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SDL Mercurial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 := main SDL_PATH := ../SDL
SDL_IMAGE_PATH := ../SDL2_image
SDL_TTF_PATH := ../SDL_ttf LOCAL_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.c LOCAL_SHARED_LIBRARIES := SDL2
LOCAL_SHARED_LIBRARIES += SDL2_image
LOCAL_SHARED_LIBRARIES += SDL2_ttf LOCAL_LDLIBS := -lGLESv1_CM -lGLESv2 -llog include $(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 screen
const int SCREEN_WIDTH = ;
const int SCREEN_HEIGHT = ; 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 ,
* 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 screen
const int SCREEN_WIDTH = ;
const int SCREEN_HEIGHT = ; 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 screen
const int SCREEN_WIDTH = ;
const int SCREEN_HEIGHT = ; 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 screen
const int SCREEN_WIDTH = ;
const int SCREEN_HEIGHT = ; 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[]; 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) + );
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) + );
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) + );
strcpy(font_file, filefolder);
strcat(font_file, font_temp);
LOGI("natvie_SDL font_file : %s", font_file); if (SDL_Init(SDL_INIT_EVERYTHING) != ) {
LOGE("SDL_Init failed %s", SDL_GetError());
return ;
} if (TTF_Init() != ) {
LOGE("TTF_Init failed %s", SDL_GetError());
SDL_Quit();
return ;
} window = SDL_CreateWindow("lesson5", , , SCREEN_WIDTH, SCREEN_HEIGHT,
SDL_WINDOW_SHOWN);
if (window == NULL) {
LOGE("SDL_CreateWindow failed %s", SDL_GetError());
TTF_Quit();
SDL_Quit();
return ;
} render = SDL_CreateRenderer(window, -,
SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
if (render == NULL) {
LOGE("SDL_CreateRenderer failed %s", SDL_GetError());
cleanup_window(window);
TTF_Quit();
SDL_Quit();
return ;
} SDL_Color color = { , , , }; image = renderText("TTF fonts are cool !", font_file, color, , render); if (image == NULL) {
cleanup_texture(image);
cleanup_render(render);
cleanup_window(window);
TTF_Quit();
SDL_Quit();
return ;
} //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 / - iW / ;
int y = SCREEN_HEIGHT / - iH / ; SDL_Event e;
int quit = ;
while (quit != ) {
//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 = ;
}
if (e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_ESCAPE) {
quit = ;
}
} //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 ;
}
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：