PyQt从窗口A打开窗口B

Question

我知道它看起来像是复制品，但不是。我什么都试过了，却打不开第二扇窗户。我有一个主类，打开主播放器窗口（成功）。 这是我的主要课程：

class Main(QtGui.QMainWindow, Ui_Main_Window):
    def __init__(self):
        QtGui.QMainWindow.__init__(self)
        self.ui = Ui_Main_Window()
        self.ui.setupUi(self)


if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    window = Main()
    window.show()
    check_db()
    sys.exit(app.exec_())

然后我称之为类A和B。类A在程序启动时打开，因为它是从main启动的。类B是必须从此方法运行的小窗口：

def create_new_window(self):
    self.LibSettings = LibSettings()
    self.LibSettings.show()

LibSettings类：

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

# Form implementation generated from reading ui file 'library_settings.ui'
#
# Created by: PyQt4 UI code generator 4.11.4
#
# WARNING! All changes made in this file will be lost!

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s

try:
    _encoding = QtGui.QApplication.UnicodeUTF8


    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)


class LibSettings(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(537, 325)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.gridLayout_2 = QtGui.QGridLayout(self.centralwidget)
        self.gridLayout_2.setObjectName(_fromUtf8("gridLayout_2"))
        self.listView = QtGui.QListView(self.centralwidget)
        self.listView.setFrameShape(QtGui.QFrame.NoFrame)
        self.listView.setFrameShadow(QtGui.QFrame.Plain)
        self.listView.setObjectName(_fromUtf8("listView"))
        self.gridLayout_2.addWidget(self.listView, 2, 0, 1, 1)
        self.lineEdit = QtGui.QLineEdit(self.centralwidget)
        self.lineEdit.setCursor(QtGui.QCursor(QtCore.Qt.IBeamCursor))
        self.lineEdit.setAutoFillBackground(True)
        self.lineEdit.setClearButtonEnabled(True)
        self.lineEdit.setObjectName(_fromUtf8("lineEdit"))
        self.gridLayout_2.addWidget(self.lineEdit, 0, 0, 1, 1)
        self.verticalLayout = QtGui.QVBoxLayout()
        self.verticalLayout.setObjectName(_fromUtf8("verticalLayout"))
        self.pushButton_4 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_4.setFocusPolicy(QtCore.Qt.NoFocus)
        icon = QtGui.QIcon()
        icon.addPixmap(QtGui.QPixmap(_fromUtf8("PycharmProjects/SirenPlayer v0.1/artwork/plus.png")),
                       QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.pushButton_4.setIcon(icon)
        self.pushButton_4.setObjectName(_fromUtf8("pushButton_4"))
        self.verticalLayout.addWidget(self.pushButton_4)
        self.pushButton_3 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_3.setFocusPolicy(QtCore.Qt.NoFocus)
        icon1 = QtGui.QIcon()
        icon1.addPixmap(QtGui.QPixmap(_fromUtf8("PycharmProjects/SirenPlayer v0.1/artwork/minus.png")),
                        QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.pushButton_3.setIcon(icon1)
        self.pushButton_3.setObjectName(_fromUtf8("pushButton_3"))
        self.verticalLayout.addWidget(self.pushButton_3)
        self.verticalLayout_2 = QtGui.QVBoxLayout()
        self.verticalLayout_2.setObjectName(_fromUtf8("verticalLayout_2"))
        spacerItem = QtGui.QSpacerItem(20, 40, QtGui.QSizePolicy.Minimum, QtGui.QSizePolicy.Expanding)
        self.verticalLayout_2.addItem(spacerItem)
        self.pushButton_5 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_5.setFocusPolicy(QtCore.Qt.NoFocus)
        icon2 = QtGui.QIcon()
        icon2.addPixmap(QtGui.QPixmap(_fromUtf8("PycharmProjects/SirenPlayer v0.1/artwork/cancel.png")),
                        QtGui.QIcon.Normal, QtGui.QIcon.Off)
        self.pushButton_5.setIcon(icon2)
        self.pushButton_5.setObjectName(_fromUtf8("pushButton_5"))
        self.verticalLayout_2.addWidget(self.pushButton_5)
        spacerItem1 = QtGui.QSpacerItem(20, 40, QtGui.QSizePolicy.Minimum, QtGui.QSizePolicy.Expanding)
        self.verticalLayout_2.addItem(spacerItem1)
        self.pushButton_6 = QtGui.QPushButton(self.centralwidget)
        self.pushButton_6.setFocusPolicy(QtCore.Qt.NoFocus)
        icon3 = QtGui.QIcon()
        icon3.addPixmap(QtGui.QPixmap(_fromUtf8("PycharmProjects/SirenPlayer v0.1/artwork/ok.png")), QtGui.QIcon.Normal,
                        QtGui.QIcon.Off)
        self.pushButton_6.setIcon(icon3)
        self.pushButton_6.setObjectName(_fromUtf8("pushButton_6"))
        self.verticalLayout_2.addWidget(self.pushButton_6)
        self.verticalLayout.addLayout(self.verticalLayout_2)
        self.gridLayout_2.addLayout(self.verticalLayout, 0, 1, 3, 1)
        self.horizontalLayout = QtGui.QHBoxLayout()
        self.horizontalLayout.setObjectName(_fromUtf8("horizontalLayout"))
        self.pushButton_2 = QtGui.QPushButton(self.centralwidget)
        sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.Fixed, QtGui.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton_2.sizePolicy().hasHeightForWidth())
        self.pushButton_2.setSizePolicy(sizePolicy)
        self.pushButton_2.setMinimumSize(QtCore.QSize(35, 35))
        self.pushButton_2.setMaximumSize(QtCore.QSize(35, 35))
        self.pushButton_2.setFocusPolicy(QtCore.Qt.NoFocus)
        self.pushButton_2.setText(_fromUtf8(""))
        self.pushButton_2.setIcon(icon)
        self.pushButton_2.setIconSize(QtCore.QSize(35, 35))
        self.pushButton_2.setObjectName(_fromUtf8("pushButton_2"))
        self.horizontalLayout.addWidget(self.pushButton_2)
        self.pushButton = QtGui.QPushButton(self.centralwidget)
        sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.Fixed, QtGui.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton.sizePolicy().hasHeightForWidth())
        self.pushButton.setSizePolicy(sizePolicy)
        self.pushButton.setMinimumSize(QtCore.QSize(35, 35))
        self.pushButton.setMaximumSize(QtCore.QSize(35, 35))
        self.pushButton.setFocusPolicy(QtCore.Qt.NoFocus)
        self.pushButton.setText(_fromUtf8(""))
        self.pushButton.setIcon(icon1)
        self.pushButton.setIconSize(QtCore.QSize(35, 35))
        self.pushButton.setObjectName(_fromUtf8("pushButton"))
        self.horizontalLayout.addWidget(self.pushButton)
        spacerItem2 = QtGui.QSpacerItem(40, 20, QtGui.QSizePolicy.Expanding, QtGui.QSizePolicy.Minimum)
        self.horizontalLayout.addItem(spacerItem2)
        self.gridLayout_2.addLayout(self.horizontalLayout, 1, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 537, 19))
        self.menubar.setObjectName(_fromUtf8("menubar"))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName(_fromUtf8("statusbar"))
        MainWindow.setStatusBar(self.statusbar)

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

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow", None))
        self.pushButton_4.setText(_translate("MainWindow", "Browse", None))
        self.pushButton_3.setText(_translate("MainWindow", "Clear selected", None))
        self.pushButton_5.setText(_translate("MainWindow", "Cancel", None))
        self.pushButton_6.setText(_translate("MainWindow", "Apply", None))

类A和B都没有任何__init__方法。它们由QtCreator生成，只有Class和def setupUI带有小部件设置和定位。为什么类A（UI_Main_Window）启动时没有问题，而另一个（LibSettings）没有问题。我是一个新的和这是一个里程碑，所以我不能进一步进行。欢迎任何帮助。请为一个脑死的人解释一下。你知道吗