ResolvingDataSource

@UnstableApi
public final class ResolvingDataSource implements DataSource

DataSource wrapper allowing just-in-time resolution of DataSpecs.

Summary

Nested types
public final class ResolvingDataSource.Factory implements DataSource.Factory

DataSource.Factory for ResolvingDataSource instances.

Resolves DataSpecs.

Public constructors
ResolvingDataSource(
    DataSource upstreamDataSource,
    ResolvingDataSource.Resolver resolver
)

Public methods
void

Adds a TransferListener to listen to data transfers.
void

Closes the source.
Map<String, List<String>>

When the source is open, returns the response headers associated with the last open call.
@Nullable Uri

When the source is open, returns the Uri from which data is being read.
long
open(DataSpec dataSpec)

Opens the source to read the specified data.
int
read(byte[] buffer, int offset, int length)

Reads up to length bytes of data from the input.

Public constructors

ResolvingDataSource

public ResolvingDataSource(
    DataSource upstreamDataSource,
    ResolvingDataSource.Resolver resolver
)
Parameters
DataSource upstreamDataSource

The wrapped DataSource.
ResolvingDataSource.Resolver resolver

The Resolver to resolve the DataSpecs.

Public methods

addTransferListener

public void addTransferListener(TransferListener transferListener)

Adds a TransferListener to listen to data transfers. This method is not thread-safe.

Parameters
TransferListener transferListener

A TransferListener.

close

public void close()

Closes the source. This method must be called even if the corresponding call to open threw an IOException.

Throws
java.io.IOException

If an error occurs closing the source.

getResponseHeaders

public Map<String, List<String>> getResponseHeaders()

When the source is open, returns the response headers associated with the last open call. Otherwise, returns an empty map.

Key look-up in the returned map is case-insensitive.

getUri

public @Nullable Uri getUri()

When the source is open, returns the Uri from which data is being read. The returned Uri will be identical to the one passed open in the DataSpec unless redirection has occurred. If redirection has occurred, the Uri after redirection is returned.

Returns
@Nullable Uri

The Uri from which data is being read, or null if the source is not open.

open

public long open(DataSpec dataSpec)

Opens the source to read the specified data. If an IOException is thrown, callers must still call close to ensure that any partial effects of the invocation are cleaned up.

The following edge case behaviors apply:

Parameters
DataSpec dataSpec

Defines the data to be read.
Returns
long

The number of bytes that can be read from the opened source. For unbounded requests (i.e., requests where length equals LENGTH_UNSET) this value is the resolved length of the request, or LENGTH_UNSET if the length is still unresolved. For all other requests, the value returned will be equal to the request's length.
Throws
java.io.IOException

If an error occurs opening the source. DataSourceException can be thrown or used as a cause of the thrown exception to specify the reason of the error.

read

public int read(byte[] buffer, int offset, int length)

Reads up to length bytes of data from the input.

If readLength is zero then 0 is returned. Otherwise, if no data is available because the end of the opened range has been reached, then RESULT_END_OF_INPUT is returned. Otherwise, the call will block until at least one byte of data has been read and the number of bytes read is returned.

Parameters
byte[] buffer

A target array into which data should be written.
int offset

The offset into the target array at which to write.
int length

The maximum number of bytes to read from the input.
Returns
int

The number of bytes read, or RESULT_END_OF_INPUT if the input has ended. This may be less than length because the end of the input (or available data) was reached, the method was interrupted, or the operation was aborted early for another reason.
Throws
java.io.IOException

If an error occurs reading from the input.