Subgroup: Task

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: 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.

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

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
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 above 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()