PyQt - 使用 QListWidget 自定義滾動

Question

我試圖找出一種方法來定制滾動條的QListWidget有滾動條上方及以下QListWidget ，而不是正常的垂直和水平滾動條。

如果您不明白我的意思，請查看下面的示例。
在下面的示例中，我使用QPushButtons和QTimers控制滾動代替滾動條，但我正在尋找的是滾動條，就像啟用菜單滾動時QMenu中的滾動條。

如果這不是一個選項，我想知道是否有滾動條信號或我可以嘗試使用的東西來了解滾動條何時正常激活？ 這樣我就可以根據需要顯示/隱藏按鈕。 謝謝。

import sys
from PyQt5.QtCore import pyqtSignal, QTimer, Qt
from PyQt5.QtGui import QPainter
from PyQt5.QtWidgets import QWidget, QPushButton, QVBoxLayout, \
    QApplication, QStyle, QListWidget, QStyleOptionButton, QListWidgetItem

class UpBtn(QPushButton):
    mouseHover = pyqtSignal()
    def __init__(self):
        QPushButton.__init__(self)
        self.setMouseTracking(True)
        self.timer = QTimer()

    def paintEvent(self, event):
        painter = QPainter()
        painter.begin(self)
        opt = QStyleOptionButton()
        self.initStyleOption(opt)
        self.style().drawControl(QStyle.CE_ScrollBarSubLine, opt, painter, self)
        painter.end()

    def startScroll(self):
        self.mouseHover.emit()

    def enterEvent(self, event):
        self.timer.timeout.connect(self.startScroll)
        self.timer.start(120)

    def leaveEvent(self, event):
        self.timer.stop()

class DwnBtn(QPushButton):
    mouseHover = pyqtSignal()
    def __init__(self):
        QPushButton.__init__(self)
        self.setMouseTracking(True)
        self.timer = QTimer()

    def paintEvent(self, event):
        painter = QPainter()
        painter.begin(self)
        opt = QStyleOptionButton()
        self.initStyleOption(opt)
        self.style().drawControl(QStyle.CE_ScrollBarAddLine, opt, painter, self)
        painter.end()

    def startScroll(self):
        self.mouseHover.emit()

    def enterEvent(self, event):
        self.timer.timeout.connect(self.startScroll)
        self.timer.start(120)

    def leaveEvent(self, event):
        self.timer.stop()

class Window(QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.layout = QVBoxLayout()
        self.layout.setContentsMargins(0, 0, 0, 0)
        self.layout.setSpacing(0)
        self.upBtn = UpBtn()
        self.upBtn.setFixedWidth(230)
        self.layout.addWidget(self.upBtn)

        self.listWidget = QListWidget()
        self.listWidget.setFixedWidth(230)
        self.listWidget.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.listWidget.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.layout.addWidget(self.listWidget)

        self.downBtn = DwnBtn()
        self.downBtn.setFixedWidth(230)
        self.layout.addWidget(self.downBtn)

        self.setLayout(self.layout)
        self.upBtn.clicked.connect(self.upBtnClicked)
        self.upBtn.mouseHover.connect(self.upBtnClicked)
        self.downBtn.clicked.connect(self.downBtnClicked)
        self.downBtn.mouseHover.connect(self.downBtnClicked)

        for i in range(100):
            item = QListWidgetItem()
            item.setText("list item " + str(i))
            self.listWidget.addItem(item)

    def upBtnClicked(self):
        cur = self.listWidget.currentRow()
        self.listWidget.setCurrentRow(cur - 1)

    def downBtnClicked(self):
        cur = self.listWidget.currentRow()
        self.listWidget.setCurrentRow(cur + 1)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

編輯：這是我正在談論的示例圖像。 這是一個可滾動的QMenu 。

編輯：
可滾動的QMenu代碼。
取消注釋注釋部分以獲得圖像中的固定大小。 通常 Qmenu 滾動僅在菜單項超過屏幕高度時才起作用。 我只是在尋找頂部和底部懸停樣式滾動，但要在QListWidget 。

import sys
from PyQt5.QtCore import QPoint, QEvent
from PyQt5.QtWidgets import QWidget, QPushButton, QVBoxLayout, \
    QApplication, QAction, QMenu, QProxyStyle, QStyle

class MyMenu(QMenu):
    def event(self, event):
        if event.type() == QEvent.Show:
            self.move(self.parent().mapToGlobal(QPoint(-108, 0)))
        return super(MyMenu, self).event(event)

# class CustomStyle(QProxyStyle):
#     def pixelMetric(self, QStyle_PixelMetric, option=None, widget=None):
#         if QStyle_PixelMetric == QStyle.PM_MenuScrollerHeight:
#             return 15
#         if QStyle_PixelMetric == QStyle.PM_MenuDesktopFrameWidth:
#             return 290
#         else:
#             return QProxyStyle.pixelMetric(self, QStyle_PixelMetric, option, widget)

class MainWindow(QWidget):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.layout = QVBoxLayout()
        self.btn = QPushButton("Button")
        self.btn.setFixedHeight(30)
        self.btn.setFixedWidth(100)
        self.myMenu = MyMenu("Menu", self.btn)
        self.btn.setMenu(self.myMenu)
        self.layout.addWidget(self.btn)
        self.setLayout(self.layout)
        menus = []
        for _ in range(5):
            myMenus = QMenu("Menu"+str(_+1), self.btn)
            # myMenus.setFixedHeight(120)
            myMenus.setStyleSheet("QMenu{menu-scrollable: 1; }")
            menus.append(myMenus)
        for i in menus:
            self.btn.menu().addMenu(i)
            for item in range(100):
                action = QAction("item" + str(item), self)
                i.addAction(action)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    # app.setStyle(CustomStyle())
    w = MainWindow()
    w.show()
    app.exec_()

Answer 1

這個想法是獲取將決定按鈕是否隱藏的上下元素的行，為此我們使用方法 itemAt () 返回給定幾何坐標的項目。 另一方面，我改進了每次更改 QListView 中的項目數時必須執行的計算，因為我們使用內部模型的信號。

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class Button(QtWidgets.QPushButton):
    moveSignal = QtCore.pyqtSignal()
    def __init__(self, *args, **kwargs):
        super(Button, self).__init__(*args, **kwargs)
        self.m_timer = QtCore.QTimer(self, interval=120)
        self.m_timer.timeout.connect(self.moveSignal)
        self.setMouseTracking(True)
        self.setFixedHeight(20)

    def mouseReleaseEvent(self, e):
        super(Button, self).mousePressEvent(e)
        self.setDown(True)

    def enterEvent(self, e):
        self.setDown(True)
        self.m_timer.start()
        super(Button, self).enterEvent(e)

    def leaveEvent(self, e):
        self.setDown(False)
        self.m_timer.stop()
        super(Button, self).leaveEvent(e)


class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.setFixedWidth(230)

        icon = self.style().standardIcon(QtWidgets.QStyle.SP_ArrowUp)
        self.upBtn = Button(icon=icon)
        self.upBtn.moveSignal.connect(self.moveUp)
        icon = self.style().standardIcon(QtWidgets.QStyle.SP_ArrowDown)
        self.downBtn = Button(icon=icon)
        self.downBtn.moveSignal.connect(self.moveDown)

        self.listWidget = QtWidgets.QListWidget()
        self.listWidget.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.listWidget.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)

        layout = QtWidgets.QVBoxLayout(self)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.setSpacing(0)
        layout.addWidget(self.upBtn)
        layout.addWidget(self.listWidget)
        layout.addWidget(self.downBtn)
        self.adjust_buttons()
        self.create_connections()

    def create_connections(self):
        self.listWidget.currentItemChanged.connect(self.adjust_buttons)
        model = self.listWidget.model()
        model.rowsInserted.connect(self.adjust_buttons)
        model.rowsRemoved.connect(self.adjust_buttons)
        model.rowsMoved.connect(self.adjust_buttons)
        model.modelReset.connect(self.adjust_buttons)
        model.layoutChanged.connect(self.adjust_buttons)

    @QtCore.pyqtSlot()
    def adjust_buttons(self):
        first = self.listWidget.itemAt(QtCore.QPoint())
        r = self.listWidget.row(first)
        self.upBtn.setVisible(r != 0 and  r!= -1)
        last = self.listWidget.itemAt(self.listWidget.viewport().rect().bottomRight())
        r = self.listWidget.row(last)
        self.downBtn.setVisible( r != (self.listWidget.count() -1) and r != -1)

    @QtCore.pyqtSlot()
    def moveUp(self):
        ix = self.listWidget.moveCursor(QtWidgets.QAbstractItemView.MoveUp, QtCore.Qt.NoModifier)
        self.listWidget.setCurrentIndex(ix)

    @QtCore.pyqtSlot()
    def moveDown(self):
        ix = self.listWidget.moveCursor(QtWidgets.QAbstractItemView.MoveDown, QtCore.Qt.NoModifier)
        self.listWidget.setCurrentIndex(ix)

    @QtCore.pyqtSlot(str)
    def add_item(self, text):
        item = QtWidgets.QListWidgetItem(text)
        self.listWidget.addItem(item)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    for i in range(100):
        window.add_item("item {}".format(i))
    window.show()
    sys.exit(app.exec_())