如何在 Flutter 中调用上滑面板？

Question

我正在使用https://pub.dev/packages/sliding_up_panel，我想在现有面板上按下按钮后触发新面板的打开。

    @override
    Widget build(BuildContext context) {
      BorderRadiusGeometry radius = BorderRadius.only(
        topLeft: Radius.circular(24.0),
        topRight: Radius.circular(24.0),
      );

      return Scaffold(
        appBar: AppBar(
          title: Text("SlidingUpPanelExample"),
        ),
        body: SlidingUpPanel(
          panel: Center(
            child: RaisedButton(
                  child: Text('Show new panel'),
                  onPressed: () {

                    **///want to add code 
here to trigger the callback of the new panel.** 

                  },
             ),
          ),

          collapsed: Container(
            decoration: BoxDecoration(
              color: Colors.blueGrey,
              borderRadius: radius
            ),
            child: Center(
              child: Text(
                "This is the collapsed Widget",
                style: TextStyle(color: Colors.white),
              ),
            ),
          ),

          body: Center(
            child: Text("This is the Widget behind the sliding panel"),
          ),

          borderRadius: radius,
        ),
      );
    }

此依赖项能够在控制器的帮助下调用 open() 方法，但我无法理解如何使用它调用新的向上滑动面板（并且显然关闭现有面板）。 这是 open() 操作的代码：

PanelController _pc = new PanelController();
...
  RaisedButton(
          child: Text("Open"),
          onPressed: () => _pc.open(),
        ),

Answer 1

您可以在下面复制粘贴运行完整代码
您可以使用Column 并将这两个SlidingUpPanel 包装成Visibility 并将maintainState、maintainAnimation 设置为true
工作演示显示SlidingUpPanel 1 和 2 之间的切换

代码sn-p

body: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          Visibility(
            maintainState: true,
            maintainAnimation: true,
            visible: _visible,
            child: SlidingUpPanel(
              controller: _pc1,
              panel: Center(
                child: RaisedButton(
                  child: Text('Show new panel 2'),
                  onPressed: () {
                    _pc1.close();
                    _visible = false;
                    setState(() {});
                    _pc2.open();
                  },

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:sliding_up_panel/sliding_up_panel.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  PanelController _pc1 = new PanelController();
  PanelController _pc2 = new PanelController();
  bool _visible = true;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    BorderRadiusGeometry radius = BorderRadius.only(
      topLeft: Radius.circular(24.0),
      topRight: Radius.circular(24.0),
    );

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          Visibility(
            maintainState: true,
            maintainAnimation: true,
            visible: _visible,
            child: SlidingUpPanel(
              controller: _pc1,
              panel: Center(
                child: RaisedButton(
                  child: Text('Show new panel 2'),
                  onPressed: () {
                    _pc1.close();
                    _visible = false;
                    setState(() {});
                    _pc2.open();
                  },
                ),
              ),
              collapsed: Container(
                decoration:
                    BoxDecoration(color: Colors.blueGrey, borderRadius: radius),
                child: Center(
                  child: Text(
                    "Panel 1",
                    style: TextStyle(color: Colors.orange),
                  ),
                ),
              ),
              body: Center(
                  child: Text(
                      "Panel 1 This is the Widget behind the sliding panel")),
              borderRadius: radius,
            ),
          ),
          Visibility(
            maintainState: true,
            maintainAnimation: true,
            visible: !_visible,
            child: SlidingUpPanel(
              controller: _pc2,
              panel: Center(
                child: RaisedButton(
                  child: Text('Show new panel 1'),
                  onPressed: () {
                    _pc2.close();
                    _visible = true;
                    setState(() {});
                    _pc1.open();
                  },
                ),
              ),
              collapsed: Container(
                decoration:
                    BoxDecoration(color: Colors.blueGrey, borderRadius: radius),
                child: Center(
                  child: Text(
                    "Panel 2 ",
                    style: TextStyle(color: Colors.red),
                  ),
                ),
              ),
              body: Center(
                child:
                    Text("Panel 2 This is the Widget behind the sliding panel"),
              ),
              borderRadius: radius,
            ),
          ),
        ],
      ),
    );
  }
}