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来自「GUI Programming with Python」· HTM 代码 · 共 283 行
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<table border="0" cellspacing="0" cellpadding="3" width="100%"><tr><td> <div align="center" id="bldcontent"> <a href="../default.htm"><img src="../images/opendocs.png" width="63" height="76" border="0"></a> <br> <div class="symbol">Your OpenSource Publisher™</div> </div> </td></tr></table> <div align="center" class="author"> <a href="../products.lxp">Products</a> | <a href="../wheretobuy.lxp">Where to buy</a> | <a href="../bookstore.lxp">Retailers</a> | <a href="../faq.lxp">FAQ</a> | <a href="../writeforus.lxp">Write for Us.</a> | <a href="#contact">Contact Us.</a> </div> <table border="0" cellspacing="3" cellpadding="0" width="100%"><tr><td width="100%"> <div class="content"> <table border="0" cellspacing="2" cellpadding="0" width="100%"><tr><td width="100%"> <div align="center"><H4 CLASS="AUTHOR"><A NAME="AEN5">Boudewijn Rempt</A><br><a href="../../https@secure.linuxports.com/opendocs/default.htm"><img src=odpyqt125.png></a><br>ISBN: 0-97003300-4-4<br><a href="../../https@secure.linuxports.com/opendocs/default.htm">Available from bookstores everywhere or you can order it here.</a><p>You can download the source files for the book <a href="pyqtsrc.tgz">(code / eps) here.</a><hr></div> <HTML><HEAD><TITLE>Initiating drags</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.72"><LINKREL="HOME"TITLE="GUI Programming with Python: QT Edition"HREF="book1.htm"><LINKREL="UP"TITLE="Drag and drop"HREF="c8016.htm"><LINKREL="PREVIOUS"TITLE="Drag and drop"HREF="c8016.htm"><LINKREL="NEXT"TITLE="Conclusion"HREF="x8095.htm"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#0000FF"VLINK="#840084"ALINK="#0000FF"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">GUI Programming with Python: QT Edition</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><A accesskey="P" href="index.lxp@lxpwrap=c8016_252ehtm.htm">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 23. Drag and drop</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><A accesskey="N" href="index.lxp@lxpwrap=x8095_252ehtm.htm">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1">Initiating drags</A></H1><P>Initiating drag operations is a bit more difficult, because you must determine when exactly a drag begins. Users expect that holding down the mouse-button on the object they want to drag and moving it should start dragging. However, everyone moves the mouse very slightly, even if just single-clicking on an object. Thus, we must determine how many pixels the mouse pointer should move (while the first mouse button is depressed) to enter a drag operation.</P><P>We cannot do this using <TTCLASS="CLASSNAME">QMultiLineEdit</TT>. A class like <TTCLASS="CLASSNAME">QIconView</TT> offers special support for starting drags by allowing you to re-implement the <TTCLASS="FUNCTION">dragObject</TT> function:</P><PRECLASS="PROGRAMLISTING">class MyIconView(QIconView): def dragObject(self): return QTextDrag(self.currentItem().text(), self) </PRE><P>Once you have determined what should start a drag (and this can be anything, really), starting a drag operation is a simple matter of creating a new <TTCLASS="CLASSNAME">QDragObject</TT>. This could be, for instance, a <TTCLASS="CLASSNAME">QTextDrag</TT> or a <TTCLASS="CLASSNAME">QImageDrag</TT>. Take care that you keep a reference to the drag object—if you delete it, or allow it to go out of scope, it will disappear.</P><P>In the next example, simply moving a mouse will start a drag operation:</P><DIVCLASS="EXAMPLE"></A><P><B>Example 23-2. Drag and drop</B></P><PRECLASS="PROGRAMLISTING">#!/usr/bin/env pythonfrom sys import argvfrom qt import *class DropDemo(QListView): def __init__(self,parent=None,name=None): QListView.__init__(self,parent,name) self.setAcceptDrops(1) self.setGeometry(10,10,100,60) self.addColumn("Column 1") self.i = QListViewItem(self, "Hello") self.ii = QListViewItem(self, "Hello 2") r = self.itemRect(self.i) r = self.itemRect(self.ii) def dragEnterEvent(self, event): event.accept(QTextDrag.canDecode(event)) def dropEvent(self, event): text = QString() pos = QPoint(event.pos().x(), event.pos().y() - self.header().height()) item = self.itemAt(pos) text=QString() def mouseMoveEvent(self, event): self.startDrag() def startDrag(self): d = QTextDrag("blabla",self) # keep a reference to d d.dragCopy() if __name__ == '__main__': a = QApplication(argv) w = DropDemo() w.setCaption("Drag and Drop Test") w.resize(120,80) a.setMainWidget(w) w.show() a.exec_loop() </PRE></DIV></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><A accesskey="P" href="index.lxp@lxpwrap=c8016_252ehtm.htm">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><A accesskey="H" href="index.lxp@lxpwrap=book1_252ehtm">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><A accesskey="N" href="index.lxp@lxpwrap=x8095_252ehtm.htm">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">Drag and drop</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><A accesskey="U" href="index.lxp@lxpwrap=c8016_252ehtm.htm">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">Conclusion</TD></TR></TABLE></DIV></BODY></HTML> </td> </tr> </table> </td> </tr> </table> ⌨️ 快捷键说明
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