ch18.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！

difficult, but fortunately the QuickReport components make it easy. The best way
for me to explain how to create reports by hand is to take you through an exercise.
This exercise creates a simple application that displays and prints a report in list
form. I won't tell you to perform every single step in this exercise. For example,
I won't tell you to save the project or give you filenames to use--you can figure
those out for yourself. Also, you don't have to worry about making the report real
pretty at this point. You can go back later and tidy up.</P>
<P>The first step is to create the main form of the application. After that's done,
you create the basic outline of the report. Here goes:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Create a new application. Place two buttons on the main form. Change
	the caption of the first button to Preview Report and the caption of the second button
	to Print Report.
	<P>
	<DT></DT>
	<DD><B>2. </B>Choose File|New. Double-click the Report icon in the Object Repository.
	Delphi creates a new QuickReport form.
	<P>
	<DT></DT>
	<DD><B>3. </B>Place a Table component on the QuickReport form. Change the DatabaseName
	property to DBDEMOS and the TableName property to EMPLOYEE.DB. Set the Active property
	to True.
	<P>
	<DT></DT>
	<DD><B>4. </B>Select the QuickReport form. Change the DataSet property to Table1
	and change the ReportTitle property to Employee Report.
	<P>
	<DT></DT>
	<DD><B>5. </B>Switch back to the main form. Double-click the button labeled Preview
	Report. Type this code in the OnClick event handler:
	<P>
</DL>



<BLOCKQUOTE>
	<PRE>QuickReport2.Preview;</PRE>

</BLOCKQUOTE>

<PRE></PRE>

<DL>
	<DT></DT>
	<DD><B>6. </B>Double-click the Print Report button and type the following in the
	OnClick event handler:
	<P>
</DL>



<BLOCKQUOTE>
	<PRE>QuickReport2.Print;</PRE>

</BLOCKQUOTE>

<PRE></PRE>

<DL>
	<DT></DT>
	<DD><B>7. </B>Choose File|Use Unit and include the QuickReport form.
	<P>
</DL>

<P>Now you have a blank report. What you need to do next is add a title band, a column
header band, and a detail band. For the next few steps you might want to look ahead
to Figure 18.6 to see the final result. Follow these steps:</P>

<DL>
	<DT></DT>
	<DD><B>1. </B>Select a QRBand component from the QReport tab of the Component palette
	and place it on the report. The band is a title band by default.
	<P>
	<DT></DT>
	<DD><B>2. </B>Select a QRLabel component and place it on the title band. Change the
	Caption property to Employee Report and change the Font property to your preference
	(I used Arial, 18 point, bold). Align the component so that it is centered on the
	band.
	<P>
	<DT></DT>
	<DD><B>3. </B>Place another band on the report. Change the BandType property to rbColumnHeader
	and change the Font to bold and underlined.
	<P>
	<DT></DT>
	<DD><B>4. </B>Place a QRLabel on the left side of the column header band and change
	the Caption property to Employee Number. Place a second QRLabel on the band to the
	right of the first and change the Caption property to Name. Place a third QRLabel
	on the band to the right of the last label and change the Caption to Salary.
	<P>
	<DT></DT>
	<DD><B>5. </B>Place another band on the report and change the BandType property to
	rbDetail. Notice that the band moves below the other bands after you change the band
	type.
	<P>
	<DT></DT>
	<DD><B>6. </B>Place a QRDBText component on the left edge of the detail band (align
	it with the Employee Number label on the column header band). Change the DataSet
	property to Table1 and the DataField property to EmpNo.
	<P>
	<DT></DT>
	<DD><B>7. </B>Place another QRDBText on the detail band and align it with the Name
	component on the column header band. Change the DataSet property to Table1 and the
	DataField property to FirstName. Place another QRDBText just to the right of the
	last one (see Figure 18.6). Attach it to the LastName field of the database table.
	<P>
</DL>

<PRE><B>	8.	</B>Add a final QRDBText component on the detail band. Place it below the Salary component on the column header band and attach it to the Salary field in the table. Your form now looks like Figure 18.6. 
</PRE>
<P><A HREF="javascript:popUp('28671806.gif')"><B>FIGURE 18.6.</B></A><B> </B><I>Your
QuickReport form.</I></P>

<P>You are probably wondering what the report will look like on paper. Guess what?
You don't have to wait to find out. Just right-click on the QuickReport form and
choose Preview from the context menu. The QuickReport preview window is displayed,
and you can preview the report.</P>
<P>To print the report, click the Print button. When you are done with the report
preview, click the Close button. You can now run the program and try out the Preview
Report and Print Report buttons.</P>


<BLOCKQUOTE>
	<P>
<HR>
<strong>NOTE:</strong> The report you just created is double-spaced. To change the spacing,
	reduce the height of the detail band. 
<HR>


</BLOCKQUOTE>

<P>Before leaving this discussion of reports, let me show you one other nice feature
of QuickReport. Right-click on the QuickReport form and choose Report settings from
the context menu. The Report Settings dialog will be displayed, as shown in Figure
18.7. This dialog enables you to set the primary properties of the QuickRep component
visually rather than use the Object Inspector.</P>
<P><A HREF="javascript:popUp('28671807.gif')"><B>FIGURE 18.7.</B></A><B> </B><I>The
QuickReport Report Settings dialog.</I></P>
<H3><A NAME="Heading14"></A>Creating Reports the Easy Way</H3>
<P>Delphi comes with three built-in QuickReport forms, which can be found on the
Forms tab of the Object Repository. The forms are called Quick Report Labels, Quick
Report List, and Quick Report Master/Detail. These forms give you a head start on
creating reports. You can generate one of the forms from the Object Repository and
then modify the form as needed.</P>
<P>
<H2><A NAME="Heading15"></A>Deploying a Delphi Database Application</H2>
<P>As I said on Day 16, the Borland Database Engine (BDE) is a collection of DLLs
and drivers that enable your Delphi application to talk to various types of databases.
When you ship an application that uses the BDE, you need to make sure that you ship
the proper BDE files and that they are properly registered on your users' machines.</P>
<P>The most sensible way to do this is with a Borland-approved installation program.
Here at TurboPower Software, we use the Wise Install System from Great Lakes Business
Solutions (<A target="_new" HREF="http://www.glbs.com">http://www.glbs.com</A>). Others include
InstallShield and its little brother, InstallShield Express. Conveniently, InstallShield
Express comes with Delphi Professional and Client/Server, so if you have one of those
versions of Delphi, you don't have to rush right out and buy an installation program.</P>
<P>You might be wondering why Borland is involved in dictating how the BDE must be
deployed. The reason is simple when you think about it: There are many BDE versions
in use. Some folks might be writing and deploying applications that use the BDE from
Delphi 1. Others might be using the BDE from C++Builder 1. Still others could be
using the BDE that comes with Delphi 4 in their applications.</P>
<P>The important point to realize is that the BDE is backward compatible. Newer BDE
versions are guaranteed to work with applications written for older BDE versions.
This system will only work, however, as long as everyone plays by the rules. Part
of the rules say, &quot;Thou shalt not arbitrarily overwrite existing BDE files.&quot;
Certified installation programs check the version number of any BDE files they find.
If the file being installed is older than the existing file, the installation program
leaves the existing file in place.</P>
<P>This ensures that the user will always have the latest BDE files on his or her
system. Another service that these certified installation programs provide is to
determine exactly which files you need to deploy for your application. You should
read DEPLOY.TXT in the Delphi root directory for more details on deploying applications
that use the BDE.</P>
<P>
<H2><A NAME="Heading16"></A>Summary</H2>
<P>There's no question that creating database applications requires a lot of work.
The good news is that Delphi makes the job much easier than other development environments.
Today you found out something about the nonvisual aspects of database programming.
You also found out about data modules and how to use them. You ended the day with
a look at QuickReport. QuickReport makes creating reports for your database applications
easy. I also explained what is required to deploy a database application.</P>
<P>
<H2>Workshop</H2>
<P>The Workshop contains quiz questions to help you solidify your understanding of
the material covered and exercises to provide you with experience in using what you
have learned. You can find answers to the quiz questions in Appendix A, &quot;Answers
to the Quiz Questions.&quot;</P>
<P>
<H3><A NAME="Heading17"></A>Q&amp;A</H3>

<DL>
	<DT></DT>
	<DD><B>Q I am trying to create a database at runtime. I have created a BDE alias
	and set all the field definitions, but the table is never created on my hard disk.
	What have I done wrong?</B>
	<P>
	<DT></DT>
	<DD><B>A </B>You have probably failed to call the CreateTable method. You must call
	this method to physically create the table.
	<P>
	<DT></DT>
	<DD><B>Q When designing a report, can I set all my report's properties at one time?</B>
	<P>
	<DT></DT>
	<DD><B>A </B>Yes. Just right-click the QuickRep component and choose Report settings
	from the context menu. The Report Settings dialog is displayed, and you can set most
	of the report properties visually.
	<P>
	<DT></DT>
	<DD><B>Q Can a data module include code as well as components?</B>
	<P>
	<DT></DT>
	<DD><B>A </B>Yes. A data module can contain any code necessary to carry out operation
	of the data module. The data module can contain event handlers or methods that you
	create. The methods you create can be public or private (for the data module's use
	only).
	<P>
	<DT></DT>
	<DD><B>Q When I preview my report, it is blank. What is wrong?</B>
	<P>
	<DT></DT>
	<DD><B>A </B>More than likely you have not set the Active property of the dataset
	to True. The dataset must be open before the report will function.
	<P>
	<DT></DT>
	<DD><B>Q Can I use more than one detail band on a report?</B>
	<P>
	<DT></DT>
	<DD><B>A </B>No. You can place more than one detail band on a report, but only the
	first one will be used when the report is generated.
	<P>
	<DT></DT>
	<DD><B>Q Why do I need a Borland-approved installation program to install my database
	application?</B>
	<P>
	<DT></DT>
	<DD><B>A</B> The BDE is complicated to install, and an approved installation program
	is guaranteed to do the installation correctly.
	<P>
</DL>

<H3><A NAME="Heading18"></A>Quiz</H3>

<DL>
	<DD><B>1. </B>What method do you call to create a database table at runtime?
	<DT></DT>
	<DD><B>2. </B>What does the Edit method of TTable do?
	<P>
	<DT></DT>
	<DD><B>3. </B>What method do you call when you want to apply the changes made to
	a record?
	<P>
	<DT></DT>
	<DD><B>4. </B>How do you create a new data module?
	<P>
	<DT></DT>
	<DD><B>5. </B>Is a data module a regular form?
	<P>
	<DT></DT>
	<DD><B>6. </B>What method do you call to print a QuickReport?
	<P>
	<DT></DT>
	<DD><B>7. </B>What type of QuickReport band displays the dataset's data?
	<P>
	<DT></DT>
	<DD><B>8. </B>What component is used to display the page number on a report?
	<P>
	<DT></DT>
	<DD><B>9. </B>How can you preview a report at design time?
	<P>
	<DT></DT>
	<DD><B>10. </B>What is the QRExpr component used for?
	<P>
</DL>

<H3><A NAME="Heading19"></A>Exercises</H3>

<DL>
	<DT></DT>
	<DD><B>1. </B>Create a database (a BDE alias) and a table for the database, either
	through code or by using the Delphi database tools.
	<P>
	<DD><B>2. </B>Create a data module containing the database table from exercise 1.
	<DT></DT>
	<DD><B>3. </B>Generate a report that creates mailing labels. (Hint: Start with a
	QuickReport Labels object from the Forms page of the Object Repository.)
	<P>
	<DT></DT>
	<DD><B>4. </B>Modify the QuickReport you created in this chapter so that the employee's
	first and last names are displayed by a QRExpr component.
	<P>
	<DT></DT>
	<DD><B>5. </B>Read the DEPLOY.TXT file in your Delphi directory to understand what
	is involved in deploying a Delphi database application.
</DL>

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