Android編譯SDL2和demo展示（2.0.5）

 

我的視頻課程（基礎）：《（NDK）FFmpeg打造Android萬能音頻播放器》

我的視頻課程（進階）：《（NDK）FFmpeg打造Android視頻播放器》

我的視頻課程（編碼直播推流）：《Android視頻編碼和直播推流》

 

什麼是SDL（摘自百度百科）：

 

SDL（Simple DirectMedia Layer）是一套開放源代碼的跨平臺多媒體開發庫，使用C語言寫成。SDL提供了數種控制圖像、聲音、輸出入的函數，讓開發者只要用相同或是相似的代碼就可以開發出跨多個平臺（Linux、Windows、Mac OS X等）的應用軟件。目前SDL多用於開發遊戲、模擬器、媒體播放器等多媒體應用領域。

由此可見SDL是跨平臺的，而Android是基於Linux的，所以同理SDL也可以在Android編譯成可用的動態庫來使用。那麼SDL在Android上面有什麼作用呢，因爲我本身是做應用開發的，所以自然想到的是媒體播放器了（哈哈），結合FFmpeg就可以播放音頻和視頻，不過這是後面要研究的了。

一：SDL下載

1）官方下載地址（https://www.libsdl.org/download-2.0.php），現在最新版本是(SDL2-2.0.5)

2）解壓SDL2-2.0.5.zip，我們需要的是android-project、include、src和Android.mk

 

二：創建SDL項目

1）創建一個新的純Android項目（包名就取android-project中一樣的：org.libsdl.app）

2）在Android項目根目錄下創建jni目錄，然後在jni目錄下面創建SDL目錄，並把SDL2-2.0.5根目錄下的include和src拷貝到SDL目錄下：

3）把Android項目轉換成C/C++項目：在Android項目上右鍵->Android tools->Add Native support

這裏就默認名稱就行。

轉換後的項目中jni目錄中生成了Android.mk和一個.cpp文件，我習慣把.cpp改成.c

4）現在是重要的地方了

1、在SDL的目錄android-project中我們發現在jni中有src、Android.mk和Application.mk3個文件：

2、而在src目錄裏面還有Android.mk和Android_static.mk文件：

3、這就是官方爲我們做的重要的事了，mk的編譯腳本，src中的兩個分爲動態和靜態（static）庫編譯腳本。這裏我們把src中的Android.mk（動態庫shared library）複製到SDL目錄下：

 

 

4、接下來我們把SDL2-2.0.5根目錄下的Android.mk文件中的shared library代碼拷貝到SDL中Android.mk中，最後SDL中Android.mk文件內容如下：

 

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := main

SDL_PATH := ../SDL

LOCAL_C_INCLUDES := $(LOCAL_PATH)/$(SDL_PATH)/include

# Add your application source files here...
LOCAL_SRC_FILES := $(SDL_PATH)/src/main/android/SDL_android_main.c \
	YourSourceHere.c

LOCAL_SHARED_LIBRARIES := SDL2

LOCAL_LDLIBS := -lGLESv1_CM -lGLESv2 -llog

include $(BUILD_SHARED_LIBRARY)

###########################
#
# SDL shared library
#
###########################

include $(CLEAR_VARS)

LOCAL_MODULE := SDL2

LOCAL_C_INCLUDES := $(LOCAL_PATH)/include

LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES)

LOCAL_SRC_FILES := \
	$(subst $(LOCAL_PATH)/,, \
	$(wildcard $(LOCAL_PATH)/src/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/dummy/*.c) \
	$(LOCAL_PATH)/src/atomic/SDL_atomic.c \
	$(LOCAL_PATH)/src/atomic/SDL_spinlock.c.arm \
	$(wildcard $(LOCAL_PATH)/src/core/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/cpuinfo/*.c) \
	$(wildcard $(LOCAL_PATH)/src/dynapi/*.c) \
	$(wildcard $(LOCAL_PATH)/src/events/*.c) \
	$(wildcard $(LOCAL_PATH)/src/file/*.c) \
	$(wildcard $(LOCAL_PATH)/src/haptic/*.c) \
	$(wildcard $(LOCAL_PATH)/src/haptic/dummy/*.c) \
	$(wildcard $(LOCAL_PATH)/src/joystick/*.c) \
	$(wildcard $(LOCAL_PATH)/src/joystick/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/loadso/dlopen/*.c) \
	$(wildcard $(LOCAL_PATH)/src/power/*.c) \
	$(wildcard $(LOCAL_PATH)/src/power/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/filesystem/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/render/*.c) \
	$(wildcard $(LOCAL_PATH)/src/render/*/*.c) \
	$(wildcard $(LOCAL_PATH)/src/stdlib/*.c) \
	$(wildcard $(LOCAL_PATH)/src/thread/*.c) \
	$(wildcard $(LOCAL_PATH)/src/thread/pthread/*.c) \
	$(wildcard $(LOCAL_PATH)/src/timer/*.c) \
	$(wildcard $(LOCAL_PATH)/src/timer/unix/*.c) \
	$(wildcard $(LOCAL_PATH)/src/video/*.c) \
	$(wildcard $(LOCAL_PATH)/src/video/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/test/*.c))

LOCAL_CFLAGS += -DGL_GLEXT_PROTOTYPES
LOCAL_LDLIBS := -ldl -lGLESv1_CM -lGLESv2 -llog -landroid

include $(BUILD_SHARED_LIBRARY)

5）現在把項目中jni目錄下的Android.mk的內容改成include $(call all-subdir-makefiles)其實就是SDL2-2.0.5\android-project\jni中Android.mk的內容，這一句的意思是調用子目錄下所有的mk文件，這樣SDL目錄中的mk文件就能執行了。然後再把SDL2-2.0.5\android-project\jni中的Application.mk複製到項目jni目錄下，最終如圖所示：

 

 

 

6）接下來我們爲SDL4Android.c文件添加如下代碼：

 

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#include "SDL.h"

typedef struct Sprite
{
	SDL_Texture* texture;
	Uint16 w;
	Uint16 h;
} Sprite;

/* Adapted from SDL's testspriteminimal.c */
Sprite LoadSprite(const char* file, SDL_Renderer* renderer)
{
	Sprite result;
	result.texture = NULL;
	result.w = 0;
	result.h = 0;

    SDL_Surface* temp;

    /* Load the sprite image */
    temp = SDL_LoadBMP(file);
    if (temp == NULL)
	{
        fprintf(stderr, "Couldn't load %s: %s\n", file, SDL_GetError());
        return result;
    }
    result.w = temp->w;
    result.h = temp->h;

    /* Create texture from the image */
    result.texture = SDL_CreateTextureFromSurface(renderer, temp);
    if (!result.texture) {
        fprintf(stderr, "Couldn't create texture: %s\n", SDL_GetError());
        SDL_FreeSurface(temp);
        return result;
    }
    SDL_FreeSurface(temp);

    return result;
}

void draw(SDL_Window* window, SDL_Renderer* renderer, const Sprite sprite)
{
	int w, h;
	SDL_GetWindowSize(window, &w, &h);
	SDL_Rect destRect = {w/2 - sprite.w/2, h/2 - sprite.h/2, sprite.w, sprite.h};
	/* Blit the sprite onto the screen */
	SDL_RenderCopy(renderer, sprite.texture, NULL, &destRect);
}

int main(int argc, char *argv[])
{
    SDL_Window *window;
    SDL_Renderer *renderer;

    if(SDL_CreateWindowAndRenderer(0, 0, 0, &window, &renderer) < 0)
        exit(2);

	Sprite sprite = LoadSprite("zx.bmp", renderer);
    if(sprite.texture == NULL)
        exit(2);

    /* Main render loop */
    Uint8 done = 0;
    SDL_Event event;
    while(!done)
	{
        /* Check for events */
        while(SDL_PollEvent(&event))
		{
            if(event.type == SDL_QUIT || event.type == SDL_KEYDOWN || event.type == SDL_FINGERDOWN)
			{
                //done = 1;
            }
        }


		/* Draw a gray background */
		SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
		SDL_RenderClear(renderer);

		draw(window, renderer, sprite);

		/* Update the screen! */
		SDL_RenderPresent(renderer);

		SDL_Delay(10);
    }

    exit(0);
}

這段代碼是根據（http://www.dinomage.com/wp-content/uploads/2013/01/main.c）改的，寫好後把SDL4Android.c移動到SDL中src目錄下，裏面的zx.bmp圖片（最終成功顯示的圖片）是添加到assets裏面的：

 

把SDL中的Android.mk中的YourSourceHere.c改成$(SDL_PATH)/src/SDL4Android.c，最終改後的Android.mk文件內容爲：

 

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := main

SDL_PATH := ../SDL

LOCAL_C_INCLUDES := $(LOCAL_PATH)/$(SDL_PATH)/include

# Add your application source files here...
LOCAL_SRC_FILES := $(SDL_PATH)/src/main/android/SDL_android_main.c \
	$(SDL_PATH)/src/SDL4Android.c

LOCAL_SHARED_LIBRARIES := SDL2

LOCAL_LDLIBS := -lGLESv1_CM -lGLESv2 -llog

include $(BUILD_SHARED_LIBRARY)


###########################
#
# SDL shared library
#
###########################

include $(CLEAR_VARS)

LOCAL_MODULE := SDL2

LOCAL_C_INCLUDES := $(LOCAL_PATH)/include

LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES)

LOCAL_SRC_FILES := \
	$(subst $(LOCAL_PATH)/,, \
	$(wildcard $(LOCAL_PATH)/src/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/audio/dummy/*.c) \
	$(LOCAL_PATH)/src/atomic/SDL_atomic.c \
	$(LOCAL_PATH)/src/atomic/SDL_spinlock.c.arm \
	$(wildcard $(LOCAL_PATH)/src/core/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/cpuinfo/*.c) \
	$(wildcard $(LOCAL_PATH)/src/dynapi/*.c) \
	$(wildcard $(LOCAL_PATH)/src/events/*.c) \
	$(wildcard $(LOCAL_PATH)/src/file/*.c) \
	$(wildcard $(LOCAL_PATH)/src/haptic/*.c) \
	$(wildcard $(LOCAL_PATH)/src/haptic/dummy/*.c) \
	$(wildcard $(LOCAL_PATH)/src/joystick/*.c) \
	$(wildcard $(LOCAL_PATH)/src/joystick/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/loadso/dlopen/*.c) \
	$(wildcard $(LOCAL_PATH)/src/power/*.c) \
	$(wildcard $(LOCAL_PATH)/src/power/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/filesystem/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/render/*.c) \
	$(wildcard $(LOCAL_PATH)/src/render/*/*.c) \
	$(wildcard $(LOCAL_PATH)/src/stdlib/*.c) \
	$(wildcard $(LOCAL_PATH)/src/thread/*.c) \
	$(wildcard $(LOCAL_PATH)/src/thread/pthread/*.c) \
	$(wildcard $(LOCAL_PATH)/src/timer/*.c) \
	$(wildcard $(LOCAL_PATH)/src/timer/unix/*.c) \
	$(wildcard $(LOCAL_PATH)/src/video/*.c) \
	$(wildcard $(LOCAL_PATH)/src/video/android/*.c) \
	$(wildcard $(LOCAL_PATH)/src/test/*.c))

LOCAL_CFLAGS += -DGL_GLEXT_PROTOTYPES
LOCAL_LDLIBS := -ldl -lGLESv1_CM -lGLESv2 -llog -landroid

include $(BUILD_SHARED_LIBRARY)

7）到了這一步，我們的工作基本做完了，剩下的是把SDL2-2.0.5\android-project中的src中的SDLActivity.java和
res中的資源文件複製替換掉項目中的資源，刪掉不需要的文件，並把SDLActivity改成啓動Activity如圖：

 

8）好了現在可以編譯項目了：

最終生成了我們需要的.so庫：

最後運行我們的項目：

 

至此就成功的在Android平臺上面編譯了SDL庫，接下來就是和FFmpeg整合了，後面研究了再分享給大家。

源碼下載地址：GitHub

睡覺了， 晚安各位！！！