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Flutter WebView 键盘问题

字数统计: 1.5k阅读时长: 6 min
2019/12/19 Share

Flutter_Webview 键盘弹出问题


webview_flutter ^0.3.7+1 pub链接

webview_flutter在Android上没有办法弹出键盘,github上的issue已经提了很久,但是官方的milestone还要到19年的十月 issue #19718,(截止发稿时已经有一个PR到master分支了,但是stable分支的同学可能就还要等一哈了),但是PR的解决方案在AndroidN之前并没有用…comment

1.来自其他同学的启发

隐藏TextField方案,这个方案的简单思路就是在onPageFinish时给Webview注入一段js代码,监听input/textarea的focus事件,然后通过JSChannel发送给隐藏在WebView之后的TextField,通过TextField间接唤起软键盘然后,通过监听TextField的onChange事件给input/textarea设置新的值

下面是他的JS代码实现:他用js监听某个网站的几个需要弹出输入法的element,focus事件/focusout事件

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inputs = document.getElementsByClassName('search-bar');
header=document.getElementsByClassName('site-header');
header[0].style.display = 'none';
buttons = document.getElementsByClassName('icon');
buttons[0].focus();
if (inputs != null) {
input = inputs[0];
InputValue.postMessage(input.value);
input.addEventListener('focus', (_) => {
Focus.postMessage('focus');
}, true);
input.addEventListener('focusout', (_) => {
Focus.postMessage('focusout');
}, true)
}

JSChannel:

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javascriptChannels: Set.from(
[
// Listening for Javascript messages to get Notified of Focuschanges and the current input Value of the Textfield.
JavascriptChannel(
name: 'Focus',
// get notified of focus changes on the input field and open/close the Keyboard.
onMessageReceived: (JavascriptMessage focus) {
print(focus.message);
if (focus.message == 'focus') {
FocusScope.of(context)
.requestFocus(_focusNode);
} else if (focus.message == 'focusout') {
_focusNode.unfocus();
}
},
),
JavascriptChannel(
name: 'InputValue',
// set the value of the native input field to the one on the website to always make sure they have the same input.
onMessageReceived: (JavascriptMessage value) {
_textController.value =
TextEditingValue(text: value.toString());
},
)
],
),

接收事件更改TextField的text,通过focusNode来唤起/隐藏 软键盘

这个方案看起来很好,但是手写监听所有Classname可太笨了…而且如果用户在弹出键盘后手动关闭键盘(按软键盘上的关闭按钮),软键盘就再也弹不出来了…

2.自己的方案升级

  1. 用两个TextField交替接收事件来解决无法在手动关闭键盘后重新唤起的问题
  2. 注入JS监听所有input/textarea element,不监听focus/focusout事件,监听click事件,有几个好处
    1. 可以获取用户当前文字选择/光标位置
    2. 可以判断再次点击事件
  3. 记录当前focus的element,用于判断是否需要重新唤起新的键盘

下面的简单的代码实现:

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var inputs = document.getElementsByTagName('input');
var textArea = document.getElementsByTagName('textarea');
var current;

for (var i = 0; i < inputs.length; i++) {
console.log(i);
inputs[i].addEventListener('click', (e) => {
var json = {
"funcName": "requestFocus",
"data": {
"initText": e.target.value,
"selectionStart":e.target.selectionStart,
"selectionEnd":e.target.selectionEnd
}
};
json.data.refocus = (document.activeElement == current);

current = e.target;
var param = JSON.stringify(json);
console.log(param);
UserState.postMessage(param);
})

}
for (var i = 0; i < textArea.length; i++) {
console.log(i);
textArea[i].addEventListener('click', (e) => {
var json = {
"funcName": "requestFocus",
"data": {
"initText": e.target.value,
"selectionStart":e.target.selectionStart,
"selectionEnd":e.target.selectionEnd
}
};

json.data.refocus = (document.activeElement == current);

current = e.target;
var param = JSON.stringify(json);
console.log(param);

UserState.postMessage(param);
})
};
console.log('===JS CODE INJECTED INTO MY WEBVIEW===');

UserState是定义好的jsChannel,接收一个jsonString形式的参数,data.initText是初始文字,selectEnd selectStart是文字选择位置,refocus是判断是否重新点击focus的Element的标记,element被点击时:

*  先判断是不是refocus,发送给channel

接下来要处理JSChannel收到的数据了,其中showAndroidKeyboard是自己编写的一个PlatformChannel,用来显示软键盘,代码还可以简化,我这里就不写了,有改进的请和作者联系…也是在踩坑中.

  • 关键是TextField交替获取焦点,当TextField - A获取焦点,进行一番编辑之后,用户手动关闭了软键盘,这个时候FocusScop.of(context).requestFocus(focusNodeA)是无法唤起键盘的,所以需要另一个TextField-B来请求焦点,
  • showAndroidKeyboard()是为了在某些情况下备用focusNode也没获取焦点,需要我们手动唤起焦点
  • 隐藏键盘的事件还没有很好的解决方案
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bool refocus = data['refocus'] as bool;
if (_focusNode2.hasFocus) {
if (!refocus) FocusScope.of(context).requestFocus(_focusNode1);
//FocusScope.of(context).requestFocus(_focusNode);
if (!_focusNode1.hasFocus) {
//hideAndroidKeyboard();
showAndroidKeyboard();
}
//把初始文本设置给隐藏TextField
String initText = data['initText'];
var selectionStart = data['selectionStart'];
var selectionEnd = data['selectionEnd'];

int end = initText.length;
int start = initText.length;
if (selectionEnd is int) {
end = selectionEnd;
}
if (selectionStart is int) {
start = selectionEnd;
}
print(selectionEnd);
textController1.value = TextEditingValue(
text: initText,
selection: TextSelection(baseOffset: start, extentOffset: end),
);
//TextField请求显示键盘
FocusScope.of(context).requestFocus(_focusNode1);
} else {
if (!refocus) FocusScope.of(context).requestFocus(_focusNode2);
//FocusScope.of(context).requestFocus(_focusNode);
if (!_focusNode2.hasFocus) {
//hideAndroidKeyboard();
showAndroidKeyboard();
}
//把初始文本设置给隐藏TextField
String initText = data['initText'];
var selectionStart = data['selectionStart'];
var selectionEnd = data['selectionEnd'];

int end = initText.length;
int start = initText.length;
if (selectionEnd is int) {
end = selectionEnd;
}
if (selectionStart is int) {
start = selectionEnd;
}
print(selectionEnd);
textController2.value = TextEditingValue(
text: initText,
selection: TextSelection(baseOffset: start, extentOffset: end),
);
//TextField请求显示键盘
FocusScope.of(context).requestFocus(_focusNode2);
}

webview后面隐藏的TextField

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return Stack(
children: <Widget>[
TextField(
autofocus: false,
focusNode: _focusNode1,
controller: textController1,
onChanged: (text) {
controller.evaluateJavascript('''
if(current != null){
current.value = '${textController1.text}';
current.selectionStart = ${textController1.selection.start};
current.selectionEnd = ${textController1.selection.end};
current.dispatchEvent(new Event('input'));
}
''');
},
onSubmitted: (text) {
controller.evaluateJavascript('''
if(current != null)
current.submit();
''');
_focusNode1.unfocus();
},
),
TextField(
autofocus: false,
focusNode: _focusNode2,
controller: textController2,
onChanged: (text) {
controller.evaluateJavascript('''
if(current != null){
current.value = '${textController2.text}';
current.selectionStart = ${textController2.selection.start};
current.selectionEnd = ${textController2.selection.end};
current.dispatchEvent(new Event('input'));
}
''');
},
onSubmitted: (text) {
controller.evaluateJavascript('''
if(current != null)
current.submit();
''');
_focusNode2.unfocus();
},
),
WebView(....)
]
);
  • 在TextField的onChange中改编当前focus的Element的text/selection,然后发送一个input事件来触发Element改变current.dispatchEvent(new Event('input'));,这里的大家应该都很好理解了.

不得不说谷歌太坑了,webview竟然有这样的大缺陷,不过也没办法毕竟版本号还没到1.0.0呢…本文的方法只是一个临时的解决方案,比如点击空白隐藏软键盘等功能还没实现,只使用一些简单的文本输入的webview还是可以的,还有一些input标签作为按钮的可能还要手动隐藏下键盘,以上.

CATALOG
  1. 1. 1.来自其他同学的启发
  2. 2. 2.自己的方案升级