A complication is any feature that is displayed on a watch face in addition to the time. For example, a battery indicator is a complication. The Complications API is for both watch faces and data source apps.
The rest of this document describes data sources, watch faces, and complication types.
Complication data source
Apps that provide data such as battery level, weather, or step counts to watch faces for complications are called complication data sources. These data sources supply raw data and are not responsible for controlling how their data is rendered on a watch face. To learn about writing apps that provide data to watch faces, see Expose data to complications.
The following diagram shows how Wear OS by Google mediates the flow of data from sources to watch faces.
Complications on watch faces
Watch faces receive data from complication data sources, which lets them include complications without needing code for getting the underlying data. Watch faces retain control over how the data is rendered, so they can integrate data naturally with their design. For more information, see the design guide about Complications.
To learn how to add complications to a watch face, see Add complications to a watch face.
Complication types define what kinds of data can be shown in a
complication or supplied by
a data source. For example, use the
SHORT_TEXT type when the
primarily of a short string. A
ComplicationData object always has a single
complication type that defines required and optional fields. A required
represents the primary piece of data; most types take their name from
the required field.
Data sources use complication types differently from watch faces:
- A data source chooses the types of complication data to supply,
including which optional fields of those types to supply, and
how many different types can be supported. For example, a step-count
source might support the
SHORT_TEXTtypes, and a next-meeting source might support the
- You can choose how many complications to include in your watch face
and the complication
types to support. For example, a dial complication on a watch face
RANGED_VALUEtypes. A gauge on the watch face might support only the
To learn more about different complication types and fields supported by each type, see Complication types.