public final class TextMeasurer extends Object implements Cloneable
TextMeasurer class provides the primitive operations
needed for line break: measuring up to a given advance, determining the
advance of a range of characters, and generating a
TextLayout for a range of characters. It also provides
methods for incremental editing of paragraphs.
A TextMeasurer object is constructed with an
AttributedCharacterIterator
representing a single paragraph of text. The value returned by the
getBeginIndex
method of AttributedCharacterIterator
defines the absolute index of the first character. The value
returned by the
getEndIndex
method of AttributedCharacterIterator defines the index
past the last character. These values define the range of indexes to
use in calls to the TextMeasurer. For example, calls to
get the advance of a range of text or the line break of a range of text
must use indexes between the beginning and end index values. Calls to
insertChar
and
deleteChar
reset the TextMeasurer to use the beginning index and end
index of the AttributedCharacterIterator passed in those calls.
Most clients will use the more convenient LineBreakMeasurer,
which implements the standard line break policy (placing as many words
as will fit on each line).
LineBreakMeasurer| Constructor and Description |
|---|
TextMeasurer(AttributedCharacterIterator text,
FontRenderContext frc)
Constructs a
TextMeasurer from the source text. |
| Modifier and Type | Method and Description |
|---|---|
protected Object |
clone()
Creates and returns a copy of this object.
|
void |
deleteChar(AttributedCharacterIterator newParagraph,
int deletePos)
Updates the
TextMeasurer after a single character has
been deleted
from the paragraph currently represented by this
TextMeasurer. |
float |
getAdvanceBetween(int start,
int limit)
Returns the graphical width of a line beginning at
start
and including characters up to limit. |
TextLayout |
getLayout(int start,
int limit)
Returns a
TextLayout on the given character range. |
int |
getLineBreakIndex(int start,
float maxAdvance)
Returns the index of the first character which will not fit on
on a line beginning at
start and possible
measuring up to maxAdvance in graphical width. |
void |
insertChar(AttributedCharacterIterator newParagraph,
int insertPos)
Updates the
TextMeasurer after a single character has
been inserted
into the paragraph currently represented by this
TextMeasurer. |
public TextMeasurer(AttributedCharacterIterator text, FontRenderContext frc)
TextMeasurer from the source text.
The source text should be a single entire paragraph.text - the source paragraph. Cannot be null.frc - the information about a graphics device which is needed
to measure the text correctly. Cannot be null.protected Object clone()
Objectx, the expression:
will be true, and that the expression:x.clone() != x
will bex.clone().getClass() == x.getClass()
true, but these are not absolute requirements.
While it is typically the case that:
will bex.clone().equals(x)
true, this is not an absolute requirement.
By convention, the returned object should be obtained by calling
super.clone. If a class and all of its superclasses (except
Object) obey this convention, it will be the case that
x.clone().getClass() == x.getClass().
By convention, the object returned by this method should be independent
of this object (which is being cloned). To achieve this independence,
it may be necessary to modify one or more fields of the object returned
by super.clone before returning it. Typically, this means
copying any mutable objects that comprise the internal "deep structure"
of the object being cloned and replacing the references to these
objects with references to the copies. If a class contains only
primitive fields or references to immutable objects, then it is usually
the case that no fields in the object returned by super.clone
need to be modified.
The method clone for class Object performs a
specific cloning operation. First, if the class of this object does
not implement the interface Cloneable, then a
CloneNotSupportedException is thrown. Note that all arrays
are considered to implement the interface Cloneable and that
the return type of the clone method of an array type T[]
is T[] where T is any reference or primitive type.
Otherwise, this method creates a new instance of the class of this
object and initializes all its fields with exactly the contents of
the corresponding fields of this object, as if by assignment; the
contents of the fields are not themselves cloned. Thus, this method
performs a "shallow copy" of this object, not a "deep copy" operation.
The class Object does not itself implement the interface
Cloneable, so calling the clone method on an object
whose class is Object will result in throwing an
exception at run time.
public int getLineBreakIndex(int start,
float maxAdvance)
start and possible
measuring up to maxAdvance in graphical width.start - the character index at which to start measuring.
start is an absolute index, not relative to the
start of the paragraphmaxAdvance - the graphical width in which the line must fitstart, which is not longer
than maxAdvance in graphical widthIllegalArgumentException - if start is
less than the beginning of the paragraph.public float getAdvanceBetween(int start,
int limit)
start
and including characters up to limit.
start and limit are absolute indices,
not relative to the start of the paragraph.start - the character index at which to start measuringlimit - the character index at which to stop measuringstart
and including characters up to limitIndexOutOfBoundsException - if limit is less
than startIllegalArgumentException - if start or
limit is not between the beginning of
the paragraph and the end of the paragraph.public TextLayout getLayout(int start, int limit)
TextLayout on the given character range.start - the index of the first characterlimit - the index after the last character. Must be greater
than startTextLayout for the characters beginning at
start up to (but not including) limitIndexOutOfBoundsException - if limit is less
than startIllegalArgumentException - if start or
limit is not between the beginning of
the paragraph and the end of the paragraph.public void insertChar(AttributedCharacterIterator newParagraph, int insertPos)
TextMeasurer after a single character has
been inserted
into the paragraph currently represented by this
TextMeasurer. After this call, this
TextMeasurer is equivalent to a new
TextMeasurer created from the text; however, it will
usually be more efficient to update an existing
TextMeasurer than to create a new one from scratch.newParagraph - the text of the paragraph after performing
the insertion. Cannot be null.insertPos - the position in the text where the character was
inserted. Must not be less than the start of
newParagraph, and must be less than the end of
newParagraph.IndexOutOfBoundsException - if insertPos is less
than the start of newParagraph or greater than
or equal to the end of newParagraphNullPointerException - if newParagraph is
nullpublic void deleteChar(AttributedCharacterIterator newParagraph, int deletePos)
TextMeasurer after a single character has
been deleted
from the paragraph currently represented by this
TextMeasurer. After this call, this
TextMeasurer is equivalent to a new TextMeasurer
created from the text; however, it will usually be more efficient
to update an existing TextMeasurer than to create a new one
from scratch.newParagraph - the text of the paragraph after performing
the deletion. Cannot be null.deletePos - the position in the text where the character was removed.
Must not be less than
the start of newParagraph, and must not be greater than the
end of newParagraph.IndexOutOfBoundsException - if deletePos is
less than the start of newParagraph or greater
than the end of newParagraphNullPointerException - if newParagraph is
null Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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