Teach Yourself Borland C++ in 14 Days - portal

478 Day 13
Giving the New Form Life
When your form is all set up visually, you still need to attach code to its events in order for
it to do anything. The biggest event that you’ll customize is the OnBeginRetrieval event of
the THTML component. Of course, you’ll also attach custom code to the OnClick event of both
your buttons and also to the OnChange event of your TTabControl.
Begin by clicking on your TTabControl and then double-clicking its OnChange event in the
Object Inspector. Type the following code into the C++Builder Code Editor:
NOTE
cbURL->Text=tcURL->Tabs->Strings[tcURL->TabIndex];
cbURL->SelectAll();
bbGo->Click();
This code sample and the others in this chapter assume you’ve adopted
some sort of naming conventions for the objects in your application. I
always prefix identifier names with a two-character mnemonic that
allows me to identify the type of component represented by the
identifier. Here, cbURL refers to the TComboBox control you placed on the
bottom TPanel, tcURL refers to the TTabControl at the top of the form,
and bbGo refers to the Go! TBitBtn component.
Setting cbURL’s Text property to the text of the tab that was clicked when the OnChange event
fired ensures that the cbURL control and the tcURL control stay synchronized. Calling the
SelectAll() method ensures that the TComboBox’s Text property value is highlighted. The call
to bbGo’s Click() event simulates actually clicking the button. This allows clicking a tab and
clicking the Go! button to behave identically.
Now that the tab control is set up, click on the THTML component and then double-click on
its OnBeginRetrieve event in the C++Builder Object Inspector. Type this code into the Code
Editor:
Cursor=(TCursor)crHourGlass;
if (cbURL->Items->IndexOf(htBrowser->URL)==-1) {
cbURL->Items->Add(htBrowser->URL);
cbURL->Text=htBrowser->URL;
cbURL->SelectAll();
tcURL->Tabs->Add(htBrowser->URL);
tcURL->TabIndex=tcURL->Tabs->Count-1;
bbGo->Click();
}
This code checks whether the list of URLs maintained by the TComboBox contains the one
about to be browsed. If the URL isn’t there, the code adds it to both the TComboBox and the
TTabControl.