Python PyQt5 实现图片瀑布流（Flow Layout）布局详解

流式布局概述

流式布局

流式布局，亦称瀑布流布局，是网页设计中常见的一种排版方式。其核心原理是保持图片高度固定，而让图片宽度根据容器自适应调整，从而使加载后的图片呈现出如瀑布般整齐下流的视觉效果。

PyQt5 中的流式布局实现

在 PyQt5 中实现流式布局

PyQt5 原生并未提供直接的流式布局控件，因此需要开发者自行封装实现。以下是流式布局类的封装代码示例。

class FlowLayout(QLayout):
 def __init__(self, parent=None, margin=0, spacing=-1):
  super(FlowLayout, self).__init__(parent)

  if parent is not None:
   self.setContentsMargins(margin, margin, margin, margin)

  self.setSpacing(spacing)

  self.itemList = []

 def __del__(self):
  item = self.takeAt(0)
  while item:
   item = self.takeAt(0)

 def addItem(self, item):
  self.itemList.append(item)

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

 def itemAt(self, index):
  if index >= 0 and index < len(self.itemList):
   return self.itemList[index]

  return None

 def takeAt(self, index):
  if index >= 0 and index < len(self.itemList):
   return self.itemList.pop(index)

  return None

 def expandingDirections(self):
  return Qt.Orientations(Qt.Orientation(0))

 def hasHeightForWidth(self):
  return True

 def heightForWidth(self, width):
  height = self.doLayout(QRect(0, 0, width, 0), True)
  return height

 def setGeometry(self, rect):
  super(FlowLayout, self).setGeometry(rect)
  self.doLayout(rect, False)

 def sizeHint(self):
  return self.minimumSize()

 def minimumSize(self):
  size = QSize()

  for item in self.itemList:
   size = size.expandedTo(item.minimumSize())

  margin, _, _, _ = self.getContentsMargins()

  size += QSize(2 * margin, 2 * margin)
  return size

 def doLayout(self, rect, testOnly):
  x = rect.x()
  y = rect.y()
  lineHeight = 0

  for item in self.itemList:
   wid = item.widget()
   spaceX = self.spacing() + wid.style().layoutSpacing(QSizePolicy.PushButton,
                QSizePolicy.PushButton, Qt.Horizontal)
   spaceY = self.spacing() + wid.style().layoutSpacing(QSizePolicy.PushButton,
                QSizePolicy.PushButton, Qt.Vertical)
   nextX = x + item.sizeHint().width() + spaceX
   if nextX - spaceX > rect.right() and lineHeight > 0:
    x = rect.x()
    y = y + lineHeight + spaceY
    nextX = x + item.sizeHint().width() + spaceX
    lineHeight = 0

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

   x = nextX
   lineHeight = max(lineHeight, item.sizeHint().height())

  return y + lineHeight - rect.y()

布局类的使用说明

封装完成的流式布局类，只需将其传入相应的布局容器中，它即可自动计算页面元素的位置，并适应窗口的宽度变化。

图片瀑布流显示示例

接下来展示一段使用上述流式布局显示图片的完整代码示例。

from PyQt5.QtCore import QPoint, QRect, QSize, Qt
import os
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import (
  QApplication, QLayout, QPushButton, QSizePolicy, QWidget, QGridLayout)

class Window(QWidget):
  def __init__(self):
    self.imageheight = 100
    super(Window, self).__init__()
    self.resize(400, 300)

    flowLayout = FlowLayout()

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

    print()
    for file in iter(self.files_it):
      layout = QGridLayout()
      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)
        print(autoWidth)
        label.setFixedWidth(autoWidth)
        #label.setFixedSize(100, 50)
        layout.addWidget(label)

        widget = QWidget()
        widget.setLayout(layout)
        flowLayout.addWidget(widget)

    self.setLayout(flowLayout)

    self.setWindowTitle("Flow Layout")

class FlowLayout(QLayout):
  def __init__(self, parent=None, margin=0, spacing=-1):
    super(FlowLayout, self).__init__(parent)

    if parent is not None:
      self.setContentsMargins(margin, margin, margin, margin)

    self.setSpacing(spacing)

    self.itemList = []

  def __del__(self):
    item = self.takeAt(0)
    while item:
      item = self.takeAt(0)

  def addItem(self, item):
    self.itemList.append(item)

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

  def itemAt(self, index):
    if index >= 0 and index < len(self.itemList):
      return self.itemList[index]

    return None

  def takeAt(self, index):
    if index >= 0 and index < len(self.itemList):
      return self.itemList.pop(index)

    return None

  def expandingDirections(self):
    return Qt.Orientations(Qt.Orientation(0))

  def hasHeightForWidth(self):
    return True

  def heightForWidth(self, width):
    height = self.doLayout(QRect(0, 0, width, 0), True)
    return height

  def setGeometry(self, rect):
    super(FlowLayout, self).setGeometry(rect)
    self.doLayout(rect, False)

  def sizeHint(self):
    return self.minimumSize()

  def minimumSize(self):
    size = QSize()

    for item in self.itemList:
      size = size.expandedTo(item.minimumSize())

    margin, _, _, _ = self.getContentsMargins()

    size += QSize(2 * margin, 2 * margin)
    return size

  def doLayout(self, rect, testOnly):
    x = rect.x()
    y = rect.y()
    lineHeight = 0

    for item in self.itemList:
      wid = item.widget()
      spaceX = self.spacing() + wid.style().layoutSpacing(QSizePolicy.PushButton,
                                QSizePolicy.PushButton, Qt.Horizontal)
      spaceY = self.spacing() + wid.style().layoutSpacing(QSizePolicy.PushButton,
                                QSizePolicy.PushButton, Qt.Vertical)
      nextX = x + item.sizeHint().width() + spaceX
      if nextX - spaceX > rect.right() and lineHeight > 0:
        x = rect.x()
        y = y + lineHeight + spaceY
        nextX = x + item.sizeHint().width() + spaceX
        lineHeight = 0

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

      x = nextX
      lineHeight = max(lineHeight, item.sizeHint().height())

    return y + lineHeight - rect.y()

if __name__ == '__main__':

  import sys

  app = QApplication(sys.argv)
  mainWin = Window()
  mainWin.show()
  sys.exit(app.exec_())

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