PyQt5 - 使用箭头键在窗口内移动标签位置

在本文中，我们将了解如何使用箭头键在窗口内移动标签，即当箭头键（方向键）被按下时，它会朝那个方向移动。例如，当用户按下向上箭头键时，标签将类似地向上移动，其他箭头键标签也会改变其位置。

概念：我们可以通过增加/减少标签的坐标值来改变标签的位置，但如果它到达边的任何一端，则不要增加或减少下面是每个箭头键按下时给出的数据.

When Up arrow key is pressed : X Co-ordinate remain same, decrement the Y Co-ordinate 
When Down arrow key is pressed : X Co-ordinate remain same, increment the Y Co-ordinate 
When Left arrow key is pressed : Decrement X Co-ordinate, Y Co-ordinate remain same
When Right arrow key is pressed : Increment X Co-ordinate, Y Co-ordinate remain same

下面是边缘限制数据，因此标签应保留在窗口中

For top edge the y- co-ordinate should be always greater than 0
For bottom edge the y- co-ordinate should be always less than height of window – height of label
For left edge the x- co-ordinate should be always greater than 0
For right edge the x- co-ordinate should be always less than width of window – width of label

Implementation Steps :
1. Create a Main window
2. Create a label inside the main window
3. Add style sheet geometry to the label
4. Create a speed variable
5. Override the key press event
6. Inside the key press event get the current x and y co-ordinates of the label
7. And check which key key is pressed and check if side end is not reached then update the x and y co-ordinates with the help of move method by incrementing/decrementing speed value from them

下面是实现

# importing libraries
from PyQt5.QtWidgets import * 
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import * 
from PyQt5.QtCore import * 
import sys
  
  
class Window(QMainWindow):
  
    def __init__(self):
        super().__init__()
  
        # setting title
        self.setWindowTitle("Python ")
  
        # width of window
        self.w_width = 500
  
        # height of window
        self.w_height = 500
  
        # setting geometry
        self.setGeometry(100, 100, self.w_width, self.w_height)
  
        # calling method
        self.UiComponents()
  
        # showing all the widgets
        self.show()
  
        # speed variable
        self.speed = 15
  
    # method for components
    def UiComponents(self):
  
        # creating a label
        self.label = QLabel(self)
  
        # label width
        self.l_width = 40
  
        # label height
        self.l_height = 40
  
        # setting geometry to the label
        self.label.setGeometry(200, 200, self.l_width, self.l_height)
  
        # setting stylesheet to the label
        self.label.setStyleSheet("QLabel"
                                 "{"
                                 "border : 4px solid darkgreen;"
                                 "background : lightgreen;"
                                 "}")
  
  
  
    # override the key press event
    def keyPressEvent(self, event):
  
        # get the current co-ordinates of the label
        # X Co-ordinate
        x = self.label.x()
  
        # Y Co-ordinate
        y = self.label.y()
  
        # if up arrow key is pressed
        if event.key() == Qt.Key_Up:
  
            # if top position is attained
            if y > 0:
                self.label.move(x, y - self.speed)
  
        # if down arrow key is pressed
        elif event.key() == Qt.Key_Down:
  
            # if bottom position is attained
            # for bottom point, bottom co-ordinate will be
            # height of window - height of label
            if y < self.w_height - self.l_height:
                self.label.move(x, y + self.speed)
  
        # if left arrow key is pressed
        elif event.key() == Qt.Key_Left:
  
            # if left end position is attained
            if x > 0:
                self.label.move(x - self.speed, y)
  
        # if down arrow key is pressed
        elif event.key() == Qt.Key_Right:
  
            # if right end position is attained
            # for right end point, right co-ordinate will be
            # width of window - width of label
            if x < self.w_width - self.l_width:
                self.label.move(x + self.speed, y)
  
  
  
  
  
# create pyqt5 app
App = QApplication(sys.argv)
  
# create the instance of our Window
window = Window()
  
# start the app
sys.exit(App.exec())

输出 ：