public abstract class ContentProvider extends Object implements ComponentCallbacks2
ContentResolver
interface. A content provider is only required if you need to share
data between multiple applications. For example, the contacts data is used by multiple
applications and must be stored in a content provider. If you don't need to share data amongst
multiple applications you can use a database directly via
SQLiteDatabase
.
When a request is made via
a ContentResolver
the system inspects the authority of the given URI and passes the
request to the content provider registered with the authority. The content provider can interpret
the rest of the URI however it wants. The UriMatcher
class is helpful for parsing
URIs.
The primary methods that need to be implemented are:
onCreate()
which is called to initialize the providerquery(android.net.Uri, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String)
which returns data to the callerinsert(android.net.Uri, android.content.ContentValues)
which inserts new data into the content providerupdate(android.net.Uri, android.content.ContentValues, java.lang.String, java.lang.String[])
which updates existing data in the content providerdelete(android.net.Uri, java.lang.String, java.lang.String[])
which deletes data from the content providergetType(android.net.Uri)
which returns the MIME type of data in the content providerData access methods (such as insert(android.net.Uri, android.content.ContentValues)
and
update(android.net.Uri, android.content.ContentValues, java.lang.String, java.lang.String[])
) may be called from many threads at once, and must be thread-safe.
Other methods (such as onCreate()
) are only called from the application
main thread, and must avoid performing lengthy operations. See the method
descriptions for their expected thread behavior.
Requests to ContentResolver
are automatically forwarded to the appropriate
ContentProvider instance, so subclasses don't have to worry about the details of
cross-process calls.
For more information about using content providers, read the Content Providers developer guide.
Modifier and Type | Class and Description |
---|---|
static interface |
ContentProvider.PipeDataWriter<T>
Interface to write a stream of data to a pipe.
|
TRIM_MEMORY_BACKGROUND, TRIM_MEMORY_COMPLETE, TRIM_MEMORY_MODERATE, TRIM_MEMORY_RUNNING_CRITICAL, TRIM_MEMORY_RUNNING_LOW, TRIM_MEMORY_RUNNING_MODERATE, TRIM_MEMORY_UI_HIDDEN
Constructor and Description |
---|
ContentProvider()
Construct a ContentProvider instance.
|
ContentProvider(Context context,
String readPermission,
String writePermission,
PathPermission[] pathPermissions)
Constructor just for mocking.
|
Modifier and Type | Method and Description |
---|---|
ContentProviderResult[] |
applyBatch(ArrayList<ContentProviderOperation> operations)
Override this to handle requests to perform a batch of operations, or the
default implementation will iterate over the operations and call
ContentProviderOperation.apply(android.content.ContentProvider, android.content.ContentProviderResult[], int) on each of them. |
void |
attachInfo(Context context,
ProviderInfo info)
After being instantiated, this is called to tell the content provider
about itself.
|
int |
bulkInsert(Uri uri,
ContentValues[] values)
Override this to handle requests to insert a set of new rows, or the
default implementation will iterate over the values and call
insert(android.net.Uri, android.content.ContentValues) on each of them. |
Bundle |
call(String method,
String arg,
Bundle extras)
Call a provider-defined method.
|
static ContentProvider |
coerceToLocalContentProvider(IContentProvider abstractInterface)
Given an IContentProvider, try to coerce it back to the real
ContentProvider object if it is running in the local process.
|
abstract int |
delete(Uri uri,
String selection,
String[] selectionArgs)
Implement this to handle requests to delete one or more rows.
|
void |
dump(FileDescriptor fd,
PrintWriter writer,
String[] args)
Print the Provider's state into the given stream.
|
Context |
getContext()
Retrieves the Context this provider is running in.
|
IContentProvider |
getIContentProvider()
Returns the Binder object for this provider.
|
PathPermission[] |
getPathPermissions()
Return the path-based permissions required for read and/or write access to
this content provider.
|
String |
getReadPermission()
Return the name of the permission required for read-only access to
this content provider.
|
String[] |
getStreamTypes(Uri uri,
String mimeTypeFilter)
Called by a client to determine the types of data streams that this
content provider supports for the given URI.
|
abstract String |
getType(Uri uri)
Implement this to handle requests for the MIME type of the data at the
given URI.
|
String |
getWritePermission()
Return the name of the permission required for read/write access to
this content provider.
|
abstract Uri |
insert(Uri uri,
ContentValues values)
Implement this to handle requests to insert a new row.
|
protected boolean |
isTemporary()
Returns true if this instance is a temporary content provider.
|
void |
onConfigurationChanged(Configuration newConfig)
Called by the system when the device configuration changes while your
component is running.
|
abstract boolean |
onCreate()
Implement this to initialize your content provider on startup.
|
void |
onLowMemory()
This is called when the overall system is running low on memory, and
would like actively running process to try to tighten their belt.
|
void |
onTrimMemory(int level)
Called when the operating system has determined that it is a good
time for a process to trim unneeded memory from its process.
|
AssetFileDescriptor |
openAssetFile(Uri uri,
String mode)
This is like
openFile(android.net.Uri, java.lang.String) , but can be implemented by providers
that need to be able to return sub-sections of files, often assets
inside of their .apk. |
ParcelFileDescriptor |
openFile(Uri uri,
String mode)
Override this to handle requests to open a file blob.
|
protected ParcelFileDescriptor |
openFileHelper(Uri uri,
String mode)
Convenience for subclasses that wish to implement
openFile(android.net.Uri, java.lang.String)
by looking up a column named "_data" at the given URI. |
<T> ParcelFileDescriptor |
openPipeHelper(Uri uri,
String mimeType,
Bundle opts,
T args,
ContentProvider.PipeDataWriter<T> func)
A helper function for implementing
openTypedAssetFile(android.net.Uri, java.lang.String, android.os.Bundle) , for
creating a data pipe and background thread allowing you to stream
generated data back to the client. |
AssetFileDescriptor |
openTypedAssetFile(Uri uri,
String mimeTypeFilter,
Bundle opts)
Called by a client to open a read-only stream containing data of a
particular MIME type.
|
abstract Cursor |
query(Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String sortOrder)
Implement this to handle query requests from clients.
|
Cursor |
query(Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String sortOrder,
CancellationSignal cancellationSignal)
Implement this to handle query requests from clients with support for cancellation.
|
protected void |
setPathPermissions(PathPermission[] permissions)
Change the path-based permission required to read and/or write data in
the content provider.
|
protected void |
setReadPermission(String permission)
Change the permission required to read data from the content
provider.
|
protected void |
setWritePermission(String permission)
Change the permission required to read and write data in the content
provider.
|
void |
shutdown()
Implement this to shut down the ContentProvider instance.
|
abstract int |
update(Uri uri,
ContentValues values,
String selection,
String[] selectionArgs)
Implement this to handle requests to update one or more rows.
|
public ContentProvider()
ContentResolver
, and created
automatically by the system, so applications usually do not create
ContentProvider instances directly.
At construction time, the object is uninitialized, and most fields and
methods are unavailable. Subclasses should initialize themselves in
onCreate()
, not the constructor.
Content providers are created on the application main thread at application launch time. The constructor must not perform lengthy operations, or application startup will be delayed.
public ContentProvider(Context context, String readPermission, String writePermission, PathPermission[] pathPermissions)
context
- A Context object which should be some mock instance (like the
instance of MockContext
).readPermission
- The read permision you want this instance should have in the
test, which is available via getReadPermission()
.writePermission
- The write permission you want this instance should have
in the test, which is available via getWritePermission()
.pathPermissions
- The PathPermissions you want this instance should have
in the test, which is available via getPathPermissions()
.public static ContentProvider coerceToLocalContentProvider(IContentProvider abstractInterface)
abstractInterface
- The ContentProvider interface that is to be
coerced.public final Context getContext()
onCreate()
has been called -- this will return null in the
constructor.protected final void setReadPermission(String permission)
permission
- Name of the permission required for read-only access.public final String getReadPermission()
protected final void setWritePermission(String permission)
permission
- Name of the permission required for read/write access.public final String getWritePermission()
protected final void setPathPermissions(PathPermission[] permissions)
permissions
- Array of path permission descriptions.public final PathPermission[] getPathPermissions()
public abstract boolean onCreate()
You should defer nontrivial initialization (such as opening,
upgrading, and scanning databases) until the content provider is used
(via query(android.net.Uri, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String)
, insert(android.net.Uri, android.content.ContentValues)
, etc). Deferred initialization
keeps application startup fast, avoids unnecessary work if the provider
turns out not to be needed, and stops database errors (such as a full
disk) from halting application launch.
If you use SQLite, SQLiteOpenHelper
is a helpful utility class that makes it easy to manage databases,
and will automatically defer opening until first use. If you do use
SQLiteOpenHelper, make sure to avoid calling
SQLiteOpenHelper.getReadableDatabase()
or
SQLiteOpenHelper.getWritableDatabase()
from this method. (Instead, override
SQLiteOpenHelper.onOpen(android.database.sqlite.SQLiteDatabase)
to initialize the
database when it is first opened.)
public void onConfigurationChanged(Configuration newConfig)
At the time that this function has been called, your Resources object will have been updated to return resource values matching the new configuration. This method is always called on the application main thread, and must not perform lengthy operations.
The default content provider implementation does nothing. Override this method to take appropriate action. (Content providers do not usually care about things like screen orientation, but may want to know about locale changes.)
onConfigurationChanged
in interface ComponentCallbacks
newConfig
- The new device configuration.public void onLowMemory()
Applications that want to be nice can implement this method to release any caches or other unnecessary resources they may be holding on to. The system will perform a gc for you after returning from this method. This method is always called on the application main thread, and must not perform lengthy operations.
The default content provider implementation does nothing. Subclasses may override this method to take appropriate action.
onLowMemory
in interface ComponentCallbacks
public void onTrimMemory(int level)
ComponentCallbacks2
To retrieve the processes current trim level at any point, you can
use ActivityManager.getMyMemoryState(RunningAppProcessInfo)
.
onTrimMemory
in interface ComponentCallbacks2
level
- The context of the trim, giving a hint of the amount of
trimming the application may like to perform. May be
ComponentCallbacks2.TRIM_MEMORY_COMPLETE
, ComponentCallbacks2.TRIM_MEMORY_MODERATE
,
ComponentCallbacks2.TRIM_MEMORY_BACKGROUND
, ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN
,
ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL
, ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW
,
or ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE
.public abstract Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
Example client call:
// Request a specific record. Cursor managedCursor = managedQuery( ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2), projection, // Which columns to return. null, // WHERE clause. null, // WHERE clause value substitution People.NAME + " ASC"); // Sort order.Example implementation:
// SQLiteQueryBuilder is a helper class that creates the // proper SQL syntax for us. SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder(); // Set the table we're querying. qBuilder.setTables(DATABASE_TABLE_NAME); // If the query ends in a specific record number, we're // being asked for a specific record, so set the // WHERE clause in our query. if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){ qBuilder.appendWhere("_id=" + uri.getPathLeafId()); } // Make the query. Cursor c = qBuilder.query(mDb, projection, selection, selectionArgs, groupBy, having, sortOrder); c.setNotificationUri(getContext().getContentResolver(), uri); return c;
uri
- The URI to query. This will be the full URI sent by the client;
if the client is requesting a specific record, the URI will end in a record number
that the implementation should parse and add to a WHERE or HAVING clause, specifying
that _id value.projection
- The list of columns to put into the cursor. If
null all columns are included.selection
- A selection criteria to apply when filtering rows.
If null then all rows are included.selectionArgs
- You may include ?s in selection, which will be replaced by
the values from selectionArgs, in order that they appear in the selection.
The values will be bound as Strings.sortOrder
- How the rows in the cursor should be sorted.
If null then the provider is free to define the sort order.public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder, CancellationSignal cancellationSignal)
Example client call:
// Request a specific record. Cursor managedCursor = managedQuery( ContentUris.withAppendedId(Contacts.People.CONTENT_URI, 2), projection, // Which columns to return. null, // WHERE clause. null, // WHERE clause value substitution People.NAME + " ASC"); // Sort order.Example implementation:
// SQLiteQueryBuilder is a helper class that creates the // proper SQL syntax for us. SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder(); // Set the table we're querying. qBuilder.setTables(DATABASE_TABLE_NAME); // If the query ends in a specific record number, we're // being asked for a specific record, so set the // WHERE clause in our query. if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){ qBuilder.appendWhere("_id=" + uri.getPathLeafId()); } // Make the query. Cursor c = qBuilder.query(mDb, projection, selection, selectionArgs, groupBy, having, sortOrder); c.setNotificationUri(getContext().getContentResolver(), uri); return c;
If you implement this method then you must also implement the version of
query(Uri, String[], String, String[], String)
that does not take a cancellation
signal to ensure correct operation on older versions of the Android Framework in
which the cancellation signal overload was not available.
uri
- The URI to query. This will be the full URI sent by the client;
if the client is requesting a specific record, the URI will end in a record number
that the implementation should parse and add to a WHERE or HAVING clause, specifying
that _id value.projection
- The list of columns to put into the cursor. If
null all columns are included.selection
- A selection criteria to apply when filtering rows.
If null then all rows are included.selectionArgs
- You may include ?s in selection, which will be replaced by
the values from selectionArgs, in order that they appear in the selection.
The values will be bound as Strings.sortOrder
- How the rows in the cursor should be sorted.
If null then the provider is free to define the sort order.cancellationSignal
- A signal to cancel the operation in progress, or null if none.
If the operation is canceled, then OperationCanceledException
will be thrown
when the query is executed.public abstract String getType(Uri uri)
vnd.android.cursor.item
for a single record,
or vnd.android.cursor.dir/
for multiple items.
This method can be called from multiple threads, as described in
Processes
and Threads.
Note that there are no permissions needed for an application to access this information; if your content provider requires read and/or write permissions, or is not exported, all applications can still call this method regardless of their access permissions. This allows them to retrieve the MIME type for a URI when dispatching intents.
uri
- the URI to query.public abstract Uri insert(Uri uri, ContentValues values)
notifyChange()
after inserting.
This method can be called from multiple threads, as described in
Processes
and Threads.uri
- The content:// URI of the insertion request.values
- A set of column_name/value pairs to add to the database.public int bulkInsert(Uri uri, ContentValues[] values)
insert(android.net.Uri, android.content.ContentValues)
on each of them.
As a courtesy, call notifyChange()
after inserting.
This method can be called from multiple threads, as described in
Processes
and Threads.uri
- The content:// URI of the insertion request.values
- An array of sets of column_name/value pairs to add to the database.public abstract int delete(Uri uri, String selection, String[] selectionArgs)
notifyDelete()
after deleting.
This method can be called from multiple threads, as described in
Processes
and Threads.
The implementation is responsible for parsing out a row ID at the end
of the URI, if a specific row is being deleted. That is, the client would
pass in content://contacts/people/22
and the implementation is
responsible for parsing the record number (22) when creating a SQL statement.
uri
- The full URI to query, including a row ID (if a specific record is requested).selection
- An optional restriction to apply to rows when deleting.SQLException
public abstract int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
notifyChange()
after updating.
This method can be called from multiple threads, as described in
Processes
and Threads.uri
- The URI to query. This can potentially have a record ID if this
is an update request for a specific record.values
- A Bundle mapping from column names to new column values (NULL is a
valid value).selection
- An optional filter to match rows to update.public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException
FileNotFoundException
.
This method can be called from multiple threads, as described in
Processes
and Threads.
This method returns a ParcelFileDescriptor, which is returned directly to the caller. This way large data (such as images and documents) can be returned without copying the content.
The returned ParcelFileDescriptor is owned by the caller, so it is their responsibility to close it when done. That is, the implementation of this method should create a new ParcelFileDescriptor for each call.
uri
- The URI whose file is to be opened.mode
- Access mode for the file. May be "r" for read-only access,
"rw" for read and write access, or "rwt" for read and write access
that truncates any existing file.FileNotFoundException
- Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.SecurityException
- Throws SecurityException if the caller does
not have permission to access the file.openAssetFile(Uri, String)
,
openFileHelper(Uri, String)
public AssetFileDescriptor openAssetFile(Uri uri, String mode) throws FileNotFoundException
openFile(android.net.Uri, java.lang.String)
, but can be implemented by providers
that need to be able to return sub-sections of files, often assets
inside of their .apk.
This method can be called from multiple threads, as described in
Processes
and Threads.
If you implement this, your clients must be able to deal with such
file slices, either directly with
ContentResolver.openAssetFileDescriptor(android.net.Uri, java.lang.String)
, or by using the higher-level
ContentResolver.openInputStream
or ContentResolver.openOutputStream
methods.
If you are implementing this to return a full file, you
should create the AssetFileDescriptor with
AssetFileDescriptor.UNKNOWN_LENGTH
to be compatible with
applications that can not handle sub-sections of files.
uri
- The URI whose file is to be opened.mode
- Access mode for the file. May be "r" for read-only access,
"w" for write-only access (erasing whatever data is currently in
the file), "wa" for write-only access to append to any existing data,
"rw" for read and write access on any existing data, and "rwt" for read
and write access that truncates any existing file.FileNotFoundException
- Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.SecurityException
- Throws SecurityException if the caller does
not have permission to access the file.openFile(Uri, String)
,
openFileHelper(Uri, String)
protected final ParcelFileDescriptor openFileHelper(Uri uri, String mode) throws FileNotFoundException
openFile(android.net.Uri, java.lang.String)
by looking up a column named "_data" at the given URI.uri
- The URI to be opened.mode
- The file mode. May be "r" for read-only access,
"w" for write-only access (erasing whatever data is currently in
the file), "wa" for write-only access to append to any existing data,
"rw" for read and write access on any existing data, and "rwt" for read
and write access that truncates any existing file.FileNotFoundException
public String[] getStreamTypes(Uri uri, String mimeTypeFilter)
uri
- The data in the content provider being queried.mimeTypeFilter
- The type of data the client desires. May be
a pattern, such as *\/* to retrieve all possible data types.getType(Uri)
,
openTypedAssetFile(Uri, String, Bundle)
,
ClipDescription.compareMimeTypes(String, String)
public AssetFileDescriptor openTypedAssetFile(Uri uri, String mimeTypeFilter, Bundle opts) throws FileNotFoundException
openAssetFile(Uri, String)
,
except the file can only be read-only and the content provider may
perform data conversions to generate data of the desired type.
The default implementation compares the given mimeType against the
result of getType(Uri)
and, if the match, simple calls
openAssetFile(Uri, String)
.
See ClipData
for examples of the use and implementation
of this method.
uri
- The data in the content provider being queried.mimeTypeFilter
- The type of data the client desires. May be
a pattern, such as *\/*, if the caller does not have specific type
requirements; in this case the content provider will pick its best
type matching the pattern.opts
- Additional options from the client. The definitions of
these are specific to the content provider being called.FileNotFoundException
- Throws FileNotFoundException if there is
no file associated with the given URI or the mode is invalid.SecurityException
- Throws SecurityException if the caller does
not have permission to access the data.IllegalArgumentException
- Throws IllegalArgumentException if the
content provider does not support the requested MIME type.getStreamTypes(Uri, String)
,
openAssetFile(Uri, String)
,
ClipDescription.compareMimeTypes(String, String)
public <T> ParcelFileDescriptor openPipeHelper(Uri uri, String mimeType, Bundle opts, T args, ContentProvider.PipeDataWriter<T> func) throws FileNotFoundException
openTypedAssetFile(android.net.Uri, java.lang.String, android.os.Bundle)
, for
creating a data pipe and background thread allowing you to stream
generated data back to the client. This function returns a new
ParcelFileDescriptor that should be returned to the caller (the caller
is responsible for closing it).uri
- The URI whose data is to be written.mimeType
- The desired type of data to be written.opts
- Options supplied by caller.args
- Your own custom arguments.func
- Interface implementing the function that will actually
stream the data.FileNotFoundException
protected boolean isTemporary()
public IContentProvider getIContentProvider()
public void attachInfo(Context context, ProviderInfo info)
context
- The context this provider is running ininfo
- Registered information about this content providerpublic ContentProviderResult[] applyBatch(ArrayList<ContentProviderOperation> operations) throws OperationApplicationException
ContentProviderOperation.apply(android.content.ContentProvider, android.content.ContentProviderResult[], int)
on each of them.
If all calls to ContentProviderOperation.apply(android.content.ContentProvider, android.content.ContentProviderResult[], int)
succeed
then a ContentProviderResult
array with as many
elements as there were operations will be returned. If any of the calls
fail, it is up to the implementation how many of the others take effect.
This method can be called from multiple threads, as described in
Processes
and Threads.operations
- the operations to applyOperationApplicationException
- thrown if any operation fails.ContentProviderOperation.apply(android.content.ContentProvider, android.content.ContentProviderResult[], int)
public Bundle call(String method, String arg, Bundle extras)
method
- method name to call. Opaque to framework, but should not be null.arg
- provider-defined String argument. May be null.extras
- provider-defined Bundle argument. May be null.public void shutdown()
Android normally handles ContentProvider startup and shutdown automatically. You do not need to start up or shut down a ContentProvider. When you invoke a test method on a ContentProvider, however, a ContentProvider instance is started and keeps running after the test finishes, even if a succeeding test instantiates another ContentProvider. A conflict develops because the two instances are usually running against the same underlying data source (for example, an sqlite database).
Implementing shutDown() avoids this conflict by providing a way to terminate the ContentProvider. This method can also prevent memory leaks from multiple instantiations of the ContentProvider, and it can ensure unit test isolation by allowing you to completely clean up the test fixture before moving on to the next test.
public void dump(FileDescriptor fd, PrintWriter writer, String[] args)
prefix
- Desired prefix to prepend at each line of output.fd
- The raw file descriptor that the dump is being sent to.writer
- The PrintWriter to which you should dump your state. This will be
closed for you after you return.args
- additional arguments to the dump request.