docs/README-android.md
author Philipp Wiesemann <philipp.wiesemann@arcor.de>
Mon, 11 Aug 2014 23:13:20 +0200
changeset 9050 bc9616da37cd
parent 9025 d09d4b578e77
child 9055 868b523403e0
permissions -rw-r--r--
Fixed doxygen warning 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 	src/com/gamemaker/game/MyGame.java
   145 
   146 Here's an example of a minimal class file:
   147 
   148     --- MyGame.java --------------------------
   149     package com.gamemaker.game;
   150     
   151     import org.libsdl.app.SDLActivity; 
   152     
   153     /* 
   154      * A sample wrapper class that just calls SDLActivity 
   155      */ 
   156     
   157     public class MyGame extends SDLActivity { }
   158     
   159     ------------------------------------------
   160 
   161 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   162 class, .e.g. "MyGame"
   163 
   164 ================================================================================
   165  Customizing your application icon
   166 ================================================================================
   167 
   168 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   169 the drawable directories under the res directory. There are four directories for
   170 different screen sizes. These can be replaced with one dir called "drawable",
   171 containing an icon file "ic_launcher.png" with dimensions 48x48 or 72x72.
   172 
   173 You may need to change the name of your icon in AndroidManifest.xml to match
   174 this icon filename.
   175 
   176 ================================================================================
   177  Loading assets
   178 ================================================================================
   179 
   180 Any files you put in the "assets" directory of your android-project directory
   181 will get bundled into the application package and you can load them using the
   182 standard functions in SDL_rwops.h.
   183 
   184 There are also a few Android specific functions that allow you to get other
   185 useful paths for saving and loading data:
   186 SDL_AndroidGetInternalStoragePath()
   187 SDL_AndroidGetExternalStorageState()
   188 SDL_AndroidGetExternalStoragePath()
   189 
   190 See SDL_system.h for more details on these functions.
   191 
   192 The asset packaging system will, by default, compress certain file extensions.
   193 SDL includes two asset file access mechanisms, the preferred one is the so
   194 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   195 GC, but given this method does not work on compressed assets, there is also the
   196 "Input Stream" method, which is automatically used as a fall back by SDL. You
   197 may want to keep this fact in mind when building your APK, specially when large
   198 files are involved.
   199 For more information on which extensions get compressed by default and how to
   200 disable this behaviour, see for example:
   201     
   202 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   203 
   204 ================================================================================
   205  Pause / Resume behaviour
   206 ================================================================================
   207 
   208 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   209 the event loop will block itself when the app is paused (ie, when the user
   210 returns to the main Android dashboard). Blocking is better in terms of battery
   211 use, and it allows your app to spring back to life instantaneously after resume
   212 (versus polling for a resume message).
   213 
   214 Upon resume, SDL will attempt to restore the GL context automatically.
   215 In modern devices (Android 3.0 and up) this will most likely succeed and your
   216 app can continue to operate as it was.
   217 
   218 However, there's a chance (on older hardware, or on systems under heavy load),
   219 where the GL context can not be restored. In that case you have to listen for
   220 a specific message, (which is not yet implemented!) and restore your textures
   221 manually or quit the app (which is actually the kind of behaviour you'll see
   222 under iOS, if the OS can not restore your GL context it will just kill your app)
   223 
   224 ================================================================================
   225  Threads and the Java VM
   226 ================================================================================
   227 
   228 For a quick tour on how Linux native threads interoperate with the Java VM, take
   229 a look here: http://developer.android.com/guide/practices/jni.html
   230 If you want to use threads in your SDL app, it's strongly recommended that you
   231 do so by creating them using SDL functions. This way, the required attach/detach
   232 handling is managed by SDL automagically. If you have threads created by other
   233 means and they make calls to SDL functions, make sure that you call
   234 Android_JNI_SetupThread before doing anything else otherwise SDL will attach
   235 your thread automatically anyway (when you make an SDL call), but it'll never
   236 detach it.
   237 
   238 ================================================================================
   239  Using STL
   240 ================================================================================
   241 
   242 You can use STL in your project by creating an Application.mk file in the jni
   243 folder and adding the following line:
   244 APP_STL := stlport_static
   245 
   246 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   247 
   248 ================================================================================
   249  Additional documentation
   250 ================================================================================
   251 
   252 The documentation in the NDK docs directory is very helpful in understanding the
   253 build process and how to work with native code on the Android platform.
   254 
   255 The best place to start is with docs/OVERVIEW.TXT
   256 
   257 
   258 ================================================================================
   259  Using Eclipse
   260 ================================================================================
   261 
   262 First make sure that you've installed Eclipse and the Android extensions as described here:
   263 	http://developer.android.com/tools/sdk/eclipse-adt.html
   264 
   265 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   266  * File -> New -> Other
   267  * Select the Android -> Android Project wizard and click Next
   268  * Enter the name you'd like your project to have
   269  * Select "Create project from existing source" and browse for your project directory
   270  * Make sure the Build Target is set to Android 2.0
   271  * Click Finish
   272 
   273 
   274 ================================================================================
   275  Using the emulator
   276 ================================================================================
   277 
   278 There are some good tips and tricks for getting the most out of the
   279 emulator here: http://developer.android.com/tools/devices/emulator.html
   280 
   281 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   282 
   283 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   284 Using a real device works better.
   285 
   286 ================================================================================
   287  Troubleshooting
   288 ================================================================================
   289 
   290 You can create and run an emulator from the Eclipse IDE:
   291  * Window -> Android SDK and AVD Manager
   292 
   293 You can see if adb can see any devices with the following command:
   294 	adb devices
   295 
   296 You can see the output of log messages on the default device with:
   297 	adb logcat
   298 
   299 You can push files to the device with:
   300 	adb push local_file remote_path_and_file
   301 
   302 You can push files to the SD Card at /sdcard, for example:
   303 	adb push moose.dat /sdcard/moose.dat
   304 
   305 You can see the files on the SD card with a shell command:
   306 	adb shell ls /sdcard/
   307 
   308 You can start a command shell on the default device with:
   309 	adb shell
   310 
   311 You can remove the library files of your project (and not the SDL lib files) with:
   312 	ndk-build clean
   313 
   314 You can do a build with the following command:
   315 	ndk-build
   316 
   317 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   318 	ndk-build V=1
   319 
   320 If your application crashes in native code, you can use addr2line to convert the
   321 addresses in the stack trace to lines in your code.
   322 
   323 For example, if your crash looks like this:
   324 
   325     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   326     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   327     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   328     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   329     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   330     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   331     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   332     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   333     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   334 
   335 You can see that there's a crash in the C library being called from the main code.
   336 I run addr2line with the debug version of my code:
   337 	arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   338 and then paste in the number after "pc" in the call stack, from the line that I care about:
   339 000014bc
   340 
   341 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   342 
   343 You can add logging to your code to help show what's happening:
   344 
   345 #include <android/log.h>
   346 
   347 	__android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   348 
   349 If you need to build without optimization turned on, you can create a file called
   350 "Application.mk" in the jni directory, with the following line in it:
   351 APP_OPTIM := debug
   352 
   353 
   354 ================================================================================
   355  Memory debugging
   356 ================================================================================
   357 
   358 The best (and slowest) way to debug memory issues on Android is valgrind.
   359 Valgrind has support for Android out of the box, just grab code using:
   360 	svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   361 ... and follow the instructions in the file README.android to build it.
   362 
   363 One thing I needed to do on Mac OS X was change the path to the toolchain,
   364 and add ranlib to the environment variables:
   365 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   366 
   367 Once valgrind is built, you can create a wrapper script to launch your
   368 application with it, changing org.libsdl.app to your package identifier:
   369 
   370     --- start_valgrind_app -------------------
   371     #!/system/bin/sh
   372     export TMPDIR=/data/data/org.libsdl.app
   373     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   374     ------------------------------------------
   375 
   376 Then push it to the device:
   377 	adb push start_valgrind_app /data/local
   378 
   379 and make it executable:
   380 	adb shell chmod 755 /data/local/start_valgrind_app
   381 
   382 and tell Android to use the script to launch your application:
   383 	adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   384 
   385 If the setprop command says "could not set property", it's likely that
   386 your package name is too long and you should make it shorter by changing
   387 AndroidManifest.xml and the path to your class file in android-project/src
   388 
   389 You can then launch your application normally and waaaaaaaiiittt for it.
   390 You can monitor the startup process with the logcat command above, and
   391 when it's done (or even while it's running) you can grab the valgrind
   392 output file:
   393 	adb pull /sdcard/valgrind.log
   394 
   395 When you're done instrumenting with valgrind, you can disable the wrapper:
   396 	adb shell setprop wrap.org.libsdl.app ""
   397 
   398 ================================================================================
   399  Why is API level 10 the minimum required?
   400 ================================================================================
   401 
   402 API level 10 is the minimum required level at runtime (that is, on the device) 
   403 because SDL requires some functionality for running not
   404 available on older devices. Since the incorporation of joystick support into SDL,
   405 the minimum SDK required to *build* SDL is version 12. Devices running API levels
   406 10-11 are still supported, only with the joystick functionality disabled.
   407 
   408 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
   409 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
   410 has since then been obsoleted, with the recommendation to developers to bump the
   411 required API level to 10.
   412 As of this writing, according to http://developer.android.com/about/dashboards/index.html
   413 about 90% of the Android devices accessing Google Play support API level 10 or
   414 higher (March 2013).
   415 
   416 ================================================================================
   417  A note regarding the use of the "dirty rectangles" rendering technique
   418 ================================================================================
   419 
   420 If your app uses a variation of the "dirty rectangles" rendering technique,
   421 where you only update a portion of the screen on each frame, you may notice a
   422 variety of visual glitches on Android, that are not present on other platforms.
   423 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   424 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   425 documentation for the function "The contents of ancillary buffers are always 
   426 undefined after calling eglSwapBuffers".
   427 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   428 is not possible for SDL as it requires EGL 1.4, available only on the API level
   429 17+, so the only workaround available on this platform is to redraw the entire
   430 screen each frame.
   431 
   432 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   433 
   434 ================================================================================
   435  Known issues
   436 ================================================================================
   437 
   438 - The number of buttons reported for each joystick is hardcoded to be 36, which
   439 is the current maximum number of buttons Android can report.
   440