动态更新 QChart

Question

我有一个 class 可以绘制给定数据的烛台。我正在尝试在收到新数据后立即动态更新绘图。不定期接收数据。

我可以使用什么机制让 class 知道是时候更新绘图并根据新收到的数据点更新绘图了？

Class 函数 append_data_and_plot() 追加数据，但图表永远不会更新。有人可以解释一下问题是什么吗？

import sys
from PyQt5.QtChart import QCandlestickSeries, QChart, QChartView, QCandlestickSet
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtCore import Qt, QPointF
from PyQt5 import QtChart as qc
import time

class myCandlestick():
    def __init__(self, data):
        self.data = data
        self.app = QApplication(sys.argv)

        self.series = QCandlestickSeries()
        self.series.setDecreasingColor(Qt.red)
        self.series.setIncreasingColor(Qt.green)

        self.ma5 = qc.QLineSeries() 
        self.tm = []

        for num, o, h, l, c, m in self.data:
            self.series.append(QCandlestickSet(o, h, l, c))
            self.ma5.append(QPointF(num, m))
            self.tm.append(str(num))

        self.chart = QChart()

        self.chart.addSeries(self.series)  # candle
        self.chart.addSeries(self.ma5)  # ma5 line

        self.chart.createDefaultAxes()
        self.chart.legend().hide()

        self.chart.axisX(self.series).setCategories(self.tm)
        self.chart.axisX(self.ma5).setVisible(False)

        self.chartview = QChartView(self.chart)
        self.ui = QMainWindow()
        self.ui.setGeometry(50, 50, 500, 300)
        self.ui.setCentralWidget(self.chartview)
        self.ui.show()
        sys.exit(self.app.exec_())

    def append_data_and_plot(self, d):
        '''Append and update the plot'''
        num, o, h, l, c, m = d
        self.series.append(QCandlestickSet(o, h, l, c))
        self.ui.show()
        #sys.exit(self.app.exec_())


data = ((1, 7380, 7520, 7380, 7510, 7324),
        (2, 7520, 7580, 7410, 7440, 7372),
        (3, 7440, 7650, 7310, 7520, 7434),
        (4, 7450, 7640, 7450, 7550, 7480),
        (5, 7510, 7590, 7460, 7490, 7502),
        (6, 7500, 7590, 7480, 7560, 7512),
        (7, 7560, 7830, 7540, 7800, 7584))

m = myCandlestick(data)

# Data is received at irregular intervals
time.sleep(1)
m.append_data_and_plot((8, 7560, 7830, 7540, 7800, 7584))

# Data is received at irregular intervals
time.sleep(0.1)
m.append_data_and_plot((9, 7450, 7640, 7450, 7550, 7480))

# Data is received at irregular intervals
time.sleep(2.5)
m.append_data_and_plot((10, 7380, 7520, 7380, 7510, 7324))

Answer 1

Qt使用事件循环来处理gui的事件和任务，也就是代码“app.exec_()”所以该行之后的所有代码都不会执行，如果是添加到使用 sys.exit () 将使应用程序在 Qt 事件循环结束时终止。

解决方案是使用事件循环来更新图形用户界面，例如使用 QTimer：

import sys
from PyQt5.QtChart import QCandlestickSeries, QChart, QChartView, QCandlestickSet
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtCore import Qt, QPointF, QObject, pyqtSignal, QTimer
from PyQt5 import QtChart as qc

import random


class MainWindow(QMainWindow):
    def __init__(self, data, parent=None):
        super().__init__(parent)
        self.data = data

        self.series = QCandlestickSeries()
        self.series.setDecreasingColor(Qt.red)
        self.series.setIncreasingColor(Qt.green)

        self.ma5 = qc.QLineSeries()
        self.tm = []

        self.chart = QChart()

        self.chart.addSeries(self.series)  # candle
        self.chart.addSeries(self.ma5)  # ma5 line

        self.chart.createDefaultAxes()
        self.chart.legend().hide()

        self.chart.axisX(self.series).setCategories(self.tm)
        self.chart.axisX(self.ma5).setVisible(False)

        self.chartview = QChartView(self.chart)
        self.setGeometry(50, 50, 500, 300)
        self.setCentralWidget(self.chartview)

    def append_data_and_plot(self, d):
        """Append and update the plot"""
        num, o, h, l, c, m = d

        ax1 = self.chart.axisX(self.ma5)
        ay1 = self.chart.axisY(self.ma5)

        xmin = xmax = num
        ymin = ymax = m

        step = 10
        offset = 100

        for p in self.ma5.pointsVector()[-step:]:
            xmin = min(p.x(), xmin)
            xmax = max(p.x(), xmax)

            ymin = min(p.y(), ymin) - offset
            ymax = max(p.y(), ymax) + offset

        xmin = max(0, xmax - step)

        ax1.setMin(xmin)
        ax1.setMax(xmax)
        ay1.setMin(ymin)
        ay1.setMax(ymax)

        self.ma5.append(QPointF(num, m))
        self.tm.append(str(num))

        self.series.append(QCandlestickSet(o, h, l, c))
        ax2 = self.chart.axisX(self.series)
        ax2.setCategories(self.tm)
        ax2.setMin(str(xmin))
        ax2.setMax(str(xmax))

        ay2 = self.chart.axisY(self.series)
        ay2.setMin(ymin)
        ay2.setMax(ymax)


def create_data():


    i = 1
    while True:
        i += 1
        yield (
            i,
            random.randint(7000, 8000),
            random.randint(7000, 8000),
            random.randint(7000, 8000),
            random.randint(7000, 8000),
            random.randint(7000, 8000),
        )


class Producer(QObject):
    dataChanged = pyqtSignal(list)

    def __init__(self, parent=None):
        super().__init__(parent)
        self.iter = create_data()
        QTimer.singleShot(random.randint(0, 1500), self.send_data)

    def send_data(self):
        d = list(next(self.iter))
        self.dataChanged.emit(d)
        QTimer.singleShot(random.randint(0, 1500), self.send_data)


def main():
    app = QApplication(sys.argv)

    data = ((1, 7380, 7520, 7380, 7510, 7324),)
    w = MainWindow(data)
    w.show()

    p = Producer()
    p.dataChanged.connect(w.append_data_and_plot)

    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

动态更新 QChart

Dynamically updating a QChart

python

candlestick-chart

pyqt5

qchart