Tkcalendar:将日历下拉列表与日期项右对齐

Question

默认情况下，日历下拉列表&；DateEntry小部件是左对齐的。在一种情况下，日历正在脱离屏幕，如图所示。我们是否可以将日历下拉列表与相应的DateEntry小部件右对齐

Answer 1

通过重写DateEntry的drop_down()方法，可以右对齐下拉列表。下拉菜单是一个顶层，位于屏幕上，带有

self._top_cal.geometry('+%i+%i' % (x, y))

其中（x，y）是下拉列表的左上角。因此，对于左对齐下拉列表

x = self.winfo_rootx()  # the left side of the entry 

现在要得到一个右对齐的下拉列表，我们需要将x改为

x = self.winfo_rootx() + self.winfo_width() - self._top_cal.winfo_reqwidth()

即（条目右侧的位置）-（下拉列表的宽度）

完整代码：

from tkcalendar import DateEntry
import tkinter as tk

class MyDateEntry(DateEntry):
    def __init__(self, master=None, align='left', **kw):
        DateEntry.__init__(self, master, **kw)
        self.align = align

    def drop_down(self):
        """Display or withdraw the drop-down calendar depending on its current state."""
        if self._calendar.winfo_ismapped():
            self._top_cal.withdraw()
        else:
            self._validate_date()
            date = self.parse_date(self.get())
            if self.align == 'left':  # usual DateEntry
                x = self.winfo_rootx()
            else:  # right aligned drop-down
                x = self.winfo_rootx() + self.winfo_width() - self._top_cal.winfo_reqwidth()
            y = self.winfo_rooty() + self.winfo_height()
            if self.winfo_toplevel().attributes('-topmost'):
                self._top_cal.attributes('-topmost', True)
            else:
                self._top_cal.attributes('-topmost', False)
            self._top_cal.geometry('+%i+%i' % (x, y))
            self._top_cal.deiconify()
            self._calendar.focus_set()
            self._calendar.selection_set(date)


root = tk.Tk()

tk.Label(root, text='left align').grid(row=0, column=0)
tk.Label(root, text='right align').grid(row=0, column=1)
MyDateEntry(root).grid(row=1, column=0)
MyDateEntry(root, align='right').grid(row=1, column=1)

root.mainloop()    

编辑：您还可以检测下拉列表是否将脱离屏幕，并自动调整下拉列表位置以避免出现以下情况：

def drop_down(self):
    """Display or withdraw the drop-down calendar depending on its current state."""
    if self._calendar.winfo_ismapped():
        self._top_cal.withdraw()
    else:
        self._validate_date()
        date = self.parse_date(self.get())
        h = self._top_cal.winfo_reqheight()
        w = self._top_cal.winfo_reqwidth()
        x_max = self.winfo_screenwidth()
        y_max = self.winfo_screenheight()
        # default: left-aligned drop-down below the entry
        x = self.winfo_rootx()
        y = self.winfo_rooty() + self.winfo_height()
        if x + w > x_max:  # the drop-down goes out of the screen
            # right-align the drop-down
            x += self.winfo_width() - w
        if y + h > y_max:  # the drop-down goes out of the screen
            # bottom-align the drop-down
            y -= self.winfo_height() + h
        if self.winfo_toplevel().attributes('-topmost'):
            self._top_cal.attributes('-topmost', True)
        else:
            self._top_cal.attributes('-topmost', False)
        self._top_cal.geometry('+%i+%i' % (x, y))
        self._top_cal.deiconify()
        self._calendar.focus_set()
        self._calendar.selection_set(date)

请注意，由于tkinter只检测一个大矩形屏幕，因此使用多个监视器时，此解决方案无法正常工作