{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 事件\n",
    "\n",
    "您可以注册协程或函数，以便在以下事件发生时被调用：\n",
    "\n",
    "- `app.on_startup`：在 NiceGUI 启动或重启时调用\n",
    "- `app.on_shutdown`：在 NiceGUI 关闭或重启时调用\n",
    "- `app.on_connect`：每个连接的客户端都会调用（可选参数：`nicegui.Client`）\n",
    "- `app.on_disconnect`：每个断开连接的客户端都会调用（可选参数：`nicegui.Client`）\n",
    "- `app.on_exception`：发生异常时调用（可选参数：`exception`）\n",
    "\n",
    "当 NiceGUI 关闭或重启时，所有仍在执行的任务将自动取消。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<nicegui.elements.timer.Timer at 0x2174637ab10>"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from datetime import datetime\n",
    "from nicegui import app, ui\n",
    "\n",
    "dt = datetime.now()\n",
    "\n",
    "def handle_connection():\n",
    "    global dt\n",
    "    dt = datetime.now()\n",
    "app.on_connect(handle_connection)\n",
    "\n",
    "label = ui.label()\n",
    "ui.timer(1, lambda: label.set_text(f'Last new connection: {dt:%H:%M:%S}'))\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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