TextFieldDragGestureFilter.kt
/*
* Copyright 2020 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.text
import androidx.compose.foundation.Interaction
import androidx.compose.foundation.InteractionState
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.composed
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.gesture.DragObserver
import androidx.compose.ui.gesture.dragGestureFilter
import androidx.compose.ui.gesture.pressIndicatorGestureFilter
/**
* Helper composable for tracking drag position.
*/
@Suppress("ModifierInspectorInfo")
internal fun Modifier.dragPositionGestureFilter(
onPress: (Offset) -> Unit,
onRelease: (Offset) -> Unit,
interactionState: InteractionState?,
enabled: Boolean = true
): Modifier = if (enabled) composed {
val tracker = remember { DragEventTracker() }
// TODO(shepshapard): PressIndicator doesn't seem to be the right thing to use here. It
// actually may be functionally correct, but might mostly suggest that it should not
// actually be called PressIndicator, but instead something else.
DisposableEffect(interactionState) {
onDispose {
interactionState?.removeInteraction(Interaction.Pressed)
}
}
pressIndicatorGestureFilter(
onStart = {
interactionState?.addInteraction(Interaction.Pressed, it)
tracker.init(it)
onPress(it)
},
onStop = {
interactionState?.removeInteraction(Interaction.Pressed)
onRelease(tracker.getPosition())
},
onCancel = {
interactionState?.removeInteraction(Interaction.Pressed)
}
)
.dragGestureFilter(
dragObserver = object :
DragObserver {
override fun onDrag(dragDistance: Offset): Offset {
tracker.onDrag(dragDistance)
return Offset.Zero
}
}
)
} else this
/**
* Helper class for tracking dragging event.
*/
internal class DragEventTracker {
private var origin = Offset.Zero
private var distance = Offset.Zero
/**
* Restart the tracking from given origin.
*
* @param origin The origin of the drag gesture.
*/
fun init(origin: Offset) {
this.origin = origin
}
/**
* Pass distance parameter called by DragGestureDetector$onDrag callback
*
* @param distance The distance from the origin of the drag origin.
*/
fun onDrag(distance: Offset) {
this.distance = distance
}
/**
* Returns the current position.
*
* @return The position of the current drag point.
*/
fun getPosition(): Offset {
return origin + distance
}
}