commonMain.androidx.compose.foundation.interaction.DragInteraction.kt Maven / Gradle / Ivy

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/*
 * 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.foundation.interaction

import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.State
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import kotlinx.coroutines.flow.collect

// An interface, not a sealed class, to allow adding new types here in a safe way (and not break
// exhaustive when clauses)
/**
 * An interaction related to drag events.
 *
 * @see androidx.compose.foundation.gestures.draggable
 * @see Start
 * @see Stop
 * @see Cancel
 */
interface DragInteraction : Interaction {
    /**
     * An interaction representing a drag event on a component.
     *
     * @see androidx.compose.foundation.gestures.draggable
     * @see Stop
     * @see Cancel
     */
    class Start : DragInteraction

    /**
     * An interaction representing the stopping of a [Start] event on a component.
     *
     * @property start the source [Start] interaction that is being stopped
     *
     * @see androidx.compose.foundation.gestures.draggable
     * @see Start
     */
    class Stop(val start: Start) : DragInteraction

    /**
     * An interaction representing the cancellation of a [Start] event on a component.
     *
     * @property start the source [Start] interaction that is being cancelled
     *
     * @see androidx.compose.foundation.gestures.draggable
     * @see Start
     */
    class Cancel(val start: Start) : DragInteraction
}

/**
 * Subscribes to this [MutableInteractionSource] and returns a [State] representing whether this
 * component is dragged or not.
 *
 * [DragInteraction] is typically set by interactions
 * such as [androidx.compose.foundation.gestures.draggable] and
 * [androidx.compose.foundation.gestures.scrollable], and higher level components such as
 * [androidx.compose.foundation.lazy.LazyRow], available through
 * [androidx.compose.foundation.lazy.LazyListState.interactionSource].
 *
 * @return [State] representing whether this component is being dragged or not
 */
@Composable
fun InteractionSource.collectIsDraggedAsState(): State {
    val isDragged = remember { mutableStateOf(false) }
    LaunchedEffect(this) {
        val dragInteractions = mutableListOf()
        interactions.collect { interaction ->
            when (interaction) {
                is DragInteraction.Start -> dragInteractions.add(interaction)
                is DragInteraction.Stop -> dragInteractions.remove(interaction.start)
                is DragInteraction.Cancel -> dragInteractions.remove(interaction.start)
            }
            isDragged.value = dragInteractions.isNotEmpty()
        }
    }
    return isDragged
}