如何将 QLineEdit() 和 QPushButton 带到登录 window 的中心？

Question

我正在创建一个 LoginWindow 并使用 QLineEdit 来为我的用户输入他们的详细信息。 现在，我专注于创建 GUI。 如图所示，考虑到我如何将setAlignment为AlignCenter ，我不确定为什么布局看起来像这样。 这也适用于 QPushButton。 是否有 class 我不知道要解决此格式问题？

import sys
from PyQt5 import QtCore
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QMainWindow, QApplication, QWidget, QPushButton, QLineEdit, QVBoxLayout
import time #For time sleep

class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.setWindowTitle("MidiScribe - Login Window")
        self.setFixedSize(800,800)
        self.setStyleSheet("""background-color: crimson;
                            border-color: maroon;
                            border: 2.5px outset rgb(128, 128, 128);
                            border-radius: 3px;""")
        container = QWidget()
        self.setCentralWidget(container)
        mainLayout = QVBoxLayout(container)

        self.username = QLineEdit()
        self.username.setFixedWidth(300)
        self.username.setStyleSheet("""background-color: white;""")
        mainLayout.addWidget(self.username)
        self.username.setAlignment(QtCore.Qt.AlignCenter)
        self.setLayout(mainLayout)

        self.password = QLineEdit()
        self.password.setFixedWidth(300)
        self.password.setStyleSheet("""background-color: white""")
        mainLayout.addWidget(self.password)
        self.password.setAlignment(QtCore.Qt.AlignCenter)
        self.setLayout(mainLayout)

        self.loginbutton = QPushButton("Login")
        self.loginbutton.setFixedSize(50,50)
        self.loginbutton.setStyleSheet("QPushButton { background-color: lightcoral }"
                        "QPushButton:Hover { background-color: lightpink }"
                      "QPushButton:pressed { background-color: indianred }" )
        mainLayout.addWidget(self.loginbutton)

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

Answer 1

这种情况有很多解决方案，但其中一个是使用具有最小尺寸的容器来显示所有小部件，并且通过 QGridLayout 建立：

class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super(MainWindow, self).__init__(*args, **kwargs)
        self.setWindowTitle("MidiScribe - Login Window")
        self.setFixedSize(800, 800)
        self.setStyleSheet(
            """background-color: crimson;
                            border-color: maroon;
                            border: 2.5px outset rgb(128, 128, 128);
                            border-radius: 3px;"""
        )

        self.username = QLineEdit(alignment=QtCore.Qt.AlignCenter)
        self.username.setFixedWidth(300)
        self.username.setStyleSheet("""background-color: white;""")

        self.password = QLineEdit(alignment=QtCore.Qt.AlignCenter)
        self.password.setFixedWidth(300)
        self.password.setStyleSheet("""background-color: white""")

        self.loginbutton = QPushButton("Login")
        self.loginbutton.setFixedSize(50, 50)
        self.loginbutton.setStyleSheet(
            "QPushButton { background-color: lightcoral }"
            "QPushButton:Hover { background-color: lightpink }"
            "QPushButton:pressed { background-color: indianred }"
        )

        container = QWidget(objectName="container")
        container.setStyleSheet("QWidget#container{border: none}")
        container.setContentsMargins(0, 0, 0, 0)
        lay = QVBoxLayout(container)
        lay.addWidget(self.username, alignment=QtCore.Qt.AlignCenter)
        lay.addWidget(self.password, alignment=QtCore.Qt.AlignCenter)
        lay.addWidget(self.loginbutton, alignment=QtCore.Qt.AlignCenter)
        container.setFixedSize(container.sizeHint())

        central_widget = QWidget()
        self.setCentralWidget(central_widget)

        grid_layout = QGridLayout(central_widget)
        grid_layout.addWidget(container, 1, 1)

Answer 2

只需对 mainLayout 执行 alignment ：

mainLayout.addWidget(self.loginbutton, alignment=QtCore.Qt.AlignCenter)
mainLayout.setAlignment(QtCore.Qt.AlignCenter)