DataSource
| com.facebook.datasource.DataSource<T> |
 Known Indirect Subclasses
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Class Overview
An alternative to Java Futures for the image pipeline.
Unlike Futures, DataSource can issue a series of results, rather than just one. A prime example is decoding progressive images, which have a series of intermediate results before the final one.
DataSources MUST be closed (close() is called on the DataSource) else resources may leak.
Summary
| Public Methods | |||||||||||
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| abstract boolean |
close()
Cancels the ongoing request and releases all associated resources.
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| abstract Map<String, Object> | getExtras() | ||||||||||
| abstract Throwable | getFailureCause() | ||||||||||
| abstract float | getProgress() | ||||||||||
| abstract T |
getResult()
The most recent result of the asynchronous computation.
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| abstract boolean | hasFailed() | ||||||||||
| abstract boolean | hasMultipleResults() | ||||||||||
| abstract boolean | hasResult() | ||||||||||
| abstract boolean | isClosed() | ||||||||||
| abstract boolean | isFinished() | ||||||||||
| abstract void |
subscribe(DataSubscriber<T> dataSubscriber, Executor executor)
Subscribe for notifications whenever the state of the DataSource changes.
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Public Methods
public abstract boolean close ()
Cancels the ongoing request and releases all associated resources.
Subsequent calls to getResult() will return null.
Returns
- true if the data source is closed for the first time
public abstract Map<String, Object> getExtras ()
Returns
- an object with extra data for this datasource
public abstract Throwable getFailureCause ()
Returns
- failure cause if the source has failed, else null
public abstract float getProgress ()
Returns
- progress in range [0, 1]
public abstract T getResult ()
The most recent result of the asynchronous computation.
The caller gains ownership of the object and is responsible for releasing it. Note that subsequent calls to getResult might give different results. Later results should be considered to be of higher quality.
This method will return null in the following cases:
- when the DataSource does not have a result (
hasResultreturns false). - when the last result produced was null.
Returns
- current best result
public abstract boolean hasFailed ()
Returns
- true if request finished due to error
public abstract boolean hasMultipleResults ()
Returns
- true if the data source has multiple results (e.g. multiple images). This can be used for example by a RetainingDataSource to correctly display images.
public abstract boolean hasResult ()
Returns
- true if any result (possibly of lower quality) is available right now, false otherwise
public abstract boolean isClosed ()
Returns
- true if the data source is closed, false otherwise
public abstract boolean isFinished ()
Returns
- true if request is finished, false otherwise
public abstract void subscribe (DataSubscriber<T> dataSubscriber, Executor executor)
Subscribe for notifications whenever the state of the DataSource changes.
All changes will be observed on the provided executor.