README.android
author David Ludwig <dludwig@pobox.com>
Tue, 12 Feb 2013 12:57:06 -0500
changeset 8424 3cf9501008f1
parent 6678 afb9be20f8d2
child 6816 b3d3ef1e15b5
permissions -rw-r--r--
WinRT: fixed bug: SDL_CreateWindow wouldn't work after an initial window was created + destroyed
     1 ================================================================================
     2 Simple DirectMedia Layer for Android
     3 ================================================================================
     4 
     5 Requirements:
     6 
     7 Android SDK
     8 http://developer.android.com/sdk/index.html
     9 
    10 Android NDK r4 or later
    11 http://developer.android.com/sdk/ndk/index.html
    12 
    13 
    14 ================================================================================
    15  How the port works
    16 ================================================================================
    17 
    18 - Android applications are Java-based, optionally with parts written in C
    19 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to 
    20 the SDL library
    21 - This means that your application C code must be placed inside an android 
    22 Java project, along with some C support code that communicates with Java
    23 - This eventually produces a standard Android .apk package
    24 
    25 The Android Java code implements an "activity" and can be found in:
    26 android-project/src/org/libsdl/app/SDLActivity.java
    27 
    28 The Java code loads your game code, the SDL shared library, and
    29 dispatches to native functions implemented in the SDL library:
    30 src/SDL_android.cpp
    31 
    32 Your project must include some glue code that starts your main() routine:
    33 src/main/android/SDL_android_main.cpp
    34 
    35 
    36 ================================================================================
    37  Building an app
    38 ================================================================================
    39 
    40 Instructions:
    41 1. Copy the android-project directory wherever you want to keep your projects
    42    and rename it to the name of your project.
    43 2. Move or symlink this SDL directory into the <project>/jni directory
    44 3. Edit <project>/jni/src/Android.mk to include your source files
    45 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
    46 
    47 If you want to use the Eclipse IDE, skip to the Eclipse section below.
    48 
    49 5. Edit <project>/local.properties to point to the Android SDK directory
    50 6. Run 'ant debug' in android/project. This compiles the .java and eventually 
    51    creates a .apk with the native code embedded
    52 7. 'ant debug install' will push the apk to the device or emulator (if connected)
    53 
    54 Here's an explanation of the files in the Android project, so you can customize them:
    55 
    56 android-project/
    57 	AndroidManifest.xml	- package manifest. Among others, it contains the class name
    58 				  of the main activity.
    59 	build.properties	- empty
    60 	build.xml		- build description file, used by ant. The actual application name
    61 				  is specified here.
    62 	default.properties	- holds the target ABI for the application, can range between
    63 				  android-5 and android-16
    64 	local.properties	- holds the SDK path, you should change this to the path to your SDK
    65 	jni/			- directory holding native code
    66 	jni/Android.mk		- Android makefile that can call recursively the Android.mk files
    67 				  in all subdirectories
    68 	jni/SDL/		- (symlink to) directory holding the SDL library files
    69 	jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
    70 	jni/src/		- directory holding your C/C++ source
    71 	jni/src/Android.mk	- Android makefile that you should customize to include your 
    72                                   source code and any library references
    73 	res/			- directory holding resources for your application
    74 	res/drawable-*		- directories holding icons for different phone hardware. Could be
    75 				  one dir called "drawable".
    76 	res/layout/main.xml	- Usually contains a file main.xml, which declares the screen layout.
    77 				  We don't need it because we use the SDL video output.
    78 	res/values/strings.xml	- strings used in your application, including the application name
    79 				  shown on the phone.
    80 	src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
    81 				  to SDL.  Be very careful changing this, as the SDL library relies
    82 				  on this implementation.
    83 
    84 
    85 ================================================================================
    86  Customizing your application name
    87 ================================================================================
    88 
    89 To customize your application name, edit AndroidManifest.xml and replace
    90 "org.libsdl.app" with an identifier for your product package.
    91 
    92 Then create a Java class extending SDLActivity and place it in a directory
    93 under src matching your package, e.g.
    94 	src/com/gamemaker/game/MyGame.java
    95 
    96 Here's an example of a minimal class file:
    97 --- MyGame.java --------------------------
    98 package com.gamemaker.game;
    99 
   100 import org.libsdl.app.SDLActivity; 
   101 
   102 /* 
   103  * A sample wrapper class that just calls SDLActivity 
   104  */ 
   105 
   106 public class MyGame extends SDLActivity { }
   107 
   108 ------------------------------------------
   109 
   110 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   111 class, .e.g. "MyGame"
   112 
   113 ================================================================================
   114  Customizing your application icon
   115 ================================================================================
   116 
   117 Conceptually changing your icon is just replacing the icon.png files in the
   118 drawable directories under the res directory. There are 3 directories for
   119 different screen sizes. These can be replaced with 1 dir called 'drawable',
   120 containing an icon file 'icon.png' with dimensions 48x48 or 72x72.
   121 
   122 You may need to change the name of your icon in AndroidManifest.xml to match
   123 this icon filename.
   124 
   125 ================================================================================
   126  Loading assets
   127 ================================================================================
   128 
   129 Any files you put in the "assets" directory of your android-project directory
   130 will get bundled into the application package and you can load them using the
   131 standard functions in SDL_rwops.h.
   132 
   133 There are also a few Android specific functions that allow you to get other
   134 useful paths for saving and loading data:
   135 SDL_AndroidGetInternalStoragePath()
   136 SDL_AndroidGetExternalStorageState()
   137 SDL_AndroidGetExternalStoragePath()
   138 
   139 See SDL_system.h for more details on these functions.
   140 
   141 ================================================================================
   142  Pause / Resume behaviour
   143 ================================================================================
   144 
   145 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   146 the event loop will block itself when the app is paused (ie, when the user
   147 returns to the main Android dashboard). Blocking is better in terms of battery
   148 use, and it allows your app to spring back to life instantaneously after resume
   149 (versus polling for a resume message).
   150 
   151 Upon resume, SDL will attempt to restore the GL context automatically.
   152 In modern devices (Android 3.0 and up) this will most likely succeed and your
   153 app can continue to operate as it was.
   154 
   155 However, there's a chance (on older hardware, or on systems under heavy load),
   156 where the GL context can not be restored. In that case you have to listen for
   157 a specific message, (which is not yet implemented!) and restore your textures
   158 manually or quit the app (which is actually the kind of behaviour you'll see
   159 under iOS, if the OS can not restore your GL context it will just kill your app)
   160 
   161 ================================================================================
   162  Threads and the JAVA VM
   163 ================================================================================
   164 
   165 For a quick tour on how Linux native threads interoperate with the JAVA VM, take
   166 a look here: http://developer.android.com/guide/practices/jni.html
   167 If you want to use threads in your SDL app, it's strongly recommended that you
   168 do so by creating them using SDL functions. This way, the required attach/detach
   169 handling is managed by SDL automagically. If you have threads created by other
   170 means and they make calls to SDL functions, make sure that you call
   171 Android_JNI_SetupThread before doing anything else otherwise SDL will attach
   172 your thread automatically anyway (when you make an SDL call), but it'll never
   173 detach it.
   174 
   175 ================================================================================
   176  Using STL
   177 ================================================================================
   178 
   179 You can use STL in your project by creating an Application.mk file in the jni
   180 folder and adding the following line:
   181 APP_STL := stlport_static
   182 
   183 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   184 
   185 ================================================================================
   186  Additional documentation
   187 ================================================================================
   188 
   189 The documentation in the NDK docs directory is very helpful in understanding the
   190 build process and how to work with native code on the Android platform.
   191 
   192 The best place to start is with docs/OVERVIEW.TXT
   193 
   194 
   195 ================================================================================
   196  Using Eclipse
   197 ================================================================================
   198 
   199 First make sure that you've installed Eclipse and the Android extensions as described here:
   200 	http://developer.android.com/sdk/eclipse-adt.html
   201 
   202 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   203  * File -> New -> Other
   204  * Select the Android -> Android Project wizard and click Next
   205  * Enter the name you'd like your project to have
   206  * Select "Create project from existing source" and browse for your project directory
   207  * Make sure the Build Target is set to Android 2.0
   208  * Click Finish
   209 
   210 
   211 ================================================================================
   212  Using the emulator
   213 ================================================================================
   214 
   215 There are some good tips and tricks for getting the most out of the
   216 emulator here: http://developer.android.com/tools/devices/emulator.html
   217 
   218 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   219 
   220 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   221 Using a real device works better.
   222 
   223 ================================================================================
   224  Troubleshooting
   225 ================================================================================
   226 
   227 You can create and run an emulator from the Eclipse IDE:
   228  * Window -> Android SDK and AVD Manager
   229 
   230 You can see if adb can see any devices with the following command:
   231 	adb devices
   232 
   233 You can see the output of log messages on the default device with:
   234 	adb logcat
   235 
   236 You can push files to the device with:
   237 	adb push local_file remote_path_and_file
   238 
   239 You can push files to the SD Card at /sdcard, for example:
   240 	adb push moose.dat /sdcard/moose.dat
   241 
   242 You can see the files on the SD card with a shell command:
   243 	adb shell ls /sdcard/
   244 
   245 You can start a command shell on the default device with:
   246 	adb shell
   247 
   248 You can remove the library files of your project (and not the SDL lib files) with:
   249 	ndk-build clean
   250 
   251 You can do a build with the following command:
   252 	ndk-build
   253 
   254 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   255 	ndk-build V=1
   256 
   257 If your application crashes in native code, you can use addr2line to convert the
   258 addresses in the stack trace to lines in your code.
   259 
   260 For example, if your crash looks like this:
   261 I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   262 I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   263 I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   264 I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   265 I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   266 I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   267 I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   268 I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   269 I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   270 
   271 You can see that there's a crash in the C library being called from the main code.
   272 I run addr2line with the debug version of my code:
   273 	arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   274 and then paste in the number after "pc" in the call stack, from the line that I care about:
   275 000014bc
   276 
   277 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   278 
   279 You can add logging to your code to help show what's happening:
   280 
   281 #include <android/log.h>
   282 
   283 	__android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   284 
   285 If you need to build without optimization turned on, you can create a file called
   286 "Application.mk" in the jni directory, with the following line in it:
   287 APP_OPTIM := debug
   288 
   289 
   290 ================================================================================
   291  Memory debugging
   292 ================================================================================
   293 
   294 The best (and slowest) way to debug memory issues on Android is valgrind.
   295 Valgrind has support for Android out of the box, just grab code using:
   296 	svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   297 ... and follow the instructions in the file README.android to build it.
   298 
   299 One thing I needed to do on Mac OS X was change the path to the toolchain,
   300 and add ranlib to the environment variables:
   301 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   302 
   303 Once valgrind is built, you can create a wrapper script to launch your
   304 application with it, changing org.libsdl.app to your package identifier:
   305 --- start_valgrind_app -------------------
   306 #!/system/bin/sh
   307 export TMPDIR=/data/data/org.libsdl.app
   308 exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   309 ------------------------------------------
   310 
   311 Then push it to the device:
   312 	adb push start_valgrind_app /data/local
   313 
   314 and make it executable:
   315 	adb shell chmod 755 /data/local/start_valgrind_app
   316 
   317 and tell Android to use the script to launch your application:
   318 	adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   319 
   320 If the setprop command says "could not set property", it's likely that
   321 your package name is too long and you should make it shorter by changing
   322 AndroidManifest.xml and the path to your class file in android-project/src
   323 
   324 You can then launch your application normally and waaaaaaaiiittt for it.
   325 You can monitor the startup process with the logcat command above, and
   326 when it's done (or even while it's running) you can grab the valgrind
   327 output file:
   328 	adb pull /sdcard/valgrind.log
   329 
   330 When you're done instrumenting with valgrind, you can disable the wrapper:
   331 	adb shell setprop wrap.org.libsdl.app ""
   332 
   333 
   334 ================================================================================
   335  Known issues
   336 ================================================================================
   337 
   338 - TODO. I'm sure there's a bunch more stuff I haven't thought of