You can use UQuery to find elements from a visual tree. UQuery was inspired by JQuery and Linq, and is designed to limit dynamic memory allocation. This allows for optimal performance on mobile platforms.
You can use UQuery through the Q
and Query
extension methods. Internally, the Q
and Query
methods use UQueryBuilder
to construct a query. These extension methods reduce the verbosity of creating a UQueryBuilder
.
To use UQuery to find elements, you must load and instantiate the UXML first.
To use Query
and Q
, construct specified selections rules on a root visual element. Query
returns a list of elements that match the selection rules. Q
is the shorthand for Query<T>.First()
. It returns the first element that matches the selection rules.
You can filter the return results of Query
with the public methods of UQueryBuilder
, such as First, Last, AtIndex, Children, and Where.
You can query elements by their name, their USS class, or their element type(C# type). You can also query with a predicate or make complex hierarchical queries.
The following sections use this example UXML to demonstrate how to find elements:
<UXML xmlns="UnityEngine.UIElements">
<VisualElement name="container1">
<Button name="OK" text="OK" />
<Button name="Cancel" text="Cancel" />
</VisualElement>
<VisualElement name="container2">
<Button name="OK" class="yellow" text="OK" />
<Button name="Cancel" text="Cancel" />
</VisualElement>
<VisualElement name="container3">
<Button name="OK" class="yellow" text="OK" />
<Button name="Cancel" class="yellow" text="Cancel" />
</VisualElement>
</UXML>
To find elements by their name, use Query(name: "element-name")
or Q(name: "element-name")
. You can omit name
as it’s the first argument. For example:
//Find a list of elements named "Ok".
List<VisualElement> result1 = root.Query("OK").ToList();
//Find the first element named "Ok" and add a tooltip for it.
VisualElement result2 = root.Query("OK").First(); //or VisualElement result = root.Q("OK");
result.tooltip = "This is a tooltip!";
//Find the second element named "Ok".
VisualElement result3 = root.Query("OK").AtIndex(1);
//Find the last element named "Ok".
VisualElement result4 = root.Query("OK").Last();
To find elements by a USS class, use Query(className: "class-name")
or Q(className: "class-name")
. For example:
//Find all the elements that have the class "yellow" and assign them to a list.
List<VisualElement> result = root.Query(className: "yellow").ToList();
//Find the first element that has the class "yellow".
VisualElement result = root.Q(className: "yellow");
To find elements by their element type(C# type), use Query<Type>
or Q<Type>
. For example:
//Find the first button and add a tooltip for it.
VisualElement result = root.Q<Button>();
result.tooltip = "This is a tooltip!";
//Find the third button.
VisualElement result = root.Query<Button>().AtIndex(2);
Note: You can only query by the actual type of the element, not base classes.
Other than to query element by name, class, and type, you can also use the Where
method to select all elements that satisfy a predicate. The predicate must be a function callback that takes a single VisualElement
argument. For example, the following code snippet finds the all the elements with the “yellow” USS class that have no tool tips:
List<VisualElement> result = root.Query(className: "yellow").Where(elem => elem.tooltip == "").ToList();
You can combine name, class, and type to make complex hierarchical queries. For example:
//Find the first button named "OK" that has a class of "yellow".
VisualElement result = root.Query<Button>(className: "yellow", name: "OK").First();
result.tooltip = "This is a tooltip!";
//Find the child cancel button of the "container2".
VisualElement result = root.Query<VisualElement>("container2").Children<Button>("Cancel").First();
You can use the ForEach method to operate directly on the query results. For example, the following code snippet adds a tool tip for any elements that have no tool tips:
root.Query().Where(elem => elem.tooltip == "").ForEach(elem => elem.tooltip="This is a tooltip!");
Consider the following when you use UQuery:
QueryState
struct (returned by the element.Query()
method) and enumerate it to avoid creating lists. You can also construct a query once and execute it on different elements.VisualElement
variables inside closures.Did you find this page useful? Please give it a rating:
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