File Doc Category Size Date Package
Player.java API Doc J2ME MIDP 2.0 24237 Thu Nov 07 12:02:30 GMT 2002 javax.microedition.media

Player

public interface Player implements Controllable

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.

Simple Playback

A Player can be created from one of the Manager's createPlayer methods. After the Player is created, calling start 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.

Player Life Cycle

A Player 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, the Player performs the communication necessary to locate all of the resources it needs to function (such as communicating with a server or a file system). The realize 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 the stop method is invoked. When that happens, the Player 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 the Player's state transition methods.

Player States

This section describes the semantics of each of the Player states.
UNREALIZED State

A Player starts in the UNREALIZED state. An unrealized Player 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.

getContentType
setMediaTime
getControls
getControl
An IllegalStateException will be thrown.
The realize method transitions the Player from the UNREALIZED state to the REALIZED state.

REALIZED State

A Player is in the REALIZED state when it has obtained the information required to acquire the media resources. Realizing a Player can be a resource and time consuming process. The Player 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. After realize has been invoked on a Player, the only way it can return to the UNREALIZED state is if deallocate is invoked before realize is completed. Once a Player 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, a Player 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. Calling prefetch on the Player carries out these tasks.
Once a Player is in the PREFETCHED state, it may be started. Prefetching reduces the startup latency of a Player to the minimum possible value.
When a started Player stops, it returns to the PREFETCHED state.

STARTED State

Once prefetched, a Player can enter the STARTED state by calling the start method. A STARTED Player means the Player is running and processing data. A Player returns to the PREFETCHED state when it stops, because the stop 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 a STARTED event. When it moves from the STARTED state to the PREFETCHED state, it posts a STOPPED, 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:

setLoopCount
An IllegalStateException will be thrown.

CLOSED state

Calling close on the Player puts it in the CLOSED state. In the CLOSED state, the Player has released most of its resources and must not be used again.
The Player's five states and the state transition methods are summarized in the following diagram:

Player Events

Player events asynchronously deliver information about the Player's state changes and other relevant information from the Player's Controls.
To receive events, an object must implement the PlayerListener interface and use the addPlayerListener method to register its interest in a Player's events. All Player 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, the STARTED event must always preceed the END_OF_MEDIA event.
An ERROR event may be sent any time an irrecoverable error has occured. When that happens, the Player is in the CLOSED state.
The Player event mechanism is extensible and some Players define events other than the ones described here. For a list of pre-defined player events, check the PlayerListener interface.

Managing the Resources Used by a Player

The prefetch method is used to acquire scarce or exclusive resources such as the audio device. Conversely, the deallocate method is used to release the scarce or exclusive resources. By using these two methods, an application can programmatically manage the Player's resources.
For example, in an implementation with an exclusive audio device, to alternate the audio playback of multiple Players, an application can selectively deallocate and prefetch individual Players.

Player's Controls

Player implements Controllable which provides extra controls via some type-specific Control interfaces. getControl and getControls cannot be called when the Player is in the UNREALIZED or CLOSED state. An IllegalStateException will be thrown.

Simple Playback Example

try {
Player p = Manager.createPlayer("http://abc.wav");
p.start();
} catch (MediaException pe) {
} catch (IOException ioe) {
}

Fields Summary
int
UNREALIZED
The state of the Player indicating that it has not acquired the required information and resources to function.
Value 100 is assigned to UNREALIZED.
int
REALIZED
The state of the Player indicating that it has acquired the required information but not the resources to function.
Value 200 is assigned to REALIZED.
int
PREFETCHED
The state of the Player indicating that it has acquired all the resources to begin playing.
Value 300 is assigned to PREFETCHED.
int
STARTED
The state of the Player indicating that the Player has already started.
Value 400 is assigned to STARTED.
int
CLOSED
The state of the Player indicating that the Player is closed.
Value 0 is assigned to CLOSED.
long
TIME_UNKNOWN
The returned value indicating that the requested time is unknown.
Value -1 is assigned to TIME_UNKNOWN.
Constructors Summary
Methods Summary
public void addPlayerListener(PlayerListener playerListener)
Add a player listener for this player.
param
playerListener the listener to add. If null is used, the request will be ignored.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
see
#removePlayerListener
public void close()
Close the 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 PlayerListeners.
If close is called on a closed Player the request is ignored.
public void deallocate()
Release the scarce or exclusive resources like the audio device acquired by the 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.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
public java.lang.String getContentType()
Get the content type of the media that's being played back by this Player.
See content type for the syntax of the content type returned.
return
The content type being played back by this Player.
exception
IllegalStateException Thrown if the Player is in the UNREALIZED or CLOSED state.
public long getDuration()
Get the duration of the media. The value returned is the media's duration when played at the default rate.
If the duration cannot be determined (for example, the Player is presenting live media) getDuration returns TIME_UNKNOWN.
return
The duration in microseconds or TIME_UNKNOWN.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
public long getMediaTime()
Gets this Player's current media time. If the media time cannot be determined, getMediaTime returns TIME_UNKNOWN.
return
The current media time in microseconds or TIME_UNKNOWN.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
see
#setMediaTime
public int getState()
Gets the current state of this Player. The possible states are: UNREALIZED, REALIZED, PREFETCHED, STARTED, CLOSED.
return
The Player's current state.
public void prefetch()
Acquires the scarce and exclusive resources and processes as much data as necessary to reduce the start latency.
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.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
exception
MediaException Thrown if the Player cannot be prefetched.
exception
SecurityException Thrown if the caller does not have security permission to prefetch the Player.
public void realize()
Constructs portions of the 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.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
exception
MediaException Thrown if the Player cannot be realized.
exception
SecurityException Thrown if the caller does not have security permission to realize the Player.
public void removePlayerListener(PlayerListener playerListener)
Remove a player listener for this player.
param
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.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
see
#addPlayerListener
public void setLoopCount(int count)
Set the number of times the 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.
param
count indicates the number of times the content will be played. 1 is the default. 0 is invalid. -1 indicates looping indefintely.
exception
IllegalArgumentException Thrown if the given count is invalid.
exception
IllegalStateException Thrown if the Player is in the STARTED or CLOSED state.
public long setMediaTime(long now)
Sets the 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.
param
now The new media time in microseconds.
return
The actual media time set in microseconds.
exception
IllegalStateException Thrown if the Player is in the UNREALIZED or CLOSED state.
exception
MediaException Thrown if the media time cannot be set.
see
#getMediaTime
public void start()
Starts the 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 PlayerListeners. 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.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
exception
MediaException Thrown if the Player cannot be started.
exception
SecurityException Thrown if the caller does not have security permission to start the Player.
public void stop()
Stops the 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 PlayerListeners.
If stop is called on a stopped Player, the request is ignored.
exception
IllegalStateException Thrown if the Player is in the CLOSED state.
exception
MediaException Thrown if the Player cannot be stopped.