Multithreading in SDL Mobile

SDL Development
1

Hi everyone
My name TPham, I am a Game Dev
I have a problem for using multithreading in my project.
I make a function from multihreading to show image “loading data” while the app is loading total data for game lesson.
But, the image “loading data” was not shown.
I run my project on windows, the image is show
But on Android studio. the image is not shown

My Code:
The Init Function:

bool GameMain::LoadData()
{
    DataGame* dataGame = new DataGame();
    dataGame->sWidth = m_ScreenWidth;
    dataGame->sHeight = m_ScreenHeight;
    dataGame->screen = m_Screen;
    SDL_Thread* threadID = SDL_CreateThread(LoadingFunction, "LoadingThread", (void*)dataGame);
    LoadTexture();
    InitLesson1();
    InitLesson2();
    InitLesson3();
    InitLesson4();
    InitEndLesson();
    
    g_Finished = true;  // global variable

    return true;
}

The Thread Function

int LoadingFunction(void* data_game)
{
    DataGame* dataGame = (DataGame*)data_game;
    if (dataGame != NULL)
    {
        DataResize data_resize{ dataGame->sWidth, dataGame->sHeight, true };
        BaseObject bkgnObj;
        bkgnObj.SetIsBackGround(true);
        bkgnObj.SetScreenSize(dataGame->sWidth, dataGame->sHeight);
        bkgnObj.SetDataResize(data_resize);
        bool ret = bkgnObj.LoadImg("bkgn_loading.png", dataGame->screen);
        bkgnObj.SetRect(0, 0);

        while (!g_Finished)
        {
            SDL_SetRenderDrawColor(dataGame->screen, RENDER_DRAW_COLOR,..);
            SDL_RenderClear(dataGame->screen);
            bkgnObj.RenderBkgn(dataGame->screen);
            SDL_RenderPresent(dataGame->screen);
        }
    }

    return 0;
}

I want to get help from everyone. Thank you so much.

2

All references to textures must be made from the ‘main’ thread (the thread which created the renderer). You can access surfaces from other threads, but not textures.

3

Thank for your reply.
you mean. I should to using render image from surface in other thread.
Example: SDL_BlitSurface ?

4

SDL_BlitSurface() is safe to call from another thread, yes. Possibly you could blit your “Loading data” message to a surface in your worker thread, then convert the surface to a texture in your main thread for display.

But might it not be simpler to have a Boolean flag set by your worker thread and tested by your main thread, which directly causes the “Loading data” message to be displayed?