在Flutter中使用pushNamed导航后如何使OverlayEntry消失 [英] How to make OverlayEntry disappear after navigating with pushNamed in Flutter

问题描述

我正在尝试进行如下所示的覆盖: https://www.didierboelens.com/2018/06/how-to-create-a-toast-or-notifications-notion-of-overlay/ 使用 OverlayEntry .

I am trying to make an overlay such as that shown here: https://www.didierboelens.com/2018/06/how-to-create-a-toast-or-notifications-notion-of-overlay/ using OverlayEntry.

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

class ShowNotificationIcon {

    void show(BuildContext context) async {
        OverlayState overlayState = Overlay.of(context);
        OverlayEntry overlayEntry = new OverlayEntry(builder: _build);

        overlayState.insert(overlayEntry);
    }

    Widget _build(BuildContext context){
      return new Positioned(
        top: 50.0,
        left: 50.0,
        child: new Material(
            color: Colors.transparent,
            child: new Icon(Icons.warning, color: Colors.purple),
        ),
      );
    }
}

调用者:

ShowNotificationIcon _icon = new ShowNotificationIcon();

_icon.show(context);

但是，当我尝试导航到其他屏幕时，覆盖层仍保留在屏幕中.

However, when I try to navigate to other screens, the overlay remains in the screen.

如何仅在被调用的屏幕上显示叠加层，而在其他屏幕上不显示?

How do I show the overlay only in the screen it is being called and not in the others?

以防万一，这是我在有状态的小部件中尝试过的操作:

Just in case, this is what I had tried inside my stateful widget:

  ShowNotificationIcon _icon = new ShowNotificationIcon();

  @override
  void initState() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _icon.show(context);
    });

    super.initState();
  }

  @override
  void dispose() {
    _icon.remove();
    super.dispose();
  }

推荐答案

通常使用RouteAware + RouteObserver执行此操作.

This is typically performed using RouteAware+RouteObserver.

RouteObserver是一个对象，通过该对象，实现RouteAware的对象可以对与路由相关的某些更改做出反应，其中包括:

RouteObserver is an object that lets objects that implements RouteAware react to some changes related to routing, which includes:

• 一条路线已推到当前路线的顶部
• 路线又回到了第一个计划

然后您可以使用这两个事件来隐藏/显示叠加层

You can then use these two events to hide/show your overlay

首先，您需要一个RouteObserver.

可以将其创建为全局变量，并且需要将其传递给您的Navigator.在基于MaterialApp的应用中，通常如下所示:

This can be created as a global variable and needs to be passed to your Navigator. In a MaterialApp based app, it'll typically look like this:

final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

void main() {
  runApp(MaterialApp(
    home: Container(),
    navigatorObservers: [routeObserver],
  ));
}

然后，拥有OverlayEntry的窗口小部件现在可以像下面这样实现RouteAware:

Then, your widget that owns the OverlayEntry can now implement RouteAware like so:

class RouteAwareWidget extends StatefulWidget {
  State<RouteAwareWidget> createState() => RouteAwareWidgetState();
}

// Implement RouteAware in a widget's state and subscribe it to the RouteObserver.
class RouteAwareWidgetState extends State<RouteAwareWidget> with RouteAware {

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    // routeObserver is the global variable we created before
    routeObserver.subscribe(this, ModalRoute.of(context));
  }

  @override
  void dispose() {
    routeObserver.unsubscribe(this);
    super.dispose();
  }

  @override
  void didPush() {
    // Route was pushed onto navigator and is now topmost route.
  }

  @override
  void didPopNext() {
    // Covering route was popped off the navigator.
  }

  @override
  Widget build(BuildContext context) => Container();

}

此时，您可以使用didPush和didPopNext显示/隐藏您的OverlayEntry:

At this point, you can use didPush and didPopNext to show/hide your OverlayEntry:

OverlayEntry myOverlay;

@override
void didPush() {
  myOverlay.remove();
}

@override
void didPopNext() {
  Overlay.of(context).insert(myOverlay);
}

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