Self

Building SDL2 for Android

Contents

  1. Existing documentation
  2. Pre-requisites
  3. Simple builds
    1. SDL wrapper for simple programs
      1. Troubleshooting
    2. SDL wrapper + SDL_image NDK module
  4. Build an autotools-friendly environment
    1. Compile a shared binaries bundle for SDL and SDL_*
    2. Install SDL in a GCC toolchain
    3. Building other dependencies
    4. Build your autotools app
    5. Build your CMake app
  5. Troubleshootings

1. Existing documentation

A lot of information can be found in SDL/docs/README-android.md.

This page is more walkthrough-oriented.

2. Pre-requisites

3. Simple builds

3.1. SDL wrapper for simple programs

Notes:

3.1.1. Troubleshooting

    repositories {
        jcenter()
    }

to 

    repositories {
        jcenter()
        google()
    }

 classpath 'com.android.tools.build:gradle:3.1.0' 

 distributionUrl=https\://services.gradle.org/distributions/gradle-4.9-all.zip 

3.2. SDL wrapper + SDL_image NDK module

Let's modify SDL2_image/showimage.c to show a simple embedded image (e.g. XPM). 

#include "SDL.h"
#include "SDL_image.h"

/* XPM */
static char * icon_xpm[] = {
  "32 23 3 1",
  "     c #FFFFFF",
  ".    c #000000",
  "+    c #FFFF00",
  "                                ",
  "            ........            ",
  "          ..++++++++..          ",
  "         .++++++++++++.         ",
  "        .++++++++++++++.        ",
  "       .++++++++++++++++.       ",
  "      .++++++++++++++++++.      ",
  "      .+++....++++....+++.      ",
  "     .++++.. .++++.. .++++.     ",
  "     .++++....++++....++++.     ",
  "     .++++++++++++++++++++.     ",
  "     .++++++++++++++++++++.     ",
  "     .+++++++++..+++++++++.     ",
  "     .+++++++++..+++++++++.     ",
  "     .++++++++++++++++++++.     ",
  "      .++++++++++++++++++.      ",
  "      .++...++++++++...++.      ",
  "       .++............++.       ",
  "        .++..........++.        ",
  "         .+++......+++.         ",
  "          ..++++++++..          ",
  "            ........            ",
  "                                "};

int main(int argc, char *argv[])
{
  SDL_Window *window;
  SDL_Renderer *renderer;
  SDL_Surface *surface;
  SDL_Texture *texture;
  int done;
  SDL_Event event;

  if (SDL_CreateWindowAndRenderer(0, 0, 0, &window, &renderer) < 0) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
        "SDL_CreateWindowAndRenderer() failed: %s", SDL_GetError());
    return(2);
  }

  surface = IMG_ReadXPMFromArray(icon_xpm);
  texture = SDL_CreateTextureFromSurface(renderer, surface);
  if (!texture) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
        "Couldn't load texture: %s", SDL_GetError());
    return(2);
  }
  SDL_SetWindowSize(window, 800, 480);

  done = 0;
  while (!done) {
    while (SDL_PollEvent(&event)) {
      if (event.type == SDL_QUIT)
        done = 1;
    }
    SDL_RenderCopy(renderer, texture, NULL, NULL);
    SDL_RenderPresent(renderer);
    SDL_Delay(100);
  }
  SDL_DestroyTexture(texture);

  SDL_Quit();
  return(0);
}

Then let's make an Android app out of it. To compile: 

cd /usr/src/SDL2/build-scripts/
./androidbuild.sh org.libsdl.showimage /usr/src/SDL2_image/showimage.c
cd /usr/src/SDL2/build/org.libsdl.showimage/
ln -s /usr/src/SDL2_image jni/
ln -s /usr/src/SDL2_image/external/libwebp-0.3.0 jni/webp
sed -i -e 's/^LOCAL_SHARED_LIBRARIES.*/& SDL2_image/' jni/src/Android.mk
ndk-build -j$(nproc)
ant debug install

Notes:

4. Build an autotools-friendly environment

You use autotools in your project and can't be bothering understanding ndk-build's cryptic errors? This guide is for you!

Note: this environment can be used for CMake too.

4.1. Compile a shared binaries bundle for SDL and SDL_*

Note: no need to add System.loadLibrary calls in SDLActivity.java, your application will be linked to them and Android's ld-linux loads them automatically.

4.2. Install SDL in a GCC toolchain

Now:

4.3. Building other dependencies

You can add any other libraries (e.g.: SDL2_gfx, freetype, gettext, gmp...) using commands like: 

mkdir cross-android/ && cd cross-android/
../configure --host=arm-linux-androideabi --prefix=$NDK_STANDALONE/sysroot/usr \
  --with-some-option --enable-another-option \
  --disable-shared
make -j$(nproc)
make install

Static builds (--disable-shared) are recommended for simplicity (no additional .so to declare).

Example with SDL2_gfx: 

VERSION=1.0.3
wget http://www.ferzkopp.net/Software/SDL2_gfx/SDL2_gfx-$VERSION.tar.gz
tar xf SDL2_gfx-$VERSION.tar.gz
mv SDL2_gfx-$VERSION/ SDL2_gfx/
cd SDL2_gfx/
mkdir cross-android/ && cd cross-android/
../configure --host=arm-linux-androideabi --prefix=$NDK_STANDALONE/sysroot/usr \
  --disable-shared --disable-mmx
make -j$(nproc)
make install

You can compile YOUR application using this technique, with some more steps to tell Android how to run it using JNI.

4.4. Build your autotools app

First, prepare an Android project:

Make your project Android-aware:

Now you can install your pre-built binaries and build the Android project:

4.5. Build your CMake app

(Work In Progress)

You can use our Android GCC toolchain using a simple toolchain file: 

# CMake toolchain file
SET(CMAKE_SYSTEM_NAME Linux)  # Tell CMake we're cross-compiling
include(CMakeForceCompiler)
# Prefix detection only works with compiler id "GNU"
CMAKE_FORCE_C_COMPILER(arm-linux-androideabi-gcc GNU)
SET(ANDROID TRUE)

You then call CMake like this: 

PATH=$NDK_STANDALONE/bin:$PATH
cmake \
  -D CMAKE_TOOLCHAIN_FILE=../android_toolchain.cmake \
  ...

5. Troubleshootings

If ant installd categorically refuses to install with Failure [INSTALL_FAILED_INSUFFICIENT_STORAGE], even if you have free local storage, that may mean anything. Check logcat first: 

adb logcat

If the error logs are not helpful (likely ;')) try locating all past traces of the application: 

find / -name "org...."

and remove them all.

If the problem persists, you may try installing on the SD card: 

adb install -s bin/app-debug.apk

If you get in your logcat: 

SDL: Couldn't locate Java callbacks, check that they're named and typed correctly

this probably means your SDLActivity.java is out-of-sync with your libSDL2.so.

None: Android (last edited 2020-06-20 10:53:57 by SylvainBeucler)