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QGIS Actions

Ujaval Gandhi

ujaval@spatialthoughts.com

PyQGIS Masterclass

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CC BY-4.0

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What are QGIS Actions?

  • A built-in feature of QGIS Desktop.
  • An action is something that happens when you click on a feature.
  • Allows you to run a command or Python code when you click on a feature

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When should you use an action?

Use actions to add custom functionality where you need to do something in response to a user action on a layer.

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Actions are ‘baby plugins’!

Many QGIS customizations can be an Action instead of a plugin.

Actions provide you with an built-in functionality to

  • Add a button in the toolbar/attribute table/attribute form.
  • Execute any Python code or Processing Algorithm when the user picks an action and clicks on a feature.
  • Distribute your customizations with a QGIS Project.

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What can you do with Actions?

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Extract a Feature from a Layer

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Select Features

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Update Field Values

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Load and Remove Raster Layers

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Select Features in a Buffer Zone

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Reverse Line Direction

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Run Processing Algorithms

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View Panorama from Mapillary

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Action Basics

  • Actions are defined for a layer.
    • Action button is enabled if there are 1 or more actions defined for the selected layer
  • Actions are saved along with a QGIS Project
    • Easy sharing of additional functionality

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Action Scopes

An action scope defines where the action is shown.

Depending on the scope, the action code has access to additional variables.

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Action Scopes

  • Canvas
    • Shown in the ‘Action’ button in the Toolbar
    • Access to @layer and all attributes of the clicked feature
    • Access to @click_x and @click_y in map coordinates.
  • Feature
    • Shown in attribute table and feature form.
    • Access to @layer and all attributes of the clicked feature
  • Field
    • Shown in right-click menus of attribute table and feature form
    • Access to @field_index, @field_name and @field_value
  • Layer
    • Show in attribute table and work on the layer or selection
    • Access to @layer
  • Form
    • Shown in feature form designed using the drag-and-drop mode
    • Access to form variable

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Fields and Variables

  • [%name%] : Will replace this with the value of the name field.
  • [%@layer%]: Will be replaced with the value of the @layer variable.
  • [%$id%]: Will be replaced with the feature id.

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Let’s build some actions

https://courses.spatialthoughts.com/pyqgis-masterclass.html#qgis-actions

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Resources

  • QGIS Actions Course