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来自「GUI Programming with Python」· HTM 代码 · 共 780 行 · 第 1/2 页

        </P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
>QGrid</A
></H3
><P
>It will come as no surprise that the
          <TT
CLASS="CLASSNAME"
>QGrid</TT
> is a simple grid layout
          manager &#8212; for more complicated layouts, with differently
          sized columns, you really need
          <TT
CLASS="CLASSNAME"
>QGridLayout</TT
>.
        </P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
>QGroupBox</A
></H3
><P
>A <TT
CLASS="CLASSNAME"
>QGroupBox</TT
>
          gives you a frame (which can be drawn in as many flavors as
          <TT
CLASS="CLASSNAME"
>QFrame</TT
> supports) and with a title
          text which will appear on top of the frame. A
          <TT
CLASS="CLASSNAME"
>QGroupBox</TT
> can hold child widgets.
          Those widgets will be aligned horizontally, vertically or in
          a grid. The grid can also be filled in columns (for
          vertically oriented frames), or in strips (for horizontally
          oriented frames).
        </P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
>QLayout</A
></H2
><P
><TT
CLASS="CLASSNAME"
>QLayout</TT
> is
        foundation of all complex Qt layout managers. Built on
        <TT
CLASS="CLASSNAME"
>QLayout</TT
>, there are three
        layoutmanagers: one for horizontal layouts, one for vertical
        layouts and one for grids. It's also quite possible to build a
        new layoutmanager on <TT
CLASS="CLASSNAME"
>QLayout</TT
>, one, for
        instance, that manages playing cards on a stack, or perhaps
        items in circle.</P
><P
>You can not only add widgets to layouts;
        but also layouts. In this way, quite complex layouts can
        achieved with very little pain.</P
><P
>All layout managers work by maintaining
        a list of layoutitems. Those items can be
        <TT
CLASS="CLASSNAME"
>QLayoutItem</TT
>s,
        <TT
CLASS="CLASSNAME"
>QLayoutWidget</TT
>s or
        <TT
CLASS="CLASSNAME"
>QSpacerItem</TT
>s. It's interesting to note
        that <TT
CLASS="CLASSNAME"
>QLayout</TT
> <SPAN
><I
CLASS="EMPHASIS"
>is</I
></SPAN
> a
        <TT
CLASS="CLASSNAME"
>QLayoutItem</TT
>, and can thus be managed by
        another layoutmanager.</P
><P
>Every layout item proxies for a widget.
        A <TT
CLASS="CLASSNAME"
>QSpacerItem</TT
> is rather special, since
        it doesn't represent a widget, but rather space. A
        <TT
CLASS="CLASSNAME"
>QSpacerItem</TT
> &#8216;pushes' other
        widgets, either horizontally or vertically. You can use them
        to push all pushbuttons to the top of the dialog, instead of
        having them spread out over the whole height by the layout
        manager.
      </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
>QBoxLayout and children</A
></H2
><P
><TT
CLASS="CLASSNAME"
>QBoxLayout</TT
> is the
        parent class of the horizontal and vertical box layout
        managers &#8212; you will never use this class on its own, but
        its useful to look at the methods it offers, because those are
        inherited by <TT
CLASS="CLASSNAME"
>QHBoxLayout</TT
> and
        <TT
CLASS="CLASSNAME"
>QVBoxLayout</TT
></P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
>QGridLayout</A
></H2
><P
>While you can handle many layout
        problems with combinations of horizontal and vertical box
        layout managers, other problems are more suited for a
        grid-based layout. The <TT
CLASS="CLASSNAME"
>QGridLayout</TT
>
        class provides a flexible layout manager.
      </P
><P
>The grid managed by a
        <TT
CLASS="CLASSNAME"
>QGridLayout</TT
> consists of cells laid out
        in rows and columns: the grid cannot be as complicated as a
        html table, but you can add widgets (or sub-layouts) that span
        multiple rows and columns. Rows (or columns) can be given a
        stretch factor and spacing.</P
><DIV
CLASS="EXAMPLE"
></A
><P
><B
>Example 10-12. layout.py - two box layouts and adding and removing buttons
          dynamically to a layout</B
></P
><PRE
CLASS="PROGRAMLISTING"
>#
# layout.py - adding and removing widgets to a layout
#
import sys
from qt import *


class MainWindow(QMainWindow):

    def __init__(self, *args):
        apply(QMainWindow.__init__, (self, ) + args)
        self.setCaption("Adding and deleting widgets")
        self.setName("main window")
        self.mainWidget=QWidget(self) # dummy widget to contain the
                                      # layout manager
        self.setCentralWidget(self.mainWidget)
        self.mainLayout=QVBoxLayout(self.mainWidget, 5, 5, "main")
        self.buttonLayout=QHBoxLayout(self.mainLayout, 5, "button")
        self.widgetLayout=QVBoxLayout(self.mainLayout, 5, "widget")

        self.bnAdd=QPushButton("Add widget", self.mainWidget, "add")
        self.connect(self.bnAdd, SIGNAL("clicked()"),
                     self.slotAddWidget)

        self.bnRemove=QPushButton("Remove widget",
                                  self.mainWidget, "remove")
        self.connect(self.bnRemove, SIGNAL("clicked()"),
                     self.slotRemoveWidget)

        self.buttonLayout.addWidget(self.bnAdd)
        self.buttonLayout.addWidget(self.bnRemove)

        self.buttons = []

    def slotAddWidget(self):
        widget=QPushButton("test", self.mainWidget)
        self.widgetLayout.addWidget(widget)
        self.buttons.append(widget)
        widget.show()

    def slotRemoveWidget(self):
        self.widgetLayout.parent().removeChild(self.widgetLayout)
        self.widgetLayout=QVBoxLayout(self.mainLayout, 5, "widget")
        self.buttons[-1].parent().removeChild(self.buttons[-1])
        del self.buttons[-1:]


def main(args):
    app=QApplication(args)
    win=MainWindow()
    win.show()
    app.connect(app, SIGNAL("lastWindowClosed()")
                                 , app
                                 , SLOT("quit()")
                                 )
    app.exec_loop()

if __name__=="__main__":
    main(sys.argv)
          </PRE
></DIV
><P
>This example shows that it is not only
        possible to dynamically add widgets to a layout, but also to
        remove them again. Removing means first severing the link from
        the widget to the parent, and then deleting (using
        <TT
CLASS="FUNCTION"
>del</TT
>) all Python references to the widget.
        When the last reference has been removed, the widget
        disappears.</P
><DIV
CLASS="MEDIAOBJECT"
><P
><DIV
CLASS="CAPTION"
><P
>layout.py</P
></DIV
></P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
>setGeometry</A
></H2
><P
>You can use
        <TT
CLASS="FUNCTION"
>setGeometry</TT
> to set the size of every
        individual widget yourself. There's another useful application
        of <TT
CLASS="FUNCTION"
>setGeometry()</TT
>, too: if you save the
        size of the application window when the last window closes in
        a configuration file, you can bring the window back to its
        last size and position the next time the user starts opens it.
        </P
><DIV
CLASS="EXAMPLE"
></A
><P
><B
>Example 10-13. geometry.py - setting the initial size of an
          application</B
></P
><PRE
CLASS="PROGRAMLISTING"
>#
# geometry.py
#
import sys
from qt import *

class MainWindow(QMainWindow):
        
    def __init__(self, *args):
        apply(QMainWindow.__init__, (self,) + args)
        self.editor=QMultiLineEdit(self)
        self.setCentralWidget(self.editor)
        
def main(args):
    app=QApplication(args)
    win=MainWindow()
    win.setGeometry(100,100,300,300)
    win.show()
        
    app.connect(app, SIGNAL("lastWindowClosed()")
                           , app
                           , SLOT("quit()")
                           )
    app.exec_loop()
    
if __name__=="__main__":
    main(sys.argv)
        </PRE
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