OnPlacedModifier.kt
/*
* Copyright 2021 The Android Open Source Project
*
* 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.
*/
package androidx.compose.ui.layout
import androidx.compose.runtime.Stable
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.InspectorInfo
import androidx.compose.ui.platform.InspectorValueInfo
import androidx.compose.ui.platform.debugInspectorInfo
/**
* Invoke [onPlaced] after the parent [LayoutModifier] and parent layout has been placed and before
* child [LayoutModifier] is placed. This allows child [LayoutModifier] to adjust its
* own placement based on where the parent is.
*
* @sample androidx.compose.ui.samples.OnPlaced
*/
@ExperimentalComposeUiApi
@Stable
fun Modifier.onPlaced(
onPlaced: (LayoutCoordinates) -> Unit
) = this.then(
OnPlacedModifierImpl(
callback = onPlaced,
inspectorInfo = debugInspectorInfo {
name = "onPlaced"
properties["onPlaced"] = onPlaced
}
)
)
@OptIn(ExperimentalComposeUiApi::class)
private class OnPlacedModifierImpl(
val callback: (LayoutCoordinates) -> Unit,
inspectorInfo: InspectorInfo.() -> Unit
) : OnPlacedModifier, InspectorValueInfo(inspectorInfo) {
override fun onPlaced(coordinates: LayoutCoordinates) {
callback(coordinates)
}
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (other !is OnPlacedModifierImpl) return false
return callback == other.callback
}
override fun hashCode(): Int {
return callback.hashCode()
}
}
/**
* A modifier whose [onPlaced] is called after the parent [LayoutModifier] and parent layout has
* been placed and before child [LayoutModifier] is placed. This allows child
* [LayoutModifier] to adjust its own placement based on where the parent is.
*
* @sample androidx.compose.ui.samples.OnPlaced
*/
@ExperimentalComposeUiApi
interface OnPlacedModifier : Modifier.Element {
/**
* [onPlaced] is called after parent [LayoutModifier] and parent layout gets placed and
* before any child [LayoutModifier] is placed.
*
* [coordinates] provides [LayoutCoordinates] of the [OnPlacedModifier]. Placement in both
* parent [LayoutModifier] and parent layout can be calculated using the [LayoutCoordinates].
*/
fun onPlaced(coordinates: LayoutCoordinates)
}