在 PlotWidget 中添加自定义标签

Posted 2023-03-25

【中文标题】在 PlotWidget 中添加自定义标签

【英文标题】：Add custom label inside PlotWidget

【发布时间】：2021-02-25 01:21:23

【问题描述】：

我正在尝试在绘图的右上角添加一个标签，以显示最新的数据值。我尝试使用pg.LabelItem 并将其添加到pg.PlotWidget 并在每次新数据更新时更新标签，但我无法让标签出现。这是我正在尝试做的一些图片：

我有什么：

我想要做什么：

我无法让白色标签出现在情节上。这是我的代码：

from PyQt4 import QtCore, QtGui
from threading import Thread
import pyqtgraph as pg
import numpy as np
import random
import sys
import time

class SimplePlot(QtGui.QWidget):
    def __init__(self, parent=None):
        super(SimplePlot, self).__init__(parent)
        
        # Desired Frequency (Hz) = 1 / self.FREQUENCY
        # USE FOR TIME.SLEEP (s)
        self.FREQUENCY = .004

        # Frequency to update plot (ms)
        # USE FOR TIMER.TIMER (ms)
        self.TIMER_FREQUENCY = self.FREQUENCY * 1000

        # Set X Axis range. If desired is [-10,0] then set LEFT_X = -10 and RIGHT_X = 0
        self.LEFT_X = -10
        self.RIGHT_X = 0
        self.X_Axis = np.arange(self.LEFT_X, self.RIGHT_X, self.FREQUENCY)
        self.buffer = int((abs(self.LEFT_X) + abs(self.RIGHT_X))/self.FREQUENCY)
        self.data = [] 

        # Create Plot Widget 
        self.simple_plot_widget = pg.PlotWidget()

        # Enable/disable plot squeeze (Fixed axis movement)
        self.simple_plot_widget.plotItem.setMouseEnabled(x=False, y=False)
        self.simple_plot_widget.setXRange(self.LEFT_X, self.RIGHT_X)
        self.simple_plot_widget.setTitle('Plot')
        self.simple_plot_widget.setLabel('left', 'Value')
        self.simple_plot_widget.setLabel('bottom', 'Time (s)')
        
        self.simple_plot = self.simple_plot_widget.plot()
        self.simple_plot.setPen(197,235,255)

        self.label_value = pg.LabelItem('', **'color': '#FFF')
        self.simple_plot_widget.addItem(self.label_value)

        self.layout = QtGui.QGridLayout()
        self.layout.addWidget(self.simple_plot_widget)

        self.read_position_thread()
        self.start()
                
    # Update plot
    def start(self):
        self.position_update_timer = QtCore.QTimer()
        self.position_update_timer.timeout.connect(self.plot_updater)
        self.position_update_timer.start(self.get_simple_plot_timer_frequency())
    
    # Read in data using a thread
    def read_position_thread(self):
        self.current_position_value = 0
        self.old_current_position_value = 0
        self.position_update_thread = Thread(target=self.read_position, args=())
        self.position_update_thread.daemon = True
        self.position_update_thread.start()

    def read_position(self):
        frequency = self.get_simple_plot_frequency()
        while True:
            try:
                # Add data
                self.current_position_value = self.current_position_value + random.uniform(-1, -5)
                self.old_current_position_value = self.current_position_value
                time.sleep(frequency)
            except:
                self.current_position_value = self.old_current_position_value

    def plot_updater(self):
        self.dataPoint = float(self.current_position_value)

        if len(self.data) >= self.buffer:
            del self.data[:1]
        self.data.append(self.dataPoint)
        self.simple_plot.setData(self.X_Axis[len(self.X_Axis) - len(self.data):], self.data)

        # Update label value
        self.label_value.setText(str(self.dataPoint))

    def clear_simple_plot(self):
        self.data[:] = []

    def get_simple_plot_frequency(self):
        return self.FREQUENCY
    
    def get_simple_plot_timer_frequency(self):
        return self.TIMER_FREQUENCY

    def get_simple_plot_layout(self):
        return self.layout

    def get_current_position_value(self):
        return self.current_position_value

    def get_simple_plot_widget(self):
        return self.simple_plot_widget

if __name__ == '__main__':
    app = QtGui.QApplication([])
    mw = QtGui.QMainWindow()
    mw.setWindowTitle('Plot')

    simple_plot_widget = SimplePlot()

    cw = QtGui.QWidget()
    ml = QtGui.QGridLayout()
    cw.setLayout(ml)
    mw.setCentralWidget(cw)

    ml.addLayout(simple_plot_widget.get_simple_plot_layout(),0,0)
    mw.show()

    # Start Qt event loop unless running in interactive mode or using pyside
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

【参考方案1】：

这可能是因为你的情节不断地重新缩放，LabelItem 的大小并没有随之改变，而且它似乎位于 x 轴的正侧，所以你无法可视化文本.

Pyqtgraph 建议 here 使用 TextItem 而不是 LabelItem，在缩放视图中显示文本。

我尝试使用TextItem，它工作正常，但它的默认位置不好，可能是因为你的情节在负象限。只需像这样使用setPos() 方法：

# Update label value
self.label_value.setPos(QtCore.QPointF(-9, 0.6*min(self.data)))
self.label_value.setText(str(self.dataPoint))

它应该做你想做的。