PrecomputedText
public
class
PrecomputedText
extends Object
implements
Spannable
A text which has the character metrics data.
A text object that contains the character metrics data and can be used to improve the performance
of text layout operations. When a PrecomputedText is created with a given CharSequence
,
it will measure the text metrics during the creation. This PrecomputedText instance can be set on
TextView
or StaticLayout
. Since the text layout information will
be included in this instance, TextView
or StaticLayout
will not
have to recalculate this information.
Note that the PrecomputedText
created from different parameters of the target TextView
will be rejected internally and compute the text layout again with the
current TextView
parameters.
An example usage is:
static void asyncSetText(TextView textView, final String longString, Executor bgExecutor) {
// construct precompute related parameters using the TextView that we will set the text on.
final PrecomputedText.Params params = textView.getTextMetricsParams();
final Reference textViewRef = new WeakReference<>(textView);
bgExecutor.submit(() -> {
TextView textView = textViewRef.get();
if (textView == null) return;
final PrecomputedText precomputedText = PrecomputedText.create(longString, params);
textView.post(() -> {
TextView textView = textViewRef.get();
if (textView == null) return;
textView.setText(precomputedText);
});
});
}
Note that the
PrecomputedText
created from different parameters of the target
TextView
will be rejected.
Note that any
NoCopySpan
attached to the original text won't be passed to
PrecomputedText.
Summary
Inherited constants |
From interface
android.text.Spanned
int |
SPAN_COMPOSING
This flag is set on spans that are being used to apply temporary
styling information on the composing text of an input method, so that
they can be found and removed when the composing text is being
replaced.
|
int |
SPAN_EXCLUSIVE_EXCLUSIVE
Spans of type SPAN_EXCLUSIVE_EXCLUSIVE do not expand
to include text inserted at either their starting or ending point.
|
int |
SPAN_EXCLUSIVE_INCLUSIVE
Non-0-length spans of type SPAN_EXCLUSIVE_INCLUSIVE expand
to include text inserted at their ending point but not at their
starting point.
|
int |
SPAN_INCLUSIVE_EXCLUSIVE
Non-0-length spans of type SPAN_INCLUSIVE_EXCLUSIVE expand
to include text inserted at their starting point but not at their
ending point.
|
int |
SPAN_INCLUSIVE_INCLUSIVE
Spans of type SPAN_INCLUSIVE_INCLUSIVE expand
to include text inserted at either their starting or ending point.
|
int |
SPAN_INTERMEDIATE
This flag will be set for intermediate span changes, meaning there
is guaranteed to be another change following it.
|
int |
SPAN_MARK_MARK
0-length spans with type SPAN_MARK_MARK behave like text marks:
they remain at their original offset when text is inserted
at that offset.
|
int |
SPAN_MARK_POINT
SPAN_MARK_POINT is a synonym for SPAN_INCLUSIVE_INCLUSIVE .
|
int |
SPAN_PARAGRAPH
SPAN_PARAGRAPH behaves like SPAN_INCLUSIVE_EXCLUSIVE
(SPAN_MARK_MARK), except that if either end of the span is
at the end of the buffer, that end behaves like _POINT
instead (so SPAN_INCLUSIVE_INCLUSIVE if it starts in the
middle and ends at the end, or SPAN_EXCLUSIVE_INCLUSIVE
if it both starts and ends at the end).
|
int |
SPAN_POINT_MARK
SPAN_POINT_MARK is a synonym for SPAN_EXCLUSIVE_EXCLUSIVE .
|
int |
SPAN_POINT_MARK_MASK
Bitmask of bits that are relevent for controlling point/mark behavior
of spans.
|
int |
SPAN_POINT_POINT
0-length spans with type SPAN_POINT_POINT behave like cursors:
they are pushed forward by the length of the insertion when text
is inserted at their offset.
|
int |
SPAN_PRIORITY
The bits specified by the SPAN_PRIORITY bitmap determine the order
of change notifications -- higher numbers go first.
|
int |
SPAN_PRIORITY_SHIFT
The bits numbered just above SPAN_PRIORITY_SHIFT determine the order
of change notifications -- higher numbers go first.
|
int |
SPAN_USER
The bits specified by the SPAN_USER bitfield are available
for callers to use to store scalar data associated with their
span object.
|
int |
SPAN_USER_SHIFT
The bits numbered SPAN_USER_SHIFT and above are available
for callers to use to store scalar data associated with their
span object.
|
|
Public methods |
char
|
charAt(int index)
Returns the char value at the specified index.
|
static
PrecomputedText
|
create(CharSequence text, PrecomputedText.Params params)
Create a new PrecomputedText which will pre-compute text measurement and glyph
positioning information.
|
void
|
getBounds(int start, int end, Rect bounds)
Retrieves the text bounding box for the given range.
|
void
|
getFontMetricsInt(int start, int end, Paint.FontMetricsInt outMetrics)
Retrieves the text font metrics for the given range.
|
int
|
getParagraphCount()
Returns the count of paragraphs.
|
int
|
getParagraphEnd(int paraIndex)
Returns the paragraph end offset of the text.
|
int
|
getParagraphStart(int paraIndex)
Returns the paragraph start offset of the text.
|
PrecomputedText.Params
|
getParams()
Returns the layout parameters used to measure this text.
|
int
|
getSpanEnd(Object tag)
Return the end of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
|
int
|
getSpanFlags(Object tag)
Return the flags that were specified when Spannable.setSpan was
used to attach the specified markup object, or 0 if the specified
object has not been attached.
|
int
|
getSpanStart(Object tag)
Return the beginning of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
|
<T>
T[]
|
getSpans(int start, int end, Class<T> type)
Return an array of the markup objects attached to the specified
slice of this CharSequence and whose type is the specified type
or a subclass of it.
|
float
|
getWidth(int start, int end)
Returns text width for the given range.
|
int
|
length()
Returns the length of this character sequence.
|
int
|
nextSpanTransition(int start, int limit, Class<T> type)
Return the first offset greater than start where a markup
object of class type begins or ends, or limit
if there are no starts or ends greater than start but less
than limit .
|
void
|
removeSpan(Object what)
Remove the specified object from the range of text to which it
was attached, if any.
|
void
|
setSpan(Object what, int start, int end, int flags)
Attach the specified markup object to the range start…end
of the text, or move the object to that range if it was already
attached elsewhere.
|
CharSequence
|
subSequence(int start, int end)
Returns a CharSequence that is a subsequence of this sequence.
|
String
|
toString()
Returns a string representation of the object.
|
Inherited methods |
From class
java.lang.Object
Object
|
clone()
Creates and returns a copy of this object.
|
boolean
|
equals(Object obj)
Indicates whether some other object is "equal to" this one.
|
void
|
finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
|
final
Class<?>
|
getClass()
Returns the runtime class of this Object .
|
int
|
hashCode()
Returns a hash code value for the object.
|
final
void
|
notify()
Wakes up a single thread that is waiting on this object's
monitor.
|
final
void
|
notifyAll()
Wakes up all threads that are waiting on this object's monitor.
|
String
|
toString()
Returns a string representation of the object.
|
final
void
|
wait(long timeoutMillis, int nanos)
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted, or until a
certain amount of real time has elapsed.
|
final
void
|
wait(long timeoutMillis)
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted, or until a
certain amount of real time has elapsed.
|
final
void
|
wait()
Causes the current thread to wait until it is awakened, typically
by being notified or interrupted.
|
|
From interface
android.text.Spannable
abstract
void
|
removeSpan(Object what)
Remove the specified object from the range of text to which it
was attached, if any.
|
abstract
void
|
setSpan(Object what, int start, int end, int flags)
Attach the specified markup object to the range start…end
of the text, or move the object to that range if it was already
attached elsewhere.
|
|
From interface
android.text.Spanned
abstract
int
|
getSpanEnd(Object tag)
Return the end of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
|
abstract
int
|
getSpanFlags(Object tag)
Return the flags that were specified when Spannable.setSpan was
used to attach the specified markup object, or 0 if the specified
object has not been attached.
|
abstract
int
|
getSpanStart(Object tag)
Return the beginning of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
|
abstract
<T>
T[]
|
getSpans(int start, int end, Class<T> type)
Return an array of the markup objects attached to the specified
slice of this CharSequence and whose type is the specified type
or a subclass of it.
|
abstract
int
|
nextSpanTransition(int start, int limit, Class<T> type)
Return the first offset greater than start where a markup
object of class type begins or ends, or limit
if there are no starts or ends greater than start but less
than limit .
|
|
From interface
java.lang.CharSequence
abstract
char
|
charAt(int index)
Returns the char value at the specified index.
|
default
IntStream
|
chars()
Returns a stream of int zero-extending the char values
from this sequence.
|
default
IntStream
|
codePoints()
Returns a stream of code point values from this sequence.
|
static
int
|
compare(CharSequence cs1, CharSequence cs2)
Compares two CharSequence instances lexicographically.
|
default
boolean
|
isEmpty()
Returns true if this character sequence is empty.
|
abstract
int
|
length()
Returns the length of this character sequence.
|
abstract
CharSequence
|
subSequence(int start, int end)
Returns a CharSequence that is a subsequence of this sequence.
|
abstract
String
|
toString()
Returns a string containing the characters in this sequence in the same
order as this sequence.
|
|
Public methods
charAt
public char charAt (int index)
Returns the char
value at the specified index. An index ranges from zero
to length() - 1
. The first char
value of the sequence is at
index zero, the next at index one, and so on, as for array
indexing.
If the char
value specified by the index is a
surrogate, the surrogate
value is returned.
Parameters |
index |
int : the index of the char value to be returned |
Returns |
char |
the specified char value |
create
public static PrecomputedText create (CharSequence text,
PrecomputedText.Params params)
Create a new PrecomputedText
which will pre-compute text measurement and glyph
positioning information.
This can be expensive, so computing this on a background thread before your text will be
presented can save work on the UI thread.
Note that any
NoCopySpan
attached to the text won't be passed to the
created PrecomputedText.
Parameters |
text |
CharSequence : the text to be measured
This value cannot be null . |
params |
PrecomputedText.Params : parameters that define how text will be precomputed
This value cannot be null . |
getBounds
public void getBounds (int start,
int end,
Rect bounds)
Retrieves the text bounding box for the given range.
Both start
and end
offset need to be in the same paragraph, otherwise
IllegalArgumentException will be thrown.
Parameters |
start |
int : the inclusive start offset in the text
Value is 0 or greater |
end |
int : the exclusive end offset in the text
Value is 0 or greater |
bounds |
Rect : the output rectangle
This value cannot be null . |
getFontMetricsInt
public void getFontMetricsInt (int start,
int end,
Paint.FontMetricsInt outMetrics)
Retrieves the text font metrics for the given range.
Both start
and end
offset need to be in the same paragraph, otherwise
IllegalArgumentException will be thrown.
Parameters |
start |
int : the inclusive start offset in the text
Value is 0 or greater |
end |
int : the exclusive end offset in the text
Value is 0 or greater |
outMetrics |
Paint.FontMetricsInt : the output font metrics
This value cannot be null . |
getParagraphCount
public int getParagraphCount ()
Returns the count of paragraphs.
Returns |
int |
Value is 0 or greater |
getParagraphEnd
public int getParagraphEnd (int paraIndex)
Returns the paragraph end offset of the text.
Parameters |
paraIndex |
int : Value is 0 or greater |
Returns |
int |
Value is 0 or greater |
getParagraphStart
public int getParagraphStart (int paraIndex)
Returns the paragraph start offset of the text.
Parameters |
paraIndex |
int : Value is 0 or greater |
Returns |
int |
Value is 0 or greater |
getSpanEnd
public int getSpanEnd (Object tag)
Return the end of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
getSpanFlags
public int getSpanFlags (Object tag)
Return the flags that were specified when Spannable.setSpan
was
used to attach the specified markup object, or 0 if the specified
object has not been attached.
getSpanStart
public int getSpanStart (Object tag)
Return the beginning of the range of text to which the specified
markup object is attached, or -1 if the object is not attached.
getSpans
public T[] getSpans (int start,
int end,
Class<T> type)
Return an array of the markup objects attached to the specified
slice of this CharSequence and whose type is the specified type
or a subclass of it. Specify Object.class for the type if you
want all the objects regardless of type.
Parameters |
start |
int |
end |
int |
type |
Class |
getWidth
public float getWidth (int start,
int end)
Returns text width for the given range.
Both start
and end
offset need to be in the same paragraph, otherwise
IllegalArgumentException will be thrown.
Parameters |
start |
int : the inclusive start offset in the text
Value is 0 or greater |
end |
int : the exclusive end offset in the text
Value is 0 or greater |
Returns |
float |
the text width
Value is 0 or greater |
length
public int length ()
Returns the length of this character sequence. The length is the number
of 16-bit char
s in the sequence.
Returns |
int |
the number of char s in this sequence |
nextSpanTransition
public int nextSpanTransition (int start,
int limit,
Class<T> type)
Return the first offset greater than start
where a markup
object of class type
begins or ends, or limit
if there are no starts or ends greater than start
but less
than limit
. Specify null
or Object.class for
the type if you want every transition regardless of type.
Parameters |
start |
int |
limit |
int |
type |
Class |
removeSpan
public void removeSpan (Object what)
Remove the specified object from the range of text to which it
was attached, if any. It is OK to remove an object that was never
attached in the first place.
setSpan
public void setSpan (Object what,
int start,
int end,
int flags)
Attach the specified markup object to the range start…end
of the text, or move the object to that range if it was already
attached elsewhere. See Spanned
for an explanation of
what the flags mean. The object can be one that has meaning only
within your application, or it can be one that the text system will
use to affect text display or behavior. Some noteworthy ones are
the subclasses of CharacterStyle
and
ParagraphStyle
, and
TextWatcher
and
SpanWatcher
.
Parameters |
what |
Object |
start |
int |
end |
int |
flags |
int |
subSequence
public CharSequence subSequence (int start,
int end)
Returns a CharSequence
that is a subsequence of this sequence.
The subsequence starts with the char
value at the specified index and
ends with the char
value at index end - 1
. The length
(in char
s) of the
returned sequence is end - start
, so if start == end
then an empty sequence is returned.
Parameters |
start |
int : the start index, inclusive |
end |
int : the end index, exclusive |
toString
public String toString ()
Returns a string representation of the object.
Returns |
String |
a string representation of the object. |