flutter软键盘相关

键盘
1.是否弹起
MediaQuery.of(context).viewInsets.bottom > 0

viewInsets.bottom就是键盘的顶部距离底部的高度，也就是弹起的键盘高度。如果你想实时过去键盘的弹出状态，配合使用didChangeMetrics。完整如下：

import ‘package:flutter/material.dart’;

typedef KeyboardShowCallback = void Function(bool isKeyboardShowing);

class KeyboardDetector extends StatefulWidget {

KeyboardShowCallback keyboardShowCallback;

Widget content;

KeyboardDetector({this.keyboardShowCallback, @required this.content});

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

class _KeyboardDetectorState extends State
with WidgetsBindingObserver {
@override
void initState() {
WidgetsBinding.instance.addObserver(this);
super.initState();
}

@override
void didChangeMetrics() {
super.didChangeMetrics();
WidgetsBinding.instance.addPostFrameCallback((_) {
print(MediaQuery.of(context).viewInsets.bottom);
setState(() {
widget.keyboardShowCallback
?.call(MediaQuery.of(context).viewInsets.bottom > 0);
});
});
}

@override
void dispose() {
WidgetsBinding.instance.removeObserver(this);
super.dispose();
}

@override
Widget build(BuildContext context) {
return widget.content;
}
}

代码来自项目GSYFlutterDemo：https://github.com/CarGuo/GSYFlutterDemo

2.弹出键盘
if (MediaQuery.of(context).viewInsets.bottom == 0){
final focusScope = FocusScope.of(context);
focusScope.requestFocus(FocusNode());
Future.delayed(Duration.zero, () => focusScope.requestFocus(_focusNode));
}