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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.database;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.content.ContentResolver;
import android.net.Uri;
import android.os.Bundle;
import java.io.Closeable;
import java.util.Arrays;
import java.util.List;
/**
* This interface provides random read-write access to the result set returned
* by a database query.
*
* Cursor implementations are not required to be synchronized so code using a Cursor from multiple
* threads should perform its own synchronization when using the Cursor.
*
* Implementations should subclass {@link AbstractCursor}.
*
*/
public interface Cursor extends Closeable {
/*
* Values returned by {@link #getType(int)}.
* These should be consistent with the corresponding types defined in CursorWindow.h
*/
/** Value returned by {@link #getType(int)} if the specified column is null */
static final int FIELD_TYPE_NULL = 0;
/** Value returned by {@link #getType(int)} if the specified column type is integer */
static final int FIELD_TYPE_INTEGER = 1;
/** Value returned by {@link #getType(int)} if the specified column type is float */
static final int FIELD_TYPE_FLOAT = 2;
/** Value returned by {@link #getType(int)} if the specified column type is string */
static final int FIELD_TYPE_STRING = 3;
/** Value returned by {@link #getType(int)} if the specified column type is blob */
static final int FIELD_TYPE_BLOB = 4;
/**
* Returns the numbers of rows in the cursor.
*
* @return the number of rows in the cursor.
*/
int getCount();
/**
* Returns the current position of the cursor in the row set.
* The value is zero-based. When the row set is first returned the cursor
* will be at positon -1, which is before the first row. After the
* last row is returned another call to next() will leave the cursor past
* the last entry, at a position of count().
*
* @return the current cursor position.
*/
int getPosition();
/**
* Move the cursor by a relative amount, forward or backward, from the
* current position. Positive offsets move forwards, negative offsets move
* backwards. If the final position is outside of the bounds of the result
* set then the resultant position will be pinned to -1 or count() depending
* on whether the value is off the front or end of the set, respectively.
*
* This method will return true if the requested destination was
* reachable, otherwise, it returns false. For example, if the cursor is at
* currently on the second entry in the result set and move(-5) is called,
* the position will be pinned at -1, and false will be returned.
*
* @param offset the offset to be applied from the current position.
* @return whether the requested move fully succeeded.
*/
boolean move(int offset);
/**
* Move the cursor to an absolute position. The valid
* range of values is -1 <= position <= count.
*
*
This method will return true if the request destination was reachable,
* otherwise, it returns false.
*
* @param position the zero-based position to move to.
* @return whether the requested move fully succeeded.
*/
boolean moveToPosition(int position);
/**
* Move the cursor to the first row.
*
*
This method will return false if the cursor is empty.
*
* @return whether the move succeeded.
*/
boolean moveToFirst();
/**
* Move the cursor to the last row.
*
*
This method will return false if the cursor is empty.
*
* @return whether the move succeeded.
*/
boolean moveToLast();
/**
* Move the cursor to the next row.
*
*
This method will return false if the cursor is already past the
* last entry in the result set.
*
* @return whether the move succeeded.
*/
boolean moveToNext();
/**
* Move the cursor to the previous row.
*
*
This method will return false if the cursor is already before the
* first entry in the result set.
*
* @return whether the move succeeded.
*/
boolean moveToPrevious();
/**
* Returns whether the cursor is pointing to the first row.
*
* @return whether the cursor is pointing at the first entry.
*/
boolean isFirst();
/**
* Returns whether the cursor is pointing to the last row.
*
* @return whether the cursor is pointing at the last entry.
*/
boolean isLast();
/**
* Returns whether the cursor is pointing to the position before the first
* row.
*
* @return whether the cursor is before the first result.
*/
boolean isBeforeFirst();
/**
* Returns whether the cursor is pointing to the position after the last
* row.
*
* @return whether the cursor is after the last result.
*/
boolean isAfterLast();
/**
* Returns the zero-based index for the given column name, or -1 if the column doesn't exist.
* If you expect the column to exist use {@link #getColumnIndexOrThrow(String)} instead, which
* will make the error more clear.
*
* @param columnName the name of the target column.
* @return the zero-based column index for the given column name, or -1 if
* the column name does not exist.
* @see #getColumnIndexOrThrow(String)
*/
int getColumnIndex(String columnName);
/**
* Returns the zero-based index for the given column name, or throws
* {@link IllegalArgumentException} if the column doesn't exist. If you're not sure if
* a column will exist or not use {@link #getColumnIndex(String)} and check for -1, which
* is more efficient than catching the exceptions.
*
* @param columnName the name of the target column.
* @return the zero-based column index for the given column name
* @see #getColumnIndex(String)
* @throws IllegalArgumentException if the column does not exist
*/
int getColumnIndexOrThrow(String columnName) throws IllegalArgumentException;
/**
* Returns the column name at the given zero-based column index.
*
* @param columnIndex the zero-based index of the target column.
* @return the column name for the given column index.
*/
String getColumnName(int columnIndex);
/**
* Returns a string array holding the names of all of the columns in the
* result set in the order in which they were listed in the result.
*
* @return the names of the columns returned in this query.
*/
String[] getColumnNames();
/**
* Return total number of columns
* @return number of columns
*/
int getColumnCount();
/**
* Returns the value of the requested column as a byte array.
*
*
The result and whether this method throws an exception when the
* column value is null or the column type is not a blob type is
* implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a byte array.
*/
byte[] getBlob(int columnIndex);
/**
* Returns the value of the requested column as a String.
*
*
The result and whether this method throws an exception when the
* column value is null or the column type is not a string type is
* implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a String.
*/
String getString(int columnIndex);
/**
* Retrieves the requested column text and stores it in the buffer provided.
* If the buffer size is not sufficient, a new char buffer will be allocated
* and assigned to CharArrayBuffer.data
* @param columnIndex the zero-based index of the target column.
* if the target column is null, return buffer
* @param buffer the buffer to copy the text into.
*/
void copyStringToBuffer(int columnIndex, CharArrayBuffer buffer);
/**
* Returns the value of the requested column as a short.
*
*
The result and whether this method throws an exception when the
* column value is null, the column type is not an integral type, or the
* integer value is outside the range [Short.MIN_VALUE,
* Short.MAX_VALUE] is implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a short.
*/
short getShort(int columnIndex);
/**
* Returns the value of the requested column as an int.
*
*
The result and whether this method throws an exception when the
* column value is null, the column type is not an integral type, or the
* integer value is outside the range [Integer.MIN_VALUE,
* Integer.MAX_VALUE] is implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as an int.
*/
int getInt(int columnIndex);
/**
* Returns the value of the requested column as a long.
*
*
The result and whether this method throws an exception when the
* column value is null, the column type is not an integral type, or the
* integer value is outside the range [Long.MIN_VALUE,
* Long.MAX_VALUE] is implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a long.
*/
long getLong(int columnIndex);
/**
* Returns the value of the requested column as a float.
*
*
The result and whether this method throws an exception when the
* column value is null, the column type is not a floating-point type, or the
* floating-point value is not representable as a float value is
* implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a float.
*/
float getFloat(int columnIndex);
/**
* Returns the value of the requested column as a double.
*
*
The result and whether this method throws an exception when the
* column value is null, the column type is not a floating-point type, or the
* floating-point value is not representable as a double value is
* implementation-defined.
*
* @param columnIndex the zero-based index of the target column.
* @return the value of that column as a double.
*/
double getDouble(int columnIndex);
/**
* Returns data type of the given column's value.
* The preferred type of the column is returned but the data may be converted to other types
* as documented in the get-type methods such as {@link #getInt(int)}, {@link #getFloat(int)}
* etc.
*
* Returned column types are
*
* - {@link #FIELD_TYPE_NULL}
* - {@link #FIELD_TYPE_INTEGER}
* - {@link #FIELD_TYPE_FLOAT}
* - {@link #FIELD_TYPE_STRING}
* - {@link #FIELD_TYPE_BLOB}
*
*
*
* @param columnIndex the zero-based index of the target column.
* @return column value type
*/
int getType(int columnIndex);
/**
* Returns true if the value in the indicated column is null.
*
* @param columnIndex the zero-based index of the target column.
* @return whether the column value is null.
*/
boolean isNull(int columnIndex);
/**
* Deactivates the Cursor, making all calls on it fail until {@link #requery} is called.
* Inactive Cursors use fewer resources than active Cursors.
* Calling {@link #requery} will make the cursor active again.
* @deprecated Since {@link #requery()} is deprecated, so too is this.
*/
@Deprecated
void deactivate();
/**
* Performs the query that created the cursor again, refreshing its
* contents. This may be done at any time, including after a call to {@link
* #deactivate}.
*
* Since this method could execute a query on the database and potentially take
* a while, it could cause ANR if it is called on Main (UI) thread.
* A warning is printed if this method is being executed on Main thread.
*
* @return true if the requery succeeded, false if not, in which case the
* cursor becomes invalid.
* @deprecated Don't use this. Just request a new cursor, so you can do this
* asynchronously and update your list view once the new cursor comes back.
*/
@Deprecated
boolean requery();
/**
* Closes the Cursor, releasing all of its resources and making it completely invalid.
* Unlike {@link #deactivate()} a call to {@link #requery()} will not make the Cursor valid
* again.
*/
void close();
/**
* return true if the cursor is closed
* @return true if the cursor is closed.
*/
boolean isClosed();
/**
* Register an observer that is called when changes happen to the content backing this cursor.
* Typically the data set won't change until {@link #requery()} is called.
*
* @param observer the object that gets notified when the content backing the cursor changes.
* @see #unregisterContentObserver(ContentObserver)
*/
void registerContentObserver(ContentObserver observer);
/**
* Unregister an observer that has previously been registered with this
* cursor via {@link #registerContentObserver}.
*
* @param observer the object to unregister.
* @see #registerContentObserver(ContentObserver)
*/
void unregisterContentObserver(ContentObserver observer);
/**
* Register an observer that is called when changes happen to the contents
* of the this cursors data set, for example, when the data set is changed via
* {@link #requery()}, {@link #deactivate()}, or {@link #close()}.
*
* @param observer the object that gets notified when the cursors data set changes.
* @see #unregisterDataSetObserver(DataSetObserver)
*/
void registerDataSetObserver(DataSetObserver observer);
/**
* Unregister an observer that has previously been registered with this
* cursor via {@link #registerContentObserver}.
*
* @param observer the object to unregister.
* @see #registerDataSetObserver(DataSetObserver)
*/
void unregisterDataSetObserver(DataSetObserver observer);
/**
* Register to watch a content URI for changes. This can be the URI of a specific data row (for
* example, "content://my_provider_type/23"), or a a generic URI for a content type.
*
* Calling this overrides any previous call to
* {@link #setNotificationUris(ContentResolver, List)}.
*
* @param cr The content resolver from the caller's context. The listener attached to
* this resolver will be notified.
* @param uri The content URI to watch.
*/
void setNotificationUri(ContentResolver cr, Uri uri);
/**
* Similar to {@link #setNotificationUri(ContentResolver, Uri)}, except this version allows
* to watch multiple content URIs for changes.
*
*
If this is not implemented, this is equivalent to calling
* {@link #setNotificationUri(ContentResolver, Uri)} with the first URI in {@code uris}.
*
*
Calling this overrides any previous call to
* {@link #setNotificationUri(ContentResolver, Uri)}.
*
* @param cr The content resolver from the caller's context. The listener attached to
* this resolver will be notified.
* @param uris The content URIs to watch.
*/
default void setNotificationUris(@NonNull ContentResolver cr, @NonNull List uris) {
setNotificationUri(cr, uris.get(0));
}
/**
* Return the URI at which notifications of changes in this Cursor's data
* will be delivered, as previously set by {@link #setNotificationUri}.
* @return Returns a URI that can be used with
* {@link ContentResolver#registerContentObserver(android.net.Uri, boolean, ContentObserver)
* ContentResolver.registerContentObserver} to find out about changes to this Cursor's
* data. May be null if no notification URI has been set.
*/
Uri getNotificationUri();
/**
* Return the URIs at which notifications of changes in this Cursor's data
* will be delivered, as previously set by {@link #setNotificationUris}.
*
* If this is not implemented, this is equivalent to calling {@link #getNotificationUri()}.
*
* @return Returns URIs that can be used with
* {@link ContentResolver#registerContentObserver(android.net.Uri, boolean, ContentObserver)
* ContentResolver.registerContentObserver} to find out about changes to this Cursor's
* data. May be null if no notification URI has been set.
*/
default @Nullable List getNotificationUris() {
final Uri notifyUri = getNotificationUri();
return notifyUri == null ? null : Arrays.asList(notifyUri);
}
/**
* onMove() will only be called across processes if this method returns true.
* @return whether all cursor movement should result in a call to onMove().
*/
boolean getWantsAllOnMoveCalls();
/**
* Sets a {@link Bundle} that will be returned by {@link #getExtras()}.
*
* @param extras {@link Bundle} to set, or null to set an empty bundle.
*/
void setExtras(Bundle extras);
/**
* Returns a bundle of extra values. This is an optional way for cursors to provide out-of-band
* metadata to their users. One use of this is for reporting on the progress of network requests
* that are required to fetch data for the cursor.
*
* These values may only change when requery is called.
* @return cursor-defined values, or {@link android.os.Bundle#EMPTY Bundle.EMPTY} if there
* are no values. Never null.
*/
Bundle getExtras();
/**
* This is an out-of-band way for the the user of a cursor to communicate with the cursor. The
* structure of each bundle is entirely defined by the cursor.
*
*
One use of this is to tell a cursor that it should retry its network request after it
* reported an error.
* @param extras extra values, or {@link android.os.Bundle#EMPTY Bundle.EMPTY}.
* Never null.
* @return extra values, or {@link android.os.Bundle#EMPTY Bundle.EMPTY}.
* Never null.
*/
Bundle respond(Bundle extras);
}