| /* |
| * Copyright 2019 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.gestures |
| |
| import androidx.compose.onDispose |
| import androidx.ui.core.DensityAmbient |
| import androidx.ui.core.Direction |
| import androidx.ui.core.Modifier |
| import androidx.ui.core.composed |
| import androidx.ui.core.gesture.ScrollCallback |
| import androidx.ui.core.gesture.dragGestureFilter |
| import androidx.ui.core.gesture.scrollGestureFilter |
| import androidx.ui.core.gesture.scrollorientationlocking.Orientation |
| import androidx.compose.foundation.Interaction |
| import androidx.compose.foundation.InteractionState |
| import androidx.ui.geometry.Offset |
| import androidx.ui.unit.Density |
| |
| /** |
| * Configure touch dragging for the UI element in a single [Orientation]. The drag distance is |
| * reported to [onDrag] as a single [Float] value in pixels. |
| * |
| * The common usecase for this component is when you need to be able to drag something |
| * inside the component on the screen and represent this state via one float value |
| * |
| * If you need to control the whole dragging flow, consider using [dragGestureFilter] instead. |
| * |
| * If you are implementing scroll/fling behavior, consider using [scrollable]. |
| * |
| * @sample androidx.compose.foundation.samples.DraggableSample |
| * |
| * @param orientation orientation of the drag |
| * @param enabled whether or not drag is enabled |
| * @param reverseDirection reverse the direction of the scroll, so top to bottom scroll will |
| * behave like bottom to top and left to right will behave like right to left. |
| * @param interactionState [InteractionState] that will be updated when this draggable is |
| * being dragged, using [Interaction.Dragged]. |
| * @param startDragImmediately when set to true, draggable will start dragging immediately and |
| * prevent other gesture detectors from reacting to "down" events (in order to block composed |
| * press-based gestures). This is intended to allow end users to "catch" an animating widget by |
| * pressing on it. It's useful to set it when value you're dragging is settling / animating. |
| * @param canDrag callback to indicate whether or not dragging is allowed for given [Direction] |
| * @param onDragStarted callback that will be invoked when drag has been started after touch slop |
| * has been passed, with starting position provided |
| * @param onDragStopped callback that will be invoked when drag stops, with velocity provided |
| * @param onDrag callback to be invoked when the drag occurs with the delta dragged from the |
| * previous event. [Density] provided in the scope for the convenient conversion between px and dp |
| */ |
| fun Modifier.draggable( |
| orientation: Orientation, |
| enabled: Boolean = true, |
| reverseDirection: Boolean = false, |
| interactionState: InteractionState? = null, |
| startDragImmediately: Boolean = false, |
| canDrag: (Direction) -> Boolean = { enabled }, |
| onDragStarted: (startedPosition: Offset) -> Unit = {}, |
| onDragStopped: (velocity: Float) -> Unit = {}, |
| onDrag: Density.(Float) -> Unit |
| ): Modifier = composed { |
| val density = DensityAmbient.current |
| onDispose { |
| interactionState?.removeInteraction(Interaction.Dragged) |
| } |
| |
| scrollGestureFilter( |
| scrollCallback = object : ScrollCallback { |
| |
| override fun onStart(downPosition: Offset) { |
| if (enabled) { |
| interactionState?.addInteraction(Interaction.Dragged) |
| onDragStarted(downPosition) |
| } |
| } |
| |
| override fun onScroll(scrollDistance: Float): Float { |
| if (!enabled) return scrollDistance |
| val toConsume = if (reverseDirection) scrollDistance * -1 else scrollDistance |
| with(density) { onDrag(toConsume) } |
| // we explicitly disallow nested scrolling in draggable, as it should be |
| // accessible via Modifier.scrollable. For drags, usually nested dragging is not |
| // required |
| return scrollDistance |
| } |
| |
| override fun onCancel() { |
| if (enabled) { |
| interactionState?.removeInteraction(Interaction.Dragged) |
| onDragStopped(0f) |
| } |
| } |
| |
| override fun onStop(velocity: Float) { |
| if (enabled) { |
| interactionState?.removeInteraction(Interaction.Dragged) |
| onDragStopped(if (reverseDirection) velocity * -1 else velocity) |
| } |
| } |
| }, |
| orientation = orientation, |
| canDrag = canDrag, |
| startDragImmediately = startDragImmediately |
| ) |
| } |