在 Flutter 中仅使一个小部件浮在键盘上方

Question

I want to display a "Close keyboard" button above the keyboard when it is visible.

I know that the resizeToAvoidBottomInset can impact how the keyboard interact with the rest of the application, however it doesn't do exactly what I want.

I have a background image and others widgets (not shown in the sample below) which should not be resized and not moved when the keyboards is shown. This is an ok behavior when the resizeToAvoidBottomInset attribute is set to false.

However, I would like to add a button which should appear above the keyboard.

How can I do that? I only want one widget floating above the keyboard, not all the app.

Here is a sample code:

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

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

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

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      resizeToAvoidBottomInset: false,
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: _getBody(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {},
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }

  Widget _getBody() {
    return Stack(children: <Widget>[
      Container(
        decoration: BoxDecoration(
            image: DecorationImage(
                image: AssetImage("assets/sample.jpg"), fit: BoxFit.fitWidth)),
        // color: Color.fromARGB(50, 200, 50, 20),
        child: Column(
          children: <Widget>[TextField()],
        ),
      ),
      Positioned(
        bottom: 0,
        left: 0,
        right: 0,
        child: Container(
          height: 50,
          child: Text("Aboveeeeee"),
          decoration: BoxDecoration(color: Colors.pink),
        ),
      ),
    ]);
  }
}

Answer 1

Your Positioned widget has a bottom of 0, replacing with an appropriate value should do the job.

MediaQuery.of(context).viewInsets.bottom will give you the value of the height covered by the system UI(in this case the keyboard).

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

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

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

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      resizeToAvoidBottomInset: false,
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: _getBody(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {},
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }

  Widget _getBody() {
    return Stack(children: <Widget>[
      Container(
        decoration: BoxDecoration(
            image: DecorationImage(
                image: AssetImage("assets/sample.jpg"), fit: BoxFit.fitWidth)),
        // color: Color.fromARGB(50, 200, 50, 20),
        child: Column(
          children: <Widget>[TextField()],
        ),
      ),
      Positioned(
        bottom: MediaQuery.of(context).viewInsets.bottom,
        left: 0,
        right: 0,
        child: Container(
          height: 50,
          child: Text("Aboveeeeee"),
          decoration: BoxDecoration(color: Colors.pink),
        ),
      ),
    ]);
  }
}

Answer 2

To achieve keyboard-visibility-based animated padding, here are a few modifications over @10101010's great answer:

If you want the bottom change when keyboard changes visibility to be animated AND you want extra padding under your floating child then:

1- Use keyboard_visibility flutter pub

To listen when keyboard is appearing/disappearing, like so:

  bool isKeyboardVisible = false;

  @override
  void initState() {
    super.initState();

    KeyboardVisibilityNotification().addNewListener(
      onChange: (bool visible) {
        isKeyboardVisible = visible;
      },
    );
  }

Optionally you can write your own native plugins, but it's already there you can check the pub's git repo.

2- Consume visibility flag in your AnimatedPostioned :

For fine-tuned animated padding, like so:

Widget _getBody() {
    double bottomPadding = 0;
    if (isKeyboardVisible) {
      // when keyboard is shown, our floating widget is above the keyboard and its accessories by `16`
      bottomPadding = MediaQuery.of(context).viewInsets.bottom + 16;
    } else {
      // when keyboard is hidden, we should have default spacing
      bottomPadding = 48; // MediaQuery.of(context).size.height * 0.15;
    }

    return Stack(children: <Widget>[
      Container(
        decoration: BoxDecoration(
            image: DecorationImage(
                image: AssetImage("assets/sample.jpg"), fit: BoxFit.fitWidth)),
        // color: Color.fromARGB(50, 200, 50, 20),
        child: Column(
          children: <Widget>[TextField()],
        ),
      ),
      AnimatedPositioned(
        duration: Duration(milliseconds: 500),
        bottom: bottomPadding,
        left: 0,
        right: 0,
        child: Container(
          height: 50,
          child: Text("Aboveeeeee"),
          decoration: BoxDecoration(color: Colors.pink),
        ),
      ),
    ]);
}

3- Keyboard-specific animation curve and duration for synchronized animation

For now this is still an known ongoing issue

Answer 3

检查这个包，它可以在键盘上方显示一个关闭按钮。

Answer 4

You can use bottomSheet parameter of the Scaffold, which keep a persistent bottom sheet. See below code.

class InputScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Close')),
      bottomSheet: Container(
          padding: const EdgeInsets.symmetric(horizontal: 18, vertical: 16),
          color: Colors.black,
          child: const SizedBox(width: double.infinity, height: 10)),
      body: Column(
        children: [
          const TextField(
            decoration: InputDecoration(
              border: OutlineInputBorder(),
              hintText: 'Enter your input here',
            ),
          ),
          ElevatedButton(
            onPressed: () {},
            child: const Text('Submit'),
          ),
        ],
      ),
    );
  }
}

Answer 5

You can use the bottomSheet of a Scaffold widget.

Example:

    return Scaffold(
      appBar: AppBar(
        title: const Text("New Game"),
      ),
      bottomSheet: Container(
          padding: const EdgeInsets.symmetric(horizontal: 18, vertical: 16),
          color: Colors.blue,
          child: const SizedBox(
            width: double.infinity,
            height: 20,
            child: Text("Above Keyboard"),
          ))
...
)