EEPW论坛

请问定义SUPPORT_BG有什么作用，比不定义SUPPORT_BG有什么功能不能实现吗？新建工程默认是定义SUPPORT_BG的，可为什么定义了SUPPORT_BG后，发送SMS消息或Start call后屏幕不能正常显示，而是出现“please delete layer”（如图）？


代码如下：
#include "vmsys.h"
#include "vmio.h"
#include "vmgraph.h"
#include "vmchset.h"
#include "vmstdlib.h"

/* ---------------------------------------------------------------------------
 * global variables
 * ------------------------------------------------------------------------ */

#define  SUPPORT_BG

VMINT  layer_hdl[1];    // layer handle array.

/* ---------------------------------------------------------------------------
 * local variables
 * ------------------------------------------------------------------------ */
/*
 * system events
 */
void handle_sysevt(VMINT message, VMINT param);

/*
 * key events
 */
void handle_keyevt(VMINT event, VMINT keycode);

/*
 * pen events
 */
void handle_penevt(VMINT event, VMINT x, VMINT y);

/*
 * demo
 */
static void draw_hello(void);

/**
 * entry
 */
void vm_main(void)
{
 layer_hdl[0] = -1;

 vm_reg_sysevt_callback(handle_sysevt);
 vm_reg_keyboard_callback(handle_keyevt);
 vm_reg_pen_callback(handle_penevt);
}

void handle_sysevt(VMINT message, VMINT param)
{
#ifdef  SUPPORT_BG 
 /* The application updates the screen when receiving the message VM_MSG_PAINT
 *  what is sent after the application is activated. The application can skip
 *  the process on screen when the VM_MSG_ACTIVE or VM_MSG_INACTIVE is received.
 */
 switch (message)
    {
  case VM_MSG_CREATE:
   /* the GDI operation is not recommended as the response of the message*/
   break;
  case VM_MSG_PAINT:
   /* cerate base layer that has same size as the screen*/
            /*If rotating screen is needed, and it rotates successful,
            the application will receive the VM_MSG_PAINT event, then,
            the application needs to delete the level and recreate it. */  
   if( layer_hdl[0] != -1 )
   {
    vm_graphic_delete_layer(layer_hdl[0]);
    layer_hdl[0] = -1;
   }

   if( layer_hdl[0] == -1 )
   {
    layer_hdl[0] = vm_graphic_create_layer(0, 0,
     vm_graphic_get_screen_width(),
     vm_graphic_get_screen_height(), -1); 
   }

   /* set clip area */
   vm_graphic_set_clip(0, 0,
    vm_graphic_get_screen_width(),
    vm_graphic_get_screen_height());

   draw_hello();
   break;
  case VM_MSG_SCREEN_ROTATE:
   /*The application can rotate the screen*/
   break;
  case VM_MSG_HIDE:
            if( layer_hdl[0] != -1 )
            {
                vm_graphic_delete_layer(layer_hdl[0]);
                layer_hdl[0] = -1;
   }
            break;
  case VM_MSG_QUIT:
   if( layer_hdl[0] != -1 )
   {
    vm_graphic_delete_layer(layer_hdl[0]);
    layer_hdl[0] = -1;
   }
            vm_exit_app();
   break;
 }
#else
 switch (message)
    {
  case VM_MSG_CREATE:
  case VM_MSG_ACTIVE:
   /*cerate base layer that has same size as the screen*/
   if( layer_hdl[0] == -1 )
   {
    layer_hdl[0] = vm_graphic_create_layer(0, 0,
     vm_graphic_get_screen_width(),
     vm_graphic_get_screen_height(), -1); 
   }
   
   /* set clip area*/
   vm_graphic_set_clip(0, 0,
    vm_graphic_get_screen_width(),
    vm_graphic_get_screen_height());
   break;

   /*If rotating screen is needed, and it rotates successful,
            the application will receive the VM_MSG_PAINT event, then,
            the application needs to delete the level and recreate it. */  
  case VM_MSG_PAINT:
   draw_hello();
   break;
  case VM_MSG_SCREEN_ROTATE: 
   /*The application can rotate the screen*/
   break;
  case VM_MSG_INACTIVE:
            if( layer_hdl[0] != -1 )
            {
                vm_graphic_delete_layer(layer_hdl[0]);
                layer_hdl[0] = -1;
   }
            break;
  case VM_MSG_QUIT:
   if( layer_hdl[0] != -1 )
   {
    vm_graphic_delete_layer(layer_hdl[0]);
    layer_hdl[0] = -1;
   }
            vm_exit_app();
   break; 
 }
#endif
}

void handle_keyevt(VMINT event, VMINT keycode)
{
 /* press any key and return*/
 if( layer_hdl[0] != -1 )
 {
  vm_graphic_delete_layer(layer_hdl[0]);
  layer_hdl[0] = -1;
 }

 vm_exit_app();
}

void handle_penevt(VMINT event, VMINT x, VMINT y)
{
 /* touch and return*/
 if( layer_hdl[0] != -1 )
 {
  vm_graphic_delete_layer(layer_hdl[0]);
  layer_hdl[0] = -1;
 }

 vm_exit_app();
}

static void draw_hello(void)
{
 VMWCHAR s[50];
 VMUINT8* buf; 
 int x, y, w;
 
 vm_gb2312_to_ucs2(s, 50, "Hello, world!");
 w = vm_graphic_get_string_width(s);
 x = (vm_graphic_get_screen_width() - w) / 2;
 y = (vm_graphic_get_screen_height() - vm_graphic_get_character_height()) / 2;
 
 /* get the target buffer*/
 buf = vm_graphic_get_layer_buffer(layer_hdl[0]);  
 
 /* fill the screen*/
 vm_graphic_fill_rect(buf, 0, 0, vm_graphic_get_screen_width(),
  vm_graphic_get_screen_height(), VM_COLOR_WHITE, VM_COLOR_BLACK);
 
 /* draw text */
 vm_graphic_textout(buf, x, y, s, wstrlen(s), VM_COLOR_BLUE);
 
 /* flush the screen with data in the buffer*/
 vm_graphic_flush_layer(layer_hdl, 1);
}