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# mainwindow.cpp Example File
sql/masterdetail/mainwindow.cpp

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     #include "mainwindow.h"
     #include "dialog.h"

     #include <QtGui>
     #include <QtSql>
     #include <QtXml>

     extern int uniqueAlbumId;
     extern int uniqueArtistId;

     MainWindow::MainWindow(const QString &artistTable, const QString &albumTable,
                            QFile *albumDetails, QWidget *parent)
          : QMainWindow(parent)
     {
         file = albumDetails;
         readAlbumData();

         model = new QSqlRelationalTableModel(this);
         model->setTable(albumTable);
         model->setRelation(2, QSqlRelation(artistTable, "id", "artist"));
         model->select();

         QGroupBox *artists = createArtistGroupBox();
         QGroupBox *albums = createAlbumGroupBox();
         QGroupBox *details = createDetailsGroupBox();

         artistView->setCurrentIndex(0);
         uniqueAlbumId = model->rowCount();
         uniqueArtistId = artistView->count();

         connect(model, SIGNAL(rowsInserted(QModelIndex,int,int)),
                 this, SLOT(updateHeader(QModelIndex,int,int)));
         connect(model, SIGNAL(rowsRemoved(QModelIndex,int,int)),
                 this, SLOT(updateHeader(QModelIndex,int,int)));

         QGridLayout *layout = new QGridLayout;
         layout->addWidget(artists, 0, 0);
         layout->addWidget(albums, 1, 0);
         layout->addWidget(details, 0, 1, 2, 1);
         layout->setColumnStretch(1, 1);
         layout->setColumnMinimumWidth(0, 500);

         QWidget *widget = new QWidget;
         widget->setLayout(layout);
         setCentralWidget(widget);
         createMenuBar();

         showImageLabel();
         resize(850, 400);
         setWindowTitle(tr("Music Archive"));
     }

     void MainWindow::changeArtist(int row)
     {
         if (row > 0) {
             QModelIndex index = model->relationModel(2)->index(row, 1);
             model->setFilter("artist = '" + index.data().toString() + '\'') ;
             showArtistProfile(index);
         } else if (row == 0) {
             model->setFilter(QString());
             showImageLabel();
         } else {
             return;
         }
     }

     void MainWindow::showArtistProfile(QModelIndex index)
     {
         QSqlRecord record = model->relationModel(2)->record(index.row());

         QString name = record.value("artist").toString();
         QString count = record.value("albumcount").toString();
         profileLabel->setText(tr("Artist : %1 \n" \
                                  "Number of Albums: %2").arg(name).arg(count));

         profileLabel->show();
         iconLabel->show();

         titleLabel->hide();
         trackList->hide();
         imageLabel->hide();
     }

     void MainWindow::showAlbumDetails(QModelIndex index)
     {
         QSqlRecord record = model->record(index.row());

         QString artist = record.value("artist").toString();
         QString title = record.value("title").toString();
         QString year = record.value("year").toString();
         QString albumId = record.value("albumid").toString();

         showArtistProfile(indexOfArtist(artist));
         titleLabel->setText(tr("Title: %1 (%2)").arg(title).arg(year));
         titleLabel->show();

         QDomNodeList albums = albumData.elementsByTagName("album");
         for (int i = 0; i < albums.count(); i++) {
             QDomNode album = albums.item(i);
             if (album.toElement().attribute("id") == albumId) {
                 getTrackList(album.toElement());
                 break;
             }
         }
         if (!trackList->count() == 0)
             trackList->show();
     }

     void MainWindow::getTrackList(QDomNode album)
     {
         trackList->clear();

         QDomNodeList tracks = album.childNodes();
         QDomNode track;
         QString trackNumber;

         for (int j = 0; j < tracks.count(); j++) {

             track = tracks.item(j);
             trackNumber = track.toElement().attribute("number");

             QListWidgetItem *item = new QListWidgetItem(trackList);
             item->setText(trackNumber + ": " + track.toElement().text());
         }
     }

     void MainWindow::addAlbum()
     {
         Dialog *dialog = new Dialog(model, albumData, file, this);
         int accepted = dialog->exec();

         if (accepted == 1) {
             int lastRow = model->rowCount() - 1;
             albumView->selectRow(lastRow);
             albumView->scrollToBottom();
             showAlbumDetails(model->index(lastRow, 0));
         }
     }

     void MainWindow::deleteAlbum()
     {
         QModelIndexList selection = albumView->selectionModel()->selectedRows(0);

         if (!selection.empty()) {
             QModelIndex idIndex = selection.at(0);
             int id = idIndex.data().toInt();
             QString title = idIndex.sibling(idIndex.row(), 1).data().toString();
             QString artist = idIndex.sibling(idIndex.row(), 2).data().toString();

             QMessageBox::StandardButton button;
             button = QMessageBox::question(this, tr("Delete Album"),
                                            QString(tr("Are you sure you want to " \
                                                       "delete '%1' by '%2'?"))
                                                   .arg(title).arg(artist),
                                            QMessageBox::Yes | QMessageBox::No);

             if (button == QMessageBox::Yes) {
                 removeAlbumFromFile(id);
                 removeAlbumFromDatabase(idIndex);
                 decreaseAlbumCount(indexOfArtist(artist));

                 showImageLabel();
             }
         } else {
             QMessageBox::information(this, tr("Delete Album"),
                                      tr("Select the album you want to delete."));
         }
     }

     void MainWindow::removeAlbumFromFile(int id)
     {

         QDomNodeList albums = albumData.elementsByTagName("album");

         for (int i = 0; i < albums.count(); i++) {
             QDomNode node = albums.item(i);
             if (node.toElement().attribute("id").toInt() == id) {
                 albumData.elementsByTagName("archive").item(0).removeChild(node);
                 break;
             }
         }
     /*
         The following code is commented out since the example uses an in
         memory database, i.e., altering the XML file will bring the data
         out of sync.

         if (!file->open(QIODevice::WriteOnly)) {
             return;
         } else {
             QTextStream stream(file);
             albumData.elementsByTagName("archive").item(0).save(stream, 4);
             file->close();
         }
     */
     }

     void MainWindow::removeAlbumFromDatabase(QModelIndex index)
     {
         model->removeRow(index.row());
     }

     void MainWindow::decreaseAlbumCount(QModelIndex artistIndex)
     {
         int row = artistIndex.row();
         QModelIndex albumCountIndex = artistIndex.sibling(row, 2);
         int albumCount = albumCountIndex.data().toInt();

         QSqlTableModel *artists = model->relationModel(2);

         if (albumCount == 1) {
             artists->removeRow(row);
             showImageLabel();
         } else {
             artists->setData(albumCountIndex, QVariant(albumCount - 1));
         }
     }

     void MainWindow::readAlbumData()
     {
         if (!file->open(QIODevice::ReadOnly))
             return;

         if (!albumData.setContent(file)) {
             file->close();
             return;
         }
         file->close();
     }

     QGroupBox* MainWindow::createArtistGroupBox()
     {
         artistView = new QComboBox;
         artistView->setModel(model->relationModel(2));
         artistView->setModelColumn(1);

         connect(artistView, SIGNAL(currentIndexChanged(int)),
                 this, SLOT(changeArtist(int)));

         QGroupBox *box = new QGroupBox(tr("Artist"));

         QGridLayout *layout = new QGridLayout;
         layout->addWidget(artistView, 0, 0);
         box->setLayout(layout);

         return box;
     }

     QGroupBox* MainWindow::createAlbumGroupBox()
     {
         QGroupBox *box = new QGroupBox(tr("Album"));

         albumView = new QTableView;
         albumView->setEditTriggers(QAbstractItemView::NoEditTriggers);
         albumView->setSortingEnabled(true);
         albumView->setSelectionBehavior(QAbstractItemView::SelectRows);
         albumView->setSelectionMode(QAbstractItemView::SingleSelection);
         albumView->setShowGrid(false);
         albumView->verticalHeader()->hide();
         albumView->setAlternatingRowColors(true);
         albumView->setModel(model);
         adjustHeader();

         QLocale locale = albumView->locale();
         locale.setNumberOptions(QLocale::OmitGroupSeparator);
         albumView->setLocale(locale);

         connect(albumView, SIGNAL(clicked(QModelIndex)),
                 this, SLOT(showAlbumDetails(QModelIndex)));
         connect(albumView, SIGNAL(activated(QModelIndex)),
                 this, SLOT(showAlbumDetails(QModelIndex)));

         QVBoxLayout *layout = new QVBoxLayout;
         layout->addWidget(albumView, 0, 0);
         box->setLayout(layout);

         return box;
     }

     QGroupBox* MainWindow::createDetailsGroupBox()
     {
         QGroupBox *box = new QGroupBox(tr("Details"));

         profileLabel = new QLabel;
         profileLabel->setWordWrap(true);
         profileLabel->setAlignment(Qt::AlignBottom);

         titleLabel = new QLabel;
         titleLabel->setWordWrap(true);
         titleLabel->setAlignment(Qt::AlignBottom);

         iconLabel = new QLabel();
         iconLabel->setAlignment(Qt::AlignBottom | Qt::AlignRight);
         iconLabel->setPixmap(QPixmap(":/images/icon.png"));

         imageLabel = new QLabel;
         imageLabel->setWordWrap(true);
         imageLabel->setAlignment(Qt::AlignCenter);
         imageLabel->setPixmap(QPixmap(":/images/image.png"));

         trackList = new QListWidget;

         QGridLayout *layout = new QGridLayout;
         layout->addWidget(imageLabel, 0, 0, 3, 2);
         layout->addWidget(profileLabel, 0, 0);
         layout->addWidget(iconLabel, 0, 1);
         layout->addWidget(titleLabel, 1, 0, 1, 2);
         layout->addWidget(trackList, 2, 0, 1, 2);
         layout->setRowStretch(2, 1);
         box->setLayout(layout);

         return box;
     }

     void MainWindow::createMenuBar()
     {
         QAction *addAction = new QAction(tr("&Add album..."), this);
         QAction *deleteAction = new QAction(tr("&Delete album..."), this);
         QAction *quitAction = new QAction(tr("&Quit"), this);
         QAction *aboutAction = new QAction(tr("&About"), this);
         QAction *aboutQtAction = new QAction(tr("About &Qt"), this);

         addAction->setShortcut(tr("Ctrl+A"));
         deleteAction->setShortcut(tr("Ctrl+D"));
         quitAction->setShortcuts(QKeySequence::Quit);

         QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
         fileMenu->addAction(addAction);
         fileMenu->addAction(deleteAction);
         fileMenu->addSeparator();
         fileMenu->addAction(quitAction);

         QMenu *helpMenu = menuBar()->addMenu(tr("&Help"));
         helpMenu->addAction(aboutAction);
         helpMenu->addAction(aboutQtAction);

         connect(addAction, SIGNAL(triggered(bool)), this, SLOT(addAlbum()));
         connect(deleteAction, SIGNAL(triggered(bool)), this, SLOT(deleteAlbum()));
         connect(quitAction, SIGNAL(triggered(bool)), this, SLOT(close()));
         connect(aboutAction, SIGNAL(triggered(bool)), this, SLOT(about()));
         connect(aboutQtAction, SIGNAL(triggered(bool)), qApp, SLOT(aboutQt()));
     }

     void MainWindow::showImageLabel()
     {
         profileLabel->hide();
         titleLabel->hide();
         iconLabel->hide();
         trackList->hide();

         imageLabel->show();
     }

     QModelIndex MainWindow::indexOfArtist(const QString &artist)
     {
         QSqlTableModel *artistModel = model->relationModel(2);

         for (int i = 0; i < artistModel->rowCount(); i++) {
             QSqlRecord record =  artistModel->record(i);
             if (record.value("artist") == artist)
                 return artistModel->index(i, 1);
         }
         return QModelIndex();
     }

     void MainWindow::updateHeader(QModelIndex, int, int)
     {
         adjustHeader();
     }

     void MainWindow::adjustHeader()
     {
         albumView->hideColumn(0);
         albumView->horizontalHeader()->setResizeMode(1, QHeaderView::Stretch);
         albumView->resizeColumnToContents(2);
         albumView->resizeColumnToContents(3);
     }

     void MainWindow::about()
     {
         QMessageBox::about(this, tr("About Music Archive"),
                 tr("<p>The <b>Music Archive</b> example shows how to present "
                    "data from different data sources in the same application. "
                    "The album titles, and the corresponding artists and release dates, "
                    "are kept in a database, while each album's tracks are stored "
                    "in an XML file. </p><p>The example also shows how to add as "
                    "well as remove data from both the database and the "
                    "associated XML file using the API provided by the QtSql and "
                    "QtXml modules, respectively.</p>"));
     }