Attribute Form Configuration

QField creates forms similar to, but not equal to QGIS.

Suppress Attribute Form

The setting “suppress attribute form” is directly applied to the QField form.

Field widget

The field widgets from QGIS are supported on a best effort basis.

Widget type Support Notes
Text Edit
  • HTML is not supported
  • Numerical input is enforced based on the type.
Check Box  
Value Map  
Hidden  
Attachment This field is combined with camera integration. It is also able to open other files like pdf and doc (if the user has an appropriate viewer) Attachment (photo settings)
Date Time  
Relation Reference  
Relation Widget  
Value Relation  
Others Funding

Relation Widget

For more information refer to the relations chapter of the official QGIS Documentation.

../_images/relation_editor_widget_list.png

The relation widget shows all the referencing child features in a list. It is possible to add, delete and open them.

The visual identification of the list entries are done via the “Display Expression” of the child layer.

Key handling

Since the parents primary keys are used as foreign keys on the referencing child features, these primary keys must be save to use even after the synchronization back to the original data. Therefore we recommend to use stable values such as UUIDs for primary keys.

It is possible to already add children from a parent that is about to be added. This possibility will be blocked if there is no valid primary key on the parent or the constraints are violated. In case the adding of the parent feature is canceled after some children have been added already, the children are deleted as well.

Many-To-Many relations

On many-to-many relationships, according to the cardinality setting in the QGIS Vector Layer Properties, on adding, deleting or opening an entry in the list effects directly the child layer (on direct cardinality) or the linking table (on many-to-one cardinality).

The second case is usually used when there are additional relation information (e.g. percentage) in the linking table.

../_images/relation_widget_cardinality.png

In case of the many-to-one cardinality on many-to-many relations the Display Expression needs to be set on the linking table.

Attachment (photo settings)

The widget type “Attachment” is used with fields that store the path to files.

It can be used to:

  • show and take photos
  • show links to external files like pdfs or documents
Attachement field settings

The path should be set to relative. The pictures, pdf and docs are stored then in a sub-directory of the project, where the link stored in the textfield is pointing to.

In QField the picture is displayed. By clicking the camera symbol the camera is started to update the picture with a new photo.

Picture in QField

On synchronization the sub-directory with the pictures, pdf and docs has to be copied as well.

The option “hyperlink” on the attachment widget will disable the camera functionality and enable a hyperlink to open a document (pdf, doc, …).

hyperlink_option

Value Relation

The widget “Value Relation” offers values from a related table in a combobox. You can select layer, key column and value column. Several options are available to change the standard behaviors: allow null value, order by value and allow multiple selections. The widget will display a drop-down or multiple-select list of the referenced features.

value_relation_widget

Drag and drop designer forms

Groups and Tabs from Drag and Drop designer forms are supported.

Conditional visibility

Groups can be hidden based on an expression. This is useful when certain attributes are only required under certain conditions. As an example imagine mapping trees. Some of them might have a disease and you have a list of possible deseases. To not clutter the form with many fields, make a group and configure a visibility expression for a group “diseases”. Add a field “desease” with a checkbox. Only when the checkbox is checked, the list of diseases will be available to the user.

Conditional visibility configuration

Configuration of a group box that will only be shown if the checkbox “measures_taken” is checked.

Let’s see what we got on the field:

Constraints

Attribute fields can have constraints attached. Constraints are expressions that needs to evaluate to True (or 1) in order to be able to save the form. Constraints are configured on a per-field basis and a description can be added that will be shown to the user if a constraint is not satisfied.

Constraint configuration

Configuration of a constraint within a range

Common use cases

You cannot enter an elevation value higher than the highest mountain in this country.

"elevation" < 5000

It is required to fill in an identifier.

"identifier" IS NOT NULL

Default values

Fields can have default values configured. Default values are inserted into the attribute form when digitizing a new feature. They are visible to the user and can be modified as long as the field is editable. They can be based on the geometry or expression variables.

Default value configuration

Configuration of a formatted date as default value

Additional variables

For more information regarding storing information related to your position in object attributes, refer to the deticated GNSS documentation.

Common use cases

Insert positioning information as variable:

@position_horizontal_accuracy

Insert the current date and time:

now()

Insert the length of the digitized line:

length($geometry)

Configure global variables on the device and insert them.

@operator_name

If you want to assign a region code based on the location where a new feature is inserted, you can do so by using an aggregate expression:

aggregate( layer:='regions', aggregate:='max', expression:="code", filter:=intersects( $geometry, geometry( @parent ) ) )

To transform the coordinates received from @position_coordinate to the coordinate system of your project:

x(transform(@position_coordinate, 'EPSG:4326', @project_crs ))
y(transform(@position_coordinate, 'EPSG:4326', @project_crs ))

If you want to use the snapping results after drawing a line, you can use the @snapping_results variable. The following code extracts the value of the attribute id of the snapping match of the first point of a line.

with_variable(
  'first_snapped_point',
  array_first( @snapping_results ),
  attribute(
    get_feature_by_id(
      @first_snapped_point['layer'],
      @first_snapped_point['feature_id']
    ),
    'id'
  )

)

Editable

The editable flag of fields is respected.

Remember last values

QField offers a much more fine-grained control over the last used values and ignores the QGIS setting.