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public interface Line
The Line
interface represents a mono or multi-channel
audio feed. A line is an element of the digital audio
"pipeline," such as a mixer, an input or output port,
or a data path into or out of a mixer.
A line can have controls, such as gain, pan, and reverb.
The controls themselves are instances of classes that extend the
base {@link Control}
class.
The Line
interface provides two accessor methods for
obtaining the line's controls: {@link #getControls getControls}
returns the
entire set, and {@link #getControl getControl}
returns a single control of
specified type.
Lines exist in various states at different times. When a line opens, it reserves system
resources for itself, and when it closes, these resources are freed for
other objects or applications. The {@link #isOpen()}
method lets
you discover whether a line is open or closed.
An open line need not be processing data, however. Such processing is
typically initiated by subinterface methods such as
{@link SourceDataLine#write SourceDataLine.write}
and
{@link TargetDataLine#read TargetDataLine.read}
.
You can register an object to receive notifications whenever the line's
state changes. The object must implement the {@link LineListener}
interface, which consists of the single method
{@link LineListener#update update}
.
This method will be invoked when a line opens and closes (and, if it's a
{@link DataLine}, when it starts and stops).
An object can be registered to listen to multiple lines. The event it
receives in its update
method will specify which line created
the event, what type of event it was
(OPEN
, CLOSE
, START
, or STOP
),
and how many sample frames the line had processed at the time the event occurred.
Certain line operations, such as open and close, can generate security exceptions if invoked by unprivileged code when the line is a shared audio resource.
Nested Class Summary | |
---|---|
static class |
A Line.Info object contains information about a line. |
Method Summary | |
---|---|
void |
addLineListener(LineListener listener) Adds a listener to this line. |
void |
close() Closes the line, indicating that any system resources in use by the line can be released. |
Control |
getControl(Control.Type control) Obtains a control of the specified type, if there is any. |
Control[] |
Obtains the set of controls associated with this line. |
Line.Info |
Obtains the Line.Info object describing this
line.
|
boolean |
isControlSupported(Control.Type control) Indicates whether the line supports a control of the specified type. |
boolean |
isOpen() Indicates whether the line is open, meaning that it has reserved system resources and is operational, although it might not currently be playing or capturing sound. |
void |
open() Opens the line, indicating that it should acquire any required system resources and become operational. |
void |
removeLineListener(LineListener listener) Removes the specified listener from this line's list of listeners. |
Method Detail |
---|
public void addLineListener(LineListener listener)
update()
method is called with a LineEvent
object
that describes the change.
listener
- the object to add as a listener to this linepublic void close()
CLOSE
event is dispatched
to the line's listeners.
public Control getControl(Control.Type control)
control
- the type of the requested controlpublic Control[] getControls()
public Line.Info getLineInfo()
Line.Info
object describing this
line.
public boolean isControlSupported(Control.Type control)
control
- the type of the control for which support is queriedtrue
if at least one control of the specified type is
supported, otherwise false
.public boolean isOpen()
true
if the line is open, otherwise false
public void open() throws LineUnavailableException
OPEN
event is dispatched
to the line's listeners.
Note that some lines, once closed, cannot be reopened. Attempts
to reopen such a line will always result in an LineUnavailableException
.
Some types of lines have configurable properties that may affect
resource allocation. For example, a DataLine
must
be opened with a particular format and buffer size. Such lines
should provide a mechanism for configuring these properties, such
as an additional open
method or methods which allow
an application to specify the desired settings.
This method takes no arguments, and opens the line with the current
settings. For {@link SourceDataLine}
and
{@link TargetDataLine}
objects, this means that the line is
opened with default settings. For a {@link Clip}
, however,
the buffer size is determined when data is loaded. Since this method does not
allow the application to specify any data to load, an IllegalArgumentException
is thrown. Therefore, you should instead use one of the open
methods
provided in the Clip
interface to load data into the Clip
.
For DataLine
's, if the DataLine.Info
object which was used to retrieve the line, specifies at least
one fully qualified audio format, the last one will be used
as the default format.
LineUnavailableException
- if the line cannot be
opened due to resource restrictions.public void removeLineListener(LineListener listener)
listener
- listener to remove
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