docs/README-android.md
author Philipp Wiesemann <philipp.wiesemann@arcor.de>
Tue, 12 Aug 2014 23:28:45 +0200
changeset 9055 868b523403e0
parent 9050 bc9616da37cd
child 9065 c8a8b11fd0ad
permissions -rw-r--r--
Fixed doxygen warnings and markdown formatting.
     1 Android
     2 ================================================================================
     3 
     4 Requirements:
     5 
     6 Android SDK (version 12 or later)
     7 http://developer.android.com/sdk/index.html
     8 
     9 Android NDK r7 or later
    10 http://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 sdk.dir=PATH_TO_ANDROID_SDK
    78 6. Run 'ant debug' in android/project. This compiles the .java and eventually 
    79    creates a .apk with the native code embedded
    80 7. 'ant debug install' will push the apk to the device or emulator (if connected)
    81 
    82 Here's an explanation of the files in the Android project, so you can customize them:
    83 
    84     android-project/
    85         AndroidManifest.xml	- package manifest. Among others, it contains the class name
    86         			  of the main Activity and the package name of the application.
    87         build.properties	- empty
    88         build.xml		- build description file, used by ant. The actual application name
    89         			  is specified here.
    90         default.properties	- holds the target ABI for the application, android-10 and up
    91         project.properties	- holds the target ABI for the application, android-10 and up
    92         local.properties	- holds the SDK path, you should change this to the path to your SDK
    93         jni/			- directory holding native code
    94         jni/Android.mk		- Android makefile that can call recursively the Android.mk files
    95         			  in all subdirectories
    96         jni/SDL/		- (symlink to) directory holding the SDL library files
    97         jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
    98         jni/src/		- directory holding your C/C++ source
    99         jni/src/Android.mk	- Android makefile that you should customize to include your 
   100                                   source code and any library references
   101         res/			- directory holding resources for your application
   102         res/drawable-*		- directories holding icons for different phone hardware. Could be
   103         			  one dir called "drawable".
   104         res/layout/main.xml	- Usually contains a file main.xml, which declares the screen layout.
   105         			  We don't need it because we use the SDL video output.
   106         res/values/strings.xml	- strings used in your application, including the application name
   107         			  shown on the phone.
   108         src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
   109         			  to SDL.  Be very careful changing this, as the SDL library relies
   110         			  on this implementation.
   111 
   112 
   113 ================================================================================
   114  Build an app with static linking of libSDL
   115 ================================================================================
   116 
   117 This build uses the Android NDK module system.
   118 
   119 Instructions:
   120 1. Copy the android-project directory wherever you want to keep your projects
   121    and rename it to the name of your project.
   122 2. Rename <project>/jni/src/Android_static.mk to <project>/jni/src/Android.mk
   123    (overwrite the existing one)
   124 3. Edit <project>/jni/src/Android.mk to include your source files
   125 4. create and export an environment variable named NDK_MODULE_PATH that points
   126    to the parent directory of this SDL directory. e.g.:
   127 
   128    export NDK_MODULE_PATH="$PWD"/..
   129 
   130 5. Edit <project>/src/org/libsdl/app/SDLActivity.java and remove the call to
   131    System.loadLibrary("SDL2") line 42.
   132 6. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
   133 
   134 
   135 ================================================================================
   136  Customizing your application name
   137 ================================================================================
   138 
   139 To customize your application name, edit AndroidManifest.xml and replace
   140 "org.libsdl.app" with an identifier for your product package.
   141 
   142 Then create a Java class extending SDLActivity and place it in a directory
   143 under src matching your package, e.g.
   144 
   145 	src/com/gamemaker/game/MyGame.java
   146 
   147 Here's an example of a minimal class file:
   148 
   149     --- MyGame.java --------------------------
   150     package com.gamemaker.game;
   151     
   152     import org.libsdl.app.SDLActivity; 
   153     
   154     /* 
   155      * A sample wrapper class that just calls SDLActivity 
   156      */ 
   157     
   158     public class MyGame extends SDLActivity { }
   159     
   160     ------------------------------------------
   161 
   162 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   163 class, .e.g. "MyGame"
   164 
   165 ================================================================================
   166  Customizing your application icon
   167 ================================================================================
   168 
   169 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   170 the drawable directories under the res directory. There are four directories for
   171 different screen sizes. These can be replaced with one dir called "drawable",
   172 containing an icon file "ic_launcher.png" with dimensions 48x48 or 72x72.
   173 
   174 You may need to change the name of your icon in AndroidManifest.xml to match
   175 this icon filename.
   176 
   177 ================================================================================
   178  Loading assets
   179 ================================================================================
   180 
   181 Any files you put in the "assets" directory of your android-project directory
   182 will get bundled into the application package and you can load them using the
   183 standard functions in SDL_rwops.h.
   184 
   185 There are also a few Android specific functions that allow you to get other
   186 useful paths for saving and loading data:
   187 SDL_AndroidGetInternalStoragePath()
   188 SDL_AndroidGetExternalStorageState()
   189 SDL_AndroidGetExternalStoragePath()
   190 
   191 See SDL_system.h for more details on these functions.
   192 
   193 The asset packaging system will, by default, compress certain file extensions.
   194 SDL includes two asset file access mechanisms, the preferred one is the so
   195 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   196 GC, but given this method does not work on compressed assets, there is also the
   197 "Input Stream" method, which is automatically used as a fall back by SDL. You
   198 may want to keep this fact in mind when building your APK, specially when large
   199 files are involved.
   200 For more information on which extensions get compressed by default and how to
   201 disable this behaviour, see for example:
   202     
   203 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   204 
   205 ================================================================================
   206  Pause / Resume behaviour
   207 ================================================================================
   208 
   209 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   210 the event loop will block itself when the app is paused (ie, when the user
   211 returns to the main Android dashboard). Blocking is better in terms of battery
   212 use, and it allows your app to spring back to life instantaneously after resume
   213 (versus polling for a resume message).
   214 
   215 Upon resume, SDL will attempt to restore the GL context automatically.
   216 In modern devices (Android 3.0 and up) this will most likely succeed and your
   217 app can continue to operate as it was.
   218 
   219 However, there's a chance (on older hardware, or on systems under heavy load),
   220 where the GL context can not be restored. In that case you have to listen for
   221 a specific message, (which is not yet implemented!) and restore your textures
   222 manually or quit the app (which is actually the kind of behaviour you'll see
   223 under iOS, if the OS can not restore your GL context it will just kill your app)
   224 
   225 ================================================================================
   226  Threads and the Java VM
   227 ================================================================================
   228 
   229 For a quick tour on how Linux native threads interoperate with the Java VM, take
   230 a look here: http://developer.android.com/guide/practices/jni.html
   231 If you want to use threads in your SDL app, it's strongly recommended that you
   232 do so by creating them using SDL functions. This way, the required attach/detach
   233 handling is managed by SDL automagically. If you have threads created by other
   234 means and they make calls to SDL functions, make sure that you call
   235 Android_JNI_SetupThread before doing anything else otherwise SDL will attach
   236 your thread automatically anyway (when you make an SDL call), but it'll never
   237 detach it.
   238 
   239 ================================================================================
   240  Using STL
   241 ================================================================================
   242 
   243 You can use STL in your project by creating an Application.mk file in the jni
   244 folder and adding the following line:
   245 APP_STL := stlport_static
   246 
   247 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   248 
   249 ================================================================================
   250  Additional documentation
   251 ================================================================================
   252 
   253 The documentation in the NDK docs directory is very helpful in understanding the
   254 build process and how to work with native code on the Android platform.
   255 
   256 The best place to start is with docs/OVERVIEW.TXT
   257 
   258 
   259 ================================================================================
   260  Using Eclipse
   261 ================================================================================
   262 
   263 First make sure that you've installed Eclipse and the Android extensions as described here:
   264 	http://developer.android.com/tools/sdk/eclipse-adt.html
   265 
   266 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   267  * File -> New -> Other
   268  * Select the Android -> Android Project wizard and click Next
   269  * Enter the name you'd like your project to have
   270  * Select "Create project from existing source" and browse for your project directory
   271  * Make sure the Build Target is set to Android 2.0
   272  * Click Finish
   273 
   274 
   275 ================================================================================
   276  Using the emulator
   277 ================================================================================
   278 
   279 There are some good tips and tricks for getting the most out of the
   280 emulator here: http://developer.android.com/tools/devices/emulator.html
   281 
   282 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   283 
   284 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   285 Using a real device works better.
   286 
   287 ================================================================================
   288  Troubleshooting
   289 ================================================================================
   290 
   291 You can create and run an emulator from the Eclipse IDE:
   292  * Window -> Android SDK and AVD Manager
   293 
   294 You can see if adb can see any devices with the following command:
   295 
   296 	adb devices
   297 
   298 You can see the output of log messages on the default device with:
   299 
   300 	adb logcat
   301 
   302 You can push files to the device with:
   303 
   304 	adb push local_file remote_path_and_file
   305 
   306 You can push files to the SD Card at /sdcard, for example:
   307 
   308 	adb push moose.dat /sdcard/moose.dat
   309 
   310 You can see the files on the SD card with a shell command:
   311 
   312 	adb shell ls /sdcard/
   313 
   314 You can start a command shell on the default device with:
   315 
   316 	adb shell
   317 
   318 You can remove the library files of your project (and not the SDL lib files) with:
   319 
   320 	ndk-build clean
   321 
   322 You can do a build with the following command:
   323 
   324 	ndk-build
   325 
   326 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   327 
   328 	ndk-build V=1
   329 
   330 If your application crashes in native code, you can use addr2line to convert the
   331 addresses in the stack trace to lines in your code.
   332 
   333 For example, if your crash looks like this:
   334 
   335     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   336     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   337     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   338     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   339     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   340     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   341     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   342     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   343     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   344 
   345 You can see that there's a crash in the C library being called from the main code.
   346 I run addr2line with the debug version of my code:
   347 
   348 	arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   349 
   350 and then paste in the number after "pc" in the call stack, from the line that I care about:
   351 000014bc
   352 
   353 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   354 
   355 You can add logging to your code to help show what's happening:
   356 
   357     #include <android/log.h>
   358     
   359     __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   360 
   361 If you need to build without optimization turned on, you can create a file called
   362 "Application.mk" in the jni directory, with the following line in it:
   363 APP_OPTIM := debug
   364 
   365 
   366 ================================================================================
   367  Memory debugging
   368 ================================================================================
   369 
   370 The best (and slowest) way to debug memory issues on Android is valgrind.
   371 Valgrind has support for Android out of the box, just grab code using:
   372 
   373 	svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   374 
   375 ... and follow the instructions in the file README.android to build it.
   376 
   377 One thing I needed to do on Mac OS X was change the path to the toolchain,
   378 and add ranlib to the environment variables:
   379 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   380 
   381 Once valgrind is built, you can create a wrapper script to launch your
   382 application with it, changing org.libsdl.app to your package identifier:
   383 
   384     --- start_valgrind_app -------------------
   385     #!/system/bin/sh
   386     export TMPDIR=/data/data/org.libsdl.app
   387     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   388     ------------------------------------------
   389 
   390 Then push it to the device:
   391 
   392 	adb push start_valgrind_app /data/local
   393 
   394 and make it executable:
   395 
   396 	adb shell chmod 755 /data/local/start_valgrind_app
   397 
   398 and tell Android to use the script to launch your application:
   399 
   400 	adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   401 
   402 If the setprop command says "could not set property", it's likely that
   403 your package name is too long and you should make it shorter by changing
   404 AndroidManifest.xml and the path to your class file in android-project/src
   405 
   406 You can then launch your application normally and waaaaaaaiiittt for it.
   407 You can monitor the startup process with the logcat command above, and
   408 when it's done (or even while it's running) you can grab the valgrind
   409 output file:
   410 
   411 	adb pull /sdcard/valgrind.log
   412 
   413 When you're done instrumenting with valgrind, you can disable the wrapper:
   414 
   415 	adb shell setprop wrap.org.libsdl.app ""
   416 
   417 ================================================================================
   418  Why is API level 10 the minimum required?
   419 ================================================================================
   420 
   421 API level 10 is the minimum required level at runtime (that is, on the device) 
   422 because SDL requires some functionality for running not
   423 available on older devices. Since the incorporation of joystick support into SDL,
   424 the minimum SDK required to *build* SDL is version 12. Devices running API levels
   425 10-11 are still supported, only with the joystick functionality disabled.
   426 
   427 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
   428 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
   429 has since then been obsoleted, with the recommendation to developers to bump the
   430 required API level to 10.
   431 As of this writing, according to http://developer.android.com/about/dashboards/index.html
   432 about 90% of the Android devices accessing Google Play support API level 10 or
   433 higher (March 2013).
   434 
   435 ================================================================================
   436  A note regarding the use of the "dirty rectangles" rendering technique
   437 ================================================================================
   438 
   439 If your app uses a variation of the "dirty rectangles" rendering technique,
   440 where you only update a portion of the screen on each frame, you may notice a
   441 variety of visual glitches on Android, that are not present on other platforms.
   442 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   443 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   444 documentation for the function "The contents of ancillary buffers are always 
   445 undefined after calling eglSwapBuffers".
   446 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   447 is not possible for SDL as it requires EGL 1.4, available only on the API level
   448 17+, so the only workaround available on this platform is to redraw the entire
   449 screen each frame.
   450 
   451 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   452 
   453 ================================================================================
   454  Known issues
   455 ================================================================================
   456 
   457 - The number of buttons reported for each joystick is hardcoded to be 36, which
   458 is the current maximum number of buttons Android can report.
   459