PyQt5 – 使用方向键在窗口中移动标签位置

在这篇文章中，我们将看到如何使用箭头键在窗口中移动标签，即当按下箭头键（方向键）时，标签将向该方向移动。例如，当用户按下向上的方向键时，标签会向上移动，同样，其他方向键的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，但如果标签到达任何一端，则不增加或减少，下面是每个方向键被按下时的数据。

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

下面是边缘的限制数据，以便标签保持在窗口中。

对于顶部边缘，y坐标应始终大于0

对于底部边缘，y坐标应始终小于窗口的高度–标签的高度

对于左侧边缘，x坐标应始终大于0

对于右侧边缘，x坐标应始终小于窗口的宽度–标签的宽度

实施步骤：

1.创建一个主窗口

2.在主窗口内创建一个标签

3.为标签添加样式表的几何图形

4.创建一个速度变量

5.覆盖按键事件

6.在按键事件中获取标签的当前x和y坐标

7.检查哪个键被按下，并检查是否没有到达边端，然后在移动方法的帮助下通过增加/减少速度值来更新x和y坐标。

以下是实现的过程

# 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())