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| Simple DirectMedia Layer for Android |
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| |
| Requirements: |
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| Android SDK |
| http://developer.android.com/sdk/index.html |
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| Android NDK r4 or later |
| http://developer.android.com/sdk/ndk/index.html |
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| How the port works |
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| |
| - Android applications are Java-based, optionally with parts written in C |
| - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to |
| the SDL library |
| - This means that your application C code must be placed inside an android |
| Java project, along with some C support code that communicates with Java |
| - This eventually produces a standard Android .apk package |
| |
| The Android Java code implements an "activity" and can be found in: |
| android-project/src/org/libsdl/app/SDLActivity.java |
| |
| The Java code loads your game code, the SDL shared library, and |
| dispatches to native functions implemented in the SDL library: |
| src/SDL_android.cpp |
| |
| Your project must include some glue code that starts your main() routine: |
| src/main/android/SDL_android_main.cpp |
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| Building an app |
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| Instructions: |
| 1. Copy the android-project directory wherever you want to keep your projects and rename it to the name of your project. |
| 2. Move this SDL directory into the <project>/jni directory |
| 3. Place your application source files in the <project>/jni/src directory |
| 4. Edit <project>/jni/src/Android.mk to include your source files |
| 5. Run 'ndk-build' (a script provided by the NDK). This compiles the C source |
| |
| If you want to use the Eclipse IDE, skip to the Eclipse section below. |
| |
| 6. Edit <project>/local.properties to point to the Android SDK directory |
| 7. Run 'ant debug' in android/project. This compiles the .java and eventually |
| creates a .apk with the native code embedded |
| 8. 'ant install' will push the apk to the device or emulator (if connected) |
| |
| Here's an explanation of the files in the Android project, so you can customize them: |
| |
| android-project/ |
| AndroidManifest.xml - package manifest, do not modify |
| build.properties - empty |
| build.xml - build description file, used by ant |
| default.properties - holds the ABI for the application, currently android-4 which corresponds to the Android 1.6 system image |
| local.properties - holds the SDK path, you should change this to the path to your SDK |
| jni/ - directory holding native code |
| jni/Android.mk - Android makefile that includes all subdirectories |
| jni/SDL/ - directory holding the SDL library files |
| jni/SDL/Android.mk - Android makefile for creating the SDL shared library |
| jni/src/ - directory holding your C/C++ source |
| jni/src/Android.mk - Android makefile that you should customize to include your source code and any library references |
| res/ - directory holding resources for your application |
| res/drawable-* - directories holding icons for different phone hardware |
| res/layout/main.xml - place holder for the main screen layout, overridden by the SDL video output |
| res/values/strings.xml - strings used in your application, including the application name shown on the phone. |
| src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding to SDL. Be very careful changing this, as the SDL library relies on this implementation. |
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| Additional documentation |
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| |
| The documentation in the NDK docs directory is very helpful in understanding the build process and how to work with native code on the Android platform. |
| |
| The best place to start is with docs/OVERVIEW.TXT |
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| Using Eclipse |
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| |
| First make sure that you've installed Eclipse and the Android extensions as described here: |
| http://developer.android.com/sdk/eclipse-adt.html |
| |
| Once you've copied the SDL android project and customized it, you can create an Eclipse project from it: |
| * File -> New -> Other |
| * Select the Android -> Android Project wizard and click Next |
| * Enter the name you'd like your project to have |
| * Select "Create project from existing source" and browse for your project directory |
| * Make sure the Build Target is set to Android 1.6 |
| * Click Finish |
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| Loading files and resources |
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| NEED CONTENT |
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| Troubleshooting |
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| You can create and run an emulator from the Eclipse IDE: |
| * Window -> Android SDK and AVD Manager |
| |
| You can see if adb can see any devices with the following command: |
| adb devices |
| |
| You can see the output of log messages on the default device with: |
| adb logcat |
| |
| You can push files to the device with: |
| adb push local_file remote_path_and_file |
| |
| You can push files to the SD Card at /sdcard, for example: |
| adb push moose.dat /sdcard/moose.dat |
| |
| You can see the files on the SD card with a shell command: |
| adb shell ls /sdcard/ |
| |
| You can start a command shell on the default device with: |
| adb shell |
| |
| You can do a clean build with the following commands: |
| ndk-build clean |
| ndk-build |
| |
| You can see the complete command line that ndk-build is using by passing V=1 on the command line: |
| ndk-build V=1 |
| |
| If your application crashes in native code, you can use addr2line to convert the addresses in the stack trace to lines in your code. |
| |
| For example, if your crash looks like this: |
| I/DEBUG ( 31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0 |
| I/DEBUG ( 31): r0 00000000 r1 00001000 r2 00000003 r3 400085d4 |
| I/DEBUG ( 31): r4 400085d0 r5 40008000 r6 afd41504 r7 436c6a7c |
| I/DEBUG ( 31): r8 436c6b30 r9 435c6fb0 10 435c6f9c fp 4168d82c |
| I/DEBUG ( 31): ip 8346aff0 sp 436c6a60 lr afd1c8ff pc afd1c902 cpsr 60000030 |
| I/DEBUG ( 31): #00 pc 0001c902 /system/lib/libc.so |
| I/DEBUG ( 31): #01 pc 0001ccf6 /system/lib/libc.so |
| I/DEBUG ( 31): #02 pc 000014bc /data/data/org.libsdl.app/lib/libmain.so |
| I/DEBUG ( 31): #03 pc 00001506 /data/data/org.libsdl.app/lib/libmain.so |
| |
| You can see that there's a crash in the C library being called from the main code. I run addr2line with the debug version of my code: |
| arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so |
| and then paste in the number after "pc" in the call stack, from the line that I care about: |
| 000014bc |
| |
| I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23. |
| |
| You can add logging to your code to help show what's happening: |
| |
| #include <android/log.h> |
| |
| __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x); |
| |
| If you need to build without optimization turned on, you can create a file called "Application.mk" in the jni directory, with the following line in it: |
| APP_OPTIM := debug |
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| Known issues |
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| |
| - SDL audio (although it's mostly written, just not working properly yet) |
| - TODO. I'm sure there's a bunch more stuff I haven't thought of |