README.android
author Gabriel Jacobo <gabomdq@gmail.com>
Mon, 04 Mar 2013 11:35:03 -0300
changeset 6962 6ce8edb5577b
parent 6816 b3d3ef1e15b5
child 6979 8d6ab3bdc08b
permissions -rw-r--r--
Updated the README.android file stating the required API level and reasons why.
     1 ================================================================================
     2 Simple DirectMedia Layer for Android
     3 ================================================================================
     4 
     5 Requirements:
     6 
     7 Android SDK (version 10 or later)
     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 Minimum API Level supported by SDL: 10 (Android 2.3.3)
    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/SDL_android.cpp
    32 
    33 Your project must include some glue code that starts your main() routine:
    34 src/main/android/SDL_android_main.cpp
    35 
    36 
    37 ================================================================================
    38  Building an app
    39 ================================================================================
    40 
    41 Instructions:
    42 1. Copy the android-project directory wherever you want to keep your projects
    43    and rename it to the name of your project.
    44 2. Move or symlink this SDL directory into the <project>/jni directory
    45 3. Edit <project>/jni/src/Android.mk to include your source files
    46 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
    47 
    48 If you want to use the Eclipse IDE, skip to the Eclipse section below.
    49 
    50 5. Edit <project>/local.properties to point to the Android SDK directory
    51 6. Run 'ant debug' in android/project. This compiles the .java and eventually 
    52    creates a .apk with the native code embedded
    53 7. 'ant debug install' will push the apk to the device or emulator (if connected)
    54 
    55 Here's an explanation of the files in the Android project, so you can customize them:
    56 
    57 android-project/
    58 	AndroidManifest.xml	- package manifest. Among others, it contains the class name
    59 				  of the main activity.
    60 	build.properties	- empty
    61 	build.xml		- build description file, used by ant. The actual application name
    62 				  is specified here.
    63 	default.properties	- holds the target ABI for the application, can range between
    64 				  android-5 and android-16
    65 	local.properties	- holds the SDK path, you should change this to the path to your SDK
    66 	jni/			- directory holding native code
    67 	jni/Android.mk		- Android makefile that can call recursively the Android.mk files
    68 				  in all subdirectories
    69 	jni/SDL/		- (symlink to) directory holding the SDL library files
    70 	jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
    71 	jni/src/		- directory holding your C/C++ source
    72 	jni/src/Android.mk	- Android makefile that you should customize to include your 
    73                                   source code and any library references
    74 	res/			- directory holding resources for your application
    75 	res/drawable-*		- directories holding icons for different phone hardware. Could be
    76 				  one dir called "drawable".
    77 	res/layout/main.xml	- Usually contains a file main.xml, which declares the screen layout.
    78 				  We don't need it because we use the SDL video output.
    79 	res/values/strings.xml	- strings used in your application, including the application name
    80 				  shown on the phone.
    81 	src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
    82 				  to SDL.  Be very careful changing this, as the SDL library relies
    83 				  on this implementation.
    84 
    85 
    86 ================================================================================
    87  Customizing your application name
    88 ================================================================================
    89 
    90 To customize your application name, edit AndroidManifest.xml and replace
    91 "org.libsdl.app" with an identifier for your product package.
    92 
    93 Then create a Java class extending SDLActivity and place it in a directory
    94 under src matching your package, e.g.
    95 	src/com/gamemaker/game/MyGame.java
    96 
    97 Here's an example of a minimal class file:
    98 --- MyGame.java --------------------------
    99 package com.gamemaker.game;
   100 
   101 import org.libsdl.app.SDLActivity; 
   102 
   103 /* 
   104  * A sample wrapper class that just calls SDLActivity 
   105  */ 
   106 
   107 public class MyGame extends SDLActivity { }
   108 
   109 ------------------------------------------
   110 
   111 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   112 class, .e.g. "MyGame"
   113 
   114 ================================================================================
   115  Customizing your application icon
   116 ================================================================================
   117 
   118 Conceptually changing your icon is just replacing the icon.png files in the
   119 drawable directories under the res directory. There are 3 directories for
   120 different screen sizes. These can be replaced with 1 dir called 'drawable',
   121 containing an icon file 'icon.png' with dimensions 48x48 or 72x72.
   122 
   123 You may need to change the name of your icon in AndroidManifest.xml to match
   124 this icon filename.
   125 
   126 ================================================================================
   127  Loading assets
   128 ================================================================================
   129 
   130 Any files you put in the "assets" directory of your android-project directory
   131 will get bundled into the application package and you can load them using the
   132 standard functions in SDL_rwops.h.
   133 
   134 There are also a few Android specific functions that allow you to get other
   135 useful paths for saving and loading data:
   136 SDL_AndroidGetInternalStoragePath()
   137 SDL_AndroidGetExternalStorageState()
   138 SDL_AndroidGetExternalStoragePath()
   139 
   140 See SDL_system.h for more details on these functions.
   141 
   142 The asset packaging system will, by default, compress certain file extensions.
   143 SDL includes two asset file access mechanisms, the preferred one is the so
   144 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   145 GC, but given this method does not work on compressed assets, there is also the
   146 "Input Stream" method, which is automatically used as a fall back by SDL. You
   147 may want to keep this fact in mind when building your APK, specially when large
   148 files are involved.
   149 For more information on which extensions get compressed by default and how to
   150 disable this behaviour, see for example:
   151     
   152 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   153 
   154 ================================================================================
   155  Pause / Resume behaviour
   156 ================================================================================
   157 
   158 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   159 the event loop will block itself when the app is paused (ie, when the user
   160 returns to the main Android dashboard). Blocking is better in terms of battery
   161 use, and it allows your app to spring back to life instantaneously after resume
   162 (versus polling for a resume message).
   163 
   164 Upon resume, SDL will attempt to restore the GL context automatically.
   165 In modern devices (Android 3.0 and up) this will most likely succeed and your
   166 app can continue to operate as it was.
   167 
   168 However, there's a chance (on older hardware, or on systems under heavy load),
   169 where the GL context can not be restored. In that case you have to listen for
   170 a specific message, (which is not yet implemented!) and restore your textures
   171 manually or quit the app (which is actually the kind of behaviour you'll see
   172 under iOS, if the OS can not restore your GL context it will just kill your app)
   173 
   174 ================================================================================
   175  Threads and the JAVA VM
   176 ================================================================================
   177 
   178 For a quick tour on how Linux native threads interoperate with the JAVA VM, take
   179 a look here: http://developer.android.com/guide/practices/jni.html
   180 If you want to use threads in your SDL app, it's strongly recommended that you
   181 do so by creating them using SDL functions. This way, the required attach/detach
   182 handling is managed by SDL automagically. If you have threads created by other
   183 means and they make calls to SDL functions, make sure that you call
   184 Android_JNI_SetupThread before doing anything else otherwise SDL will attach
   185 your thread automatically anyway (when you make an SDL call), but it'll never
   186 detach it.
   187 
   188 ================================================================================
   189  Using STL
   190 ================================================================================
   191 
   192 You can use STL in your project by creating an Application.mk file in the jni
   193 folder and adding the following line:
   194 APP_STL := stlport_static
   195 
   196 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
   197 
   198 ================================================================================
   199  Additional documentation
   200 ================================================================================
   201 
   202 The documentation in the NDK docs directory is very helpful in understanding the
   203 build process and how to work with native code on the Android platform.
   204 
   205 The best place to start is with docs/OVERVIEW.TXT
   206 
   207 
   208 ================================================================================
   209  Using Eclipse
   210 ================================================================================
   211 
   212 First make sure that you've installed Eclipse and the Android extensions as described here:
   213 	http://developer.android.com/sdk/eclipse-adt.html
   214 
   215 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
   216  * File -> New -> Other
   217  * Select the Android -> Android Project wizard and click Next
   218  * Enter the name you'd like your project to have
   219  * Select "Create project from existing source" and browse for your project directory
   220  * Make sure the Build Target is set to Android 2.0
   221  * Click Finish
   222 
   223 
   224 ================================================================================
   225  Using the emulator
   226 ================================================================================
   227 
   228 There are some good tips and tricks for getting the most out of the
   229 emulator here: http://developer.android.com/tools/devices/emulator.html
   230 
   231 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   232 
   233 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   234 Using a real device works better.
   235 
   236 ================================================================================
   237  Troubleshooting
   238 ================================================================================
   239 
   240 You can create and run an emulator from the Eclipse IDE:
   241  * Window -> Android SDK and AVD Manager
   242 
   243 You can see if adb can see any devices with the following command:
   244 	adb devices
   245 
   246 You can see the output of log messages on the default device with:
   247 	adb logcat
   248 
   249 You can push files to the device with:
   250 	adb push local_file remote_path_and_file
   251 
   252 You can push files to the SD Card at /sdcard, for example:
   253 	adb push moose.dat /sdcard/moose.dat
   254 
   255 You can see the files on the SD card with a shell command:
   256 	adb shell ls /sdcard/
   257 
   258 You can start a command shell on the default device with:
   259 	adb shell
   260 
   261 You can remove the library files of your project (and not the SDL lib files) with:
   262 	ndk-build clean
   263 
   264 You can do a build with the following command:
   265 	ndk-build
   266 
   267 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   268 	ndk-build V=1
   269 
   270 If your application crashes in native code, you can use addr2line to convert the
   271 addresses in the stack trace to lines in your code.
   272 
   273 For example, if your crash looks like this:
   274 I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   275 I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   276 I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   277 I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   278 I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   279 I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   280 I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   281 I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   282 I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   283 
   284 You can see that there's a crash in the C library being called from the main code.
   285 I run addr2line with the debug version of my code:
   286 	arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   287 and then paste in the number after "pc" in the call stack, from the line that I care about:
   288 000014bc
   289 
   290 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   291 
   292 You can add logging to your code to help show what's happening:
   293 
   294 #include <android/log.h>
   295 
   296 	__android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   297 
   298 If you need to build without optimization turned on, you can create a file called
   299 "Application.mk" in the jni directory, with the following line in it:
   300 APP_OPTIM := debug
   301 
   302 
   303 ================================================================================
   304  Memory debugging
   305 ================================================================================
   306 
   307 The best (and slowest) way to debug memory issues on Android is valgrind.
   308 Valgrind has support for Android out of the box, just grab code using:
   309 	svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   310 ... and follow the instructions in the file README.android to build it.
   311 
   312 One thing I needed to do on Mac OS X was change the path to the toolchain,
   313 and add ranlib to the environment variables:
   314 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   315 
   316 Once valgrind is built, you can create a wrapper script to launch your
   317 application with it, changing org.libsdl.app to your package identifier:
   318 --- start_valgrind_app -------------------
   319 #!/system/bin/sh
   320 export TMPDIR=/data/data/org.libsdl.app
   321 exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   322 ------------------------------------------
   323 
   324 Then push it to the device:
   325 	adb push start_valgrind_app /data/local
   326 
   327 and make it executable:
   328 	adb shell chmod 755 /data/local/start_valgrind_app
   329 
   330 and tell Android to use the script to launch your application:
   331 	adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   332 
   333 If the setprop command says "could not set property", it's likely that
   334 your package name is too long and you should make it shorter by changing
   335 AndroidManifest.xml and the path to your class file in android-project/src
   336 
   337 You can then launch your application normally and waaaaaaaiiittt for it.
   338 You can monitor the startup process with the logcat command above, and
   339 when it's done (or even while it's running) you can grab the valgrind
   340 output file:
   341 	adb pull /sdcard/valgrind.log
   342 
   343 When you're done instrumenting with valgrind, you can disable the wrapper:
   344 	adb shell setprop wrap.org.libsdl.app ""
   345 
   346 ================================================================================
   347  Why is API level 10 the minimum required?
   348 ================================================================================
   349 
   350 Support for OpenGL ES/ES2 applications was introduced in the NDK for API level 9, 
   351 which has since then been obsoleted, and the recommendation to developers was to 
   352 bump the required level to 10.
   353 As of this writing, according to http://developer.android.com/about/dashboards/index.html
   354 about 90% of the existing Android devices support an API level 10 or higher.
   355 
   356 ================================================================================
   357  Known issues
   358 ================================================================================
   359 
   360 - TODO. I'm sure there's a bunch more stuff I haven't thought of