// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package org.chromium.components.browser_ui.widget.dragreorder;
import android.content.Context;
import android.content.res.Resources;
import android.util.SparseArray;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.core.graphics.ColorUtils;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.RecyclerView;
import org.chromium.base.ObserverList;
import org.chromium.components.browser_ui.styles.ChromeColors;
import org.chromium.components.browser_ui.widget.R;
import org.chromium.ui.modelutil.PropertyKey;
import org.chromium.ui.modelutil.PropertyModel;
import org.chromium.ui.modelutil.PropertyModelChangeProcessor.ViewBinder;
import org.chromium.ui.modelutil.SimpleRecyclerViewAdapter;
import java.util.function.BiFunction;
/**
* MVC-compatible adapter for a {@link RecyclerView} that manages drag-reorderable lists. Used in
* same way as {@link SimpleRecyclerViewAdapter} with a few exceptions. In addition to
* registerType, there are two additional ways to register types:
* 1. registerDraggableType: This method registers a view that can be dragged. It takes one
* additional argument - a single-function interface, DragBinder, which connects some UI event
* (e.g. a touch on a drag handle) to the adapter.
* 2. registerPassivelyDraggableType: This method registers a view that can be dragged over, but
* isn't itself draggable. The call is identical to SimpleRecyclerViewAdapter#registerType
* but it keeps track of the view to make it available to drag over later.
*/
public class DragReorderableRecyclerViewAdapter extends SimpleRecyclerViewAdapter {
/**
* Responsible for binding draggable views to the items adapter. The viewHolder should add a
* listener to the correct view (e.g. a drag handle) which informs the ItemTouchHandler that
* dragging has begun. Refer to the android docs for an example:
* https://developer.android.com/reference/androidx/recyclerview/widget/ItemTouchHelper#startDrag(androidx.recyclerview.widget.RecyclerView.ViewHolder)
*/
public interface DragBinder {
void bind(ViewHolder viewHolder, ItemTouchHelper itemTouchHelper);
}
/** Controls draggability state on a per item basis. */
public interface DraggabilityProvider {
boolean isActivelyDraggable(PropertyModel propertyModel);
boolean isPassivelyDraggable(PropertyModel propertyModel);
}
/** Responsible for deciding when long-press drag is enabled. */
public interface LongPressDragDelegate {
boolean isLongPressDragEnabled();
}
/** Keep a reference to the underlying RecyclerView to attach the drag/drop helpers. */
private RecyclerView mRecyclerView;
private boolean mDragEnabled;
private int mStart;
private @Nullable LongPressDragDelegate mLongPressDragDelegate;
/** Classes to handle drag/drop functionality. */
private final ItemTouchHelper.Callback mTouchHelperCallback = new DragTouchCallback();
private final ItemTouchHelper mItemTouchHelper = new ItemTouchHelper(mTouchHelperCallback);
private final ObserverList<DragListener> mListeners = new ObserverList<>();
/** A map of view types to view binders. */
private final SparseArray<DragBinder> mDragBinderMap = new SparseArray<>();
/** A map of view types to active/passive draggability. */
private final SparseArray<DraggabilityProvider> mDraggabilityProviderMap = new SparseArray<>();
/** Styles to use while dragging */
private final int mDraggedBackgroundColor;
private final float mDraggedElevation;
/** A callback for touch actions on drag-reorderable lists. */
private class DragTouchCallback extends ItemTouchHelper.Callback {
// The view that is being dragged now; null means no view is being dragged now;
private @Nullable RecyclerView.ViewHolder mBeingDragged;
@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
int dragFlags = 0;
// This method may be called multiple times until the view is dropped
// ensure there is only one bookmark being dragged.
if ((mBeingDragged == viewHolder || mBeingDragged == null)
&& isActivelyDraggable(viewHolder)) {
dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
}
return makeMovementFlags(dragFlags, /* swipeFlags= */ 0);
}
@Override
public boolean onMove(
RecyclerView recyclerView,
RecyclerView.ViewHolder current,
RecyclerView.ViewHolder target) {
int from = current.getBindingAdapterPosition();
int to = target.getBindingAdapterPosition();
if (from == to) return false;
mListData.move(from, to);
return true;
}
@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
super.onSelectedChanged(viewHolder, actionState);
// similar to getMovementFlags, this method may be called multiple times
if (actionState == ItemTouchHelper.ACTION_STATE_DRAG && mBeingDragged != viewHolder) {
mBeingDragged = viewHolder;
mStart = viewHolder.getAdapterPosition();
onDragStateChange(true);
updateVisualState(true, viewHolder);
}
}
@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, viewHolder);
// No need to commit change if recycler view is not attached to window, such as dragging
// is terminated by destroying activity.
if (viewHolder.getAdapterPosition() != mStart && recyclerView.isAttachedToWindow()) {
// Commit the position change for the dragged item when it's dropped and
// RecyclerView has finished layout computing.
recyclerView.post(() -> onSwap());
}
mBeingDragged = null;
onDragStateChange(false);
updateVisualState(false, viewHolder);
}
@Override
public boolean isLongPressDragEnabled() {
return mLongPressDragDelegate != null
&& mLongPressDragDelegate.isLongPressDragEnabled()
&& mDragEnabled;
}
@Override
public boolean isItemViewSwipeEnabled() {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {}
@Override
public boolean canDropOver(
RecyclerView recyclerView,
RecyclerView.ViewHolder current,
RecyclerView.ViewHolder target) {
// The fact that current is being dragged is proof enough since draggable views are
// also passively draggable.
return isPassivelyDraggable(current) && isPassivelyDraggable(target);
}
/**
* Update the visual state of this row.
* @param dragged Whether this row is currently being dragged.
* @param viewHolder The DraggableRowViewHolder that is holding this row's content.
*/
private void updateVisualState(boolean dragged, RecyclerView.ViewHolder viewHolder) {
DragUtils.createViewDragAnimation(
dragged,
viewHolder.itemView,
mDraggedBackgroundColor,
mDraggedElevation)
.start();
}
}
/** Listens to drag actions in a drag-reorderable list. */
public interface DragListener {
/**
* Called when drag starts or ends.
*
* @param drag True iff drag is currently on.
*/
default void onDragStateChange(boolean drag) {}
/** Called when a drag ends and it ends up in a swap. */
default void onSwap() {}
}
/**
* @param context The context for that this DragReorderableRecyclerViewAdapter occupies.
* @param modelList The {@link ModelList} which determines what's shown in the list.
*/
public DragReorderableRecyclerViewAdapter(Context context, ModelList modelList) {
super(modelList);
Resources resources = context.getResources();
// Set the alpha to 90% when dragging which is 230/255
mDraggedBackgroundColor =
ColorUtils.setAlphaComponent(
ChromeColors.getSurfaceColor(context, R.dimen.default_elevation_4),
resources.getInteger(R.integer.list_item_dragged_alpha));
mDraggedElevation = resources.getDimension(R.dimen.list_item_dragged_elevation);
}
/** @param longPressDragDelegate The delegate which decides when long press dragging is enabled. */
public void setLongPressDragDelegate(LongPressDragDelegate longPressDragDelegate) {
mLongPressDragDelegate = longPressDragDelegate;
}
/**
* Registers a view that can be dragged. It takes one additional argument - a single-function
* interface, DragBinder, which connects some UI event (e.g. a touch on a drag handle) to the
* adapter.
* @param typeId The ID of the view type. This should not match any other view type registered
* in this adapter.
* @param builder A mechanism for building new views of the specified type.
* @param binder A means of binding a model to the provided view.
* @param dragBinder A means of binding the view to Android's drag system.
* @param draggabilityProvider A way of resolving if a given row is draggable.
*/
public <T extends View> void registerDraggableType(
int typeId,
ViewBuilder<T> builder,
ViewBinder<PropertyModel, T, PropertyKey> binder,
@NonNull DragBinder dragBinder,
@NonNull DraggabilityProvider draggabilityProvider) {
super.registerType(typeId, builder, binder);
assert mDragBinderMap.get(typeId) == null;
assert mDraggabilityProviderMap.get(typeId) == null;
mDragBinderMap.put(typeId, dragBinder);
mDraggabilityProviderMap.put(typeId, draggabilityProvider);
}
// Drag/drop helper functions.
/** Enables drag & drop interaction on the RecyclerView that this adapter is attached to. */
public void enableDrag() {
mDragEnabled = true;
mItemTouchHelper.attachToRecyclerView(mRecyclerView);
}
/** Disables drag & drop interaction. */
public void disableDrag() {
mDragEnabled = false;
mItemTouchHelper.attachToRecyclerView(null);
}
/** @param l The drag listener to be added. */
public void addDragListener(DragListener l) {
mListeners.addObserver(l);
}
/** @param l The drag listener to be removed. */
public void removeDragListener(DragListener l) {
mListeners.removeObserver(l);
}
/**
* Called when drag state changes (drag starts / ends), and notifies all listeners.
*
* @param drag True iff drag is currently on.
*/
private void onDragStateChange(boolean drag) {
for (DragListener l : mListeners) {
l.onDragStateChange(drag);
}
}
private void onSwap() {
for (DragListener dragListener : mListeners) {
dragListener.onSwap();
}
}
@VisibleForTesting
public boolean isActivelyDraggable(RecyclerView.ViewHolder viewHolder) {
return isDraggableHelper(viewHolder, (dp, pm) -> dp.isActivelyDraggable(pm));
}
@VisibleForTesting
public boolean isPassivelyDraggable(RecyclerView.ViewHolder viewHolder) {
return isDraggableHelper(viewHolder, (dp, pm) -> dp.isPassivelyDraggable(pm));
}
private boolean isDraggableHelper(
RecyclerView.ViewHolder viewHolder,
BiFunction<DraggabilityProvider, PropertyModel, Boolean> isDraggable) {
if (!mDragEnabled) return false;
DraggabilityProvider draggabilityProvider =
mDraggabilityProviderMap.get(viewHolder.getItemViewType());
if (draggabilityProvider == null) return false;
int position = viewHolder.getBindingAdapterPosition();
PropertyModel propertyModel = mListData.get(position).model;
return isDraggable.apply(draggabilityProvider, propertyModel);
}
// RecyclerView implementation.
@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {
super.onBindViewHolder(viewHolder, position);
int typeId = mListData.get(position).type;
// Overridden to given the draggable items a chance to bind correctly since a ViewHolder
// is required.
DragBinder dragBinder = mDragBinderMap.get(typeId);
if (dragBinder != null) {
dragBinder.bind(viewHolder, mItemTouchHelper);
}
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
mRecyclerView = recyclerView;
}
@Override
public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
mRecyclerView = null;
}
/**
* Simulate a drag. All items that are involved in the drag must be visible (no scrolling).
*
* @param start The index of the ViewHolder that you want to drag.
* @param end The index this ViewHolder should be dragged to and dropped at.
*/
public void simulateDragForTests(int start, int end) {
RecyclerView.ViewHolder viewHolder = mRecyclerView.findViewHolderForAdapterPosition(start);
mItemTouchHelper.startDrag(viewHolder);
int increment = start < end ? 1 : -1;
int i = start;
while (i != end) {
i += increment;
if (!mTouchHelperCallback.canDropOver(
mRecyclerView, viewHolder, mRecyclerView.findViewHolderForAdapterPosition(i))) {
break;
}
mTouchHelperCallback.onMove(
mRecyclerView, viewHolder, mRecyclerView.findViewHolderForAdapterPosition(i));
}
mTouchHelperCallback.onSelectedChanged(viewHolder, ItemTouchHelper.ACTION_STATE_IDLE);
mTouchHelperCallback.clearView(mRecyclerView, viewHolder);
}
}
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