PlaceholderSpan class abstract
An immutable placeholder that is embedded inline within text.
PlaceholderSpan represents a placeholder that acts as a stand-in for other content. A PlaceholderSpan by itself does not contain useful information to change a TextSpan. WidgetSpan from the widgets library extends PlaceholderSpan and may be used instead to specify a widget as the contents of the placeholder.
Flutter widgets such as TextField, Text and RichText do not recognize PlaceholderSpan subclasses other than WidgetSpan. Consider implementing the WidgetSpan interface instead of the Placeholder interface.
See also:
- WidgetSpan, a leaf node that represents an embedded inline widget.
- TextSpan, a node that represents text in a TextSpan tree.
- Text, a widget for showing uniformly-styled text.
- RichText, a widget for finer control of text rendering.
- TextPainter, a class for painting TextSpan objects on a Canvas.
- Inheritance
-
- Object
- DiagnosticableTree
- InlineSpan
- PlaceholderSpan
- Implementers
Constructors
- PlaceholderSpan({PlaceholderAlignment alignment = ui.PlaceholderAlignment.bottom, TextBaseline? baseline, TextStyle? style})
-
Creates a PlaceholderSpan with the given values.
const
Properties
- alignment → PlaceholderAlignment
-
How the placeholder aligns vertically with the text.
final
- baseline → TextBaseline?
-
The TextBaseline to align against when using ui.PlaceholderAlignment.baseline,
ui.PlaceholderAlignment.aboveBaseline, and ui.PlaceholderAlignment.belowBaseline.
final
- hashCode → int
-
The hash code for this object.
no setterinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
- style → TextStyle?
-
The TextStyle to apply to this span.
finalinherited
Methods
-
build(
ParagraphBuilder builder, {TextScaler textScaler = TextScaler.noScaling, List< PlaceholderDimensions> ? dimensions}) → void -
Apply the properties of this object to the given ParagraphBuilder, from
which a Paragraph can be obtained.
inherited
-
codeUnitAt(
int index) → int? -
Returns the UTF-16 code unit at the given
indexin the flattened string.inherited -
codeUnitAtVisitor(
int index, Accumulator offset) → int? -
Performs the check at each InlineSpan for if the
indexfalls within the range of the span and returns the corresponding code unit. Returns null otherwise.inherited -
compareTo(
InlineSpan other) → RenderComparison -
Describe the difference between this span and another, in terms of
how much damage it will make to the rendering. The comparison is deep.
inherited
-
computeSemanticsInformation(
List< InlineSpanSemanticsInformation> collector) → void -
Walks the InlineSpan tree and accumulates a list of
InlineSpanSemanticsInformation objects.
override
-
computeToPlainText(
StringBuffer buffer, {bool includeSemanticsLabels = true, bool includePlaceholders = true}) → void -
PlaceholderSpans are flattened to a
0xFFFCobject replacement character in the plain text representation whenincludePlaceholdersis true.override -
debugAssertIsValid(
) → bool -
In debug mode, throws an exception if the object is not in a
valid configuration. Otherwise, returns true.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of DiagnosticsNode objects describing this node's
children.
inherited
-
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
override
-
getSemanticsInformation(
) → List< InlineSpanSemanticsInformation> -
Flattens the InlineSpan tree to a list of
InlineSpanSemanticsInformation objects.
inherited
-
getSpanForPosition(
TextPosition position) → InlineSpan? -
Returns the InlineSpan that contains the given position in the text.
inherited
-
getSpanForPositionVisitor(
TextPosition position, Accumulator offset) → InlineSpan? -
Performs the check at each InlineSpan for if the
positionfalls within the range of the span and returns the span if it does.inherited -
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
toDiagnosticsNode(
{String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode -
Returns a debug representation of the object that is used by debugging
tools and by DiagnosticsNode.toStringDeep.
inherited
-
toPlainText(
{bool includeSemanticsLabels = true, bool includePlaceholders = true}) → String -
Flattens the InlineSpan tree into a single string.
inherited
-
toString(
{DiagnosticLevel minLevel = DiagnosticLevel.info}) → String -
A string representation of this object.
inherited
-
toStringDeep(
{String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a string representation of this node and its descendants.
inherited
-
toStringShallow(
{String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a one-line detailed description of the object.
inherited
-
toStringShort(
) → String -
A brief description of this object, usually just the runtimeType and the
hashCode.
inherited
-
visitChildren(
InlineSpanVisitor visitor) → bool -
Walks this InlineSpan and any descendants in pre-order and calls
visitorfor each span that has content.inherited -
visitDirectChildren(
InlineSpanVisitor visitor) → bool -
Calls
visitorfor each immediate child of this InlineSpan.inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited
Constants
- placeholderCodeUnit → const int
- The unicode character to represent a placeholder.