Representing Tabular Data in Trees in Java Printing Code 128B in Java Representing Tabular Data in Trees

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Representing Tabular Data in Trees generate, create code 128 barcode none for java projects GS1 DataBar-14 Figure 16.3 Tabular data rendered as a tree need only navigate 33 top-lev el items rather than scrolling through almost ve times that number of rows. The heart of the application is provided by the TreeOfTableModel class, a QAbstractItemModel subclass that can represent arbitrary tabular data in a tree. We use a custom subclass of this model, along with a QTreeView subclass to present the data.

The application itself can create the tree using different levels of nesting by running it from the console with a command-line argument of 1, 2, 3, or 4. Figure 16.3 shows the tree using the default nesting level of 3.

(The nesting level does not include the leaf at the end of a series of branches.) We will begin by reviewing the main form since it is very short. Then we will look at the table view subclass and the TreeOfTableModel subclass.

Next, we will review the treeoftable module, including the BranchNode and LeafNode classes, and nally, the TreeOfTableModel class itself.. class MainForm(QMainWindow): code 128b for Java def __init__(self, filename, nesting, separator, parent=None): super(MainForm, self).__init__(parent) headers = ["Country/State (US)/City/Provider", "Server", "IP"] self.treeWidget = TreeOfTableWidget(filename, nesting, separator) self.

treeWidget.model().headers = headers self.

setCentralWidget(self.treeWidget) self.connect(self.

treeWidget, SIGNAL("activated"), self.activated) self.setWindowTitle("Server Info").

16. Advanced Model/View Programming The TreeOfTableWidget is simi ANSI/AIM Code 128 for Java lar to a convenience view, since it incorporates a model inside it. The model is a ServerModel, a small TreeOfTableModel subclass that adds the ability to show ag icons. The lename is the name of a le that has data suitable for a TreeOfTableModel.

In particular, it must have one record per line, and each column ( eld) must be separated by the speci ed separator. The nesting value is the maximum number of branches that can spur off from a root, and does not count the leaves at the end. In this case, the nesting value passed in through the nesting parameter is 3 (unless it s changed on the command line), which means that we will have 3 levels of branches (country, state, city) and 1 level of leaves (provider).

Since we have 6 elds, this means that the rst 4 elds will be shown in the tree part of the tree widget, with the remaining 2 elds shown as separate columns in the rows that have leaves. The resultant tree view will have 3 columns, one containing the tree, and 2 more showing the extra elds. We set the model s headers by directly accessing the model inside the custom TreeOfTableWidget.

The activated() method is called when the user double-clicks or presses Enter on a row in the tree widget.. def activated(self, fields): self.statusBar().showMessage("*".

join(fields), 60000). The path , that is, the (cou barcode code 128 for Java ntry, city, state, provider, server, IP address) 6-tuple that the user has chosen, is shown * -separated in the status bar for a minute (60 000 milliseconds), whenever a suitable row is activated. In this context, a suitable row is one containing a leaf, since these are the only ones that have all six elds. The TreeOfTableWidget is a QTreeView subclass that contains the model it displays.

It also provides a few simple convenience methods and creates some useful signal slot connections.. class TreeOfTableWidget(QTree View): def __init__(self, filename, nesting, separator, parent=None): super(TreeOfTableWidget, self).__init__(parent) self.setSelectionBehavior(QTreeView.

SelectItems) self.setUniformRowHeights(True) model = ServerModel(self) self.setModel(model) try: model.

load(filename, nesting, separator) except IOError, e: QMessageBox.warning(self, "Server Info - Error", unicode(e)) self.connect(self, SIGNAL("activated(QModelIndex)"), self.

activated). Representing Tabular Data in Trees self.connect(self, SIGNAL("ex panded(QModelIndex)"), self.expanded) self.

expanded(). The ServerModel is a TreeOfTa jdk Code 128 Code Set A bleModel subclass. Its only purpose is to override the data() method so that it can provide suitable icons (country and state ags); we will review it shortly. After loading the model s data from the le and making the signal slot connections, we call the expanded() method to give the columns suitable widths.

. def expanded(self): for colum n in range(self.model().columnCount(QModelIndex())): self.

resizeColumnToContents(column). Whenever the user expands a b Code 128 Code Set A for Java ranch for example, by clicking one of the tree s + symbols or by navigating with the arrow keys and pressing Right Arrow this method is called. It ensures that the columns showing the expanded item s texts are wide enough for the text to be readable. In tree models, every item is either the child of another item (and therefore has a parent) or a top-level (root) item, in which case it has no parent, which is signi ed by an invalid model index.

Therefore, when we call columnCount() with a QModelIndex() (i.e., with an invalid model index), we get the column count of top-level items.

. def activated(self, index): s elf.emit(SIGNAL("activated"), self.model().

asRecord(index)). If the user activates an item code 128c for Java by double-clicking it or by pressing Enter on it, this method is called, and in turn it emits its own activated() signal. Its parameter is the full path (record), as a list of eld values, for the current model index..

def currentFields(self): retu rn self.model().asRecord(self.

currentIndex()). This method provides the same javabean code 128 code set c information as the activated() signal, but it can be called at any time to get the current record; again, as a list of eld values. The ServerModel is a TreeOfTableModel subclass that reimplements one method, data(). It does so to show ags next to the names of countries and U.

S. states..

class ServerModel(treeoftable .TreeOfTableModel): def __init__(self, parent=None): super(ServerModel, self).__init__(parent) def data(self, index, role): if role == Qt.

DecorationRole: node = self.nodeFromIndex(index) if node is None: return QVariant() if isinstance(node, treeoftable.BranchNode):.

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