This library provides a way to track whether items appear on the screen in lazy lists.
| Lazy Column | Lazy Row |
To use the impression, first create an ImpressionState with rememberImpressionState. Then, use the impression modifier to track impressions for items in your list.
val lazyListState = rememberLazyListState()
val impressionState = rememberImpressionState(lazyListState)
LaunchedEffect(Unit) {
impressionState.seenEvent.collectLatest {
// collect impression events
}
}
LazyRow(
modifier = modifier.fillMaxSize(),
state = lazyListState,
contentPadding = PaddingValues(16.dp),
horizontalArrangement = Arrangement.spacedBy(12.dp)
) {
items(list, key = { it }) {
CardItem(
key = it,
modifier = Modifier
.width(250.dp)
.height(120.dp)
.impression(it, impressionState),
)
}
}or
val lazyListState = rememberLazyListState()
val impressionState = rememberImpressionState(lazyListState)
LazyRow(
modifier = modifier.fillMaxSize(),
state = lazyListState,
contentPadding = PaddingValues(16.dp),
horizontalArrangement = Arrangement.spacedBy(12.dp)
) {
items(list, key = { it }) {
CardItem(
key = it,
modifier = Modifier
.width(250.dp)
.height(120.dp)
.impression(
key = it,
impressionState = impressionState,
onImpressionHappened = {
// collect impression event
}
),
)
}
}The VisibilityPercentImpressionValidator validates impressions based on the visibility percentage of an item.
val impressionState = rememberImpressionState(lazyListState) {
addValidator(VisibilityPercentImpressionValidator(0.5f)) // set the visibility percentage threshold to 50%
}With this configuration, when an item is 50% visible, the impression will be validated and happened.
You can create your own validator by extending from ImpressionValidator.
- Add the JitPack repository to your project-level
build.gradlefile:
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
- Add the dependency to your app-level
build.gradlefile:
dependencies {
implementation 'com.github.erolaksoy:compose-impression:0.1.1'
}
- Sync your project with Gradle files.
Copyright 2023 Erol Aksoy
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.