destroy all textures on window destruction and restore OpenGL objects when Android resumes the app

android/src/main/cpp/main.cpp

@@ -357,6 +357,7 @@ static void engine_term_display(struct engine* engine) {
     engine->display = EGL_NO_DISPLAY;
     engine->context = EGL_NO_CONTEXT;
     engine->surface = EGL_NO_SURFACE;
+    App::I.terminate();
 }
 
 /**
@@ -528,7 +529,7 @@ static void engine_handle_cmd(struct android_app* app, int32_t cmd) {
         case APP_CMD_TERM_WINDOW:
             // The window is being hidden or closed, clean it up.
             engine_term_display(engine);
-            exit(0);
+            //exit(0);
             break;
         case APP_CMD_GAINED_FOCUS:
             // When our app gains focus, we start monitoring the accelerometer.