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Cursor.javaAPI DocAndroid 5.1 API17609Thu Mar 12 22:22:10 GMT 2015android.database

Cursor

public interface Cursor implements Closeable
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}.

Fields Summary
static final int
FIELD_TYPE_NULL
Value returned by {@link #getType(int)} if the specified column is null
static final int
FIELD_TYPE_INTEGER
Value returned by {@link #getType(int)} if the specified column type is integer
static final int
FIELD_TYPE_FLOAT
Value returned by {@link #getType(int)} if the specified column type is float
static final int
FIELD_TYPE_STRING
Value returned by {@link #getType(int)} if the specified column type is string
static final int
FIELD_TYPE_BLOB
Value returned by {@link #getType(int)} if the specified column type is blob
Constructors Summary
Methods Summary
public voidclose()
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.

public voidcopyStringToBuffer(int columnIndex, CharArrayBuffer buffer)
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.

public voiddeactivate()
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.

public byte[]getBlob(int columnIndex)
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.

public intgetColumnCount()
Return total number of columns

return
number of columns

public intgetColumnIndex(java.lang.String columnName)
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)

public intgetColumnIndexOrThrow(java.lang.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

public java.lang.StringgetColumnName(int columnIndex)
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.

public java.lang.String[]getColumnNames()
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.

public intgetCount()
Returns the numbers of rows in the cursor.

return
the number of rows in the cursor.

public doublegetDouble(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.

public android.os.BundlegetExtras()
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.

public floatgetFloat(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.

public intgetInt(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.

public longgetLong(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.

public android.net.UrigetNotificationUri()
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.

public intgetPosition()
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.

public shortgetShort(int columnIndex)
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.

public java.lang.StringgetString(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.

public intgetType(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

public booleangetWantsAllOnMoveCalls()
onMove() will only be called across processes if this method returns true.

return
whether all cursor movement should result in a call to onMove().

public booleanisAfterLast()
Returns whether the cursor is pointing to the position after the last row.

return
whether the cursor is after the last result.

public booleanisBeforeFirst()
Returns whether the cursor is pointing to the position before the first row.

return
whether the cursor is before the first result.

public booleanisClosed()
return true if the cursor is closed

return
true if the cursor is closed.

public booleanisFirst()
Returns whether the cursor is pointing to the first row.

return
whether the cursor is pointing at the first entry.

public booleanisLast()
Returns whether the cursor is pointing to the last row.

return
whether the cursor is pointing at the last entry.

public booleanisNull(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.

public booleanmove(int offset)
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.

public booleanmoveToFirst()
Move the cursor to the first row.

This method will return false if the cursor is empty.

return
whether the move succeeded.

public booleanmoveToLast()
Move the cursor to the last row.

This method will return false if the cursor is empty.

return
whether the move succeeded.

public booleanmoveToNext()
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.

public booleanmoveToPosition(int position)
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.

public booleanmoveToPrevious()
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.

public voidregisterContentObserver(ContentObserver observer)
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)

public voidregisterDataSetObserver(DataSetObserver 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)

public booleanrequery()
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.

public android.os.Bundlerespond(android.os.Bundle extras)
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.

public voidsetNotificationUri(android.content.ContentResolver cr, android.net.Uri uri)
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.

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.

public voidunregisterContentObserver(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)

public voidunregisterDataSetObserver(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)