Attribute form¶
QField creates forms similar to, but not equal to QGIS. The field widgets from QGIS are supported on a best effort basis and optimized for the mobile use.
| 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 you have an appropriate viewer) Attachment (photo settings) | |
| Date Time | ||
| Range | ||
| Relation Reference | ||
| Relation Widget | ||
| Value Relation | ||
| UUID Generator | ||
| QML / HTML Widget | ||
| Others | Funding |
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.
Suppress attribute form¶
The setting suppress attribute form is directly applied to the QField form.
Drag and drop designer forms¶
Groups and Tabs from Drag and Drop designer forms are supported.
In the "Attributes Form," you can structure your forms using various containers, such as tabs and groups, and enhance interactivity by incorporating expression-based conditional visibility. By enabling the Drag and Drop Designer, you gain the flexibility to re-order attribute fields, as well as gaining access to widgets that are not directly tied to specific fields (e.g., HTML/QML widgets).
Configure a Relation Widget¶
Desktop preparation
For more information refer to the relations chapter of the official QGIS Documentation.
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.
In case of the many-to-one cardinality on many-to-many relations the Display Expression needs to be set on the linking table.
Item Threshold Configuration for Value Map Editor Widgets¶
To enhance the user experience within QField, it is possible to control the item threshold at which point the value map editor widgets switch to a toggle buttons interface. This feature allows users to quickly access items in QField when there are few and providing a more intuitive interface when dealing with a large number of items.
To Activate Toggle Button Interface¶
-
Open Layer Properties by right-clicking on the desired layer and selecting 'Properties' from the context menu.
-
Navigate to the QField tab located within the Layer Properties dialog.
-
Here, you will find an option to specify the quantity of items that will trigger the transition to a toggle button interface. Enter the preferred threshold value according to your needs.
Configure Attachment Widget¶
Desktop preparation
The widget type Attachment is used with fields that store the path to files.
It can be used to:
- show and take photos or add pictures from the gallery
- listen and record sound clips
- show and record videos
- show links to external files like PDFs or documents
The path should be set to relative. The pictures, audios, videos, pdf and docs are stored then in a sub-directory of the project, where the link stored in the textfield is pointing to.
Note
QGIS 3.30 or newer is required for the audio and video functionality
In QField the attachments are displayed. By clicking the icons symbol the camera or audio record is started to update the pictures, videos or audios with a new media.
On synchronization the sub-directory with the pictures, videos audios, 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, ...).
Configurable attachment path¶
Desktop preparation
QFieldSync provides the possibility to configure the path of attachments.
- Go to QFieldSync plugin > Layers Properties
Use expressions to specify the path of the attachments. By default, pictures are saved into the "DCIM" folder, audio recordings are saved into the "audio" folder and videos are saved into "video" with a timestamp as name.
Configure a Value Relation Widget¶
Desktop preparation
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.
Configure Conditional Visibility¶
Desktop preparation
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 you.
Let's see what we got on the field:
Define Constraints¶
Desktop preparation
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 if a
constraint is not satisfied.
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
Define Default Values¶
Desktop preparation
Fields can have default values configured. Default values are inserted into the attribute form when digitizing a new feature. They are visible and can be modified as long as the field is editable. They can be based on the geometry or expression variables.
When creating expressions for projects intended to be used with QField, it is recommended to use layer names rather than layer IDs. This recommendation stems from the fact that during the project conversion process via QFieldSync, the resulting layers may receive different IDs, which can lead to incorrect expression evaluations. By using layer names, you ensure that expressions are evaluated consistently and accurately across different project states.
Additional variables¶
For more information regarding storing information related to your position in object attributes, refer to the deticated GNSS documentation.
For QFieldCloud users, two variables can be used in expressions including attribute form's default values:
- @cloud_username which returns the name of the currently logged in QFieldCloud user.
- @cloud_useremail which returns the email address of the currently logged in QFieldCloud user.
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 ))
::: {#snapping_results} If you want to use the snapping results after drawing a line, you can use the [\@snapping_results]{.title-ref} variable. The following code extracts the value of the attribute [id]{.title-ref} 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'
)
)
Search in value relation and relation reference widget¶
It is possible to search value in a value relation or relation reference widget using the magnifying glass next to the field.
Note
Define the display expression for the concerned layers, this will be used for searching for features. This is configured under Vector Layer Properties > Display
Configure Auto-complete Value¶
Desktop preparation
The "Use completer" checkbox must be checked to be able to use the auto-complete in the value relation.
Here a video showing how it works on QField
Define QML Widgets¶
Custom QML widgets can be useful to integrate advanced actions into forms. In this example we define add a button that open a third-party map and navigation app. This is useful to open e.g. turn-by-turn navigations on the device-native app for the user.
import QtQuick 2.0
import QtQuick.Controls 2.0
Button {
width: 200
height: width/5
text: "Open in Maps"
onClicked: {
Qt.openUrlExternally(expression.evaluate("'geo:0,0?q=' || $y || ',' || $x"));
}
}
The geo URI above is adapted to work with Android. For Apple Maps the URI can be changed to 'geo:' || $y || ',' || $x.
