build V=1
   333 
   334 If your application crashes in native code, you can use addr2line to convert the
   335 addresses in the stack trace to lines in your code.
   336 
   337 For example, if your crash looks like this:
   338 
   339     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   340     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   341     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   342     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   343     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   344     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   345     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   346     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   347     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   348 
   349 You can see that there's a crash in the C library being called from the main code.
   350 I run addr2line with the debug version of my code:
   351 
   352     arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   353 
   354 and then paste in the number after "pc" in the call stack, from the line that I care about:
   355 000014bc
   356 
   357 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   358 
   359 You can add logging to your code to help show what's happening:
   360 
   361     #include <android/log.h>
   362     
   363     __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   364 
   365 If you need to build without optimization turned on, you can create a file called
   366 "Application.mk" in the jni directory, with the following line in it:
   367 
   368     APP_OPTIM := debug
   369 
   370 
   371 ================================================================================
   372  Memory debugging
   373 ================================================================================
   374 
   375 The best (and slowest) way to debug memory issues on Android is valgrind.
   376 Valgrind has support for Android out of the box, just grab code using:
   377 
   378     svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   379 
   380 ... and follow the instructions in the file README.android to build it.
   381 
   382 One thing I needed to do on Mac OS X was change the path to the toolchain,
   383 and add ranlib to the environment variables:
   384 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   385 
   386 Once valgrind is built, you can create a wrapper script to launch your
   387 application with it, changing org.libsdl.app to your package identifier:
   388 
   389     --- start_valgrind_app -------------------
   390     #!/system/bin/sh
   391     export TMPDIR=/data/data/org.libsdl.app
   392     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   393     ------------------------------------------
   394 
   395 Then push it to the device:
   396 
   397     adb push start_valgrind_app /data/local
   398 
   399 and make it executable:
   400 
   401     adb shell chmod 755 /data/local/start_valgrind_app
   402 
   403 and tell Android to use the script to launch your application:
   404 
   405     adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   406 
   407 If the setprop command says "could not set property", it's likely that
   408 your package name is too long and you should make it shorter by changing
   409 AndroidManifest.xml and the path to your class file in android-project/src
   410 
   411 You can then launch your application normally and waaaaaaaiiittt for it.
   412 You can monitor the startup process with the logcat command above, and
   413 when it's done (or even while it's running) you can grab the valgrind
   414 output file:
   415 
   416     adb pull /sdcard/valgrind.log
   417 
   418 When you're done instrumenting with valgrind, you can disable the wrapper:
   419 
   420     adb shell setprop wrap.org.libsdl.app ""
   421 
   422 ================================================================================
   423  Graphics debugging
   424 ================================================================================
   425 
   426 If you are developing on a compatible Tegra-based tablet, NVidia provides
   427 Tegra Graphics Debugger at their website.  Because SDL2 dynamically loads EGL
   428 and GLES libraries, you must follow their instructions for installing the
   429 interposer library on a rooted device.  The non-rooted instructions are not
   430 compatible with applications that use SDL2 for video.
   431 
   432 The Tegra Graphics Debugger is available from NVidia here:
   433 https://developer.nvidia.com/tegra-graphics-debugger
   434 
   435 ================================================================================
   436  Why is API level 10 the minimum required?
   437 ================================================================================
   438 
   439 API level 10 is the minimum required level at runtime (that is, on the device) 
   440 because SDL requires some functionality for running not
   441 available on older devices. Since the incorporation of joystick support into SDL,
   442 the minimum SDK required to *build* SDL is version 12. Devices running API levels
   443 10-11 are still supported, only with the joystick functionality disabled.
   444 
   445 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
   446 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
   447 has since then been obsoleted, with the recommendation to developers to bump the
   448 required API level to 10.
   449 As of this writing, according to https://developer.android.com/about/dashboards/index.html
   450 about 90% of the Android devices accessing Google Play support API level 10 or
   451 higher (March 2013).
   452 
   453 ================================================================================
   454  A note regarding the use of the "dirty rectangles" rendering technique
   455 ================================================================================
   456 
   457 If your app uses a variation of the "dirty rectangles" rendering technique,
   458 where you only update a portion of the screen on each frame, you may notice a
   459 variety of visual glitches on Android, that are not present on other platforms.
   460 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   461 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   462 documentation for the function "The contents of ancillary buffers are always 
   463 undefined after calling eglSwapBuffers".
   464 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   465 is not possible for SDL as it requires EGL 1.4, available only on the API level
   466 17+, so the only workaround available on this platform is to redraw the entire
   467 screen each frame.
   468 
   469 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   470 
   471 ================================================================================
   472  Known issues
   473 ================================================================================
   474 
   475 - The number of buttons reported for each joystick is hardcoded to be 36, which
   476 is the current maximum number of buttons Android can report.
   477