QTreeView中实现超链接而不使用QLabel

Question

我想在我的 QTreeView 中显示可以点击的超链接。

我按照这个问题的建议，使用 QLabels 和 QTreeView.setIndexWidget 实现了这个功能。

在 QTreeView 中的超链接

不过，我的 QTreeView 可能会很大（有上千个项目），创建上千个 QLabels 的速度很慢。

好消息是，我可以在 QTreeView 中使用 Delegate 来绘制看起来像超链接的文本。这种方法非常快。

现在的问题是，我需要这些文本像超链接一样响应（比如鼠标悬停时显示手形光标、响应点击等），但我不太确定该怎么做。

我已经通过连接 QTreeView 的 clicked() 信号来模拟这个效果，但这并不完全一样，因为它会响应整个单元格，而不仅仅是单元格内的文本。

Answer 1

谢谢你提供的代码，这是我在网上找到的最好的代码。我在我的项目中使用了你的代码，但我需要使用qss样式表，而你的代码不太适用。我把QItemDelegate换成了QStyledItemDelegate，并对你的代码做了一些修改（在html链接上做了垂直对齐，也许你可以找到更简单的解决办法），并且只在字符串以'开头时进行计算。

class LinkItemDelegate(QStyledItemDelegate):
linkActivated = pyqtSignal(str)
linkHovered = pyqtSignal(str)  # to connect to a QStatusBar.showMessage slot

def __init__(self, parentView):
    super(LinkItemDelegate, self).__init__(parentView)
    assert isinstance(parentView, QAbstractItemView), \
        "The first argument must be the view"

    # We need that to receive mouse move events in editorEvent
    parentView.setMouseTracking(True)

    # Revert the mouse cursor when the mouse isn't over 
    # an item but still on the view widget
    parentView.viewportEntered.connect(parentView.unsetCursor)

    # documents[0] will contain the document for the last hovered item
    # documents[1] will be used to draw ordinary (not hovered) items
    self.documents = []
    for i in range(2):
        self.documents.append(QTextDocument(self))
        self.documents[i].setDocumentMargin(0)
    self.lastTextPos = QPoint(0,0)

def drawDisplay(self, painter, option, rect, text): 
    # Because the state tells only if the mouse is over the row
    # we have to check if it is over the item too
    mouseOver = option.state & QStyle.State_MouseOver \
        and rect.contains(self.parent().viewport() \
            .mapFromGlobal(QCursor.pos())) \
        and option.state & QStyle.State_Enabled

    # Force to be vertically align
    fontMetrics = QFontMetrics(option.font)
    rect.moveTop(rect.y() + rect.height() / 2 - fontMetrics.height() / 2)

    if mouseOver:
        # Use documents[0] and save the text position for editorEvent
        doc = self.documents[0]
        self.lastTextPos = rect.topLeft()
        doc.setDefaultStyleSheet("")
    else:
        doc = self.documents[1]
        # Links are decorated by default, so disable it
        # when the mouse is not over the item
        doc.setDefaultStyleSheet("a {text-decoration: none; }")

    doc.setDefaultFont(option.font)
    doc.setHtml(text)

    painter.save()
    painter.translate(rect.topLeft())
    ctx = QAbstractTextDocumentLayout.PaintContext()
    ctx.palette = option.palette
    doc.documentLayout().draw(painter, ctx)
    painter.restore()

def editorEvent(self, event, model, option, index):
    if event.type() not in [QEvent.MouseMove, QEvent.MouseButtonRelease] \
        or not (option.state & QStyle.State_Enabled):
        return False
    # Get the link at the mouse position
    # (the explicit QPointF conversion is only needed for PyQt)
    pos = QPointF(event.pos() - self.lastTextPos)
    anchor = self.documents[0].documentLayout().anchorAt(pos)
    if anchor == "":
        self.parent().unsetCursor()
    else:
        self.parent().setCursor(Qt.PointingHandCursor)
        if event.type() == QEvent.MouseButtonRelease:
            self.linkActivated.emit(anchor)
            return True 
        else:
            self.linkHovered.emit(anchor)
    return False

def sizeHint(self, option, index):
    # The original size is calculated from the string with the html tags
    # so we need to subtract from it the difference between the width
    # of the text with and without the html tags
    size = super(LinkItemDelegate, self).sizeHint(option, index)
    if option.text.startswith('<a'):
        # Use a QTextDocument to strip the tags
        doc = self.documents[1]
        html = index.data() # must add .toString() for PyQt "API 1"
        doc.setHtml(html)
        plainText = doc.toPlainText()

        fontMetrics = QFontMetrics(option.font)
        diff = fontMetrics.width(html) - fontMetrics.width(plainText)
        size = size - QSize(diff, 0)

    return size

def paint(self, painter, option, index):
    if (index.isValid()):
        text = None
        options = QStyleOptionViewItem(option)
        self.initStyleOption(options,index)
        if options.text.startswith('<a'):
            text = options.text
            options.text = ""
        style = options.widget.style() if options.widget.style() else QApplication.style()
        style.drawControl(QStyle.CE_ItemViewItem, options, painter, options.widget)
        if text:
            textRect = style.subElementRect(QStyle.SE_ItemViewItemText, options, options.widget)
            self.drawDisplay(painter, option, textRect, text)

别忘了连接项目代理：

linkItemDelegate = LinkItemDelegate(self.my_treeView)
linkItemDelegate.linkActivated.connect(self.onClicLink)
self.my_treeView.setItemDelegate(linkItemDelegate) # Create custom delegate and set model and delegate to the treeview object

这样就能很好地工作了！

Answer 2

可能可以不使用QLabels，但这样可能会影响代码的可读性。

也许不需要一次性填满整个树形结构。你有没有想过根据需要生成QLabels？可以先分配足够的QLabels来覆盖一个子树，使用expand和expandAll信号来展开它们。你可以通过创建一个QLabels的池子，按需更改它们的文本（以及它们的使用位置）来实现这一点。

Answer 3

要实现这个功能，最简单的方法是通过创建一个 QItemDelegate 的子类。因为文本是通过一个单独的虚拟函数 drawDisplay 来绘制的。如果使用 QStyledItemDelegate，你几乎需要从头开始重新绘制这个项目，还需要一个额外的类来继承 QProxyStyle。

• HTML 文本是通过 QTextDocument 来绘制的，具体是用 QTextDocument.documentLayout().draw()。
• 当鼠标进入某个项目时，这个项目会被重新绘制，调用 drawDisplay，我们会保存绘制文本的位置（这个保存的位置总是鼠标所在项目的文本位置）。
• 这个位置会在 editorEvent 中使用，用来获取鼠标在文档中的相对位置，并通过 QAbstractTextDocumentLayout.anchorAt 获取该位置的链接。

import sys
from PySide.QtCore import *
from PySide.QtGui import *

class LinkItemDelegate(QItemDelegate):
    linkActivated = Signal(str)
    linkHovered = Signal(str)  # to connect to a QStatusBar.showMessage slot

    def __init__(self, parentView):
        QItemDelegate.__init__(self, parentView)
        assert isinstance(parentView, QAbstractItemView), \
            "The first argument must be the view"

        # We need that to receive mouse move events in editorEvent
        parentView.setMouseTracking(True)

        # Revert the mouse cursor when the mouse isn't over 
        # an item but still on the view widget
        parentView.viewportEntered.connect(parentView.unsetCursor)

        # documents[0] will contain the document for the last hovered item
        # documents[1] will be used to draw ordinary (not hovered) items
        self.documents = []
        for i in range(2):
            self.documents.append(QTextDocument(self))
            self.documents[i].setDocumentMargin(0)
        self.lastTextPos = QPoint(0,0)

    def drawDisplay(self, painter, option, rect, text): 
        # Because the state tells only if the mouse is over the row
        # we have to check if it is over the item too
        mouseOver = option.state & QStyle.State_MouseOver \
            and rect.contains(self.parent().viewport() \
                .mapFromGlobal(QCursor.pos())) \
            and option.state & QStyle.State_Enabled

        if mouseOver:
            # Use documents[0] and save the text position for editorEvent
            doc = self.documents[0]                
            self.lastTextPos = rect.topLeft()
            doc.setDefaultStyleSheet("")
        else:
            doc = self.documents[1]
            # Links are decorated by default, so disable it
            # when the mouse is not over the item
            doc.setDefaultStyleSheet("a {text-decoration: none}")

        doc.setDefaultFont(option.font)
        doc.setHtml(text)

        painter.save()
        painter.translate(rect.topLeft())
        ctx = QAbstractTextDocumentLayout.PaintContext()
        ctx.palette = option.palette
        doc.documentLayout().draw(painter, ctx)
        painter.restore()

    def editorEvent(self, event, model, option, index):
        if event.type() not in [QEvent.MouseMove, QEvent.MouseButtonRelease] \
            or not (option.state & QStyle.State_Enabled):
            return False                        
        # Get the link at the mouse position
        # (the explicit QPointF conversion is only needed for PyQt)
        pos = QPointF(event.pos() - self.lastTextPos)
        anchor = self.documents[0].documentLayout().anchorAt(pos)
        if anchor == "":
            self.parent().unsetCursor()
        else:
            self.parent().setCursor(Qt.PointingHandCursor)               
            if event.type() == QEvent.MouseButtonRelease:
                self.linkActivated.emit(anchor)
                return True 
            else:
                self.linkHovered.emit(anchor)
        return False

    def sizeHint(self, option, index):
        # The original size is calculated from the string with the html tags
        # so we need to subtract from it the difference between the width
        # of the text with and without the html tags
        size = QItemDelegate.sizeHint(self, option, index)

        # Use a QTextDocument to strip the tags
        doc = self.documents[1]
        html = index.data() # must add .toString() for PyQt "API 1"
        doc.setHtml(html)        
        plainText = doc.toPlainText()

        fontMetrics = QFontMetrics(option.font)                
        diff = fontMetrics.width(html) - fontMetrics.width(plainText)

        return size - QSize(diff, 0)

只要你不启用自动根据内容调整列宽（这会对每个项目调用 sizeHint），那么使用这个代理的速度似乎和不使用代理差不多。
如果使用自定义模型，可能通过直接在模型中缓存一些数据来加快速度（例如，对于未被悬停的项目，可以使用并存储 QStaticText，而不是 QTextDocument）。