String 不是 well-formed utf-16，而关键是要使用更多的符号！例如心脏或象形文字
String is not well-formed utf-16, while the point is to use more symbols! for instance heart or a Hieroglyph
我是一个飞镖小白，想做一个键盘上有符号和象形文字的键盘，所以这是我的尝试！
但是当我使用退格键时，它吓坏了：
项目在 github 上开源：https://github.com/bookla-foundation/hieroglyphs
错误：
For more information see https://dart.dev/null-safety/unsound-null-safety
I/flutter ( 4728): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 4728): The following ArgumentError was thrown during performLayout():
I/flutter ( 4728): Invalid argument(s): string is not well-formed UTF-16
I/flutter ( 4728):
I/flutter ( 4728): The relevant error-causing widget was:
I/flutter ( 4728): TextField file:///Users/xxx/workspace/dart/heeroghleefy/lib/main.dart:30:11
I/flutter ( 4728):
I/flutter ( 4728): When the exception was thrown, this was the stack:
I/flutter ( 4728): #0 ParagraphBuilder.addText (dart:ui/text.dart:2178:7)
I/flutter ( 4728): #1 TextSpan.build (package:flutter/src/painting/text_span.dart:210:15)
I/flutter ( 4728): #2 TextPainter.layout (package:flutter/src/painting/text_painter.dart:569:14)
I/flutter ( 4728): #3 RenderEditable._layoutText (package:flutter/src/rendering/editable.dart:2011:18)
I/flutter ( 4728): #4 RenderEditable.performLayout (package:flutter/src/rendering/editable.dart:2059:5)
I/flutter ( 4728): #5 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #6 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #7 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #8 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #9 RenderLeaderLayer.performLayout (package:flutter/src/rendering/proxy_box.dart:5034:11)
I/flutter ( 4728): #10 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #11 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #12 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #13 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #14 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #15 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #16 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #17 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #18 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #19 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #20 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #21 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #22 RenderCustomPaint.performLayout (package:flutter/src/rendering/custom_paint.dart:518:11)
I/flutter ( 4728): #23 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #24 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #25 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #26 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #27 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #28 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #29 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #30 _RenderDecoration._layoutLineBox (package:flutter/src/material/input_decorator.dart:931:9)
I/flutter ( 4728): #31 _RenderDecoration._layout (package:flutter/src/material/input_decorator.dart:1033:28)
I/flutter ( 4728): #32 _RenderDecoration.performLayout (package:flutter/src/material/input_decorator.dart:1294:44)
I/flutter ( 4728): #33 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #34 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #35 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #36 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #37 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #38 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #39 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #40 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #41 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #42 ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:54:11)
I/flutter ( 4728): #43 RenderFlex._computeSizes (package:flutter/src/rendering/flex.dart:830:43)
I/flutter ( 4728): #44 RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:932:32)
I/flutter ( 4728): #45 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #46 MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:171:12)
I/flutter ( 4728): #47 _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:912:7)
I/flutter ( 4728): #48 MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:243:7)
I/flutter ( 4728): #49 RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:407:14)
I/flutter ( 4728): #50 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1634:7)
I/flutter ( 4728): #51 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:884:18)
I/flutter ( 4728): #52 RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:455:19)
I/flutter ( 4728): #53 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:903:13)
I/flutter ( 4728): #54 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1119:15)
I/flutter ( 4728): #55 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1057:9)
I/flutter ( 4728): #59 _invoke (dart:ui/hooks.dart:157:10)
I/flutter ( 4728): #60 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:253:5)
I/flutter ( 4728): #61 _drawFrame (dart:ui/hooks.dart:120:31)
I/flutter ( 4728): (elided 3 frames from dart:async)
I/flutter ( 4728):
I/flutter ( 4728): The following RenderObject was being processed when the exception was fired: RenderEditable#d149e relayoutBoundary=up18 NEEDS-LAYOUT NEEDS-PAINT:
I/flutter ( 4728): creator: _Editable-[GlobalKey#5bfdd] ← Semantics ← CompositedTransformTarget ←
I/flutter ( 4728): IgnorePointer-[GlobalKey#826e3] ← Semantics ← Listener ←
I/flutter ( 4728): RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#e8b2c] ← Listener ← _ScrollableScope
I/flutter ( 4728): ← RepaintBoundary ← CustomPaint ← RepaintBoundary ← ⋯
I/flutter ( 4728): parentData: <none> (can use size)
I/flutter ( 4728): constraints: BoxConstraints(w=387.4, 0.0<=h<=Infinity)
I/flutter ( 4728): size: Size(387.4, 32.0)
I/flutter ( 4728): cursorColor: Color(0xff2196f3)
I/flutter ( 4728): showCursor: ValueNotifier<bool>#d5002(true)
I/flutter ( 4728): maxLines: 1
I/flutter ( 4728): minLines: null
I/flutter ( 4728): selectionColor: Color(0x662196f3)
I/flutter ( 4728): textScaleFactor: 1.0
I/flutter ( 4728): locale: en_US
I/flutter ( 4728): selection: TextSelection(baseOffset: 5, extentOffset: 5, affinity: TextAffinity.downstream,
I/flutter ( 4728): isDirectional: false)
I/flutter ( 4728): offset: ScrollPositionWithSingleContext#51e24(offset: 0.0, range: 0.0..0.0, viewport: 387.4,
I/flutter ( 4728): ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, IdleScrollActivity#4e8d9,
I/flutter ( 4728): ScrollDirection.idle)
I/flutter ( 4728): This RenderObject had the following child:
I/flutter ( 4728): text: TextSpan
I/flutter ( 4728): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/chatty ( 4728): uid=10135(com.example.heeroghleefy) 1.ui identical 2 lines
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Please see the documentation for computeDistanceToActualBaseline for the required calling conventions of this method.
这个问题和这个答案与文章原始版本的一个问题有关Custom In-App Keyboard in Flutter。文章现已更新，因此退格应该不会再导致崩溃。
问题是由于试图只删除代理项对的一半造成的。在删除之前修复它以检查代理的方法：
void _backspace() {
final text = _controller.text;
final textSelection = _controller.selection;
final selectionLength = textSelection.end - textSelection.start;
// There is a selection.
if (selectionLength > 0) {
final newText = text.replaceRange(
textSelection.start,
textSelection.end,
'',
);
_controller.text = newText;
_controller.selection = textSelection.copyWith(
baseOffset: textSelection.start,
extentOffset: textSelection.start,
);
return;
}
// The cursor is at the beginning.
if (textSelection.start == 0) {
return;
}
// Delete the previous character
final previousCodeUnit = text.codeUnitAt(textSelection.start - 1);
final offset = _isUtf16Surrogate(previousCodeUnit) ? 2 : 1;
final newStart = textSelection.start - offset;
final newEnd = textSelection.start;
final newText = text.replaceRange(
newStart,
newEnd,
'',
);
_controller.text = newText;
_controller.selection = textSelection.copyWith(
baseOffset: newStart,
extentOffset: newStart,
);
}
bool _isUtf16Surrogate(int value) {
return value & 0xF800 == 0xD800;
}
_controller 指的是 TextEditingController 对于 TextField。
请参阅有关删除大于单个代理项对的字素簇的相关问题：
- How to convert String index to character index in Dart
我是一个飞镖小白，想做一个键盘上有符号和象形文字的键盘，所以这是我的尝试！ 但是当我使用退格键时，它吓坏了： 项目在 github 上开源：https://github.com/bookla-foundation/hieroglyphs 错误：
For more information see https://dart.dev/null-safety/unsound-null-safety
I/flutter ( 4728): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 4728): The following ArgumentError was thrown during performLayout():
I/flutter ( 4728): Invalid argument(s): string is not well-formed UTF-16
I/flutter ( 4728):
I/flutter ( 4728): The relevant error-causing widget was:
I/flutter ( 4728): TextField file:///Users/xxx/workspace/dart/heeroghleefy/lib/main.dart:30:11
I/flutter ( 4728):
I/flutter ( 4728): When the exception was thrown, this was the stack:
I/flutter ( 4728): #0 ParagraphBuilder.addText (dart:ui/text.dart:2178:7)
I/flutter ( 4728): #1 TextSpan.build (package:flutter/src/painting/text_span.dart:210:15)
I/flutter ( 4728): #2 TextPainter.layout (package:flutter/src/painting/text_painter.dart:569:14)
I/flutter ( 4728): #3 RenderEditable._layoutText (package:flutter/src/rendering/editable.dart:2011:18)
I/flutter ( 4728): #4 RenderEditable.performLayout (package:flutter/src/rendering/editable.dart:2059:5)
I/flutter ( 4728): #5 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #6 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #7 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #8 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #9 RenderLeaderLayer.performLayout (package:flutter/src/rendering/proxy_box.dart:5034:11)
I/flutter ( 4728): #10 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #11 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #12 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #13 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #14 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #15 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #16 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #17 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #18 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #19 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #20 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #21 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #22 RenderCustomPaint.performLayout (package:flutter/src/rendering/custom_paint.dart:518:11)
I/flutter ( 4728): #23 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #24 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #25 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #26 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #27 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #28 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #29 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #30 _RenderDecoration._layoutLineBox (package:flutter/src/material/input_decorator.dart:931:9)
I/flutter ( 4728): #31 _RenderDecoration._layout (package:flutter/src/material/input_decorator.dart:1033:28)
I/flutter ( 4728): #32 _RenderDecoration.performLayout (package:flutter/src/material/input_decorator.dart:1294:44)
I/flutter ( 4728): #33 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #34 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #35 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #36 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #37 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #38 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #39 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #40 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:123:14)
I/flutter ( 4728): #41 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #42 ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:54:11)
I/flutter ( 4728): #43 RenderFlex._computeSizes (package:flutter/src/rendering/flex.dart:830:43)
I/flutter ( 4728): #44 RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:932:32)
I/flutter ( 4728): #45 RenderObject.layout (package:flutter/src/rendering/object.dart:1777:7)
I/flutter ( 4728): #46 MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:171:12)
I/flutter ( 4728): #47 _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:912:7)
I/flutter ( 4728): #48 MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:243:7)
I/flutter ( 4728): #49 RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:407:14)
I/flutter ( 4728): #50 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1634:7)
I/flutter ( 4728): #51 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:884:18)
I/flutter ( 4728): #52 RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:455:19)
I/flutter ( 4728): #53 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:903:13)
I/flutter ( 4728): #54 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1119:15)
I/flutter ( 4728): #55 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1057:9)
I/flutter ( 4728): #59 _invoke (dart:ui/hooks.dart:157:10)
I/flutter ( 4728): #60 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:253:5)
I/flutter ( 4728): #61 _drawFrame (dart:ui/hooks.dart:120:31)
I/flutter ( 4728): (elided 3 frames from dart:async)
I/flutter ( 4728):
I/flutter ( 4728): The following RenderObject was being processed when the exception was fired: RenderEditable#d149e relayoutBoundary=up18 NEEDS-LAYOUT NEEDS-PAINT:
I/flutter ( 4728): creator: _Editable-[GlobalKey#5bfdd] ← Semantics ← CompositedTransformTarget ←
I/flutter ( 4728): IgnorePointer-[GlobalKey#826e3] ← Semantics ← Listener ←
I/flutter ( 4728): RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#e8b2c] ← Listener ← _ScrollableScope
I/flutter ( 4728): ← RepaintBoundary ← CustomPaint ← RepaintBoundary ← ⋯
I/flutter ( 4728): parentData: <none> (can use size)
I/flutter ( 4728): constraints: BoxConstraints(w=387.4, 0.0<=h<=Infinity)
I/flutter ( 4728): size: Size(387.4, 32.0)
I/flutter ( 4728): cursorColor: Color(0xff2196f3)
I/flutter ( 4728): showCursor: ValueNotifier<bool>#d5002(true)
I/flutter ( 4728): maxLines: 1
I/flutter ( 4728): minLines: null
I/flutter ( 4728): selectionColor: Color(0x662196f3)
I/flutter ( 4728): textScaleFactor: 1.0
I/flutter ( 4728): locale: en_US
I/flutter ( 4728): selection: TextSelection(baseOffset: 5, extentOffset: 5, affinity: TextAffinity.downstream,
I/flutter ( 4728): isDirectional: false)
I/flutter ( 4728): offset: ScrollPositionWithSingleContext#51e24(offset: 0.0, range: 0.0..0.0, viewport: 387.4,
I/flutter ( 4728): ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, IdleScrollActivity#4e8d9,
I/flutter ( 4728): ScrollDirection.idle)
I/flutter ( 4728): This RenderObject had the following child:
I/flutter ( 4728): text: TextSpan
I/flutter ( 4728): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/chatty ( 4728): uid=10135(com.example.heeroghleefy) 1.ui identical 2 lines
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Null check operator used on a null value
I/flutter ( 4728): Another exception was thrown: Please see the documentation for computeDistanceToActualBaseline for the required calling conventions of this method.
这个问题和这个答案与文章原始版本的一个问题有关Custom In-App Keyboard in Flutter。文章现已更新，因此退格应该不会再导致崩溃。
问题是由于试图只删除代理项对的一半造成的。在删除之前修复它以检查代理的方法：
void _backspace() {
final text = _controller.text;
final textSelection = _controller.selection;
final selectionLength = textSelection.end - textSelection.start;
// There is a selection.
if (selectionLength > 0) {
final newText = text.replaceRange(
textSelection.start,
textSelection.end,
'',
);
_controller.text = newText;
_controller.selection = textSelection.copyWith(
baseOffset: textSelection.start,
extentOffset: textSelection.start,
);
return;
}
// The cursor is at the beginning.
if (textSelection.start == 0) {
return;
}
// Delete the previous character
final previousCodeUnit = text.codeUnitAt(textSelection.start - 1);
final offset = _isUtf16Surrogate(previousCodeUnit) ? 2 : 1;
final newStart = textSelection.start - offset;
final newEnd = textSelection.start;
final newText = text.replaceRange(
newStart,
newEnd,
'',
);
_controller.text = newText;
_controller.selection = textSelection.copyWith(
baseOffset: newStart,
extentOffset: newStart,
);
}
bool _isUtf16Surrogate(int value) {
return value & 0xF800 == 0xD800;
}
_controller 指的是 TextEditingController 对于 TextField。
请参阅有关删除大于单个代理项对的字素簇的相关问题：
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