Class: QgsTaskManager

class qgis.core.QgsTaskManager(parent: QObject = None)

Bases: PyQt5.QtCore.QObject

Constructor for QgsTaskManager.

Parameters

parent – parent QObject

Task manager for managing a set of long-running QgsTask tasks. This class can be created directly, or accessed via QgsApplication.taskManager()

New in version 3.0: Enums

Methods

activeTasks

Returns a list of the active (queued or running) tasks.

addTask

Adds a task to the manager.

cancelAll

Instructs all tasks tracked by the manager to terminate.

childEvent

connectNotify

count

Returns the number of tasks tracked by the manager.

countActiveTasks

Returns the number of active (queued or running) tasks.

customEvent

dependenciesSatisfied

Returns True if all dependencies for the specified task are satisfied

dependentLayers

Returns a list of layers on which as task is dependent.

disconnectNotify

isSignalConnected

receivers

sender

senderSignalIndex

task

Returns the task with matching ID.

taskId

Returns the unique task ID corresponding to a task managed by the class.

tasks

Returns all tasks tracked by the manager.

tasksDependentOnLayer

Returns a list of tasks which depend on a layer.

timerEvent

triggerTask

Triggers a task, e.g.

Signals

allTasksFinished

Emitted when all tasks are complete

countActiveTasksChanged

Emitted when the number of active tasks changes

finalTaskProgressChanged

Will be emitted when only a single task remains to complete and that task has reported a progress change

progressChanged

Will be emitted when a task reports a progress change

statusChanged

Will be emitted when a task reports a status change

taskAboutToBeDeleted

Emitted when a task is about to be deleted

taskAdded

Emitted when a new task has been added to the manager

taskTriggered

Emitted when a task is triggered.

Attributes

class TaskDefinition(task: QgsTask, dependentTasks: object = QgsTaskList())

Bases: sip.wrapper

Constructor for TaskDefinition. Ownership of the task is not transferred to the definition, but will be transferred to a QgsTaskManager.

QgsTaskManager.TaskDefinition(QgsTaskManager.TaskDefinition)

dependentTasks
task
activeTasks(self) → List[QgsTask]

Returns a list of the active (queued or running) tasks.

addTask(self, task: QgsTask, priority: int = 0) → int

Adds a task to the manager. Ownership of the task is transferred to the manager, and the task manager will be responsible for starting the task. The priority argument can be used to control the run queue’s order of execution, with larger numbers taking precedence over lower priority numbers.

Returns

unique task ID, or 0 if task could not be added

addTask(self, task: QgsTaskManager.TaskDefinition, priority: int = 0) -> int Adds a task to the manager, using a full task definition (including dependency handling). Ownership of the task is transferred to the manager, and the task manager will be responsible for starting the task. The priority argument can be used to control the run queue’s order of execution, with larger numbers taking precedence over lower priority numbers.

Returns

unique task ID, or 0 if task could not be added

allTasksFinished

Emitted when all tasks are complete

See also

countActiveTasksChanged() [signal]

cancelAll(self)

Instructs all tasks tracked by the manager to terminate. Individual tasks may take some time to cancel, or may totally ignore this instruction. Calling this does not block but will instead signal the tasks to cancel and then return immediately.

childEvent()
connectNotify()
count(self) → int

Returns the number of tasks tracked by the manager.

countActiveTasks(self) → int

Returns the number of active (queued or running) tasks.

See also

activeTasks()

countActiveTasksChanged

Emitted when the number of active tasks changes

See also

countActiveTasks() [signal]

customEvent()
dependenciesSatisfied(self, taskId: int) → bool

Returns True if all dependencies for the specified task are satisfied

dependentLayers(self, taskId: int) → List[QgsMapLayer]

Returns a list of layers on which as task is dependent. The task will automatically be canceled if any of these layers are about to be removed.

Parameters

taskId – task ID

Returns

list of layers

disconnectNotify()
finalTaskProgressChanged

Will be emitted when only a single task remains to complete and that task has reported a progress change

Parameters

progress – percent of progress, from 0.0 - 100.0 [signal]

isSignalConnected()
progressChanged

Will be emitted when a task reports a progress change

Parameters
  • taskId – ID of task

  • progress – percent of progress, from 0.0 - 100.0 [signal]

receivers()
sender()
senderSignalIndex()
statusChanged

Will be emitted when a task reports a status change

Parameters
  • taskId – ID of task

  • status – new task status [signal]

task(self, id: int) → QgsTask

Returns the task with matching ID.

Parameters

id – task ID

Returns

task if found, or None

taskAboutToBeDeleted

Emitted when a task is about to be deleted

Parameters

taskId – ID of task [signal]

taskAdded

Emitted when a new task has been added to the manager

Parameters

taskId – ID of task [signal]

taskId(self, task: QgsTask) → int

Returns the unique task ID corresponding to a task managed by the class.

Parameters

task – task to find

Returns

task ID, or -1 if task not found

taskTriggered

Emitted when a task is triggered. This occurs when a user clicks on the task from the QGIS GUI, and can be used to show detailed progress reports or re-open a related dialog.

See also

triggerTask() [signal]

tasks(self) → List[QgsTask]

Returns all tasks tracked by the manager.

tasksDependentOnLayer(self, layer: QgsMapLayer) → List[QgsTask]

Returns a list of tasks which depend on a layer.

timerEvent()
triggerTask(self, task: QgsTask)

Triggers a task, e.g. as a result of a GUI interaction.

See also

taskTriggered()