PlaceholderState
@ExperimentalWearMaterialApi
class PlaceholderState
A state object that can be used to control placeholders. Placeholders are used when the content that needs to be displayed in a component is not yet available, e.g. it is loading asynchronously.
A PlaceholderState should be created for each component that has placeholder data. The state is used to coordinate all of the different placeholder effects and animations.
Placeholder has a number of different effects designed to work together. Modifier.placeholder draws a placeholder shape on top of content that is waiting to load. There can be multiple placeholders in a component. Modifier.placeholderShimmer does a shimmer animation over the whole component that includes the placeholders. There should only be one placeholderShimmer for each component.
NOTE: The order of modifiers is important. If you are adding both Modifier.placeholder and Modifier.placeholderShimmer to the same composable then the shimmer must be before in the modifier chain. Example of Text composable with both placeholderShimmer and placeholder modifiers.
import androidx.compose.foundation.layout.width import androidx.compose.runtime.LaunchedEffect import androidx.compose.runtime.mutableStateOf import androidx.compose.runtime.remember import androidx.compose.ui.Modifier import androidx.compose.ui.text.style.TextAlign import androidx.compose.ui.text.style.TextOverflow import androidx.compose.ui.unit.dp import androidx.wear.compose.material.Text import androidx.wear.compose.material.placeholder import androidx.wear.compose.material.placeholderShimmer import androidx.wear.compose.material.rememberPlaceholderState var labelText by remember { mutableStateOf("") } val chipPlaceholderState = rememberPlaceholderState { labelText.isNotEmpty() } Text( text = labelText, overflow = TextOverflow.Ellipsis, textAlign = TextAlign.Center, modifier = Modifier.width(90.dp) .placeholderShimmer(chipPlaceholderState) .placeholder(chipPlaceholderState), ) // Simulate content loading LaunchedEffect(Unit) { delay(3000) labelText = "A label" } if (!chipPlaceholderState.isShowContent) { LaunchedEffect(chipPlaceholderState) { chipPlaceholderState.startPlaceholderAnimation() } }
Background placeholder effects are used to mask the background of components like chips and cards until all of the data has loaded. Use PlaceholderDefaults.placeholderChipColors and PlaceholderDefaults.painterWithPlaceholderOverlayBackgroundBrush to draw the component background.
Once all of the components content is loaded the shimmer will stop and a wipe off animation will remove the placeholders.
Summary
Public functions | |
|---|---|
suspend Unit | Start the animation of the placeholder state. |
Public properties | |
|---|---|
Boolean | Returns true if the placeholder content should be shown with no placeholders effects and false if either the placeholder or the wipe-off effect are being shown. |
Boolean | Should only be called when |
Float | The current value of the placeholder visual effect gradient progression. |
Public functions
startPlaceholderAnimation
suspend fun startPlaceholderAnimation(): Unit
Start the animation of the placeholder state.
Public properties
isShowContent
val isShowContent: Boolean
Returns true if the placeholder content should be shown with no placeholders effects and false if either the placeholder or the wipe-off effect are being shown.
isWipeOff
val isWipeOff: Boolean
Should only be called when isShowContent is false. Returns true if the wipe-off effect that reveals content should be shown and false if the placeholder effect should be shown.
placeholderProgression
@ExperimentalWearMaterialApi
val placeholderProgression: Float
The current value of the placeholder visual effect gradient progression. The progression gives the x coordinate to be applied to the placeholder gradient as it moves across the screen. Starting off screen to the left and progressing across the screen and finishing off the screen to the right after PLACEHOLDER_SHIMMER_DURATION_MS.