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SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
Player
controls the rendering of time based media data.
It provides the methods to manage the Player
's life
cycle, controls the playback progress and obtains the presentation
components.
APlayer
can be created from one of theManager
'screatePlayer
methods. After thePlayer
is created, callingstart
will start the playback as soon as possible. The method will return when the playback is started. The playback will continue in the background and will stop automatically when the end of media is reached.Simple playback example illustrates this.
APlayer
has five states: UNREALIZED, REALIZED, PREFETCHED, STARTED, CLOSED.The purpose of these life-cycle states is to provide programmatic control over potentially time-consuming operations. For example, when a
Player
is first constructed, it's in the UNREALIZED state. Transitioned from UNREALIZED to REALIZED, thePlayer
performs the communication necessary to locate all of the resources it needs to function (such as communicating with a server or a file system). Therealize
method allows an application to initiate this potentially time-consuming process at an appropriate time.Typically, a
Player
moves from the UNREALIZED state to the REALIZED state, then to the PREFETCHED state, and finally on to the STARTED state.A
Player
stops when it reaches the end of media; or when thestop
method is invoked. When that happens, thePlayer
moves from the STARTED state back to the PREFETCHED state. It is then ready to repeat the cycle.To use a
Player
, you must set up parameters to manage its movement through these life-cycle states and then move it through the states using thePlayer
's state transition methods.
This section describes the semantics of each of thePlayer
states.UNREALIZED State
APlayer
starts in the UNREALIZED state. An unrealizedPlayer
does not have enough information to acquire all the resources it needs to function.The following methods must not be used when the
Player
is in the UNREALIZED state.An
getContentType
setMediaTime
getControls
getControl
IllegalStateException
will be thrown.The
realize
method transitions thePlayer
from the UNREALIZED state to the REALIZED state.REALIZED State
APlayer
is in the REALIZED state when it has obtained the information required to acquire the media resources. Realizing aPlayer
can be a resource and time consuming process. ThePlayer
may have to communicate with a server, read a file, or interact with a set of objects.Although a realized
Player
does not have to acquire any resources, it is likely to have acquired all of the resources it needs except those that imply exclusive use of a scarce system resource, such as an audio device.Normally, a
Player
moves from the UNREALIZED state to the REALIZED state. Afterrealize
has been invoked on aPlayer
, the only way it can return to the UNREALIZED state is ifdeallocate
is invoked beforerealize
is completed. Once aPlayer
reaches the REALIZED state, it never returns to the UNREALIZED state. It remains in one of four states: REALIZED, PREFETCHED, STARTED or CLOSED.PREFETCHED State
Once realized, aPlayer
may still need to perform a number of time-consuming tasks before it is ready to be started. For example, it may need to acquire scarce or exclusive resources, fill buffers with media data, or perform other start-up processing. Callingprefetch
on thePlayer
carries out these tasks.Once a
Player
is in the PREFETCHED state, it may be started. Prefetching reduces the startup latency of aPlayer
to the minimum possible value.When a started
Player
stops, it returns to the PREFETCHED state.STARTED State
Once prefetched, aPlayer
can enter the STARTED state by calling thestart
method. A STARTEDPlayer
means thePlayer
is running and processing data. APlayer
returns to the PREFETCHED state when it stops, because thestop
method was invoked, or it has reached the end of the media.When the
Player
moves from the PREFETCHED to the STARTED state, it posts aSTARTED
event. When it moves from the STARTED state to the PREFETCHED state, it posts aSTOPPED
,END_OF_MEDIA
event depending on the reason it stopped.The following method must not be used when the
Player
is in the STARTED state:An
setLoopCount
IllegalStateException
will be thrown.CLOSED state
CallingTheclose
on thePlayer
puts it in the CLOSED state. In the CLOSED state, thePlayer
has released most of its resources and must not be used again.Player
's five states and the state transition methods are summarized in the following diagram:
Player
events asynchronously deliver information about thePlayer
's state changes and other relevant information from thePlayer
'sControl
s.To receive events, an object must implement the
PlayerListener
interface and use theaddPlayerListener
method to register its interest in aPlayer
's events. AllPlayer
events are posted to each registered listener.The events are guaranteed to be delivered in the order that the actions representing the events occur. For example, if a
Player
stops shortly after it starts because it is playing back a very short media file, theSTARTED
event must always preceed theEND_OF_MEDIA
event.An
ERROR
event may be sent any time an irrecoverable error has occured. When that happens, thePlayer
is in the CLOSED state.The
Player
event mechanism is extensible and somePlayers
define events other than the ones described here. For a list of pre-defined player events, check thePlayerListener
interface.
Theprefetch
method is used to acquire scarce or exclusive resources such as the audio device. Conversely, thedeallocate
method is used to release the scarce or exclusive resources. By using these two methods, an application can programmatically manage thePlayer
's resources.For example, in an implementation with an exclusive audio device, to alternate the audio playback of multiple
Player
s, an application can selectively deallocate and prefetch individualPlayer
s.
Player
implementsControllable
which provides extra controls via some type-specificControl
interfaces.getControl
andgetControls
cannot be called when thePlayer
is in the UNREALIZED or CLOSED state. AnIllegalStateException
will be thrown.
try { Player p = Manager.createPlayer("http://abc.wav"); p.start(); } catch (MediaException pe) { } catch (IOException ioe) { }
Field Summary | |
static int |
CLOSED
The state of the Player indicating that the
Player is closed. |
static int |
PREFETCHED
The state of the Player indicating that it has
acquired all the resources to begin playing. |
static int |
REALIZED
The state of the Player indicating that it has
acquired the required information but not the resources to function. |
static int |
STARTED
The state of the Player indicating that the
Player has already started. |
static long |
TIME_UNKNOWN
The returned value indicating that the requested time is unknown. |
static int |
UNREALIZED
The state of the Player indicating that it has
not acquired the required information and resources to function. |
Method Summary | |
void |
addPlayerListener(PlayerListener playerListener)
Add a player listener for this player. |
void |
close()
Close the Player and release its resources. |
void |
deallocate()
Release the scarce or exclusive resources like the audio device acquired by the Player . |
String |
getContentType()
Get the content type of the media that's being played back by this Player . |
long |
getDuration()
Get the duration of the media. |
long |
getMediaTime()
Gets this Player 's current media time. |
int |
getState()
Gets the current state of this Player . |
void |
prefetch()
Acquires the scarce and exclusive resources and processes as much data as necessary to reduce the start latency. |
void |
realize()
Constructs portions of the Player without
acquiring the scarce and exclusive resources. |
void |
removePlayerListener(PlayerListener playerListener)
Remove a player listener for this player. |
void |
setLoopCount(int count)
Set the number of times the Player will loop
and play the content. |
long |
setMediaTime(long now)
Sets the Player 's media time. |
void |
start()
Starts the Player as soon as possible. |
void |
stop()
Stops the Player . |
Methods inherited from interface javax.microedition.media.Controllable |
getControl, getControls |
Field Detail |
public static final int UNREALIZED
Player
indicating that it has
not acquired the required information and resources to function.
Value 100 is assigned to UNREALIZED
.
public static final int REALIZED
Player
indicating that it has
acquired the required information but not the resources to function.
Value 200 is assigned to REALIZED
.
public static final int PREFETCHED
Player
indicating that it has
acquired all the resources to begin playing.
Value 300 is assigned to PREFETCHED
.
public static final int STARTED
Player
indicating that the
Player
has already started.
Value 400 is assigned to STARTED
.
public static final int CLOSED
Player
indicating that the
Player
is closed.
Value 0 is assigned to CLOSED
.
public static final long TIME_UNKNOWN
Value -1 is assigned to TIME_UNKNOWN
.
Method Detail |
public void realize() throws MediaException
Player
without
acquiring the scarce and exclusive resources.
This may include examining media data and may
take some time to complete.
When realize
completes successfully,
the Player
is in the
REALIZED state.
If realize
is called when the Player
is in
the REALIZED, PREFETCHTED or STARTED state,
the request will be ignored.
IllegalStateException
- Thrown if the Player
is in the CLOSED state.MediaException
- Thrown if the Player
cannot
be realized.SecurityException
- Thrown if the caller does not
have security permission to realize the Player
.public void prefetch() throws MediaException
When prefetch
completes successfully,
the Player
is in
the PREFETCHED state.
If prefetch
is called when the Player
is in the UNREALIZED state,
it will implicitly call realize
.
If prefetch
is called when the Player
is already in the PREFETCHED state, the Player
may still process data necessary to reduce the start
latency. This is to guarantee that start latency can
be maintained at a minimum.
If prefetch
is called when the Player
is in the STARTED state,
the request will be ignored.
If the Player
cannot obtain all
of the resources it needs, it throws a MediaException
.
When that happens, the Player
will not be able to
start. However, prefetch
may be called again when
the needed resource is later released perhaps by another
Player
or application.
IllegalStateException
- Thrown if the Player
is in the CLOSED state.MediaException
- Thrown if the Player
cannot
be prefetched.SecurityException
- Thrown if the caller does not
have security permission to prefetch the Player
.public void start() throws MediaException
Player
as soon as possible.
If the Player
was previously stopped
by calling stop
,
it will resume playback
from where it was previously stopped. If the
Player
has reached the end of media,
calling start
will automatically
start the playback from the start of the media.
When start
returns successfully,
the Player
must have been started and
a STARTED
event will
be delivered to the registered PlayerListener
s.
However, the Player
is not guaranteed to be in
the STARTED state. The Player
may have
already stopped (in the PREFETCHED state) because
the media has 0 or a very short duration.
If start
is called when the Player
is in the UNREALIZED or REALIZED state,
it will implicitly call prefetch
.
If start
is called when the Player
is in the STARTED state,
the request will be ignored.
IllegalStateException
- Thrown if the Player
is in the CLOSED state.MediaException
- Thrown if the Player
cannot
be started.SecurityException
- Thrown if the caller does not
have security permission to start the Player
.public void stop() throws MediaException
Player
. It will pause the playback at
the current media time.
When stop
returns, the Player
is in the
PREFETCHED state.
A STOPPED
event will be delivered to the registered
PlayerListener
s.
If stop
is called on
a stopped Player
, the request is ignored.
IllegalStateException
- Thrown if the Player
is in the CLOSED state.MediaException
- Thrown if the Player
cannot be stopped.public void deallocate()
Player
.
When deallocate
returns, the Player
is in the UNREALIZED or REALIZED state.
If the Player
is blocked at
the realize
call while realizing, calling
deallocate
unblocks the realize
call and
returns the Player
to the UNREALIZED state.
Otherwise, calling deallocate
returns the
Player
to the REALIZED state.
If deallocate
is called when the Player
is in the UNREALIZED or REALIZED
state, the request is ignored.
If the Player
is STARTED
when deallocate
is called, deallocate
will implicitly call stop
on the Player
.
IllegalStateException
- Thrown if the Player
is in the CLOSED state.public void close()
Player
and release its resources.
When the method returns, the Player
is in the
CLOSED state and can no longer be used.
A CLOSED
event will be delivered to the registered
PlayerListener
s.
If close
is called on a closed Player
the request is ignored.
public long setMediaTime(long now) throws MediaException
Player
's media time.
For some media types, setting the media time may not be very accurate. The returned value will indicate the actual media time set.
Setting the media time to negative values will effectively set the media time to zero. Setting the media time to beyond the duration of the media will set the time to the end of media.
There are some media types that cannot support the setting
of media time. Calling setMediaTime
will throw
a MediaException
in those cases.
now
- The new media time in microseconds.IllegalStateException
- Thrown if the Player
is in the UNREALIZED or CLOSED state.MediaException
- Thrown if the media time
cannot be set.getMediaTime()
public long getMediaTime()
Player
's current media time.
If the media time cannot be determined,
getMediaTime
returns TIME_UNKNOWN
.TIME_UNKNOWN
.IllegalStateException
- Thrown if the Player
is in the CLOSED state.setMediaTime(long)
public int getState()
Player
.
The possible states are: UNREALIZED,
REALIZED, PREFETCHED, STARTED, CLOSED.Player
's current state.public long getDuration()
Player
is presenting live
media) getDuration
returns TIME_UNKNOWN
.TIME_UNKNOWN
.IllegalStateException
- Thrown if the Player
is in the CLOSED state.public String getContentType()
Player
.
See content type for the syntax of the content type returned.
Player
.IllegalStateException
- Thrown if the Player
is in the UNREALIZED or CLOSED state.public void setLoopCount(int count)
Player
will loop
and play the content.
By default, the loop count is one. That is, once started,
the Player
will start playing from the current
media time to the end of media once.
If the loop count is set to N where N is bigger than one,
starting the Player
will start playing the
content from the current media time to the end of media.
It will then loop back to the beginning of the content
(media time zero) and play till the end of the media.
The number of times it will loop to the beginning and
play to the end of media will be N-1.
Setting the loop count to 0 is invalid. An
IllegalArgumentException
will be thrown.
Setting the loop count to -1 will loop and play the content indefinitely.
If the Player
is stopped before the preset loop
count is reached either because stop
is called,
calling start
again will
resume the looping playback from where it was stopped until it
fully reaches the preset loop count.
An END_OF_MEDIA event will be posted
every time the Player
reaches the end of media.
If the Player
loops back to the beginning and
starts playing again because it has not completed the loop
count, a STARTED event will be posted.
count
- indicates the number of times the content will be
played. 1 is the default. 0 is invalid. -1 indicates looping
indefintely.IllegalArgumentException
- Thrown if the given
count is invalid.IllegalStateException
- Thrown if the
Player
is in the STARTED
or CLOSED state.public void addPlayerListener(PlayerListener playerListener)
playerListener
- the listener to add.
If null
is used, the request will be ignored.IllegalStateException
- Thrown if the Player
is in the CLOSED state.removePlayerListener(javax.microedition.media.PlayerListener)
public void removePlayerListener(PlayerListener playerListener)
playerListener
- the listener to remove.
If null
is used or the given
playerListener
is not a listener for this
Player
, the request will be ignored.IllegalStateException
- Thrown if the Player
is in the CLOSED state.addPlayerListener(javax.microedition.media.PlayerListener)
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SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |