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Национальный университет Львовская политехника

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[НЕСОРТИРОВАННОЕ]

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C# ПІДРУЧНИКИ / c# / Manning - Windows.forms.programming.with.c#.pdf

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SAVE A PHOTO’S SETTINGS ONLY WHEN NECESSARY

	Action	Result

12	Create a variable to hold	private bool _modifiedTxtNotes;
	whether the notes value has
	changed.

13	Modify the SetOriginals	protected void SetOriginals()
	method to reset this variable.	{
		. . .
		if (photo != null)
		{
		. . .
		_modifiedTxtNotes = false;
		}
		}

14	Add a TextChanged event	private void txtNotes_TextChanged
	handler for the Notes text box	(object sender, System.EventArgs e)
	to update this variable	{
	to update this variable	if (txtNotes.Focused)
	whenever the user changes	if (txtNotes.Focused)
	whenever the user changes	_modifiedTxtNotes = true;
	the text.	}

15	Create a NewControlValues	protected bool NewControlValues()
	method to determine if any of	{
	photograph’s controls have	bool result =
	photograph’s controls have	((_origCaption != txtCaption.Text)
	been modified.	((_origCaption != txtCaption.Text)
	been modified.	\|\| (_origDateTaken != dtpDateTaken.Value)
		\|\| (_origPhotographer !=
		cmbxPhotographer.Text)
		\|\| (_modifiedTxtNotes));
		return result;
		}

16	Add a variable to track whether	private bool _hasChanged = false;
	any changes have been saved.

17	Modify the SaveSettings	protected override bool SaveSettings()
	method to save the changes	{
	made to the photograph.	if (NewControlValues())
	made to the photograph.	{
		{
	Note: The _hasChanged field	// Save the photograph’s settings
	is required to track whether	Photograph photo = _album[_index];
	is required to track whether
	any photograph has been	if (photo != null)
	modified, as opposed to the	{
	current photo displayed.	photo.Caption = txtCaption.Text;
		photo.DateTaken = dtpDateTaken.Value;
		photo.Photographer
		= cmbxPhotographer.Text;
		photo.Notes = txtNotes.Text;
		_hasChanged = true;
		}
		}
		return true;
		}

18	Add a HasChanged property so	public bool HasChanged
	a caller can determine if any	{
	photographs were saved.	get { return _hasChanged; }
	photographs were saved.	}
		}

IMAGE BUTTONS

397

With these changes in place, we can finally add the click handlers for our buttons.

HANDLE THE CLICK EVENT FOR THE NEXT AND PREV BUTTONS

	Action	Result

19	Add a Click handler for the	private void btnNext_Click
	Next button.	(object sender, System.EventArgs e)
		{
		SaveSettings();
		if (_index < _album.Count - 1)
		{
		_index ++;
		ResetSettings();
		SetOriginals();
		}
		}

20	Add a Click handler for the	private void btnPrev_Click
	Prev button.	(object sender, System.EventArgs e)
		{
		SaveSettings();
		if (_index > 0)
		{
		_index --;
		ResetSettings();
		SetOriginals();
		}
		}

As we said at the start of all this, these buttons required more changes than you might initially expect. As a final change, we need to modify the Click handler for our Photo Properties menu to account for the new changes.

Set the version number of the MyPhotos application to 12.3.

UPDATE THE CLICK HANDLER TO DISPLAY THE DIALOG

	Action	Result

21	Update the Click handler for	private void menuPhotoProp_Click
	the menuPhotoProp control	(object sender, System.EventArgs e)
	to use the HasChanged	{
	to use the HasChanged	if (_album.CurrentPhoto == null)
	property.	if (_album.CurrentPhoto == null)
	property.	return;
		using (PhotoEditDlg dlg
		= new PhotoEditDlg(_album))
		{
		if (dlg.ShowDialog() == DialogResult.OK)
		{
		_bAlbumChanged = dlg.HasChanged;
		if (_bAlbumChanged)
		{
		// Redraw to pick up any changes
		this.Invalidate();
		}
		}
		}
		}

398	CHAPTER 12 A .NET ASSORTMENT

Our buttons are now ready to go. Compile and run your code to make sure the buttons work as expected. Our next topic is the creation of bitmap objects for these buttons.

12.3.2DRAWING BITMAPS FOR OUR BUTTONS

The creation of graphics for a new product is typically left to the graphic designers and marketing folks. Still, you never know when you may feel the urge to draw a bitmap or icon yourself, so let’s look at how to create them from scratch. Fortunately, Microsoft provides a fairly extensive collection of bitmaps, cursors, and icons that can be used within our application. We’ll talk about where to find these in a moment.

A bitmap is created much like any other item in a project. We will begin by creating a bitmap object for our Next button. Later in this section we’ll create another bitmap for our Prev button.

	CREATE THE NEXT BUTTON BITMAP

	Action	Result

1	In the Solution Explorer
	window, add a bitmap file
	“NextButton.bmp” to the
	MyPhotoAlbum project.
	How-to
	a. Right-click the MyPhoto-
	Album project name.
	b. Open the Add submenu.
	c. Select Add New Item to
	display the Add New
	Item dialog box.
	d. Click Resources from
	the list of Categories
	e. Click Bitmap File from
	the available Templates.
	f. Enter “NextButton.bmp”
	as the name.
	Alternately
	The Add New Item dialog
	can be displayed using the
	keyboard shortcut
	Ctrl+Shift+A.

2	Click the Open button to	The new file appears in Solution Explorer.
	create the new file.	The Bitmap Editor appears in the main window and displays
		The Bitmap Editor appears in the main window and displays
		the new bitmap with the default size, which is normally 48×48
		pixels.
		Note: The new file and Bitmap Editor are shown in
		figure 12.3.

IMAGE BUTTONS

399

	CREATE THE NEXT BUTTON BITMAP		(continued)

	Action		Result

3	Modify the bitmap to have
	size 18 ×18 pixels.
	How-to
	a. Right-click within the Bit-
	map Editor window.
	b. Select the Properties item
	c. Set the Height and Width
	items to 18.
		Note: The Colors property here is used to select between
		Monochrome, 16 Color, 256 Color, and True Color images.
		For our purposes, the default of 16 Color is fine.

4	Edit the pixels for the
	bitmap to create a right-
	direction arrow.
	How-to
	Copy the graphic shown
	here, or create your own
	version of this arrow.

This completes our Next button. Figure 12.3 shows Visual Studio .NET with this button displayed. If you are feeling creative, the editor supports a wide range of drawing controls, in many ways similar to the Microsoft Paint application installed with the Windows operating systems. In the figure, the drawing controls are available in the bottom row of toolbar buttons, and the Colors window is shown on the left side of the window. If not shown, the Colors window is displayed by right-clicking within the Bitmap Editor window and selecting the Show Colors Window item.

A bitmap for the Prev button can be created in a similar manner as described in the previous table. An alternate method of creating this file is used in the following steps:

CREATE THE PREV BUTTON BITMAP

	Action	Result

5	Make a copy of the NextButton.bmp file.	A new bitmap file called “Copy of
	How-to	NextButton.bmp” is added to the project.
	How-to
	a. Right-click on the file and select Copy.
	b. Right-click on the MyPhotoAlbum project
	name and select Paste.

6	Rename this file to “PrevButton.bmp.”

400	CHAPTER 12 A .NET ASSORTMENT

	CREATE THE PREV BUTTON BITMAP	(continued)

	Action	Result

7	Flip the existing bitmap horizontally to create a
	left-pointing arrow.
	How-to
	a. Double-click on the PrevButton.bmp file
	name to display the Bitmap Editor window.
	b. Right-click within the window to display its
	popup menu.
	c. Select the Flip Horizontal item.

Our two bitmaps are now ready for use. The next step is to assign these bitmaps to the buttons on our form.

Figure 12.3 The Bitmap Editor window displays both an actual size and a per-pixel view of the bitmap.

IMAGE BUTTONS

401

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