import sys
from PyQt5.QtWidgets import (QApplication, QMenu, QWidget)
from PyQt5.QtCore import (QEvent, QTimer, Qt)
from PyQt5.QtGui import QPainter

class MyEventDemoWindow(QWidget):
    def __init__(self, parent=None):
        super(MyEventDemoWindow, self).__init__(parent)
        self.justDoubleClikcked = False
        self.key = ""
        self.text = ""
        self.message = ""
        self.resize(400, 300)
        self.move(100, 100)
        self.setWindowTitle("Events Demo 1")
        QTimer.singleShot(1000, self.giveHelp)


    def giveHelp(self):
        self.text = "請點擊這里觸發追蹤鼠標功能"
        self.update() # 重繪事件，也就是除非paintEvent函數
    
    # 重新實現關閉事件
    def closeEvent(self, event):
        print("Closed")
    
    # 重新實現上下文菜單事件
    def contextMenuEvent(self, event):
        menu = QMenu(self)
        oneAction = menu.addAction("&One")
        twoAction = menu.addAction("&Two")
        oneAction.triggered.connect(self.one)
        twoAction.triggered.connect(self.two)
        if not self.message:
            menu.addSeparator()
            threeAction = menu.addAction("&Three")
            threeAction.triggered.connect(self.three)
        menu.exec_(event.globalPos())
        
    def one(self):
        self.message = "Menu Option One"
        self.update()
    
    def two(self):
        self.message = "Menu Option Two"
        self.update()

    def three(self):
        self.message = "Menu Option Three"
        self.update()

    '''重新實現繪制事件'''
    def paintEvent(self, event):
        text = self.text
        i = text.find("\n\n")
        if i >= 0:
            text = text[0:i]
        if self.key:
            text += "\n\n你按下了：{0}".format(self.key)
        painter = QPainter(self)
        painter.setRenderHint(QPainter.TextAntialiasing)
        painter.drawText(self.rect(), Qt.AlignCenter, text) # 繪制文本
        if self.message:
            painter.drawText(self.rect(), Qt.AlignBottom | Qt.AlignHCenter, self.message)
            QTimer.singleShot(5000, self.clearMessage)
            QTimer.singleShot(5000, self.update)

    # 清空文本信息槽函數
    def clearMessage(self):
        self.message = ""
        
    # 重新實現調整窗口大小事件
    def resizeEvent(self, event):
        self.text = "調整窗口大小為： QSize({0}, {1})".format(event.size().width(), event.size().height())
        self.update()
    
    # 重新實現鼠標釋放事件
    def mouseReleaseEvent(self, event) -> None:
        if self.justDoubleClikcked:
            self.justDoubleClikcked = False
        else :
            self.setMouseTracking(not self.hasMouseTracking()) # 單擊鼠標
            if self.hasMouseTracking():
                self.text = "你釋放了鼠標 開啟鼠標跟蹤功能.\n\n" + \
                        "請移動鼠標\n\n" + \
                        "單擊鼠標可以關閉這個功能"
            else:
                self.text = "你釋放了鼠標  關閉鼠標跟蹤功能" + \
                        "單擊鼠標可以開啟這個功能"
        self.update()
 
    '''重新實現鼠標移動事件'''
    def mouseMoveEvent(self, event):
        if not self.justDoubleClikcked:
            globalPos = self.mapToGlobal(event.pos())# 將窗口坐標轉換為屏幕坐標
            self.text = """鼠標位置：
            窗口坐標為：QPoint({0}, {1})
            屏幕坐標為：QPoint({2}, {3})""".format(event.pos().x(), event.pos().y(), globalPos.x(), globalPos.y())
            self.update()

    '''重新實現鼠標雙擊事件'''
    def mouseDoubleClickEvent(self, event):
        self.justDoubleClikcked = True
        self.text = "你雙擊了鼠標"
        self.update()

    def mousePressEvent(self, event):
        self.text = "你按下了鼠標"
        self.update()

    def keyPressEvent(self, event):
        self.text = "你按下了按鍵"
        self.key = ""
        if event.key() == Qt.Key_Home:
            self.key = "Home"
        elif event.key() == Qt.Key_End:
            self.key = "End"
        elif event.key() == Qt.Key_PageUp:
            if event.modifiers() & Qt.ControlModifier:
                self.key = "Ctrl + Page Up"
            else:
                self.key = "Page Up"
        elif event.key() == Qt.Key_PageDown:
            if event.modifiers() & Qt.ControlModifier:
                self.key = "Ctrl + Key_PageDown"
            else:
                self.key = "Key_PageDown"
        elif Qt.Key_A <= event.key() <= Qt.Key_Z:
            if event.modifiers() & Qt.ShiftModifier:
                self.key = "Shift+"
            self.key += event.text()
            
        if self.key:
            self.key = self.key
            self.update()
        else:
            QWidget.keyPressEvent(self, event)
    
    def keyReleaseEvent(self, event):
        self.text = "你釋放了按鍵"
        self.update()

    '''重新實現event，捕獲Tab鍵'''
    def event(self, event):
        if (event.type() == QEvent.KeyPress and event.key() == Qt.Key_Tab):
            self.key = "在event() 中捕獲Tab鍵"
            self.update()
            return True # 返回True表示本次事件已經執行處理
        else:
            return QWidget.event(self, event) # 繼續處理事件
        
if __name__ == "__main__":
    app = QApplication(sys.argv)
    win = MyEventDemoWindow()
    win.show()
    sys.exit(app.exec_())

import sys
from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

class EventFilter(QDialog):
    def __init__(self, parent=None):
        super(EventFilter, self).__init__(parent)
        self.setWindowTitle("事件過濾器")

        self.label1 = QLabel("請點擊")
        self.label2 = QLabel("請點擊")
        self.label3 = QLabel("請點擊")
        self.LabelState = QLabel("test")

        self.image1 = QImage("pyqt5/images/cartoon1.ico")
        self.image2 = QImage("pyqt5/images/cartoon1.ico")
        self.image3 = QImage("pyqt5/images/cartoon1.ico")

        self.width = 600
        self.height = 300

        self.resize(self.width, self.height)

        self.label1.installEventFilter(self)
        self.label2.installEventFilter(self)
        self.label3.installEventFilter(self)

        mainLayout = QGridLayout(self)
        mainLayout.addWidget(self.label1, 500, 0)
        mainLayout.addWidget(self.label2, 500, 1)
        mainLayout.addWidget(self.label3, 500, 2)
        mainLayout.addWidget(self.LabelState, 600, 1)
        self.setLayout(mainLayout)

    def eventFilter(self, watched, event):
        # print(type(watched))
        if watched == self.label1: # 只對label1的點擊事件進行過濾，重寫其行為，其它事件會被忽略
            if event.type() == QEvent.MouseButtonPress: # 這里對鼠標按下事件進行過濾，重寫其行為
                mouseEvent = QMouseEvent(event)
                if mouseEvent.buttons() == Qt.LeftButton:
                    self.LabelState.setText("按下鼠標左鍵")
                elif mouseEvent.buttons() == Qt.MidButton:
                    self.LabelState.setText("按下鼠標中鍵")
                elif mouseEvent.buttons() == Qt.RightButton:
                    self.LabelState.setText("按下鼠標右鍵")

                '''轉換圖片大小'''
                transform = QTransform()
                transform.scale(0.5, 0.5)
                tmp = self.image1.transformed(transform)
                self.label1.setPixmap(QPixmap.fromImage(tmp))

            if event.type() == QEvent.MouseButtonRelease: # 這里對鼠標釋放事件進行過濾，重寫其行為
                self.LabelState.setText("釋放鼠標按鍵")
                self.label1.setPixmap(QPixmap.fromImage(self.image1))
        return QDialog.eventFilter(self, watched, event) # 對于其它情況，會返回系統默認的事件處理方法
    
if __name__ == "__main__":
    app = QApplication(sys.argv)
    win = EventFilter()
    win.show()
    app.exec_()