public
class
SoundPool
extends Object
| java.lang.Object | |
| ↳ | android.media.SoundPool |
The SoundPool class manages and plays audio resources for applications.
A SoundPool is a collection of samples that can be loaded into memory from a resource inside the APK or from a file in the file system. The SoundPool library uses the MediaPlayer service to decode the audio into a raw 16-bit PCM mono or stereo stream. This allows applications to ship with compressed streams without having to suffer the CPU load and latency of decompressing during playback.
In addition to low-latency playback, SoundPool can also manage the number of audio streams being rendered at once. When the SoundPool object is constructed, the maxStreams parameter sets the maximum number of streams that can be played at a time from this single SoundPool. SoundPool tracks the number of active streams. If the maximum number of streams is exceeded, SoundPool will automatically stop a previously playing stream based first on priority and then by age within that priority. Limiting the maximum number of streams helps to cap CPU loading and reducing the likelihood that audio mixing will impact visuals or UI performance.
Sounds can be looped by setting a non-zero loop value. A value of -1 causes the sound to loop forever. In this case, the application must explicitly call the stop() function to stop the sound. Any other non-zero value will cause the sound to repeat the specified number of times, e.g. a value of 3 causes the sound to play a total of 4 times.
The playback rate can also be changed. A playback rate of 1.0 causes the sound to play at its original frequency (resampled, if necessary, to the hardware output frequency). A playback rate of 2.0 causes the sound to play at twice its original frequency, and a playback rate of 0.5 causes it to play at half its original frequency. The playback rate range is 0.5 to 2.0.
Priority runs low to high, i.e. higher numbers are higher priority. Priority is used when a call to play() would cause the number of active streams to exceed the value established by the maxStreams parameter when the SoundPool was created. In this case, the stream allocator will stop the lowest priority stream. If there are multiple streams with the same low priority, it will choose the oldest stream to stop. In the case where the priority of the new stream is lower than all the active streams, the new sound will not play and the play() function will return a streamID of zero.
Let's examine a typical use case: A game consists of several levels of play. For each level, there is a set of unique sounds that are used only by that level. In this case, the game logic should create a new SoundPool object when the first level is loaded. The level data itself might contain the list of sounds to be used by this level. The loading logic iterates through the list of sounds calling the appropriate SoundPool.load() function. This should typically be done early in the process to allow time for decompressing the audio to raw PCM format before they are needed for playback.
Once the sounds are loaded and play has started, the application can trigger sounds by calling SoundPool.play(). Playing streams can be paused or resumed, and the application can also alter the pitch by adjusting the playback rate in real-time for doppler or synthesis effects.
Note that since streams can be stopped due to resource constraints, the streamID is a reference to a particular instance of a stream. If the stream is stopped to allow a higher priority stream to play, the stream is no longer be valid. However, the application is allowed to call methods on the streamID without error. This may help simplify program logic since the application need not concern itself with the stream lifecycle.
In our example, when the player has completed the level, the game logic should call SoundPool.release() to release all the native resources in use and then set the SoundPool reference to null. If the player starts another level, a new SoundPool is created, sounds are loaded, and play resumes.
Nested classes | |
|---|---|
class |
SoundPool.Builder
Builder class for |
interface |
SoundPool.OnLoadCompleteListener
|
Public constructors | |
|---|---|
SoundPool(int maxStreams, int streamType, int srcQuality)
This constructor was deprecated
in API level 21.
use |
|
Public methods | |
|---|---|
final
void
|
autoPause()
Pause all active streams. |
final
void
|
autoResume()
Resume all previously active streams. |
int
|
load(Context context, int resId, int priority)
Load the sound from the specified APK resource. |
int
|
load(String path, int priority)
Load the sound from the specified path. |
int
|
load(AssetFileDescriptor afd, int priority)
Load the sound from an asset file descriptor. |
int
|
load(FileDescriptor fd, long offset, long length, int priority)
Load the sound from a FileDescriptor. |
final
void
|
pause(int streamID)
Pause a playback stream. |
final
int
|
play(int soundID, float leftVolume, float rightVolume, int priority, int loop, float rate)
Play a sound from a sound ID. |
final
void
|
release()
Release the SoundPool resources. |
final
void
|
resume(int streamID)
Resume a playback stream. |
final
void
|
setLoop(int streamID, int loop)
Set loop mode. |
void
|
setOnLoadCompleteListener(SoundPool.OnLoadCompleteListener listener)
Sets the callback hook for the OnLoadCompleteListener. |
final
void
|
setPriority(int streamID, int priority)
Change stream priority. |
final
void
|
setRate(int streamID, float rate)
Change playback rate. |
final
void
|
setVolume(int streamID, float leftVolume, float rightVolume)
Set stream volume. |
final
void
|
stop(int streamID)
Stop a playback stream. |
final
boolean
|
unload(int soundID)
Unload a sound from a sound ID. |
Protected methods | |
|---|---|
void
|
finalize()
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
Developers
SoundPool (int maxStreams,
int streamType,
int srcQuality)
This constructor was deprecated
in API level 21.
use SoundPool.Builder instead to create and configure a
SoundPool instance
Constructor. Constructs a SoundPool object with the following characteristics:
| Parameters | |
|---|---|
maxStreams |
int:
the maximum number of simultaneous streams for this
SoundPool object |
streamType |
int:
the audio stream type as described in AudioManager
For example, game applications will normally use
STREAM_MUSIC. |
srcQuality |
int:
the sample-rate converter quality. Currently has no
effect. Use 0 for the default. |
| Returns | |
|---|---|
|
a SoundPool object, or null if creation failed |
void autoPause ()
Pause all active streams. Pause all streams that are currently playing. This function iterates through all the active streams and pauses any that are playing. It also sets a flag so that any streams that are playing can be resumed by calling autoResume().
void autoResume ()
Resume all previously active streams. Automatically resumes all streams that were paused in previous calls to autoPause().
int load (Context context, int resId, int priority)
Load the sound from the specified APK resource. Note that the extension is dropped. For example, if you want to load a sound from the raw resource file "explosion.mp3", you would specify "R.raw.explosion" as the resource ID. Note that this means you cannot have both an "explosion.wav" and an "explosion.mp3" in the res/raw directory.
| Parameters | |
|---|---|
context |
Context:
the application context |
resId |
int:
the resource ID |
priority |
int:
the priority of the sound. Currently has no effect. Use
a value of 1 for future compatibility. |
| Returns | |
|---|---|
int |
a sound ID. This value can be used to play or unload the sound. |
int load (String path, int priority)
Load the sound from the specified path.
| Parameters | |
|---|---|
path |
String:
the path to the audio file |
priority |
int:
the priority of the sound. Currently has no effect. Use
a value of 1 for future compatibility. |
| Returns | |
|---|---|
int |
a sound ID. This value can be used to play or unload the sound. |
int load (AssetFileDescriptor afd, int priority)
Load the sound from an asset file descriptor.
| Parameters | |
|---|---|
afd |
AssetFileDescriptor:
an asset file descriptor |
priority |
int:
the priority of the sound. Currently has no effect. Use
a value of 1 for future compatibility. |
| Returns | |
|---|---|
int |
a sound ID. This value can be used to play or unload the sound. |
int load (FileDescriptor fd, long offset, long length, int priority)
Load the sound from a FileDescriptor. This version is useful if you store multiple sounds in a single binary. The offset specifies the offset from the start of the file and the length specifies the length of the sound within the file.
| Parameters | |
|---|---|
fd |
FileDescriptor:
a FileDescriptor object |
offset |
long:
offset to the start of the sound |
length |
long:
length of the sound |
priority |
int:
the priority of the sound. Currently has no effect. Use
a value of 1 for future compatibility. |
| Returns | |
|---|---|
int |
a sound ID. This value can be used to play or unload the sound. |
void pause (int streamID)
Pause a playback stream. Pause the stream specified by the streamID. This is the value returned by the play() function. If the stream is playing, it will be paused. If the stream is not playing (e.g. is stopped or was previously paused), calling this function will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function
|
int play (int soundID,
float leftVolume,
float rightVolume,
int priority,
int loop,
float rate)
Play a sound from a sound ID. Play the sound specified by the soundID. This is the value returned by the load() function. Returns a non-zero streamID if successful, zero if it fails. The streamID can be used to further control playback. Note that calling play() may cause another sound to stop playing if the maximum number of active streams is exceeded. A loop value of -1 means loop forever, a value of 0 means don't loop, other values indicate the number of repeats, e.g. a value of 1 plays the audio twice. The playback rate allows the application to vary the playback rate (pitch) of the sound. A value of 1.0 means play back at the original frequency. A value of 2.0 means play back twice as fast, and a value of 0.5 means playback at half speed.
| Parameters | |
|---|---|
soundID |
int:
a soundID returned by the load() function |
leftVolume |
float:
left volume value (range = 0.0 to 1.0) |
rightVolume |
float:
right volume value (range = 0.0 to 1.0) |
priority |
int:
stream priority (0 = lowest priority) |
loop |
int:
loop mode (0 = no loop, -1 = loop forever) |
rate |
float:
playback rate (1.0 = normal playback, range 0.5 to 2.0) |
| Returns | |
|---|---|
int |
non-zero streamID if successful, zero if failed |
void release ()
Release the SoundPool resources. Release all memory and native resources used by the SoundPool object. The SoundPool can no longer be used and the reference should be set to null.
void resume (int streamID)
Resume a playback stream. Resume the stream specified by the streamID. This is the value returned by the play() function. If the stream is paused, this will resume playback. If the stream was not previously paused, calling this function will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function
|
void setLoop (int streamID,
int loop)
Set loop mode. Change the loop mode. A loop value of -1 means loop forever, a value of 0 means don't loop, other values indicate the number of repeats, e.g. a value of 1 plays the audio twice. If the stream does not exist, it will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function |
loop |
int:
loop mode (0 = no loop, -1 = loop forever)
|
void setOnLoadCompleteListener (SoundPool.OnLoadCompleteListener listener)
Sets the callback hook for the OnLoadCompleteListener.
| Parameters | |
|---|---|
listener |
SoundPool.OnLoadCompleteListener
|
void setPriority (int streamID,
int priority)
Change stream priority. Change the priority of the stream specified by the streamID. This is the value returned by the play() function. Affects the order in which streams are re-used to play new sounds. If the stream does not exist, it will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function
|
priority |
int
|
void setRate (int streamID,
float rate)
Change playback rate. The playback rate allows the application to vary the playback rate (pitch) of the sound. A value of 1.0 means playback at the original frequency. A value of 2.0 means playback twice as fast, and a value of 0.5 means playback at half speed. If the stream does not exist, it will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function |
rate |
float:
playback rate (1.0 = normal playback, range 0.5 to 2.0)
|
void setVolume (int streamID,
float leftVolume,
float rightVolume)
Set stream volume. Sets the volume on the stream specified by the streamID. This is the value returned by the play() function. The value must be in the range of 0.0 to 1.0. If the stream does not exist, it will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function |
leftVolume |
float:
left volume value (range = 0.0 to 1.0) |
rightVolume |
float:
right volume value (range = 0.0 to 1.0)
|
void stop (int streamID)
Stop a playback stream. Stop the stream specified by the streamID. This is the value returned by the play() function. If the stream is playing, it will be stopped. It also releases any native resources associated with this stream. If the stream is not playing, it will have no effect.
| Parameters | |
|---|---|
streamID |
int:
a streamID returned by the play() function
|
boolean unload (int soundID)
Unload a sound from a sound ID. Unloads the sound specified by the soundID. This is the value returned by the load() function. Returns true if the sound is successfully unloaded, false if the sound was already unloaded.
| Parameters | |
|---|---|
soundID |
int:
a soundID returned by the load() function |
| Returns | |
|---|---|
boolean |
true if just unloaded, false if previously unloaded |
void finalize ()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
A subclass overrides the finalize method to dispose of
system resources or to perform other cleanup.
The general contract of finalize is that it is invoked
if and when the JavaTM virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize method may take any action, including
making this object available again to other threads; the usual purpose
of finalize, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize method of class Object performs no
special action; it simply returns normally. Subclasses of
Object may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize method causes
the finalization of this object to be halted, but is otherwise
ignored.