流式布局

所谓流式布局指的是容器中的元素像流水一样，是可以浮动的，当元素一行或者一列占满的时候，它会自动流入到下一行或者下一列。

pyqt5流式布局

pyqt中采用流式布局的方法原理是，通过contentsMargins获取到子元素距离布局的上下左右宽度，然后我们将所有子元素进行遍历，如果它加上边距可以在一行放入的话，那么就放在一行内，如果不能，就放入到下一行，具体代码如下：

m = self.contentsMargins()
effective_rect = rect.adjusted(+m.left(), +m.top(), -m.right(), -m.bottom())
    x = effective_rect.x()
    y = effective_rect.y()
    line_height = 0

    for item in self._item_list:
      wid = item.widget()

      space_x = self.spacing()
      space_y = self.spacing()
      if wid is not None:
        space_x += wid.style().layoutSpacing(
          QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Horizontal)
        space_y += wid.style().layoutSpacing(
          QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Vertical)

      next_x = x + item.sizeHint().width() + space_x
      if next_x - space_x > effective_rect.right() and line_height > 0:
        x = effective_rect.x()
        y = y + line_height + space_y
        next_x = x + item.sizeHint().width() + space_x
        line_height = 0

      if not test_only:
        item.setGeometry(QRect(QPoint(x, y), item.sizeHint()))

      x = next_x
      line_height = max(line_height, item.sizeHint().height())

滚动条的设置

pyqt中有专门的滚动条组件QScrollBar,这个组件需要配合其他组件使用，我们这里使用QScrollArea这个组件进行滚动条的设置。

滚动条的使用方法

首先，我们需要声明QScrollArea

然后，我们需要设置QScrollArea的位置大小

最后，我们将需要产生滚动条的元素放入它的内部。

q = QWidget()
qscrollarea = QtWidgets.QScrollArea(q)   qscrollarea.setGeometry(QRect(50,100,600,500))
qscrollarea.setWidgetResizable(True)
listWidget = QtWidgets.QListWidget()
qscrollarea.setWidget(listWidget)

流式布局和滚动条的结合案例：

在文件当前目录创建一个images文件夹，然后放入想要展示的多张图片，然后执行当前程序，就会看到带有滚动条的流式布局界面。

运行程序，需要安装pyqt5

from PyQt5.QtCore import QPoint, QRect, QSize, Qt,pyqtSignal
import os
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import (
  QApplication, QLayout, QPushButton, QSizePolicy, QWidget, QGridLayout)
import sys
class Window(QWidget):
  def __init__(self):
    self.imageheight = 100
    super(Window, self).__init__()
    self.resize(800, 600)

    #self.listwidget = QtWidgets.QListWidget(self)
    #self.listwidget.resize(400,300)
    #self.listwidget.setGeometry(QtCore.QRect(0, 0, 300, 200))
    #self.listwidget.addItem("test")

    highlight_dir = r"./images"
    self.files_it = iter([os.path.join(highlight_dir, file)
               for file in os.listdir(highlight_dir)])

    # self.centralwidget = QtWidgets.QWidget(MainWindow)
    # self.gongzuomoshi = QtWidgets.QGroupBox(self.centralwidget)
    self.listWidget = QtWidgets.QListWidget(self)
    #self.listWidget.setFixedWidth(600)
    container_layout = QtWidgets.QVBoxLayout()
    g = QtWidgets.QGroupBox('')
    l = FlowLayout()
    g.setLayout(l)
    for file in iter(self.files_it):
      pixmap = QtGui.QPixmap(file)
      if not pixmap.isNull():
        autoWidth = pixmap.width()*self.imageheight/pixmap.height()
        label = QtWidgets.QLabel(pixmap=pixmap)
        label.setScaledContents(True)
        label.setFixedHeight(self.imageheight)
        label.setFixedWidth(autoWidth)
        l.addWidget(label)

    container_layout.addWidget(g)
    container_layout.addStretch()
    self.listWidget.setLayout(container_layout)

    self.qscrollarea = QtWidgets.QScrollArea(self)
    self.qscrollarea.setGeometry(QRect(50,100,600,500))
    self.qscrollarea.setWidgetResizable(True)
    self.qscrollarea.setWidget(self.listWidget)
    self.setWindowTitle("Flow Layout Scroll")

class FlowLayout(QLayout):
  """流式布局,使用说明
  1.声明流式布局 layout = FlowLayout
  2.将元素放入流式布局中
  3.将QGroupBox应用流式布局
  4.如果期望水平流式,将QGroupBox放入到QHBoxLayout,如果期望垂直布局,将QGroupBox放入到QVBoxLayout
  """
  heightChanged = pyqtSignal(int)

  def __init__(self, parent=None, margin=0, spacing=-1):
    super().__init__(parent)
    if parent is not None:
      self.setContentsMargins(margin, margin, margin, margin)
    self.setSpacing(spacing)

    self._item_list = []

  def __del__(self):
    while self.count():
      self.takeAt(0)

  def addItem(self, item): # pylint: disable=invalid-name
    self._item_list.append(item)

  def addSpacing(self, size): # pylint: disable=invalid-name
    self.addItem(QSpacerItem(size, 0, QSizePolicy.Fixed, QSizePolicy.Minimum))

  def count(self):
    return len(self._item_list)

  def itemAt(self, index): # pylint: disable=invalid-name
    if 0 <= index < len(self._item_list):
      return self._item_list[index]
    return None

  def takeAt(self, index): # pylint: disable=invalid-name
    if 0 <= index < len(self._item_list):
      return self._item_list.pop(index)
    return None

  def expandingDirections(self): # pylint: disable=invalid-name,no-self-use
    return Qt.Orientations(Qt.Orientation(0))

  def hasHeightForWidth(self): # pylint: disable=invalid-name,no-self-use
    return True

  def heightForWidth(self, width): # pylint: disable=invalid-name
    height = self._do_layout(QRect(0, 0, width, 0), True)
    return height

  def setGeometry(self, rect): # pylint: disable=invalid-name
    super().setGeometry(rect)
    self._do_layout(rect, False)

  def sizeHint(self): # pylint: disable=invalid-name
    return self.minimumSize()

  def minimumSize(self): # pylint: disable=invalid-name
    size = QSize()

    for item in self._item_list:
      minsize = item.minimumSize()
      extent = item.geometry().bottomRight()
      size = size.expandedTo(QSize(minsize.width(), extent.y()))

    margin = self.contentsMargins().left()
    size += QSize(2 * margin, 2 * margin)
    return size

  def _do_layout(self, rect, test_only=False):
    m = self.contentsMargins()
    effective_rect = rect.adjusted(+m.left(), +m.top(), -m.right(), -m.bottom())
    x = effective_rect.x()
    y = effective_rect.y()
    line_height = 0

    for item in self._item_list:
      wid = item.widget()

      space_x = self.spacing()
      space_y = self.spacing()
      if wid is not None:
        space_x += wid.style().layoutSpacing(
          QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Horizontal)
        space_y += wid.style().layoutSpacing(
          QSizePolicy.PushButton, QSizePolicy.PushButton, Qt.Vertical)

      next_x = x + item.sizeHint().width() + space_x
      if next_x - space_x > effective_rect.right() and line_height > 0:
        x = effective_rect.x()
        y = y + line_height + space_y
        next_x = x + item.sizeHint().width() + space_x
        line_height = 0

      if not test_only:
        item.setGeometry(QRect(QPoint(x, y), item.sizeHint()))

      x = next_x
      line_height = max(line_height, item.sizeHint().height())

    new_height = y + line_height - rect.y()
    self.heightChanged.emit(new_height)
    return new_height

if __name__ == '__main__':
  app = QApplication(sys.argv)
  mainWin = Window()

  mainWin.show()
  sys.exit(app.exec_())

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