QGIS API Documentation 3.27.0-Master (95e00c50d2)
Public Member Functions | Protected Member Functions | List of all members
QgsProviderSublayerTask Class Reference

A QgsTask which retrieves sublayer details for a URI. More...

#include <qgsprovidersublayertask.h>

Inheritance diagram for QgsProviderSublayerTask:
Inheritance graph
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Public Member Functions

 QgsProviderSublayerTask (const QString &uri, bool includeSystemTables=false)
 Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri. More...
 
 ~QgsProviderSublayerTask () override
 
void cancel () override
 Notifies the task that it should terminate. More...
 
QList< QgsProviderSublayerDetailsresults () const
 Returns the sublayer details as calculated by the task. More...
 
- Public Member Functions inherited from QgsTask
 QgsTask (const QString &description=QString(), QgsTask::Flags flags=AllFlags)
 Constructor for QgsTask. More...
 
 ~QgsTask () override
 
void addSubTask (QgsTask *subTask, const QgsTaskList &dependencies=QgsTaskList(), SubTaskDependency subTaskDependency=SubTaskIndependent)
 Adds a subtask to this task. More...
 
bool canCancel () const
 Returns true if the task can be canceled. More...
 
virtual void cancel ()
 Notifies the task that it should terminate. More...
 
QList< QgsMapLayer * > dependentLayers () const
 Returns the list of layers on which the task depends. More...
 
QString description () const
 Returns the task's description. More...
 
qint64 elapsedTime () const
 Returns the elapsed time since the task commenced, in milliseconds. More...
 
Flags flags () const
 Returns the flags associated with the task. More...
 
void hold ()
 Places the task on hold. More...
 
bool isActive () const
 Returns true if the task is active, ie it is not complete and has not been canceled. More...
 
double progress () const
 Returns the task's progress (between 0.0 and 100.0) More...
 
void setDependentLayers (const QList< QgsMapLayer * > &dependentLayers)
 Sets a list of layers on which the task depends. More...
 
void setDescription (const QString &description)
 Sets the task's description. More...
 
TaskStatus status () const
 Returns the current task status. More...
 
void unhold ()
 Releases the task from being held. More...
 
bool waitForFinished (int timeout=30000)
 Blocks the current thread until the task finishes or a maximum of timeout milliseconds. More...
 

Protected Member Functions

bool run () override
 Performs the task's operation. More...
 
- 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). More...
 
bool isCanceled () const
 Will return true if task should terminate ASAP. More...
 
virtual bool run ()=0
 Performs the task's operation. More...
 

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...
 
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. More...
 
void progressChanged (double progress)
 Will be emitted by task when its progress changes. More...
 
void statusChanged (int status)
 Will be emitted by task when its status changes. More...
 
void taskCompleted ()
 Will be emitted by task to indicate its successful completion. More...
 
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). More...
 
- Protected Slots inherited from QgsTask
void setProgress (double progress)
 Sets the task's current progress. More...
 

Detailed Description

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.

Since
QGIS 3.22

Definition at line 46 of file qgsprovidersublayertask.h.

Constructor & Destructor Documentation

◆ QgsProviderSublayerTask()

QgsProviderSublayerTask::QgsProviderSublayerTask ( const QString &  uri,
bool  includeSystemTables = false 
)

Constructor for QgsProviderSublayerTask, which retrieves sublayer details for the specified uri.

Definition at line 24 of file qgsprovidersublayertask.cpp.

◆ ~QgsProviderSublayerTask()

QgsProviderSublayerTask::~QgsProviderSublayerTask ( )
overridedefault

Member Function Documentation

◆ cancel()

void QgsProviderSublayerTask::cancel ( )
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.

See also
isCanceled()

Reimplemented from QgsTask.

Definition at line 55 of file qgsprovidersublayertask.cpp.

◆ results()

QList< QgsProviderSublayerDetails > QgsProviderSublayerTask::results ( ) const

Returns the sublayer details as calculated by the task.

Definition at line 31 of file qgsprovidersublayertask.cpp.

◆ run()

bool QgsProviderSublayerTask::run ( )
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 39 of file qgsprovidersublayertask.cpp.


The documentation for this class was generated from the following files: