PyGTK - TreeView Class

The Treeview widget displays contents of a model implementing the gtk.TreeModel interface. PyGTK provides the following types of models −

gtk.ListStore
gtk.TreeStore
gtk.TreeModelSort

ListStore is a list model. When associated with a gtk.TreeView widget, it produces a List box containing the items to be selected from. A gtk.ListStore object is declared with following syntax −

store = gtk.ListStore(column_type)

A list may have multiple columns, the predefined type constants are −

gobject.TYPE_BOOLEAN
gobject.TYPE_BOXED
gobject.TYPE_CHAR
gobject.TYPE_DOUBLE
gobject.TYPE_ENUM
gobject.TYPE_FLOAT
gobject.TYPE_INT
gobject.TYPE_LONG
gobject.TYPE_NONE
gobject.TYPE_OBJECT
gobject.TYPE_STRING
gobject.TYPE_UCHAR
gobject.TYPE_UINT
gobject.TYPE_ULONG
gtk.gdk.pixbuf etc.

For example, a ListStore object to store string items is declared as −

store = gtk.ListStore(gobject.TYPE_STRING

In order to add items in the store, append() methods are used −

store.append (["item 1"])

TreeStore is a model for multi-columned Tree widget. For example, the following statement creates a store with one column having string item.

Store = gtk.TreeStore(gobject.TYPE_STRING)

In order to add items in a TreeStore, use the append() method. The append() method has two parameters, parent and row. To add toplevel item, parent is None.

row1 = store.append(None, ['row1'])

You need to repeat this statement to add multiple rows.

In order to add child rows, pass the toplevel row as parent parameter to the append() method −

childrow = store.append(row1, ['child1'])

You need to repeat this statement to add multiple child rows.

Now, create a TreeView widget and use the above TreeStore object as model.

treeview = gtk.TreeView(store)

We now have to create TreeViewColumn to display store data. The object of gtk.TreeViewColumn manages header and the cells using gtk.CelRenderer. TreeViewColumn object is created using the following constructor −

gtk.TreeViewColumn(title, cell_renderer,…)

In addition to title and renderer, it takes zero or more attribute=column pairs to specify from which tree model column the attribute's value is to be retrieved. These parameters can also be set using methods of TreeViewColumn class given below.

A gtk.CellRenderer is a base class for a set of objects for rendering different types of data. The derived classes are CellRendererText, CellRendererPixBuf and CellRendererToggle.

The following methods of the TreeViewColumn class are used to configure its object −

TreeViewColumn.pack_start(cell, expand = True) − This method packs the CellRenderer object into the beginning column. If expand parameter is set to True, columns entire allocated space is assigned to cell.
TreeViewColumn.add_attribute(cell, attribute, column) − This method adds an attribute mapping to the list in the tree column. The columnis the column of the tree model.
TreeViewColumn.set_attributes() − This method sets the attribute locations of the renderer using the attribute = column pairs
TreeViewColumn.set_visible() − If True, the treeview column is visible
TreeViewColumn.set_title() − This method sets the "title" property to the value specified.
TreeViewColumn.set_lickable() − If set to True, the header can take keyboard focus, and be clicked.
TreeViewColumn.set_alignment(xalign) − This method sets the "alignment" property to the value of xalign.

The "clicked" signal is emitted when the user clicks on the treeviewcolumnheader button.

After having configured the TreeViewColumn object, it is added to the TreeView widget using the append_column() method.

The following are the important methods of the TreeView class −

TreevVew.set_model() − This sets the "model" property for the treeview. If the treeview already has a model set, this method will remove it before setting the new model. If model is None, it will unset the old model.
TreeView.set_header_clickable() − If set to True, the column title buttons can be clicked.
TreeView.append_column() − This appends the specified TreeViewColumn to the list of columns.
TreeView.remove_column() − This removes the specified column from the treeview.
TreeView.insert_column() − This inserts the specified column into the treeview at the location specified by position.

The TreeView widget emits the following signals −

cursor-changed	This is emitted when the cursor moves or is set.
expand-collapse-cursor-row	This is emitted when the row at the cursor needs to be expanded or collapsed.
row-activated	This is emitted when the user double clicks a treeview row
row-collapsed	This is emitted when a row is collapsed by the user or programmatic action.
row-expanded	This is emitted when a row is expanded via the user or programmatic action.

Two examples of the TreeView widget are given below. The first example uses a ListStore to produce a simple ListView.

Here a ListStore object is created and string items are added to it. This ListStore object is used as model for TreeView object −

store = gtk.ListStore(str)
treeView = gtk.TreeView()
treeView.set_model(store)

Then a CellRendererText is added to a TreeViewColumn object and the same is appended to TreeView.

rendererText = gtk.CellRendererText()
column = gtk.TreeViewColumn("Name", rendererText, text = 0)
treeView.append_column(column)

TreeView Object is placed on the toplevel window by adding it to a Fixed container.

Example 1

Observe the following code −

import pygtk
pygtk.require('2.0')
import gtk
class PyApp(gtk.Window):
   def __init__(self):
      super(PyApp, self).__init__()
      self.set_title("TreeView with ListStore")
      self.set_default_size(250, 200)
      self.set_position(gtk.WIN_POS_CENTER)
  
      store = gtk.ListStore(str)
      store.append (["PyQt"])
      store.append (["Tkinter"])
      store.append (["WxPython"])
      store.append (["PyGTK"])
      store.append (["PySide"])
      
      treeView = gtk.TreeView()
      treeView.set_model(store)
  
      rendererText = gtk.CellRendererText()
      column = gtk.TreeViewColumn("Python GUI Libraries", rendererText, text=0)
      treeView.append_column(column)
      
      fixed = gtk.Fixed()
      lbl = gtk.Label("select a GUI toolkit")
      fixed.put(lbl, 25,75)
      fixed.put(treeView, 125,15)
  
      lbl2 = gtk.Label("Your choice is:")
      fixed.put(lbl2, 25,175)
      self.label = gtk.Label("")
  
      fixed.put(self.label, 125,175)
      self.add(fixed)
      
      treeView.connect("row-activated", self.on_activated)
      self.connect("destroy", gtk.main_quit)
      self.show_all()
  
      def on_activated(self, widget, row, col):
      model = widget.get_model()
      text = model[row][0]
      self.label.set_text(text)
  
   def main():
      gtk.main()
      return
      if __name__ == "__main__":
bcb = PyApp()
main()

The item selected by the user is displayed on a label in the window as the on_activated callback function is invoked.

Example 2

The second example builds a hierarchical TreeView from a TreeStore. This program follows the same sequence of building the store, setting it as model for TreeView, designing a TreeViewColumn and appending it to TreeView.

import gtk
class PyApp(gtk.Window):
   def __init__(self):
      super(PyApp, self).__init__()
      self.set_title("TreeView with TreeStore")
      self.set_size_request(400,200)
      self.set_position(gtk.WIN_POS_CENTER)
      vbox = gtk.VBox(False, 5)
      
      # create a TreeStore with one string column to use as the model
      store = gtk.TreeStore(str)
      
      # add row
      row1 = store.append(None, ['JAVA'])
      
      #add child rows
      store.append(row1,['AWT'])
      store.append(row1,['Swing'])
      store.append(row1,['JSF'])
      
      # add another row
      row2 = store.append(None, ['Python'])
      store.append(row2,['PyQt'])
      store.append(row2,['WxPython'])
      store.append(row2,['PyGTK'])
      
      # create the TreeView using treestore
      treeview = gtk.TreeView(store)
      tvcolumn = gtk.TreeViewColumn('GUI Toolkits')
      treeview.append_column(tvcolumn)
  
      cell = gtk.CellRendererText()
      tvcolumn.pack_start(cell, True)
      tvcolumn.add_attribute(cell, 'text', 0)
      vbox.add(treeview)
  
      self.add(vbox)
      self.connect("destroy", gtk.main_quit)
      self.show_all()
PyApp()
gtk.main()

The following TreeView is displayed as an output −

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Friday, July 20, 2018