python - Tkinter:只允许一个 Toplevel 窗口实例

Question

我有一个带有多个窗口的 tkinter 程序。这是完整的代码，以备不时之需。

import tkinter as tk
import tkinter.scrolledtext as tkst
from tkinter import ttk
import logging
import time


def popupmsg(msg):
    popup = tk.Toplevel()
    popup.wm_title("!")
    label = ttk.Label(popup, text=msg)
    label.pack(side="top", fill="x", pady=10)
    b1 = ttk.Button(popup, text="Okay", command=popup.destroy)
    b1.pack()
    popup.mainloop()


def test1():
    root.logger.error("Test")


def toggle(self):
    t_btn = self.t_btn
    if t_btn.config('text')[-1] == 'Start':
        t_btn.config(text='Stop')

        def startloop():
            if root.flag:
                now = time.strftime("%c")
                root.logger.error(now)
                root.after(30000, startloop)
            else:
                root.flag = True
                return
        startloop()
    else:
        t_btn.config(text='Start')
        root.logger.error("Loop stopped")
        root.flag = False


class TextHandler(logging.Handler):

    def __init__(self, text):
        # run the regular Handler __init__
        logging.Handler.__init__(self)
        # Store a reference to the Text it will log to
        self.text = text

    def emit(self, record):
        msg = self.format(record)

        def append():
            self.text.configure(state='normal')
            self.text.insert(tk.END, msg + '\n')
            self.text.configure(state='disabled')
            # Autoscroll to the bottom
            self.text.yview(tk.END)

        # This is necessary because we can't modify the Text from other threads
        self.text.after(0, append)

    def create(self):
        # Create textLogger
        topframe = tk.Frame(root)
        topframe.pack(side=tk.TOP)

        st = tkst.ScrolledText(topframe, bg="#00A09E", fg="white", state='disabled')
        st.configure(font='TkFixedFont')

        st.pack()

        self.text_handler = TextHandler(st)

        # Add the handler to logger
        root.logger = logging.getLogger()
        root.logger.addHandler(self.text_handler)

    def stop(self):
        root.flag = False

    def start(self):
        if root.flag:
            root.logger.error("error")
            root.after(1000, self.start)
        else:
            root.logger.error("Loop stopped")
            root.flag = True
            return

    def loop(self):
        self.start()


class HomePage(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

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

        self.menubar = tk.Menu(container)

        # Create taskbar/menu
        file = tk.Menu(self.menubar)
        file.add_command(label="Run", command=lambda: test1())
        file.add_command(label="Stop", command=lambda: test1())
        file.add_separator()
        file.add_command(label="Settings", command=lambda: Settings())
        file.add_separator()
        file.add_command(label="Quit", command=quit)
        self.menubar.add_cascade(label="File", menu=file)

        self.master.config(menu=self.menubar)

        #logger and main loop
        th = TextHandler("none")
        th.create()
        root.flag = True
        root.logger.error("Welcome to ShiptScraper!")

        bottomframe = tk.Frame(self)
        bottomframe.pack(side=tk.BOTTOM)

        topframe = tk.Frame(self)
        topframe.pack(side=tk.TOP)

        self.t_btn = tk.Button(text="Start", highlightbackground="#56B426", command=lambda: toggle(self))
        self.t_btn.pack(pady=5)

        self.exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        self.exitButton.pack()
        root.setting = False


class Settings(tk.Toplevel):

    def __init__(self, master=None):
        tk.Toplevel.__init__(self, master)
        self.wm_title("Settings")
        print(Settings.state(self))

        exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
        exitButton.pack()


class Help(tk.Toplevel):

    def __init__(self, parent):
        tk.Toplevel.__init__(self, parent)
        self.wm_title("Help")

        exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        exitButton.pack()


if __name__ == "__main__":
    root = tk.Tk()
    root.configure(background="#56B426")
    root.wm_title("ShiptScraper")
    app = HomePage(root)
    app.mainloop()

基本上我的问题是每次单击菜单中的命令 Settings 都会弹出一个新的 Settings 窗口。我不知道如何制作它，以便它可以检测一个窗口实例是否已经打开。我尝试使用 state() 作为 HomePage 类中方法的检查

#in it's respective place as shown above
file.add_command(label="Settings", command=lambda: self.open(Settings))

#outside the init as a method
def open(self, window):
    if window.state(self) != 'normal':
        window()

这会返回这个错误

Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/tkinter/__init__.py", line 1550, in __call__
    return self.func(*args)
  File "/Users/user/pythonProjects/ShiptScraper/ShiptScraperGUI.py", line 112, in <lambda>
    file.add_command(label="Settings", command=lambda: self.open(Settings))
  File "/Users/user/pythonProjects/ShiptScraper/ShiptScraperGUI.py", line 139, in open
    if window.state(self) != 'normal':
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/tkinter/__init__.py", line 1826, in wm_state
    return self.tk.call('wm', 'state', self._w, newstate)
_tkinter.TclError: window ".4319455216" isn't a top-level window

我已经尝试使用 winfo_exists() 方法，但似乎除非我已经销毁了窗口(如果它还没有打开我就没有销毁)这会对我有什么好处。尽管如此，这是我尝试过的组合之一

def open(self, window):
    if window.winfo_exists(self) != 1:
        window()

这当然什么都不做。我不会经历所有其他错误的组合。我已经尝试过了，因为老实说，此时我无法记住它们。

我也曾尝试将这些 open 方法定义为任何类之外的函数，但它们在那里也不起作用，通常是因为未定义 self 关键字的混淆在类之外，但需要成为 winfo_exists() 和 state() 方法的参数。

我还认为我的问题是，在将这些函数用作 HomePage 类中的方法时，是因为每当我引用 self 时，它都会检查 HomePage，不是我在方法中作为参数传递的任何窗口。不过我不太确定，这就是我来这里的原因。

实际上，我想做的只是在我的 HomePage 窗口中创建一个标准方法来控制菜单(以及稍后可能的按钮)如何打开一个窗口。这在逻辑上(在我自己的伪代码中)是:

def open(window)
   if window does not exist:
        open an instance of window

这可能吗，或者我应该采用更好的窗口管理方法吗？

编辑:我最初没有提到我的操作系统是运行 Mavericks 的 Mac OSX。显然这可能是一个 OSX 问题。此外，如果您要对这个问题投反对票，至少要发表评论并告诉我为什么/如何修改它以使其变得更好。

我现在已经尝试了这些组合

class Settings(tk.Toplevel):

    def __init__(self, master=None):
        tk.Toplevel.__init__(self, master)
        self.wm_title("Settings")
        # added grab_set()
        self.grab_set()
        #
        print(Settings.state(self))

        exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
        exitButton.pack()

和

class Settings(tk.Toplevel):

    def __init__(self, master=None):
        tk.Toplevel.__init__(self, master)
        self.wm_title("Settings")
        # added grab_set()
        self.grab_set()
        self.focus()
        #
        print(Settings.state(self))

        exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
        exitButton.pack()

和

class Settings(tk.Toplevel):

    def __init__(self, master=None):
        tk.Toplevel.__init__(self, master)
        self.wm_title("Settings")
        # added grab_set()
        self.attributes("-topmost", True)
        #
        print(Settings.state(self))

        exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
        exitButton.pack()

和

类设置(tk.Toplevel):

def __init__(self, master=None):
    tk.Toplevel.__init__(self, master)
    self.wm_title("Settings")
    # added grab_set()
    self.after(1, lambda: self.focus_force())

    #
    print(Settings.state(self))

    exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
    exitButton.pack()

编辑#2:

我想出了一个解决方法……我讨厌它。但它有效，至少目前如此。我绝对仍然希望有更好的解决方案。

import tkinter as tk
import tkinter.scrolledtext as tkst
from tkinter import ttk
import logging
import time



def popupmsg(msg):
    popup = tk.Toplevel()
    popup.wm_title("!")
    label = ttk.Label(popup, text=msg)
    label.pack(side="top", fill="x", pady=10)
    b1 = ttk.Button(popup, text="Okay", command=popup.destroy)
    b1.pack()
    popup.mainloop()


def test1():
    root.logger.error("Test")


def toggle(self):
    t_btn = self.t_btn
    if t_btn.config('text')[-1] == 'Start':
        t_btn.config(text='Stop')

        def startloop():
            if root.flag:
                now = time.strftime("%c")
                root.logger.error(now)
                root.after(30000, startloop)
            else:
                root.flag = True
                return
        startloop()
    else:
        t_btn.config(text='Start')
        root.logger.error("Loop stopped")
        root.flag = False


class TextHandler(logging.Handler):

    def __init__(self, text):
        # run the regular Handler __init__
        logging.Handler.__init__(self)
        # Store a reference to the Text it will log to
        self.text = text

    def emit(self, record):
        msg = self.format(record)

        def append():
            self.text.configure(state='normal')
            self.text.insert(tk.END, msg + '\n')
            self.text.configure(state='disabled')
            # Autoscroll to the bottom
            self.text.yview(tk.END)

        # This is necessary because we can't modify the Text from other threads
        self.text.after(0, append)

    def create(self):
        # Create textLogger
        topframe = tk.Frame(root)
        topframe.pack(side=tk.TOP)

        st = tkst.ScrolledText(topframe, bg="#00A09E", fg="white", state='disabled')
        st.configure(font='TkFixedFont')

        st.pack()

        self.text_handler = TextHandler(st)

        # Add the handler to logger
        root.logger = logging.getLogger()
        root.logger.addHandler(self.text_handler)

    def stop(self):
        root.flag = False

    def start(self):
        if root.flag:
            root.logger.error("error")
            root.after(1000, self.start)
        else:
            root.logger.error("Loop stopped")
            root.flag = True
            return

    def loop(self):
        self.start()


class HomePage(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

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

# NEW added a flag for the Settings window
        root.settings = False
        self.menubar = tk.Menu(container)

        # Create taskbar/menu
        file = tk.Menu(self.menubar)
        file.add_command(label="Run", command=lambda: test1())
        file.add_command(label="Stop", command=lambda: test1())
        file.add_separator()

# NEW now calling a method from Settings instead of Settings itself
        file.add_command(label="Settings", command=lambda: Settings().open())
        file.add_separator()
        file.add_command(label="Quit", command=quit)
        self.menubar.add_cascade(label="File", menu=file)

        self.master.config(menu=self.menubar)

        #logger and main loop
        th = TextHandler("none")
        th.create()
        root.flag = True
        root.logger.error("Welcome to ShiptScraper!")

        bottomframe = tk.Frame(self)
        bottomframe.pack(side=tk.BOTTOM)

        topframe = tk.Frame(self)
        topframe.pack(side=tk.TOP)

        self.t_btn = tk.Button(text="Start", highlightbackground="#56B426", command=lambda: toggle(self))
        self.t_btn.pack(pady=5)

        self.exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        self.exitButton.pack()
        root.setting = False


class Settings(tk.Toplevel):

        def __init__(self, master=None):
            tk.Toplevel.__init__(self, master)

# NEW 'open' method which is being called. This checks the root.setting flag added in the HomePage class
        def open(self):
            #NEW if root setting is false, continue creation of of Settings window
            if not root.setting:
                self.wm_title("Settings")
                # added grab_set()
                Settings.grab_set(self)

            #NEW edited the exitButton command, see close function below
                exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=lambda: close())
                exitButton.pack()
                root.setting = True
            #NEW if the root.settings flag is TRUE this cancels window creation
            else:
                self.destroy()

            #NEW when close() is called it resets the root.setting flag to false, then destroys the window
            def close():
                root.setting = False
                self.destroy()


class Help(tk.Toplevel):

    def __init__(self, parent):
        tk.Toplevel.__init__(self, parent)
        self.wm_title("Help")

        exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        exitButton.pack()


if __name__ == "__main__":
    root = tk.Tk()
    root.configure(background="#56B426")
    root.wm_title("ShiptScraper")
    app = HomePage(root)
    app.mainloop()

这感觉像是一个完整而彻底的 hack，我觉得看着它很脏，甚至因为制造这种可憎的东西而更脏......但它有效，至少现在是这样

编辑 3:

在 Jacob 的回答中添加了关闭窗口的协议(protocol)。忘了解释这一点。这是我将分享的最后一个版本，除非我想出更好的方法。

import tkinter as tk
import tkinter.scrolledtext as tkst
from tkinter import ttk
import logging
import time



def popupmsg(msg):
    popup = tk.Toplevel()
    popup.wm_title("!")
    label = ttk.Label(popup, text=msg)
    label.pack(side="top", fill="x", pady=10)
    b1 = ttk.Button(popup, text="Okay", command=popup.destroy)
    b1.pack()
    popup.mainloop()


def test1():
    root.logger.error("Test")


def toggle(self):
    t_btn = self.t_btn
    if t_btn.config('text')[-1] == 'Start':
        t_btn.config(text='Stop')

        def startloop():
            if root.flag:
                now = time.strftime("%c")
                root.logger.error(now)
                root.after(30000, startloop)
            else:
                root.flag = True
                return
        startloop()
    else:
        t_btn.config(text='Start')
        root.logger.error("Loop stopped")
        root.flag = False


class TextHandler(logging.Handler):

    def __init__(self, text):
        # run the regular Handler __init__
        logging.Handler.__init__(self)
        # Store a reference to the Text it will log to
        self.text = text

    def emit(self, record):
        msg = self.format(record)

        def append():
            self.text.configure(state='normal')
            self.text.insert(tk.END, msg + '\n')
            self.text.configure(state='disabled')
            # Autoscroll to the bottom
            self.text.yview(tk.END)

        # This is necessary because we can't modify the Text from other threads
        self.text.after(0, append)

    def create(self):
        # Create textLogger
        topframe = tk.Frame(root)
        topframe.pack(side=tk.TOP)

        st = tkst.ScrolledText(topframe, bg="#00A09E", fg="white", state='disabled')
        st.configure(font='TkFixedFont')

        st.pack()

        self.text_handler = TextHandler(st)

        # Add the handler to logger
        root.logger = logging.getLogger()
        root.logger.addHandler(self.text_handler)

    def stop(self):
        root.flag = False

    def start(self):
        if root.flag:
            root.logger.error("error")
            root.after(1000, self.start)
        else:
            root.logger.error("Loop stopped")
            root.flag = True
            return

    def loop(self):
        self.start()


class HomePage(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

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

# NEW added a flag for the Settings window
        root.setting = True
        self.menubar = tk.Menu(container)

        # Create taskbar/menu
        file = tk.Menu(self.menubar)
        file.add_command(label="Run", command=lambda: test1())
        file.add_command(label="Stop", command=lambda: test1())
        file.add_separator()

# NEW now calling a method from Settings instead of Settings itself
        file.add_command(label="Settings", command=lambda: Settings().open())
        file.add_separator()
        file.add_command(label="Quit", command=quit)
        self.menubar.add_cascade(label="File", menu=file)

        self.master.config(menu=self.menubar)

        #logger and main loop
        th = TextHandler("none")
        th.create()
        root.flag = True
        root.logger.error("Welcome to ShiptScraper!")

        bottomframe = tk.Frame(self)
        bottomframe.pack(side=tk.BOTTOM)

        topframe = tk.Frame(self)
        topframe.pack(side=tk.TOP)

        self.t_btn = tk.Button(text="Start", highlightbackground="#56B426", command=lambda: toggle(self))
        self.t_btn.pack(pady=5)

        self.exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        self.exitButton.pack()


class Settings(tk.Toplevel):

        def __init__(self, master=None):
            tk.Toplevel.__init__(self, master)

# NEW 'open' method which is being called. This checks the root.setting flag added in the HomePage class
        def open(self):
            #NEW when close() is called it resets the root.setting flag to false, then destroys the window
            def close_TopLevel():
                root.setting = True
                self.destroy()

            #NEW if root setting is false, continue creation of of Settings window
            if root.setting:
                self.wm_title("Settings")
                #NEW adjust window close protocol and change root.setting to FALSE
                self.protocol('WM_DELETE_WINDOW', close_TopLevel)
                root.setting = False

            #NEW edited the exitButton command, see close function below
                exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=lambda: close_TopLevel())
                exitButton.pack()

            #NEW if the root.settings flag is TRUE this cancels window creation
            else:
                print('shit')
                self.destroy()



class Help(tk.Toplevel):

    def __init__(self, parent):
        tk.Toplevel.__init__(self, parent)
        self.wm_title("Help")

        exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        exitButton.pack()


if __name__ == "__main__":
    root = tk.Tk()
    root.configure(background="#56B426")
    root.wm_title("ShiptScraper")
    app = HomePage(root)
    app.mainloop()

Answer 1

tkinter 的 grab_set() 正是为此而生。

将下面的代码部分改为:

class Settings(tk.Toplevel):

    def __init__(self, master=None):
        tk.Toplevel.__init__(self, master)
        self.wm_title("Settings")
        # added grab_set()
        self.grab_set()
        #
        print(Settings.state(self))

        exitButton = tk.Button(self, text="Exit", highlightbackground="#56B426", command=self.destroy)
        exitButton.pack()

现在，当您打开设置窗口时，如果设置窗口存在，主窗口将不会对按钮点击使用react。

另见 here .

---

编辑

诡计与欺骗

由于在 Tkinter/OSX 中似乎存在一个关于使用 grab_set() 的错误，它在 Linux (Ubuntu 16.04) 上运行良好，这里有一些诡计和欺骗。

我稍微编辑了你的代码。为简化示例，我将 Toplevel 窗口添加到 HomePage 类。我标记了更改 ##。

概念:

• 向您的类添加一个变量，代表设置窗口存在(或不存在)的事实:

  self.check = False
  

• 如果调用“设置”窗口，值会发生变化:

  self.check = True
  

• 调用设置窗口的功能现在是被动的。不会出现其他设置窗口:

   def call_settings(self):
      if self.check == False:
          self.settings_window()
  

• 我们向“设置”窗口添加协议(protocol)，以便在窗口停止存在时运行命令:

  self.settingswin.protocol('WM_DELETE_WINDOW', self.close_Toplevel)
  

• 然后调用的函数将重置self.check:

  def close_Toplevel(self):
      self.check = False
      self.settingswin.destroy()
  

  无论“设置”窗口如何关闭，这都会起作用。

编辑后的代码:

import tkinter as tk
import tkinter.scrolledtext as tkst
from tkinter import ttk
import logging
import time

def popupmsg(msg):
    popup = tk.Toplevel()
    popup.wm_title("!")
    label = ttk.Label(popup, text=msg)
    label.pack(side="top", fill="x", pady=10)
    b1 = ttk.Button(popup, text="Okay", command=popup.destroy)
    b1.pack()
    popup.mainloop()

def test1():
    root.logger.error("Test")

def toggle(self):
    t_btn = self.t_btn
    if t_btn.config('text')[-1] == 'Start':
        t_btn.config(text='Stop')

        def startloop():
            if root.flag:
                now = time.strftime("%c")
                root.logger.error(now)
                root.after(30000, startloop)
            else:
                root.flag = True
                return
        startloop()
    else:
        t_btn.config(text='Start')
        root.logger.error("Loop stopped")
        root.flag = False


class TextHandler(logging.Handler):

    def __init__(self, text):
        # run the regular Handler __init__
        logging.Handler.__init__(self)
        # Store a reference to the Text it will log to
        self.text = text

    def emit(self, record):
        msg = self.format(record)

        def append():
            self.text.configure(state='normal')
            self.text.insert(tk.END, msg + '\n')
            self.text.configure(state='disabled')
            # Autoscroll to the bottom
            self.text.yview(tk.END)

        # This is necessary because we can't modify the Text from other threads
        self.text.after(0, append)

    def create(self):
        # Create textLogger
        topframe = tk.Frame(root)
        topframe.pack(side=tk.TOP)

        st = tkst.ScrolledText(topframe, bg="#00A09E", fg="white", state='disabled')
        st.configure(font='TkFixedFont')

        st.pack()

        self.text_handler = TextHandler(st)

        # Add the handler to logger
        root.logger = logging.getLogger()
        root.logger.addHandler(self.text_handler)

    def stop(self):
        root.flag = False

    def start(self):
        if root.flag:
            root.logger.error("error")
            root.after(1000, self.start)
        else:
            root.logger.error("Loop stopped")
            root.flag = True
            return

    def loop(self):
        self.start()

class HomePage(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

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

        self.menubar = tk.Menu(container)
        self.check = False ### new

        # Create taskbar/menu
        file = tk.Menu(self.menubar)
        file.add_command(label="Run", command=lambda: test1())
        file.add_command(label="Stop", command=lambda: test1())
        file.add_separator()
        file.add_command(label="Settings", command=self.call_settings) #### new, changed command to run the function
        file.add_separator()
        file.add_command(label="Quit", command=quit)
        self.menubar.add_cascade(label="File", menu=file)

        self.master.config(menu=self.menubar)

        #logger and main loop
        th = TextHandler("none")
        th.create()
        root.flag = True
        root.logger.error("Welcome to ShiptScraper!")

        bottomframe = tk.Frame(self)
        bottomframe.pack(side=tk.BOTTOM)

        topframe = tk.Frame(self)
        topframe.pack(side=tk.TOP)

        self.t_btn = tk.Button(text="Start", highlightbackground="#56B426", command=lambda: toggle(self))
        self.t_btn.pack(pady=5)
        self.exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        self.exitButton.pack()
        root.setting = False

    ########## changed
    def call_settings(self):
        if self.check == False:
            self.settings_window()
    ##########

    def settings_window(self):
        self.check = True
        self.settingswin = tk.Toplevel()
        self.settingswin.wm_title("Settings") 
        self.settingswin.protocol('WM_DELETE_WINDOW', self.close_Toplevel) ##### new
        exitButton = tk.Button(self.settingswin, text="Exit", highlightbackground="#56B426", command=self.close_Toplevel)
        exitButton.pack()

    def close_Toplevel(self):
        # New, this runs when the Toplevel window closes, either by button or else
        self.check = False
        self.settingswin.destroy()

class Help(tk.Toplevel):

    def __init__(self, parent):
        tk.Toplevel.__init__(self, parent)
        self.wm_title("Help")
        exitButton = tk.Button(text="Exit", highlightbackground="#56B426", command=quit)
        exitButton.pack()

if __name__ == "__main__":
    root = tk.Tk()
    root.configure(background="#56B426")
    root.wm_title("ShiptScraper")
    app = HomePage(root)
    app.mainloop()

注意事项

一旦我们触发设置窗口的存在，我们当然可以做更多的事情，例如禁用主窗口上的所有按钮。通过这种方式，我们创建了自己的 grab_set() 版本，但更加灵活。