問題描述

這是我的代碼:

import sys
from PyQt5.QtWidgets import (QApplication, QLabel, QWidget)
from PyQt5.QtGui import QPainter, QColor, QPen
from PyQt5.QtCore import Qt

class MouseTracker(QWidget):
    distance_from_center = 0
    def __init__(self):
        super().__init__()
        self.initUI()
        self.setMouseTracking(True)

    def initUI(self):
        self.setGeometry(200, 200, 1000, 500)
        self.setWindowTitle('Mouse Tracker')
        self.label = QLabel(self)
        self.label.resize(500, 40)
        self.show()

    def mouseMoveEvent(self, event):
        distance_from_center = round(((event.y() - 250)**2 + (event.x() - 500)**2)**0.5)
        self.label.setText('Coordinates: ( %d : %d )' % (event.x(), event.y()) + "Distance from center: " + str(distance_from_center))       

        q = QPainter()  #Painting the line
        q.begin(self)
        q.drawLine(event.x(), event.y(), 250, 500)
        q.end()

    def drawPoints(self, qp, x, y):
        qp.setPen(Qt.red)
        qp.drawPoint(x, y)

app = QApplication(sys.argv)
ex = MouseTracker()
sys.exit(app.exec_())

我正在嘗試使用以下方法從鼠標位置到小部件中間繪制一條簡單的線:

What I'm trying to do is paint a simple line from the position of the mouse to the middle of the widget using this:

        q = QPainter()  #Painting the line
        q.begin(self)
        q.drawLine(event.x(), event.y(), 250, 500)
        q.end()

但是當我運行它時，看不到任何線條.我需要做什么?

But when I run it, no line is visible. What do I need to do?

推薦答案

你必須實現函數QPaintEvent，在這個函數中你必須畫線，另外你必須調用函數update() 更新繪圖.

You must implement the function QPaintEvent, in this function you must draw the line, in addition you must call the function update() to update the drawing.

import sys
from PyQt5.QtWidgets import (QApplication, QLabel, QWidget)
from PyQt5.QtGui import QPainter, QColor, QPen
from PyQt5.QtCore import Qt

class MouseTracker(QWidget):
    distance_from_center = 0
    def __init__(self):
        super().__init__()
        self.initUI()
        self.setMouseTracking(True)

    def initUI(self):
        self.setGeometry(200, 200, 1000, 500)
        self.setWindowTitle('Mouse Tracker')
        self.label = QLabel(self)
        self.label.resize(500, 40)
        self.show()
        self.pos = None

    def mouseMoveEvent(self, event):
        distance_from_center = round(((event.y() - 250)**2 + (event.x() - 500)**2)**0.5)
        self.label.setText('Coordinates: ( %d : %d )' % (event.x(), event.y()) + "Distance from center: " + str(distance_from_center))       
        self.pos = event.pos()
        self.update()

    def paintEvent(self, event):
        if self.pos:
            q = QPainter(self)
            q.drawLine(self.pos.x(), self.pos.y(), 250, 500)


app = QApplication(sys.argv)
ex = MouseTracker()
sys.exit(app.exec_())

輸出:

這篇關于如何在 PyQt5 中從鼠標到點畫一條線?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！