ch06.htm

delphi自学的好教材！特别适合刚刚起步学习delphi的人员！同样对使用者具有参考价值！

<P><strong>New Term:</strong> A <I>prototype</I> is an application that has the appearance
of a working application but lacks full functionality, usually because it's in the
early stages of design.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> Delphi is perfect for quick prototyping of an application. You can
	have the main screens and dialog boxes designed and displayed in much less time than
	it would take with traditional Windows programming tools. That is not, however, to
	say that Delphi is just for prototyping. Delphi is fully capable of handling all
	your 32-bit Windows programming needs. 
<HR>
</P>

</BLOCKQUOTE>

<H3><A NAME="Heading13"></A>Step 1: Starting a New Application</H3>

<DL>
	<DT></DT>
	<DD><B>1. </B>Choose File | New Application from the main menu. If prompted to save
	the current project, click No.
	<P>
	<DT></DT>
	<DD><B>2. </B>The form is selected, so change the Name property to MainForm.
	<P>
	<DT></DT>
	<DD><B>3. </B>Change the Caption to ScratchPad 1.0.
	<P>
	<DT></DT>
	<DD><B>4. </B>Choose Project | Options from the main menu. Click on the Application
	tab and enter ScratchPad 1.0 for the application's title. Click OK to close the Project
	Options dialog box.
	<P>
</DL>

<H3><A NAME="Heading14"></A>Step 2: Adding a Toolbar</H3>
<P>Most Windows applications these days have a toolbar. Building a toolbar requires
several steps in itself. I'm not quite ready to explain everything there is to know
about toolbars in Delphi, so I'll save that for Day 13, &quot;Beyond the Basics.&quot;
You'll add a toolbar to the ScratchPad program at that time. What you can do for
now, though, is add a toolbar that can be used as a placeholder for the real toolbar
that you add later. Follow these steps:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Click on the Win32 tab on the Component palette and choose the ToolBar
	component (it's the third from the right).
	<P>
	<DT></DT>
	<DD><B>2. </B>Click anywhere on the form to add the toolbar. Notice that the toolbar
	automatically aligns itself to the top of the form.
	<P>
	<DD><B>3. </B>Right-click on the toolbar and choose New Button. A button appears
	on the toolbar.
	<DT></DT>
	<DD><B>4. </B>Repeat step 3 to add a second button.
	<P>
</DL>

<P>That's all you are going to do with the toolbar for now. As I said, you'll make
a real toolbar for this program on Day 13.</P>
<P>
<H3><A NAME="Heading15"></A>Step 3: Adding a Status Bar</H3>
<P>Okay, so far, so good. Windows Notepad doesn't have a status bar (or a toolbar,
for that matter), but you can put one in your application by following these steps:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Click on the Win32 tab on the Component palette and choose the StatusBar
	component.
	<P>
	<DT></DT>
	<DD><B>2. </B>Click anywhere on the form. The status bar is automatically placed
	at the bottom of the form. The status bar has a default Align value of alBottom.
	<P>
	<DT></DT>
	<DD><B>3. </B>Change the Name property to StatusBar.
	<P>
</DL>

<P>The form will now look like Figure 6.16.</P>
<P><A HREF="javascript:popUp('28670616.gif')"><B>FIGURE 6.16.</B></A><B> </B><I>The
ScratchPad form up to this point.</I></P>
<P>
<H3><A NAME="Heading16"></A>Step 4: Adding the Memo Component</H3>
<P>You need some component in which to type text, so you can use a memo component
to add this feature (believe it or not, you're almost done with your prototype):</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Click on the Standard tab on the Component palette and choose a Memo
	component. Place the memo anywhere on the form's client area.
	<P>
	<DT></DT>
	<DD><B>2. </B>Change the Name property to Memo.
	<P>
	<DT></DT>
	<DD><B>3. </B>Double-click the Value column next to the Lines property. The String
	List Editor is displayed. Delete the word Memo and click OK.
	<P>
	<DT></DT>
	<DD><B>4. </B>Change the Scrollbar property to ssVertical. (Initially, you want only
	a vertical scrollbar on the memo.)
	<P>
	<DT></DT>
	<DD><B>5. </B>Change the Name property of the Font property to Fixedsys. (Because
	this is a Notepad copycat, you'll use the system font.)
	<P>
	<DT></DT>
	<DD><B>6. </B>Change the Align property to alClient. The memo expands to fill the
	client area between the toolbar and the status bar.
	<P>
</DL>

<P>Stand back and admire your work. This is starting to look like a real application!
If the form looks too large or too small, resize it by dragging the lower-right corner.
It's your program, so make it look the way you want it to look.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> Pressing the Esc key selects the parent of the control that currently
	has the selection. For example, our form's client area is covered by components,
	which makes it impossible to select the form itself. To make the form the active
	component in the Object Inspector, select the memo component and then press the Esc
	key on the keyboard. You can also choose the form from the Component Selector combo
	box on the Object Inspector. 
<HR>


</BLOCKQUOTE>

<P>Notice that all the controls automatically resize themselves to retain their relationship
with the parent window--the form, in this case. That is one of the main advantages
to the Align property. The form now looks like the one in Figure 6.17.</P>
<P>
<H3><A NAME="Heading17"></A>Running the Program</H3>
<P>You can now click the Run button to run the program. You can type text in the
window's client area and you can press the toolbar buttons (although they don't do
anything at this point). Keep in mind that this is a prototype and is mostly for
show right now. You add more to the program by the end of the day.</P>
<P><A HREF="javascript:popUp('28670617.gif')"><B>FIGURE 6.17.</B></A><B> </B><I>The
completed prototype.</I></P>
<P>You'd better save the project because you're going to use it later in the chapter.
Choose File | Save All from the main menu. Save the main form's source unit as SPMain
and the project as Scratch.</P>
<P>
<H2><A NAME="Heading18"></A>May I See a Menu, Please?</H2>
<P>Menus are a big part of most Windows applications. Some Windows programs don't
have menus, but the vast majority do. Delphi makes creating menus easy with the Menu
Designer. The Menu Designer has the following features:</P>

<UL>
	<LI>It can create both main menus and pop-up menus (context menus).
	<P>
	<LI>It provides immediate access to the Code Editor to handle the OnClick events
	for menu items.
	<P>
	<LI>It can insert menus from templates or from resource files.
	<P>
	<LI>It can save custom menus as templates.
</UL>

<P>All the Menu Designer's commands are accessed via the Menu Designer context menu
or by interacting with the Object Inspector. Figure 6.18 shows the Menu Designer's
context menu.</P>
<P>For the most part, these menu items are self-explanatory, so I'm not going to
go over each one. Rather, you can learn about them by working with them. To begin,
let's add a main menu to the ScratchPad application you created earlier. After that
you'll add a context menu.</P>
<P><A HREF="javascript:popUp('28670618.gif')"><B>FIGURE 6.18.</B></A><B> </B><I>The
Menu Designer's context menu.</I></P>
<P>
<H2><I></I></H2>
<H3><A NAME="Heading19"></A>Creating a Main Menu</H3>
<P>The Menu Designer enables you to quickly build any menu. The menu structure for
a main menu consists of a MainMenu component, which is represented by the VCL class
TMainMenu. Each item on the menu is a MenuItem component that is encapsulated in
the TMenuItem class. You don't need to be too concerned about the intricacies of
how these classes work together because the Menu Designer makes creating menus easy.
With that brief overview, let's add a main menu to the ScratchPad application.</P>
<P>
<H4>Adding a Main Menu to the Form</H4>
<P>The first thing you must do is add a MainMenu component to your form.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> By now you have had some experience with Delphi. From this point
	on I will abbreviate some steps that you need to take to perform certain actions.
	For example, from here on I'll say, &quot;Place a MainMenu component on the form&quot;
	rather than &quot;Click on the Standard tab on the Component palette. Click the MainMenu
	button and click on the form to place the component.&quot; Don't worry, I'll still
	give plenty of details when new operations are introduced. 
<HR>


</BLOCKQUOTE>


<DL>
	<DT></DT>
	<P>
	<DD><B>1. </B>Open the ScratchPad project you created earlier in the chapter.
	<P>
	<DT></DT>
	<DD><B>2. </B>Place a MainMenu component on the form and change its Name property
	to MainMenu. Notice that a MainMenu component has very few properties and no events.
	All the menu's work is done by the individual menu items.
	<P>
	<DT></DT>
	<DD><B>3. </B>Double-click on the MainMenu icon. The Menu Designer is displayed.
	<P>
</DL>

<P>The Menu Designer looks like a blank form without grid points. The Menu Designer
can be sized in any way you want. The size is just for your convenience and has no
bearing on how the menu operates at runtime. At this point, the Menu Designer is
waiting for you to begin building the menu. After you have created your first menu,
you will find that menu creation is easy and intuitive.</P>
<P>
<H4>Creating a Menu by Hand</H4>
<P>Although there are easier ways to create a File menu, you will create your first
menu by hand. The Menu Designer always has a blank menu item that acts as a placeholder
for any new menu items you will create. When you first start the Menu Designer, the
blank item is selected.</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Change the Name property to FileMenu.
	<P>
	<DT></DT>
	<DD><B>2. </B>Click on the Caption property in the Object Inspector, type &amp;File,
	and press Enter.
	<P>
</DL>



<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> The ampersand (&amp;) is used to create the underlined character
	for a menu item. The underlined character is the <I>accelerator</I> the user can
	type in combination with the Alt key to navigate a menu using the keyboard. You can
	put ampersands anywhere in the menu item's text. For instance, the customary text
	string for the Exit menu item would be E&amp;xit so that the <I>x</I> is the accelerator.
	All you have to do is provide the ampersands before the appropriate letter, Windows
	will take it from there. 
<HR>


</BLOCKQUOTE>

<P>At this point, several things happen. First, the File menu shows up in the Menu
Designer. It also appears on the main form behind the Menu Designer. The other thing
that happens is that a new, blank placeholder is added below the File menu you just
created (you'll have to click on the File menu in the Menu Designer to see the placeholder).
In addition, a new pop-up placeholder is created to the right of the File menu. The
Object Inspector is displaying a blank MenuItem component, waiting for you to enter
the Caption and Name property values. Figure 6.19 shows the Menu Designer as it appears
at this point.</P>
<P><A HREF="javascript:popUp('28670619.gif')"><B>FIGURE 6.19.</B></A><B> </B><I>The
Menu Designer and Object Inspector after creating the File menu.</I></P>
<P>Let's continue with the creation of the menu:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Change the Name property for the new item to FileNew.
	<P>
	<DT></DT>
	<DD><B>2. </B>Change the Caption property to &amp;New and press Enter. Again, a blank
	item is created in the Menu Designer.
	<P>
	<DT></DT>
	<DD><B>3. </B>Repeat steps 1 and 2 and create menu items for Open, Save, and Save
	As. If you need help on where to place the ampersand, refer to Figure 6.20. Don't
	worry that you might not get it exactly right. You can always go back later and fix
	any errors.
	<P>
</DL>



<BLOCKQUOTE>
	<P>
<HR>
<strong>TIP:</strong> Make your menus as standard as possible. Be sure that your accelerators
	(the underlined characters) are the same as in other Windows programs. Also, remember
	that an ellipsis (...) following a menu item's text is a visual cue to the user that
	choosing the menu item will invoke a dialog box. 
<HR>


</BLOCKQUOTE>

<P>At this point, you need a menu separator.</P>
<P><strong>New Term:</strong> A <I>separator</I> is the horizontal line on a menu that separates
groups of menu items.</P>
<P>Adding a separator is easy with the Delphi Menu Designer. All you have to do is
put in a hyphen for the Caption property. Select the blank menu item under Save As,
type a hyphen for the Caption, and press Enter. A separator is placed in the menu.
Continue adding menu items until your menu looks like the one in Figure 6.20. If
you need to modify a menu item, just click on it and change properties in the Object
Inspector as needed.</P>
<P><A HREF="javascript:popUp('28670620.gif')"><B>FIGURE 6.20.</B></A><B> </B><I>The
Menu Designer with the finished File menu.</I></P>


<BLOCKQUOTE>
	<P>
<HR>
<