python qt5 label 文本过长 滚动区

Question

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'untitled.ui'
#
# Created by: PyQt5 UI code generator 5.15.6
#
# WARNING: Any manual changes made to this file will be lost when pyuic5 is
# run again.  Do not edit this file unless you know what you are doing.


from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 660)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.verticalLayout_2 = QtWidgets.QVBoxLayout(self.centralwidget)
        self.verticalLayout_2.setObjectName("verticalLayout_2")
        self.horizontalLayout = QtWidgets.QHBoxLayout()
        self.horizontalLayout.setObjectName("horizontalLayout")
        self.comboBox = QtWidgets.QComboBox(self.centralwidget)
        self.comboBox.setObjectName("comboBox")
        self.comboBox.addItem("")
        self.comboBox.addItem("")
        self.horizontalLayout.addWidget(self.comboBox)
        self.lineEdit = QtWidgets.QLineEdit(self.centralwidget)
        self.lineEdit.setObjectName("lineEdit")
        self.horizontalLayout.addWidget(self.lineEdit)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setObjectName("pushButton")
        self.horizontalLayout.addWidget(self.pushButton)
        self.verticalLayout_2.addLayout(self.horizontalLayout)
        self.scrollArea = QtWidgets.QScrollArea(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.scrollArea.sizePolicy().hasHeightForWidth())
        self.scrollArea.setSizePolicy(sizePolicy)
        self.scrollArea.setMinimumSize(QtCore.QSize(650, 550))
        self.scrollArea.setWidgetResizable(True)
        self.scrollArea.setObjectName("scrollArea")
        self.scrollAreaWidgetContents = QtWidgets.QWidget()
        self.scrollAreaWidgetContents.setGeometry(QtCore.QRect(0, 0, 776, 548))
        self.scrollAreaWidgetContents.setObjectName("scrollAreaWidgetContents")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.scrollAreaWidgetContents)
        self.verticalLayout.setObjectName("verticalLayout")
        self.label = QtWidgets.QLabel(self.scrollAreaWidgetContents)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label.sizePolicy().hasHeightForWidth())
        self.label.setSizePolicy(sizePolicy)
        self.label.setMinimumSize(QtCore.QSize(400, 500))
        self.label.setText("")
        self.label.setScaledContents(True)
        self.label.setObjectName("label")
        self.verticalLayout.addWidget(self.label)
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.verticalLayout_2.addWidget(self.scrollArea)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 26))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.comboBox.setItemText(0, _translate("MainWindow", "图片文件"))
        self.comboBox.setItemText(1, _translate("MainWindow", "文本文件"))
        self.pushButton.setText(_translate("MainWindow", "确定"))


import os
import cv2
import sys
import time
from PyQt5.QtWidgets import QMessageBox, QApplication, QMainWindow, QDialog
from PyQt5 import QtGui
from untitled import Ui_MainWindow
from PyQt5.QtCore import QRunnable, QThreadPool, pyqtSlot


class ImageLoader(QRunnable):
    def __init__(self, file_path, label):
        super(ImageLoader, self).__init__()
        self.file_path = file_path
        self.label = label

    @pyqtSlot()
    def run(self):
        image = cv2.imread(self.file_path)
        if image is not None:

            image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
            qImg = QtGui.QImage(image.data, image.shape[1], image.shape[0], QtGui.QImage.Format_RGB888)
            pixmap = QtGui.QPixmap.fromImage(qImg)

            image_width = image.shape[1]
            image_height = image.shape[0]

            time.sleep(1)

            self.label.setFixedWidth(image_width)
            self.label.setFixedHeight(image_height)

            self.label.setPixmap(pixmap)

            self.label.adjustSize()  # 调整标签大小，以适应图片大小（不会对图片造成影响）
        else:
            QMessageBox.warning(None, "错误", "图像文件路径无效")




class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self):
        # 调用QMainWindow类的构造函数，初始化主窗口对象。
        super(MainWindow, self).__init__()
        self.setupUi(self)

        self.pushButton.clicked.connect(self.pushButton_function)

    def pushButton_function(self):
        content = self.comboBox.currentText()
        filePath = self.lineEdit.text()
        if content == "图片文件":

            image_loader = ImageLoader(filePath, self.label)

            QThreadPool.globalInstance().start(image_loader)

        elif content == "文本文件":
            fileExtension = os.path.splitext(filePath)[-1]
            if fileExtension == ".txt":
                with open(filePath, "r", encoding="utf-8") as text_file:
                    text = text_file.read()
                    self.label.setText(text)
            else:
                QMessageBox.warning(None, "错误", "无效的文本文件")
        else:
            QMessageBox.warning(None, "错误", "请选择正确类型")



if __name__ == "__main__":

    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

我希望在label上显示文本时，当文本太长时自动出现滚动条，可是实际上并没有出现滚动条。我也添加了滚动区，在显示图片时滚动区就正常出来了，可是文本就不行。请问该怎么修改？
不能把label换成lineEdit，因为我需要它既能显示图片，又能显示文本。

Answer 1

你们回答的都不是我想要的。我已经明白是为什么了。
这是因为我没有设置label的大小，导致label不能完整的显示文本，所以即使加了scrollarea也没有用，也不会出现滚动条。
正确的做法是先设置label的大小，确保label能完整地显示文本，这样scrollarea也会自动出现（scrollarea是为label服务的，当label过大时就会出现滚动条）。在label中设置图片也是同理。
以下是修改后的代码。

                with open(filePath, "r", encoding="utf-8") as text_file:
                    text = text_file.read()  # text 是一个字符串对象  字符串对象没有font()方法
                    text_line = text_file.readline()
                    line_count = len(text_file.readlines())

                    self.label.setText(text)

                    font_metrics = QFontMetrics(self.label.font())

                    text_height = QFontMetrics(font_metrics).lineSpacing() * line_count
                    text_width = QFontMetrics(font_metrics).width(text_line) * 2

                    self.label.setMinimumSize(text_width, text_height)

                    self.label.setText(text)

这里涉及到：Qt 中获取字体的像素高度和宽度
https://blog.csdn.net/hanzengyi/article/details/6305791#:~:text=1%201.%20QLabel%3A%3A%20fontMetrics%20%28%29.%20width%20%28QString%20s%29%3A,%E8%8E%B7%E5%8F%96%E5%AD%97%E4%BD%93%E7%9A%84%E9%AB%98%E5%BA%A6%EF%BC%8C%E5%8C%85%E6%8B%AC%E6%96%87%E5%AD%97%E7%9A%84%E5%AE%9E%E9%99%85%E5%AE%BD%E5%BA%A6%E5%92%8C%E8%A1%8C%E8%B7%9D%E3%80%82%204%204.%20QLabel%3A%3A%20fontMetrics%20%28%29.leading%20%28%29%3A%20%E8%A1%8C%E9%97%B4%E8%B7%9D