Python绘制折线图在Tkinter GUI中仅显示一半的问题求助

使用Python结合Tkinter与Matplotlib绘制折线图，数据来源于SQLite数据库，但折线图在GUI的Canvas组件中仅显示一半，剩余区域为黑色。相关代码如下：

###----------------Connecting to the database-------------##### 
import sqlite3 
DB = sqlite3.connect("personal_project.db")

CURSOR = DB.cursor()
###----------------create the SQL command to create the table and save data-------------######
COMMAND1 = """CREATE TABLE IF NOT EXISTS 
          balance (
          UserID INTEGER PRIMARY KEY,
          Date TEXT,
          Amount TEXT,
          Descriotion)"""
CURSOR.execute(COMMAND1)

from tkinter import *
from tkinter import messagebox
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

###----------------Create the window-------------#####
main_WINDOW = Tk()
main_WINDOW.title("Study App")
main_WINDOW.geometry("1940x1080")#width*length
main_WINDOW.configure(bg="#ffffff")   


###------Show Information Using Graph-------###
graquery = '''SELECT Date, Amount FROM balance'''
CURSOR.execute(graquery)
graresults = CURSOR.fetchall()
Date = [result[0] for result in graresults]
Amount = [result[1] for result in graresults]
figure = plt.figure()
plt.plot(Date, Amount)
plt.xlabel('Date')
plt.ylabel('Amount')
plt.title('Balance graph Graph')
gracanvas = Canvas(main_WINDOW, width=1070, height=452)
gracanvas.place(x=356, y=270)
figure_canvas = FigureCanvasTkAgg(figure, gracanvas)
gracanvas.create_window(0,0,window=figure_canvas.get_tk_widget(), anchor="nw") 


main_WINDOW.mainloop()

解决方案 #

问题出在Matplotlib画布与Tkinter Canvas的尺寸适配、渲染逻辑上，按以下方式修改即可修复：

1. 创建Matplotlib Figure时，指定与Tkinter Canvas匹配的尺寸（按默认DPI=100换算，像素尺寸/100得到英寸尺寸）
2. 将Matplotlib的画布组件直接填充到Tkinter Canvas中，确保尺寸完全适配
3. 调用draw()方法完成图形的完整渲染

修改后的代码：

###----------------Connecting to the database-------------##### 
import sqlite3 
DB = sqlite3.connect("personal_project.db")

CURSOR = DB.cursor()
###----------------create the SQL command to create the table and save data-------------######
COMMAND1 = """CREATE TABLE IF NOT EXISTS 
          balance (
          UserID INTEGER PRIMARY KEY,
          Date TEXT,
          Amount TEXT,
          Descriotion)"""
CURSOR.execute(COMMAND1)

from tkinter import *
from tkinter import messagebox
import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

###----------------Create the window-------------#####
main_WINDOW = Tk()
main_WINDOW.title("Study App")
main_WINDOW.geometry("1940x1080")#width*length
main_WINDOW.configure(bg="#ffffff")   


###------Show Information Using Graph-------###
graquery = '''SELECT Date, Amount FROM balance'''
CURSOR.execute(graquery)
graresults = CURSOR.fetchall()
Date = [result[0] for result in graresults]
Amount = [result[1] for result in graresults]

# 按Canvas尺寸创建对应大小的Figure
figure = plt.figure(figsize=(10.7, 4.52), dpi=100)
plt.plot(Date, Amount)
plt.xlabel('Date')
plt.ylabel('Amount')
plt.title('Balance Graph')

gracanvas = Canvas(main_WINDOW, width=1070, height=452)
gracanvas.place(x=356, y=270)

figure_canvas = FigureCanvasTkAgg(figure, gracanvas)
# 将Matplotlib画布组件填充到Tkinter Canvas中
figure_canvas.get_tk_widget().pack(fill=BOTH, expand=YES)
# 执行渲染
figure_canvas.draw()


main_WINDOW.mainloop()

额外说明：如果不想手动换算尺寸，也可以直接给figure_canvas.get_tk_widget()设置width和height属性，强制匹配Tkinter Canvas的尺寸。

内容的提问来源于stack exchange，提问作者alfih