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

Question

如果有另一个讨论已经解决了这个问题，但我找不到任何东西，我先道歉。我是 Python 的新手（就此而言，除了 90 年代的一点点 Pascal 编程之外）。

我正在构建一个带有 tk 输入框的 GUI，供用户输入值，然后将其存储在 sqlite 数据库中。我希望用户能够单击列表框中某个字段的值，然后使用所选记录的所有字段的值重新填充 tk 输入框。我已经能够完成这项工作，但它仅在第二次单击时有效，因为我将列表框绑定到函数以填充 Button-1 上的 tk 输入框。第一次点击会产生以下错误，我在其他问题中看到过该错误，但我无法将这些答案转化为我的情况：

错误：

Traceback (most recent call last): File "...\Python\Python38-32\lib\tkinter__init__.py", line 1883, in call return self.func(*args) File "fe.py", line 108, in selectitem selecteditem.append(lb1.get(ndex)) File "...\Python\Python38-32\lib\tkinter__init__.py", line 3182, in get return self.tk.call(self._w, 'get', first) _tkinter.TclError: bad listbox index "": must be active, anchor, end, @x,y, or a number

这里是复制错误的示例代码 - 要使用，首先通过设置 -> 项目菜单添加几个值，方法是填写 VAL 和 REF 框并单击添加项目按钮。然后单击列表框中的一项。第一次点击应该会产生上面的错误。第二次单击时，输入框应填充：

```
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，如果我的代码冒犯了任何人，我们深表歉意！

Answer 1

Not having 运行 your code as I have no sqlite3 database I may be way off, but listbox generates a virtual event when a value is selected <<ListboxSelect>> which you can bind to.尝试替换：

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

和

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

此外，我认为 lb1.curselection() returns 一个元组...，尝试打印它，看看会得到什么。在我检查过的代码中，我总是 lb1.curselection()[0].

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

Python tkinter listbox bind on <Button-1> only works on second click

python

sqlite

bind

listbox

tkinter