Python tkinter 列表框绑定在 <Button-1>仅适用于第二次点击

Here is example code that replicates the error - to use, first add a a couple of values through the Setup -> Items menu by filling in the VAL and REF boxes and clicking the Add Item button. Then click on one of the items in the list box. The first click should generate the error above. When you click a second time the Entry boxes should populate:

```
import sqlite3  
import itertools  
import tkinter as tk  
from tkinter import ttk  

INTRO_FONT = ("Arial", 72)  
LARGE_FONT = ("Arial", 12)  
NORMAL_FONT = ("Arial", 10)  
SMALL_FONT = ("Arial", 8)  

#Function to create database  

def create_db():  
    conn = sqlite3.connect("demo.db")  
    cur = conn.cursor()  
    cur.execute("CREATE TABLE IF NOT EXISTS demotable (id INTEGER PRIMARY KEY, val TEXT, ref TEXT)")  
    conn.commit()  
    conn.close()  

#Create database

create_db()

#Main Class to manage frames

class demo(tk.Tk):

    def __init__(self,*args,**kwargs):

        tk.Tk.__init__(self,*args,**kwargs)

        container = tk.Frame(self)
        container.pack(side="top",fill="both",expand=True)
        container.grid_rowconfigure(0,weight=1)
        container.grid_columnconfigure(0,weight=1)

        menubar = tk.Menu(container)

        filemenu = tk.Menu(menubar,tearoff=0)
        filemenu.add_command(label="Exit", command=quit)
        menubar.add_cascade(label="File", menu=filemenu)

        setupmenu = tk.Menu(menubar, tearoff=0)
        setupmenu.add_command(label="Items",command = lambda: self.show_frame(Itemsetuppage))
        menubar.add_cascade(label="Setup", menu=setupmenu)

        tk.Tk.config(self, menu=menubar)

        self.frames={}

        for F in (Itemsetuppage,Itemsetuppage):

            frame = F(container, self)

            self.frames[F] = frame

            frame.grid(row=0, column=0, sticky="nsew")

        self.show_frame(Itemsetuppage)

    def show_frame(self, cont):

        frame = self.frames[cont]
        frame.tkraise()  

# Frame that inserts and loads values

class Itemsetuppage(tk.Frame):

def __init__(self, parent, controller):

    tk.Frame.__init__(self, parent)

    #Function to populate listbox with values

    def popitemlist(self):
        lb1.delete(0, tk.END)
        for item in itemlist():
            lb1.insert(tk.END, item)

    #Function to add new item to database
    def additem():
        additem_db(val.get(), ref.get())
        val_entry.delete(0, 'end')
        ref_entry.delete(0, 'end')
        popitemlist(self)

    #Function used to populate tk.Entry boxes from database when item in listbox is clicked
    def selectitem(event):
        global selecteditem
        selecteditem = []
        ndex = lb1.curselection()
        selecteditem.append(lb1.get(ndex))
        itemquery = select_item(selecteditem)
        val_entry.delete(0, 'end')
        val_entry.insert(0, itemquery[1])
        ref_entry.delete(0, 'end')
        ref_entry.insert(0, itemquery[2])

    #Function to query database for values to populate lb1
    def itemlist():
        conn = sqlite3.connect("demo.db")
        cur = conn.cursor()
        cur.execute("SELECT DISTINCT val FROM demotable")
        results = cur.fetchall()
        itemlist = list(itertools.chain(*results))
        conn.commit()
        conn.close()
        return itemlist

    #Function to insert values from tk.Entry boxes to database
    def additem_db(val, ref):
        conn = sqlite3.connect("demo.db")
        cur = conn.cursor()
        cur.execute("INSERT OR IGNORE INTO demotable VALUES (NULL, ?, ?)",(val,ref))
        conn.commit()
        conn.close()

    #Function to query database for individual record to populate tk.Entry boxes when item is clicked in lb1
    def select_item(val):
        conn = sqlite3.connect("demo.db")
        cur = conn.cursor()
        cur.execute("SELECT * FROM demotable WHERE val=?",(val))
        results = cur.fetchall()
        itemdetail = list(itertools.chain(*results))
        conn.commit()
        conn.close()
        return itemdetail

    l1 = tk.Label(self, text="Values in database:")
    l1.grid(row=0, column=0, padx=5, pady=5)

    lb1 = tk.Listbox(self, selectmode=tk.SINGLE)
    lb1.grid(row=1, column=0, padx=5, pady=5)
    popitemlist(self)
    lb1.bind("<Button-1>", selectitem)

    l2 = tk.Label(self, text="Type val into entry box to store:")
    l2.grid(row=0, column=1, padx=5, pady=5)

    val = tk.StringVar(self)
    val_entry = tk.Entry(self, textvariable=val)
    val_entry.grid(row=0, column=2, padx=5, pady=5)

    l2 = tk.Label(self, text="Type ref into entry box to store:")
    l2.grid(row=1, column=1, padx=5, pady=5)

    ref = tk.StringVar(self)
    ref_entry = tk.Entry(self, textvariable=ref)
    ref_entry.grid(row=1, column=2, padx=5, pady=5)

    b1 = tk.Button(self, text="Add item",command=additem)
    b1.grid(row=2, column=2, padx=5, pady=5)

app = demo()  
app.geometry("480x240")  
app.mainloop()

``` 

谢谢你&如果我的代码冒犯了任何人，我们深表歉意！

lb1.bind("<Button-1>", selectitem)

lb1.bind("<<ListboxSelect>>", selectitem)