[原]零基础学习SDL开发之在Android使用SDL2.0加载字体

在上一篇文章我们知道了如何在android使用SDL2.0来渲染显示一张png图，而且在上上一篇我们知道如何使用sdl来渲染输出bmp图，那么sdl是否可以渲染输出自己喜爱的字体库的字体呢？答案是当然可以。

我们需要移植SDL_ttf字体库来支持相应的字体的渲染输出。

一、移植SDL_ttf库：

使用如下命令，从SDLMercurial获取SDL_image的源码：

hg clone https://hg.libsdl.org/SDL_ttf/

将SDL_ttf拷贝到在上一篇文章中的android-project\jni\下，将平台相关的代码去掉以及自动自动化相关的文件去掉，保留android相关的代码与文件。

二、在android中添加相关的引用：

修改android-project\jni\src\Android.mk，添加相关的引用:

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := mainSDL_PATH := ../SDLSDL_IMAGE_PATH := ../SDL2_imageSDL_TTF_PATH := ../SDL_ttfLOCAL_C_INCLUDES := $(LOCAL_PATH)/$(SDL_PATH)/include LOCAL_C_INCLUDES +=    $(LOCAL_PATH)/$(SDL_IMAGE_PATH)LOCAL_C_INCLUDES +=    $(LOCAL_PATH)/$(SDL_TTF_PATH)# Add your application source files here...LOCAL_SRC_FILES := $(SDL_PATH)/src/main/android/SDL_android_main.c \    SDL_lesson.cLOCAL_SHARED_LIBRARIES := SDL2LOCAL_SHARED_LIBRARIES += SDL2_imageLOCAL_SHARED_LIBRARIES += SDL2_ttfLOCAL_LDLIBS := -lGLESv1_CM -lGLESv2 -lloginclude $(BUILD_SHARED_LIBRARY)

三、代码中引用相关的头文件：

/* * SDL_lesson.c * Clipping Sprite Sheets *  Created on: Aug 12, 2014 *      Author: clarck */#include <jni.h>#include "SDL.h"#include "SDL_image.h"#include "SDL_ttf.h"#include "SDL_logger.h"#include "SDL_main.h"#include "SDL_cleanup.h"//The attributes of the screenconst int SCREEN_WIDTH = 640;const int SCREEN_HEIGHT = 480;struct SDL_Window *window = NULL;struct SDL_Renderer *render = NULL;struct SDL_Texture *background = NULL;struct SDL_Texture *image = NULL;struct SDL_Surface *surface = NULL;struct SDL_Texture *texture = NULL;

四、加载图片的部分修改为IMG_LoadTexture:

* SDL_lesson.c * Clipping Sprite Sheets *  Created on: Aug 12, 2014 *      Author: clarck */#include <jni.h>#include "SDL.h"#include "SDL_image.h"#include "SDL_ttf.h"#include "SDL_logger.h"#include "SDL_main.h"#include "SDL_cleanup.h"//The attributes of the screenconst int SCREEN_WIDTH = 640;const int SCREEN_HEIGHT = 480;struct SDL_Window *window = NULL;struct SDL_Renderer *render = NULL;struct SDL_Texture *background = NULL;struct SDL_Texture *image = NULL;struct SDL_Surface *surface = NULL;struct SDL_Texture *texture = NULL;/* * Loads a image into a texture on the rendering device * @param file The image file to load * @param ren The renderer to load the texture onto * @return the loaded texture, or NULL if something went wrong. */SDL_Texture* loadTexture(const char *file, SDL_Renderer *render) {    struct SDL_Texture *texture = NULL;    texture = IMG_LoadTexture(render, file);    if (texture == NULL) {        LOGE("SDL_CreateTextureFromSurface failed %s", SDL_GetError());    } else {        LOGI("SDL_CreateTextureFromSurface successful.");    }    return texture;}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height * @param tex The source texture we want to draw * @param ren The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param w The width of the texture to draw * @param h The height of the texture to draw */void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, SDL_Rect dst,        SDL_Rect *clip) {    SDL_RenderCopy(ren, tex, clip, &dst);}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height and taking a clip of the texture if desired * If a clip is passed, the clip's width and height will be used instead of the texture's * @param tex The source texture we want to draw * @param rend The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param clip The sub-section of the texture to draw (clipping rect) *        default of nullptr draws the entire texture */void renderTexture2(SDL_Texture *tex, SDL_Renderer *ren, int x, int y,        SDL_Rect *clip) {    SDL_Rect dst;    dst.x = x;    dst.y = y;    if (clip != NULL) {        dst.w = clip->w;        dst.h = clip->h;    } else {        SDL_QueryTexture(tex, NULL, NULL, &dst.w, &dst.h);    }    renderTexture(tex, ren, dst, clip);}

五、添加字体渲染功能函数：

/* * SDL_lesson.c * Clipping Sprite Sheets *  Created on: Aug 12, 2014 *      Author: clarck */#include <jni.h>#include "SDL.h"#include "SDL_image.h"#include "SDL_ttf.h"#include "SDL_logger.h"#include "SDL_main.h"#include "SDL_cleanup.h"//The attributes of the screenconst int SCREEN_WIDTH = 640;const int SCREEN_HEIGHT = 480;struct SDL_Window *window = NULL;struct SDL_Renderer *render = NULL;struct SDL_Texture *background = NULL;struct SDL_Texture *image = NULL;struct SDL_Surface *surface = NULL;struct SDL_Texture *texture = NULL;/* * Loads a image into a texture on the rendering device * @param file The image file to load * @param ren The renderer to load the texture onto * @return the loaded texture, or NULL if something went wrong. */SDL_Texture* loadTexture(const char *file, SDL_Renderer *render) {    struct SDL_Texture *texture = NULL;    texture = IMG_LoadTexture(render, file);    if (texture == NULL) {        LOGE("SDL_CreateTextureFromSurface failed %s", SDL_GetError());    } else {        LOGI("SDL_CreateTextureFromSurface successful.");    }    return texture;}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height * @param tex The source texture we want to draw * @param ren The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param w The width of the texture to draw * @param h The height of the texture to draw */void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, SDL_Rect dst,        SDL_Rect *clip) {    SDL_RenderCopy(ren, tex, clip, &dst);}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height and taking a clip of the texture if desired * If a clip is passed, the clip's width and height will be used instead of the texture's * @param tex The source texture we want to draw * @param rend The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param clip The sub-section of the texture to draw (clipping rect) *        default of nullptr draws the entire texture */void renderTexture2(SDL_Texture *tex, SDL_Renderer *ren, int x, int y,        SDL_Rect *clip) {    SDL_Rect dst;    dst.x = x;    dst.y = y;    if (clip != NULL) {        dst.w = clip->w;        dst.h = clip->h;    } else {        SDL_QueryTexture(tex, NULL, NULL, &dst.w, &dst.h);    }    renderTexture(tex, ren, dst, clip);}SDL_Texture* renderText(char *message, char *fontFile, SDL_Color color,        int fontSize, SDL_Renderer *renderer) {    //Open the font    TTF_Font *font = TTF_OpenFont(fontFile, fontSize);    if (font == NULL) {        LOGE("renderText error: %s", SDL_GetError());        return NULL;    }    surface = TTF_RenderText_Blended(font, message, color);    if (surface == NULL) {        TTF_CloseFont(font);        LOGE("TTF_RenderText_Blended error: %s", SDL_GetError());        return NULL;    }    texture = SDL_CreateTextureFromSurface(renderer, surface);    if (texture == NULL) {        LOGE("SDL_CreateTextureFromSurface error: %s", SDL_GetError());    }    //Clean up the surface and font    SDL_FreeSurface(surface);    TTF_CloseFont(font);    return texture;}

六、编写主函数功能：

/* * SDL_lesson.c * Clipping Sprite Sheets *  Created on: Aug 12, 2014 *      Author: clarck */#include <jni.h>#include "SDL.h"#include "SDL_image.h"#include "SDL_ttf.h"#include "SDL_logger.h"#include "SDL_main.h"#include "SDL_cleanup.h"//The attributes of the screenconst int SCREEN_WIDTH = 640;const int SCREEN_HEIGHT = 480;struct SDL_Window *window = NULL;struct SDL_Renderer *render = NULL;struct SDL_Texture *background = NULL;struct SDL_Texture *image = NULL;struct SDL_Surface *surface = NULL;struct SDL_Texture *texture = NULL;/* * Loads a image into a texture on the rendering device * @param file The image file to load * @param ren The renderer to load the texture onto * @return the loaded texture, or NULL if something went wrong. */SDL_Texture* loadTexture(const char *file, SDL_Renderer *render) {    struct SDL_Texture *texture = NULL;    texture = IMG_LoadTexture(render, file);    if (texture == NULL) {        LOGE("SDL_CreateTextureFromSurface failed %s", SDL_GetError());    } else {        LOGI("SDL_CreateTextureFromSurface successful.");    }    return texture;}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height * @param tex The source texture we want to draw * @param ren The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param w The width of the texture to draw * @param h The height of the texture to draw */void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, SDL_Rect dst,        SDL_Rect *clip) {    SDL_RenderCopy(ren, tex, clip, &dst);}/* * Draw an SDL_Texture to an SDL_Renderer at position x, y, preserving * the texture's width and height and taking a clip of the texture if desired * If a clip is passed, the clip's width and height will be used instead of the texture's * @param tex The source texture we want to draw * @param rend The renderer we want to draw too * @param x The x coordinate to draw too * @param y The y coordinate to draw too * @param clip The sub-section of the texture to draw (clipping rect) *        default of nullptr draws the entire texture */void renderTexture2(SDL_Texture *tex, SDL_Renderer *ren, int x, int y,        SDL_Rect *clip) {    SDL_Rect dst;    dst.x = x;    dst.y = y;    if (clip != NULL) {        dst.w = clip->w;        dst.h = clip->h;    } else {        SDL_QueryTexture(tex, NULL, NULL, &dst.w, &dst.h);    }    renderTexture(tex, ren, dst, clip);}SDL_Texture* renderText(char *message, char *fontFile, SDL_Color color,        int fontSize, SDL_Renderer *renderer) {    //Open the font    TTF_Font *font = TTF_OpenFont(fontFile, fontSize);    if (font == NULL) {        LOGE("renderText error: %s", SDL_GetError());        return NULL;    }    surface = TTF_RenderText_Blended(font, message, color);    if (surface == NULL) {        TTF_CloseFont(font);        LOGE("TTF_RenderText_Blended error: %s", SDL_GetError());        return NULL;    }    texture = SDL_CreateTextureFromSurface(renderer, surface);    if (texture == NULL) {        LOGE("SDL_CreateTextureFromSurface error: %s", SDL_GetError());    }    //Clean up the surface and font    SDL_FreeSurface(surface);    TTF_CloseFont(font);    return texture;}int main(int argc, char *argv[]) {    //char *filefolder = "/storage/sdcard0/";    char *filefolder = argv[1];    char *font_temp = "sample.ttf";    char *image_temp = "image.png";    char *background_temp = "background.png";    LOGI("natvie_SDL %s", filefolder);    char *background_file = (char*) malloc(            strlen(filefolder) + strlen(background_temp) + 1);    strcpy(background_file, filefolder);    strcat(background_file, background_temp);    LOGI("natvie_SDL background_file : %s", background_file);    char *image_file = (char*) malloc(            strlen(filefolder) + strlen(image_temp) + 1);    strcpy(image_file, filefolder);    strcat(image_file, image_temp);    LOGI("natvie_SDL image_file : %s", image_file);    char *font_file = (char*) malloc(            strlen(filefolder) + strlen(font_temp) + 1);    strcpy(font_file, filefolder);    strcat(font_file, font_temp);    LOGI("natvie_SDL font_file : %s", font_file);    if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {        LOGE("SDL_Init failed %s", SDL_GetError());        return 1;    }    if (TTF_Init() != 0) {        LOGE("TTF_Init failed %s", SDL_GetError());        SDL_Quit();        return 1;    }    window = SDL_CreateWindow("lesson5", 100, 100, SCREEN_WIDTH, SCREEN_HEIGHT,            SDL_WINDOW_SHOWN);    if (window == NULL) {        LOGE("SDL_CreateWindow failed %s", SDL_GetError());        TTF_Quit();        SDL_Quit();        return 1;    }    render = SDL_CreateRenderer(window, -1,            SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);    if (render == NULL) {        LOGE("SDL_CreateRenderer failed %s", SDL_GetError());        cleanup_window(window);        TTF_Quit();        SDL_Quit();        return 1;    }    SDL_Color color = { 255, 255, 255, 255 };    image = renderText("TTF fonts are cool !", font_file, color, 64, render);    if (image == NULL) {        cleanup_texture(image);        cleanup_render(render);        cleanup_window(window);        TTF_Quit();        SDL_Quit();        return 1;    }    //Clear the window    SDL_RenderClear(render);    //Draw our image in the center of the window    //We need the foreground image's width to properly compute the position    //of it's top left corner so that the image will be centered    int iW, iH;    int x = SCREEN_WIDTH / 2 - iW / 2;    int y = SCREEN_HEIGHT / 2 - iH / 2;    SDL_Event e;    int quit = 1;    while (quit != 0) {        //Read any events that occured, for now we'll just quit if any event occurs        while (SDL_PollEvent(&e)) {            //If user closes the window            if (e.type == SDL_QUIT) {                quit = 0;            }            if (e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_ESCAPE) {                quit = 0;            }        }        //Rendering        SDL_RenderClear(render);        //Draw the image        renderTexture2(image, render, x, y, NULL);        SDL_RenderPresent(render);    }    //Destroy the various items    cleanup_texture(image);    cleanup_render(render);    cleanup_window(window);    IMG_Quit();    SDL_Quit();    return 0;}

七、修改SDLActivity，添加SDL_ttf动态库的load：

// Load the .so    static {        System.loadLibrary("SDL2");        System.loadLibrary("SDL2_image");        //System.loadLibrary("SDL2_mixer");        //System.loadLibrary("SDL2_net");        System.loadLibrary("SDL2_ttf");        System.loadLibrary("main");    }

运行截图：

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