fix some compiling warning.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1101 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/rtgui/include/rtgui/widgets/button.h

@@ -61,8 +61,8 @@ typedef struct rtgui_button rtgui_button_t;
 
 rtgui_type_t *rtgui_button_type_get(void);
 
-rtgui_button_t* rtgui_button_create(char* text);
-rtgui_button_t* rtgui_pushbutton_create(char* text);
+rtgui_button_t* rtgui_button_create(const char* text);
+rtgui_button_t* rtgui_pushbutton_create(const char* text);
 void rtgui_button_destroy(rtgui_button_t* btn);
 
 void rtgui_button_set_pressed_image(rtgui_button_t* btn, rtgui_image_t* image);

components/rtgui/widgets/button.c

@@ -194,7 +194,7 @@ rt_bool_t rtgui_button_event_handler(struct rtgui_widget* widget, struct rtgui_e
 	return RT_FALSE;
 }
 
-rtgui_button_t* rtgui_button_create(char* text)
+rtgui_button_t* rtgui_button_create(const char* text)
 {
     struct rtgui_button* btn;
 
@@ -214,7 +214,7 @@ rtgui_button_t* rtgui_button_create(char* text)
     return btn;
 }
 
-rtgui_button_t* rtgui_pushbutton_create(char* text)
+rtgui_button_t* rtgui_pushbutton_create(const char* text)
 {
 	rtgui_button_t* btn;