英文:
Flutter: get the very last character input from the user
问题
我正在使用Flutter制作一个应用程序。
我想将用户输入的最后一个字符设置为我的状态。
例如，当我输入“apple”时，我希望字符“e”成为我的最终状态。当我将光标移动到“p”和“l”之间，然后输入“x”时，我希望状态更改为“x”，内容为“appxle”。
我尝试了所有方法。我向ChatGPT和Bard提问，但他们仍然没有答案。我能想到的最好的方法是获取事件，但我从哪里获取事件呢？从一个控制器？
英文:
I am using Flutter to make an app.
I want to set the very last character from the user as my state.
For example, when I type "apple" I want the character "e" to be my final state. When I move the cursor between "p" and "l" and type "x", I want the state to change to "x" and the content is "appxle"
I tried everything. I asked ChatGPT and Bard, and still they don't have the answer. The best way I can think of is the get the event, but where can I get the event from? A controller?
答案1
得分: 1
以下是您可以使用的实现。请参阅代码中的注释。
class CharacterAtCursor extends StatefulWidget {
const CharacterAtCursor({super.key});
@override
State<CharacterAtCursor> createState() => _CharacterAtCursorState();
}
class _CharacterAtCursorState extends State<CharacterAtCursor> {
/// Listened to in order to update the UI when the text field's text and/or
/// cursor changes.
final _textEditingController = TextEditingController();
@override
void initState() {
super.initState();
/// We add a listener so that whenever the text field's text or cursor
/// changes, we update the UI.
_textEditingController.addListener(() => setState(() {}));
}
@override
void dispose() {
/// Dispose of the text editing controller.
_textEditingController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Column(
children: [
Text(
_textEditingController.text.isEmpty
? "Type something"
: _getCharacterAtCursor(), // Called to update the text.
),
TextField(controller: _textEditingController),
],
);
}
/// Extracts the character that is after the cursor.
///
/// Modify the index to get the character before the cursor.
String _getCharacterAtCursor() {
final text = _textEditingController.text;
final selection = _textEditingController.selection;
final offset = (selection.baseOffset).clamp(0, text.length - 1);
return text[offset];
}
}
这是您可以使用的实现代码。
英文:
Here is an implementation you can use. See the comments in the code.
class CharacterAtCursor extends StatefulWidget {
const CharacterAtCursor({super.key});
@override
State<CharacterAtCursor> createState() => _CharacterAtCursorState();
}
class _CharacterAtCursorState extends State<CharacterAtCursor> {
/// Listened to in order to update the UI when the text field's text and/or
/// cursor changes.
final _textEditingController = TextEditingController();
@override
void initState() {
super.initState();
/// We add a listener so that whenever the text field's text or cursor
/// changes, we update the UI.
_textEditingController.addListener(() => setState(() {}));
}
@override
void dispose() {
/// Dispose of the text editing controller.
_textEditingController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Column(
children: [
Text(
_textEditingController.text.isEmpty
? "Type something"
: _getCharacterAtCursor(), // Called to update the text.
),
TextField(controller: _textEditingController),
],
);
}
/// Extracts the character that is after the cursor.
///
/// Modify the index to get the character before the cursor.
String _getCharacterAtCursor() {
final text = _textEditingController.text;
final selection = _textEditingController.selection;
final offset = (selection.baseOffset).clamp(0, text.length - 1);
return text[offset];
}
}
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