Dash中的多页应用程序-在其他页面中无法识别的下拉值

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output, State

app = dash.Dash(__name__)

# 全局状态变量
selected_value = None

# 页面布局
app.layout = html.Div([
    dcc.Dropdown(
        id='dropdown',
        options=[
            {'label': 'Option 1', 'value': 'option1'},
            {'label': 'Option 2', 'value': 'option2'},
            {'label': 'Option 3', 'value': 'option3'}
        ],
        value=None
    ),
    html.Button('Submit', id='submit-button'),
    html.Div(id='output')
])

# 回调函数：存储选择的下拉值
@app.callback(
    Output('output', 'children'),
    [Input('submit-button', 'n_clicks')],
    [State('dropdown', 'value')]
)
def store_selected_value(n_clicks, value):
    global selected_value
    selected_value = value
    return ''

# 在其他页面中读取选择的下拉值
@app.callback(
    Output('output', 'children'),
    [Input('dropdown', 'value')]
)
def display_selected_value(value):
    global selected_value
    if value is None:
        return ''
    elif value == selected_value:
        return f'Selected value: {value}'
    else:
        return 'Selected value is not recognized in other pages.'

if __name__ == '__main__':
    app.run_server(debug=True)