如何建立擁有者繪製清單框
本主題示範如何實作擁有者繪製的清單框。
本主題中的 C++ 程式代碼範例示範如何繪製包含五個擁有者繪製專案的清單框：四個繪圖實作和分叉。 每個清單項目都會以點陣圖的形式出現，後面接著對象的名稱。 按鈕會提示用戶選取一個不像其他人的專案。 選擇已選取分叉的按鈕會顯示「您是正確的！」訊息，並關閉對話方塊。 選擇已選取任何其他清單專案的按鈕會顯示「再試一次！」訊息。
除了標準清單框樣式之外，清單框還有LBS_OWNERDRAWFIXED和LBS_HASSTRINGS樣式。
您需要知道的事項
技術
必要條件
- C/C++
- Windows 使用者介面程序設計
指示
若要初始化擁有者繪製的清單框，您的應用程式必須載入每個清單框專案的文字字串和相關聯的點陣圖。
在下列 C++ 程式代碼範例中，對話框程式會傳送LB_ADDSTRING訊息來設定文字，然後傳送LB_SETITEMDATA訊息，以將點陣圖與每個清單框專案產生關聯，以初始化清單框IDC_LIST_STUFF清單框。 程式代碼也會藉由處理WM_MEASUREITEM訊息來設定每個清單框專案的高度，並藉由處理WM_DRAWITEM訊息來繪製每個專案的文字和位圖。
#define XBITMAP 48
#define YBITMAP 48
#define BUFFER MAX_PATH
HBITMAP hbmpPencil, hbmpCrayon, hbmpMarker, hbmpPen, hbmpFork;
HBITMAP hbmpPicture, hbmpOld;
void AddItem(HWND hwnd, PTSTR pstr, HBITMAP hbmp)
{
int lbItem;
lbItem = SendMessage(hwnd, LB_ADDSTRING, 0, (LPARAM)pstr);
SendMessage(hwnd, LB_SETITEMDATA, (WPARAM)lbItem, (LPARAM)hbmp);
}
INT_PTR CALLBACK DlgDrawProc(HWND hDlg, UINT message,
UINT wParam, LONG lParam)
{
HWND hListBox;
PMEASUREITEMSTRUCT pmis;
PDRAWITEMSTRUCT pdis;
HDC hdcMem;
HBITMAP hbmp;
TCHAR achBuffer[BUFFER];
size_t cch;
int yPos;
int lbItem;
TEXTMETRIC tm;
RECT rcBitmap;
HRESULT hr;
switch (message)
{
case WM_INITDIALOG:
// Load the bitmaps. g_hInst is the global HINSTANCE handle.
hbmpPencil = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_PENCIL));
hbmpCrayon = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_CRAYON));
hbmpMarker = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_MARKER));
hbmpPen = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_PEN));
hbmpFork = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_FORK));
// Retrieve the list box handle.
hListBox = GetDlgItem(hDlg, IDC_LIST_STUFF);
// Initialize the list box text and associate a bitmap
// with each list box item.
AddItem(hListBox, L"pencil", hbmpPencil);
AddItem(hListBox, L"crayon", hbmpCrayon);
AddItem(hListBox, L"marker", hbmpMarker);
AddItem(hListBox, L"pen", hbmpPen);
AddItem(hListBox, L"fork", hbmpFork);
SetFocus(hListBox);
SendMessage(hListBox, LB_SETCURSEL, 0, 0);
return TRUE;
case WM_MEASUREITEM:
pmis = (PMEASUREITEMSTRUCT) lParam;
// Set the height of the list box items.
pmis->itemHeight = YBITMAP;
return TRUE;
case WM_DRAWITEM:
pdis = (PDRAWITEMSTRUCT) lParam;
// If there are no list box items, skip this message.
if (pdis->itemID == -1)
{
break;
}
// Draw the bitmap and text for the list box item. Draw a
// rectangle around the bitmap if it is selected.
switch (pdis->itemAction)
{
case ODA_SELECT:
case ODA_DRAWENTIRE:
// Draw the bitmap associated with the item.
//
// Get the item bitmap.
hbmpPicture = (HBITMAP)SendMessage(pdis->hwndItem,
LB_GETITEMDATA, pdis->itemID, 0);
// Create a compatible device context.
hdcMem = CreateCompatibleDC(pdis->hDC);
// Select the item bitmap into the compatible device
// context and save the old bitmap.
hbmpOld = (HBITMAP) SelectObject(hdcMem, hbmpPicture);
// Copy the bitmap into the compatible device context.
BitBlt(pdis->hDC,
pdis->rcItem.left, pdis->rcItem.top,
pdis->rcItem.right - pdis->rcItem.left,
pdis->rcItem.bottom - pdis->rcItem.top,
hdcMem, 0, 0, SRCCOPY);
// Draw the string associated with the item.
//
// Get the item string from the list box.
SendMessage(pdis->hwndItem, LB_GETTEXT,
pdis->itemID, (LPARAM)achBuffer);
// Get the metrics for the current font.
GetTextMetrics(pdis->hDC, &tm);
// Calculate the vertical position for the item string
// so that the string will be vertically centered in the
// item rectangle.
yPos = (pdis->rcItem.bottom + pdis->rcItem.top -
tm.tmHeight) / 2;
// Get the character length of the item string.
hr = StringCchLength(achBuffer, BUFFER, &cch);
if (FAILED(hr))
{
// TODO: Handle error.
}
// Draw the string in the item rectangle, leaving a six
// pixel gap between the item bitmap and the string.
TextOut(pdis->hDC, XBITMAP + 6, yPos, achBuffer, cch);
// Clean up.
SelectObject(hdcMem, hbmpOld);
DeleteDC(hdcMem);
// Is the item selected?
if (pdis->itemState & ODS_SELECTED)
{
// Set RECT coordinates to surround only the
// bitmap.
rcBitmap.left = pdis->rcItem.left;
rcBitmap.top = pdis->rcItem.top;
rcBitmap.right = pdis->rcItem.left + XBITMAP;
rcBitmap.bottom = pdis->rcItem.top + YBITMAP;
// Draw a rectangle around bitmap to indicate
// the selection.
DrawFocusRect(pdis->hDC, &rcBitmap);
}
break;
case ODA_FOCUS:
// Do not process focus changes. The focus caret
// (outline rectangle) indicates the selection.
// The IDOK button indicates the final
// selection.
break;
}
return TRUE;
case WM_COMMAND:
switch (LOWORD(wParam))
{
case IDOK:
// Get the selected item's text.
lbItem = SendMessage(GetDlgItem(hDlg, IDC_LIST_STUFF),
LB_GETCURSEL, 0, 0);
// Get the selected item's bitmap.
hbmp = (HBITMAP) SendMessage(GetDlgItem(hDlg, IDC_LIST_STUFF),
LB_GETITEMDATA, lbItem, 0);
// If the item is not the correct answer, tell the
// user to try again.
//
// If the item is the correct answer, congratulate
// the user and destroy the dialog box.
if (hbmp != hbmpFork)
{
MessageBox(hDlg, L"Try again!", L"Oops", MB_OK);
return FALSE;
}
else
{
MessageBox(hDlg, L"You're right!",
L"Congratulations.", MB_OK);
// Fall through.
}
case IDCANCEL:
// Destroy the dialog box.
EndDialog(hDlg, TRUE);
return TRUE;
default:
return FALSE;
}
case WM_DESTROY:
// Free the bitmap resources.
DeleteObject(hbmpPencil);
DeleteObject(hbmpCrayon);
DeleteObject(hbmpMarker);
DeleteObject(hbmpPen);
DeleteObject(hbmpFork);
return TRUE;
default:
return FALSE;
}
return FALSE;
}
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