public
class
MergeCursor
extends AbstractCursor
java.lang.Object | ||
↳ | android.database.AbstractCursor | |
↳ | android.database.MergeCursor |
A convience class that lets you present an array of Cursors as a single linear Cursor. The schema of the cursors presented is entirely up to the creator of the MergeCursor, and may be different if that is desired. Calls to getColumns, getColumnIndex, etc will return the value for the row that the MergeCursor is currently pointing at.
Inherited constants |
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From
interface
android.database.Cursor
|
Inherited fields |
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From
class
android.database.AbstractCursor
|
Public constructors | |
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MergeCursor(Cursor[] cursors)
|
Public methods | |
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void
|
close()
Closes the Cursor, releasing all of its resources and making it completely invalid. |
void
|
deactivate()
Deactivates the Cursor, making all calls on it fail until |
byte[]
|
getBlob(int column)
Returns the value of the requested column as a byte array. |
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. |
int
|
getCount()
Returns the numbers of rows in the cursor. |
double
|
getDouble(int column)
Returns the value of the requested column as a double. |
float
|
getFloat(int column)
Returns the value of the requested column as a float. |
int
|
getInt(int column)
Returns the value of the requested column as an int. |
long
|
getLong(int column)
Returns the value of the requested column as a long. |
short
|
getShort(int column)
Returns the value of the requested column as a short. |
String
|
getString(int column)
Returns the value of the requested column as a String. |
int
|
getType(int column)
Returns data type of the given column's value. |
boolean
|
isNull(int column)
Returns |
boolean
|
onMove(int oldPosition, int newPosition)
This function is called every time the cursor is successfully scrolled to a new position, giving the subclass a chance to update any state it may have. |
void
|
registerContentObserver(ContentObserver observer)
Register an observer that is called when changes happen to the content backing this cursor. |
void
|
registerDataSetObserver(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
|
boolean
|
requery()
Performs the query that created the cursor again, refreshing its contents. |
void
|
unregisterContentObserver(ContentObserver observer)
Unregister an observer that has previously been registered with this
cursor via |
void
|
unregisterDataSetObserver(DataSetObserver observer)
Unregister an observer that has previously been registered with this
cursor via |
Inherited methods | |
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From
class
android.database.AbstractCursor
| |
From
class
java.lang.Object
| |
From
interface
android.database.CrossProcessCursor
| |
From
interface
android.database.Cursor
| |
From
interface
java.io.Closeable
| |
From
interface
java.lang.AutoCloseable
|
void close ()
Closes the Cursor, releasing all of its resources and making it completely invalid.
Unlike deactivate()
a call to requery()
will not make the Cursor valid
again.
void deactivate ()
Deactivates the Cursor, making all calls on it fail until requery()
is called.
Inactive Cursors use fewer resources than active Cursors.
Calling requery()
will make the cursor active again.
byte[] getBlob (int column)
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.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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byte[] |
the value of that column as a byte array. |
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.
Returns | |
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String[] |
the names of the columns returned in this query. |
int getCount ()
Returns the numbers of rows in the cursor.
Returns | |
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int |
the number of rows in the cursor. |
double getDouble (int column)
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.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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double |
the value of that column as a double. |
float getFloat (int column)
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.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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float |
the value of that column as a float. |
int getInt (int column)
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.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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int |
the value of that column as an int. |
long getLong (int column)
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.
Parameters | |
---|---|
column |
int :
the zero-based index of the target column. |
Returns | |
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long |
the value of that column as a long. |
short getShort (int column)
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.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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short |
the value of that column as a short. |
String getString (int column)
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.
Parameters | |
---|---|
column |
int :
the zero-based index of the target column. |
Returns | |
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String |
the value of that column as a String. |
int getType (int column)
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 getInt(int)
, getFloat(int)
etc.
Returned column types are
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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int |
column value type |
boolean isNull (int column)
Returns true
if the value in the indicated column is null.
Parameters | |
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column |
int :
the zero-based index of the target column. |
Returns | |
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boolean |
whether the column value is null. |
boolean onMove (int oldPosition, int newPosition)
This function is called every time the cursor is successfully scrolled to a new position, giving the subclass a chance to update any state it may have. If it returns false the move function will also do so and the cursor will scroll to the beforeFirst position.
Parameters | |
---|---|
oldPosition |
int :
the position that we're moving from |
newPosition |
int :
the position that we're moving to |
Returns | |
---|---|
boolean |
true if the move is successful, false otherwise |
void registerContentObserver (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 requery()
is called.
Parameters | |
---|---|
observer |
ContentObserver :
the object that gets notified when the content backing the cursor changes. |
void registerDataSetObserver (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
requery()
, deactivate()
, or close()
.
Parameters | |
---|---|
observer |
DataSetObserver :
the object that gets notified when the cursors data set changes. |
boolean requery ()
Performs the query that created the cursor again, refreshing its
contents. This may be done at any time, including after a call to 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.
Returns | |
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boolean |
true if the requery succeeded, false if not, in which case the cursor becomes invalid. |
void unregisterContentObserver (ContentObserver observer)
Unregister an observer that has previously been registered with this
cursor via registerContentObserver(ContentObserver)
.
Parameters | |
---|---|
observer |
ContentObserver :
the object to unregister. |
void unregisterDataSetObserver (DataSetObserver observer)
Unregister an observer that has previously been registered with this
cursor via registerContentObserver(ContentObserver)
.
Parameters | |
---|---|
observer |
DataSetObserver :
the object to unregister. |