Month: August 2020

I have many favorite prebuilt components that are included with C++Builder 10.4 Sydney. In this blog post I’ll show you how to create an RSS Feeds VCL (you can also use the same approach for a FireMonkey FMX) application using the XMLDocument, NetHTTPClient, NetHTTPRequest and WebBrowser components.

Start by creating a C++Builder VCL application. Set the form’s WindowState property to wsMaximized. Add a Panel, Button, ListBox (used to hold the list of RSS feed URLs to process) and a few labels and align them to the top of the form. Add Memo (to display the Feed XML), ListBox (to contain the title and URL for each article found in the feeds) and WebBrowser (to display the web page when you click on an item in the articles list box) components to the rest of the form.

To populate the Panel’s listbox, I use a text file, “FeedsList.txt”, which contains a number of RSS feed URLs. The panel listbox is populated in the Form’s OnShow event handler.

Clicking on the button will process all of the RSS feed URLs and add each article and URL item found into the list box of articles found.

The XMLDocument component has a DOMVendor property to select the DOM implementation to use for parsing and manipulating the XML document.

Clicking on an item in the articles list box uses the OnClick event handler to call the WebBrowser Navigate method  for the selected article URL. In C++Builder 10.4 Sydney there is a new property added to the WebBrowser component that lets you choose which browser engine will be used on Windows. I’ve chosen the EdgeIfAvailable engine.

Here is the contents of the FeedsList.txt file:

https://isocpp.org/blog/rss
https://herbsutter.com/feed/
http://feeds.hanselman.com/scotthanselman
http://feeds.dzone.com/home
https://news.ycombinator.com/rss
http://www.odbms.org/feed/
https://www.techmeme.com/feed.xml
https://techcrunch.com/feed/
http://feeds.feedburner.com/oreilly/radar/atom
http://feeds.feedburner.com/appdevelopermagazine
https://www.infoworld.com/index.rss
https://newsroom.ibm.com/announcements?pagetemplate=rss
https://www.computerworld.com/index.rss
https://techxplore.com/rss-feed/
https://sdtimes.com/feed/
https://www.geeksforgeeks.org/feed/
https://feeds.feedburner.com/venturebeat/SZYF
http://feeds.feedburner.com/ProgrammableWeb

Here is a bitmap of the running application:

Finally here is the source code for the application:

//---------------------------------------------------------------------------

#include <vcl.h>
#include <fstream>
#pragma hdrstop

#include "MainFeedUnit.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm2 *Form2;
//---------------------------------------------------------------------------
__fastcall TForm2::TForm2(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm2::ArticlesFoundListBoxClick(TObject *Sender)
{
	// for the ListBox item clicked - get the URL and Browse to the article
	LabelStatus->Caption = ArticlesFoundListBox->Items->Names[ArticlesFoundListBox->ItemIndex];
	ArticleWebBrowser->Navigate(ArticlesFoundListBox->Items->Values[ArticlesFoundListBox->Items->Names[ArticlesFoundListBox->ItemIndex]]);
}
//---------------------------------------------------------------------------
void __fastcall TForm2::Button1Click(TObject *Sender)
{
	// Find and save Title and URL for items found
	std::ofstream fs (AnsiString(FormatDateTime("yyyy-mm-dd-hhnnss",Now())+"_RSSFound.txt").c_str());
	fs << AnsiString("RSS Feed for: "+ NetHTTPRequest1->URL).c_str() << std::endl;
	fs << AnsiString(FormatDateTime("dddd mmmm dd, yyyy @ hh:nn:ss",Now())).c_str() << std::endl;
	fs << std::endl;

	// Clear the Articles Found List Box to prepare for the title and URL of articles
	ArticlesFoundListBox->Clear();
	FeedsItemsCountLabel->Caption = "Items Found = 0";

	// get all articles and URLs in all feeds
	for (int i = 0; i < FeedsListBox->Count; i++) {
		// Get the RSS feed URL string from the ListBox
		NetHTTPRequest1->URL = FeedsListBox->Items->Strings[i];

		UrlLabel->Caption = "Feed URL: "+NetHTTPRequest1->URL;
        UrlLabel->Update();

		// Use NetHTTPRequest Execute method to get the RSS Feed XML
		UnicodeString FeedString = NetHTTPRequest1->Execute()->ContentAsString();

		// copy the XML string to the Memo
		MemoFeedXML->Lines->Clear();
		MemoFeedXML->Lines->Text = FeedString;
		MemoFeedXML->Update();

		// load the RSS Feed XML into the XMLDocument
		XMLDocument1->LoadFromXML(FeedString);
		XMLDocument1->Active = True;

		LabelStatus->Caption = "Processing RSS for "+NetHTTPRequest1->URL;
		LabelStatus->Update();

		// find the RSS feed channel node
		_di_IXMLNode ChannelNode = XMLDocument1->DocumentElement->ChildNodes->FindNode ("channel");
		// test to make sure the ChannelNote is found
		if (ChannelNode != NULL) {
			for (int I=0;I<ChannelNode->ChildNodes->Count;I++) {
				// iterate through child nodes
				_di_IXMLNode ItemNode = ChannelNode->ChildNodes->Get(I);
				// if child node is an item then get the title, pubDate and URL
				if (ItemNode->NodeName == "item") {
					LabelStatus->Caption = "Processing Node " + IntToStr(I);
					LabelStatus->Update();
					UnicodeString title = ItemNode->ChildValues ["title"];
					UnicodeString pubDate = ItemNode->ChildValues ["pubDate"];
					// author := ItemNode.ChildValues ['author'];    // could be nil
					UnicodeString url = ItemNode->ChildValues ["link"];

					// populate the articles found ListBox with the pair of title and URL
					ArticlesFoundListBox->Items->AddPair(title,url);
					ArticlesFoundListBox->Update();
					FeedsItemsCountLabel->Caption = "Items Found = "+IntToStr(ArticlesFoundListBox->Count);
					FeedsItemsCountLabel->Update();

					// write the Title, pubDate and URL to the text file
					fs << AnsiString(title).c_str() << std::endl;
					fs << AnsiString(pubDate).c_str() << std::endl;
					fs << AnsiString(url).c_str() << std::endl;
					fs << std::endl;
				}
			}
		}

	}

	fs << std::endl;
	fs << AnsiString("Items Found = "+IntToStr(ArticlesFoundListBox->Count)).c_str() << std::endl;
	fs << "end of file" << std::endl;
	fs.close();   // close the text file
	LabelStatus->Caption = "RSS Processing Done!";
    UrlLabel->Caption = "";
}
//---------------------------------------------------------------------------
void __fastcall TForm2::FormShow(TObject *Sender)
{
	// load RSS Feeds ListBox with the "FeedsList.txt" text file
    // I put the text file in the same folder as the app .EXE file
	FeedsListBox->Items->Clear();
	FeedsListBox->Items->LoadFromFile("FeedsList.txt");
	LabelStatus->Caption = "RSS Feed Urls Loaded = "+IntToStr(FeedsListBox->Count);
	LabelStatus->Update();

}
//---------------------------------------------------------------------------

References

Using TXMLDocument

Using the Document Object Model

Using an HTTP Client

System.Net.HttpClientComponent.TNetHTTPClient

System.Net.HttpClientComponent.TNetHTTPRequest

Using TEdgeBrowser Component and Changes to the TWebBrowser Component

RSS 2.0 Specification

Download Source Code ZipFile for RSSFeedListsUsingTextFileVCLCpp

C++Builder Product Information

C++Builder Product Page – Native Apps that Perform. Build Windows C++ Apps 10x Faster with Less Code
C++Builder Product Editions – C++Builder is available in four editions – Professional, Enterprise, Architect and Community (free). C++Builder is also available as part of the RAD Studio development suite.