Dynamic expressions in Wear OS
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Wear OS supports dynamic updates to information that appears in your tiles
and complications.
Using dynamic expressions, you can bind data that appears on a surface of your
app–such as a tile or complication–to a particular data source. An example of
such a data source is heart rate data that the platform can read. After you've
established this binding, the system updates the data in your tiles and
complications automatically.
Create dynamic data bindings
To create a dynamic data binding, define a variable that uses a
dynamic data type. Associate this variable with the data stream that you
want to use.
For example, you can fetch values related to the system clock and health
information, as shown in the following code snippet.
Kotlin
val systemTime = DynamicInstant.platformTimeWithSecondsPrecision()
val steps: DynamicInt32 = PlatformHealthSources.dailySteps()
Java
DynamicInstant systemTime = DynamicInstant.platformTimeWithSecondsPrecision();
DynamicInt32 steps = PlatformHealthSources.dailySteps();
You can also create dynamic values from constant expressions and perform
arithmetic operations on any dynamic value, as shown in the following snippet:
Kotlin
val dynamicValue = DynamicInt32.constant(1).plus(2)
Java
DynamicInt32 dynamicValue = DynamicInt32.constant(1).plus(2)
List of possible dynamic data types
Wear OS supports the following dynamic data types:
In addition, you can transform the data type using built-in capabilities, such
as the following:
DynamicInt32
supports conversion to a DynamicString
using
format()
.
DynamicDuration
lets you extract specific parts, such as the seconds part
of a duration, as DynamicInt32
objects.
Use a limited number of dynamic expressions on each screen
The system has a limit on the number of dynamic expressions that it can process
simultaneously on a particular screen. The system converts any additional
dynamic expressions to static values.
Wear OS considers constant expressions to be dynamic expressions, too. For
example, the following code snippet contains 4 dynamic expressions:
- The
plus()
operation.
- The
animate()
operation.
- The
constant(1)
expression.
- The
constant(2)
expression, which is implied by the value 2
in the
plus()
dynamic expression.
DynamicInt32.constant(1).plus(2).animate()
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Last updated 2024-11-12 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-11-12 UTC."],[],[],null,["# Dynamic expressions in Wear OS\n\nWear OS supports dynamic updates to information that appears in your [tiles](/training/wearables/tiles)\nand [complications](/training/wearables/tiles/complications).\n\nUsing dynamic expressions, you can bind data that appears on a surface of your\napp--such as a tile or complication--to a particular data source. An example of\nsuch a data source is heart rate data that the platform can read. After you've\nestablished this binding, the system updates the data in your tiles and\ncomplications automatically.\n\nCreate dynamic data bindings\n----------------------------\n\nTo create a dynamic data binding, define a variable that uses a\n[dynamic data type](#data-types). Associate this variable with the data stream that you\nwant to use.\n\nFor example, you can fetch values related to the system clock and health\ninformation, as shown in the following code snippet.\n| **Note:** To access the data in [`PlatformHealthSources`](/reference/androidx/wear/protolayout/expression/PlatformHealthSources), you must [request a\nruntime permission](/training/permissions/requesting) in your app. \n\n### Kotlin\n\n```kotlin\nval systemTime = DynamicInstant.platformTimeWithSecondsPrecision()\nval steps: DynamicInt32 = PlatformHealthSources.dailySteps()\n```\n\n### Java\n\n```java\nDynamicInstant systemTime = DynamicInstant.platformTimeWithSecondsPrecision();\nDynamicInt32 steps = PlatformHealthSources.dailySteps();\n```\n\nYou can also create dynamic values from constant expressions and perform\narithmetic operations on any dynamic value, as shown in the following snippet: \n\n### Kotlin\n\n```kotlin\nval dynamicValue = DynamicInt32.constant(1).plus(2)\n```\n\n### Java\n\n```java\nDynamicInt32 dynamicValue = DynamicInt32.constant(1).plus(2)\n```\n\n### List of possible dynamic data types\n\nWear OS supports the following dynamic data types:\n\n- [`DynamicBool`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicBool)\n- [`DynamicColor`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicColor)\n- [`DynamicDuration`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicDuration)\n- [`DynamicFloat`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicFloat)\n- [`DynamicInstant`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicInstant)\n- [`DynamicInt32`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicInt32)\n- [`DynamicString`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicString)\n\nIn addition, you can transform the data type using built-in capabilities, such\nas the following:\n\n- `DynamicInt32` supports conversion to a `DynamicString` using [`format()`](/reference/androidx/wear/protolayout/expression/DynamicBuilders.DynamicInt32#format()).\n- `DynamicDuration` lets you extract specific parts, such as the seconds part of a duration, as `DynamicInt32` objects.\n\nUse a limited number of dynamic expressions on each screen\n----------------------------------------------------------\n\nThe system has a limit on the number of dynamic expressions that it can process\nsimultaneously on a particular screen. The system converts any additional\ndynamic expressions to static values.\n\nWear OS considers constant expressions to be dynamic expressions, too. For\nexample, the following code snippet contains 4 dynamic expressions:\n\n1. The `plus()` operation.\n2. The `animate()` operation.\n3. The `constant(1)` expression.\n4. The `constant(2)` expression, which is implied by the value `2` in the `plus()` dynamic expression.\n\n DynamicInt32.constant(1).plus(2).animate()\n\nRecommended for you\n-------------------\n\n- Note: link text is displayed when JavaScript is off\n- [Migrate to ProtoLayout namespaces](/training/wearables/tiles/migrate-to-protolayout)\n- [Side-effects in Compose](/develop/ui/compose/side-effects)\n- [AGSL Quick Reference](/develop/ui/views/graphics/agsl/agsl-quick-reference)"]]