QGIS API Documentation 3.39.0-Master (699c004a5df)
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A QgsTask which retrieves sublayer details for a URI. More...
#include <qgsprovidersublayertask.h>
Public Member Functions | |
QgsProviderSublayerTask (const QString &uri, bool includeSystemTables=false) | |
Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri. | |
QgsProviderSublayerTask (const QString &uri, const QString &providerKey, bool includeSystemTables=false) | |
Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri, restricted to a particular provider. | |
~QgsProviderSublayerTask () override | |
void | cancel () override |
Notifies the task that it should terminate. | |
QList< QgsProviderSublayerDetails > | results () const |
Returns the sublayer details as calculated by the task. | |
Public Member Functions inherited from QgsTask | |
QgsTask (const QString &description=QString(), QgsTask::Flags flags=AllFlags) | |
Constructor for QgsTask. | |
~QgsTask () override | |
void | addSubTask (QgsTask *subTask, const QgsTaskList &dependencies=QgsTaskList(), SubTaskDependency subTaskDependency=SubTaskIndependent) |
Adds a subtask to this task. | |
bool | canCancel () const |
Returns true if the task can be canceled. | |
QList< QgsMapLayer * > | dependentLayers () const |
Returns the list of layers on which the task depends. | |
QString | description () const |
Returns the task's description. | |
qint64 | elapsedTime () const |
Returns the elapsed time since the task commenced, in milliseconds. | |
Flags | flags () const |
Returns the flags associated with the task. | |
void | hold () |
Places the task on hold. | |
bool | isActive () const |
Returns true if the task is active, ie it is not complete and has not been canceled. | |
double | progress () const |
Returns the task's progress (between 0.0 and 100.0) | |
void | setDependentLayers (const QList< QgsMapLayer * > &dependentLayers) |
Sets a list of layers on which the task depends. | |
void | setDescription (const QString &description) |
Sets the task's description. | |
TaskStatus | status () const |
Returns the current task status. | |
void | unhold () |
Releases the task from being held. | |
bool | waitForFinished (int timeout=30000) |
Blocks the current thread until the task finishes or a maximum of timeout milliseconds. | |
Protected Member Functions | |
bool | run () override |
Performs the task's operation. | |
Protected Member Functions inherited from QgsTask | |
virtual void | finished (bool result) |
If the task is managed by a QgsTaskManager, this will be called after the task has finished (whether through successful completion or via early termination). | |
bool | isCanceled () const |
Will return true if task should terminate ASAP. | |
Additional Inherited Members | |
Public Types inherited from QgsTask | |
enum | Flag { CanCancel = 1 << 1 , CancelWithoutPrompt = 1 << 2 , Hidden = 1 << 3 , Silent = 1 << 4 , AllFlags = CanCancel } |
Task flags. More... | |
typedef QFlags< Flag > | Flags |
enum | SubTaskDependency { SubTaskIndependent = 0 , ParentDependsOnSubTask } |
Controls how subtasks relate to their parent task. More... | |
enum | TaskStatus { Queued , OnHold , Running , Complete , Terminated } |
Status of tasks. More... | |
Signals inherited from QgsTask | |
void | begun () |
Will be emitted by task to indicate its commencement. | |
void | progressChanged (double progress) |
Will be emitted by task when its progress changes. | |
void | statusChanged (int status) |
Will be emitted by task when its status changes. | |
void | taskCompleted () |
Will be emitted by task to indicate its successful completion. | |
void | taskTerminated () |
Will be emitted by task if it has terminated for any reason other then completion (e.g., when a task has been canceled or encountered an internal error). | |
Protected Slots inherited from QgsTask | |
void | setProgress (double progress) |
Sets the task's current progress. | |
A QgsTask which retrieves sublayer details for a URI.
This task executes a call to QgsProviderRegistry::querySublayers() in a background thread. Depending on the URI queried it can be expensive to calculate the sublayers (e.g. in the case where a full table scan is required to resolve mixed geometry type layers), so it is beneficial to perform these queries in the background wherever possible.
While QgsProviderRegistry::querySublayers() offers various flags to control how in-depth the querying will be, these flags are not exposed through QgsProviderSublayerTask. Rather QgsProviderSublayerTask will always execute the most thorough query possible, regardless of how expensive this may be.
Definition at line 46 of file qgsprovidersublayertask.h.
QgsProviderSublayerTask::QgsProviderSublayerTask | ( | const QString & | uri, |
bool | includeSystemTables = false |
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Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri.
Definition at line 25 of file qgsprovidersublayertask.cpp.
QgsProviderSublayerTask::QgsProviderSublayerTask | ( | const QString & | uri, |
const QString & | providerKey, | ||
bool | includeSystemTables = false |
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Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri, restricted to a particular provider.
Definition at line 32 of file qgsprovidersublayertask.cpp.
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overridedefault |
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overridevirtual |
Notifies the task that it should terminate.
Calling this is not guaranteed to immediately end the task, rather it sets the isCanceled() flag which task subclasses can check and terminate their operations at an appropriate time. Any subtasks owned by this task will also be canceled. Derived classes must ensure that the base class implementation is called from any overridden version.
Reimplemented from QgsTask.
Definition at line 72 of file qgsprovidersublayertask.cpp.
QList< QgsProviderSublayerDetails > QgsProviderSublayerTask::results | ( | ) | const |
Returns the sublayer details as calculated by the task.
Definition at line 40 of file qgsprovidersublayertask.cpp.
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overrideprotectedvirtual |
Performs the task's operation.
This method will be called when the task commences (ie via calling start() ), and subclasses should implement the operation they wish to perform in the background within this method.
A task must return a boolean value to indicate whether the task was completed successfully or terminated before completion.
Implements QgsTask.
Definition at line 48 of file qgsprovidersublayertask.cpp.