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/*
* Copyright 2017 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.widget.recyclerview.selection;
import static android.support.v4.util.Preconditions.checkArgument;
import static android.support.v7.widget.RecyclerView.NO_POSITION;
import static androidx.widget.recyclerview.selection.Shared.DEBUG;
import android.support.annotation.IntDef;
import android.support.annotation.NonNull;
import android.util.Log;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* Class providing support for managing range selections.
*/
final class Range {
static final int TYPE_PRIMARY = 0;
/**
* "Provisional" selection represents a overlay on the primary selection. A provisional
* selection maybe be eventually added to the primary selection, or it may be abandoned.
*
* <p>
* E.g. BandSelectionHelper creates a provisional selection while a user is actively
* selecting items with a band. GestureSelectionHelper creates a provisional selection
* while a user is active selecting via gesture.
*
* <p>
* Provisionally selected items are considered to be selected in
* {@link Selection#contains(String)} and related methods. A provisional may be abandoned or
* merged into the promary selection.
*
* <p>
* A provisional selection may intersect with the primary selection, however clearing the
* provisional selection will not affect the primary selection where the two may intersect.
*/
static final int TYPE_PROVISIONAL = 1;
@IntDef({
TYPE_PRIMARY,
TYPE_PROVISIONAL
})
@Retention(RetentionPolicy.SOURCE)
@interface RangeType {}
private static final String TAG = "Range";
private final Callbacks mCallbacks;
private final int mBegin;
private int mEnd = NO_POSITION;
/**
* Creates a new range anchored at {@code position}.
*
* @param position
* @param callbacks
*/
Range(int position, @NonNull Callbacks callbacks) {
mBegin = position;
mCallbacks = callbacks;
if (DEBUG) Log.d(TAG, "Creating new Range anchored @ " + position);
}
void extendRange(int position, @RangeType int type) {
checkArgument(position != NO_POSITION, "Position cannot be NO_POSITION.");
if (mEnd == NO_POSITION || mEnd == mBegin) {
// Reset mEnd so it can be established in establishRange.
mEnd = NO_POSITION;
establishRange(position, type);
} else {
reviseRange(position, type);
}
}
private void establishRange(int position, @RangeType int type) {
checkArgument(mEnd == NO_POSITION, "End has already been set.");
mEnd = position;
if (position > mBegin) {
if (DEBUG) log(type, "Establishing initial range at @ " + position);
updateRange(mBegin + 1, position, true, type);
} else if (position < mBegin) {
if (DEBUG) log(type, "Establishing initial range at @ " + position);
updateRange(position, mBegin - 1, true, type);
}
}
private void reviseRange(int position, @RangeType int type) {
checkArgument(mEnd != NO_POSITION, "End must already be set.");
checkArgument(mBegin != mEnd, "Beging and end point to same position.");
if (position == mEnd) {
if (DEBUG) log(type, "Ignoring no-op revision for range @ " + position);
}
if (mEnd > mBegin) {
reviseAscending(position, type);
} else if (mEnd < mBegin) {
reviseDescending(position, type);
}
// the "else" case is covered by checkState at beginning of method.
mEnd = position;
}
/**
* Updates an existing ascending selection.
*/
private void reviseAscending(int position, @RangeType int type) {
if (DEBUG) log(type, "*ascending* Revising range @ " + position);
if (position < mEnd) {
if (position < mBegin) {
updateRange(mBegin + 1, mEnd, false, type);
updateRange(position, mBegin - 1, true, type);
} else {
updateRange(position + 1, mEnd, false, type);
}
} else if (position > mEnd) { // Extending the range...
updateRange(mEnd + 1, position, true, type);
}
}
private void reviseDescending(int position, @RangeType int type) {
if (DEBUG) log(type, "*descending* Revising range @ " + position);
if (position > mEnd) {
if (position > mBegin) {
updateRange(mEnd, mBegin - 1, false, type);
updateRange(mBegin + 1, position, true, type);
} else {
updateRange(mEnd, position - 1, false, type);
}
} else if (position < mEnd) { // Extending the range...
updateRange(position, mEnd - 1, true, type);
}
}
/**
* Try to set selection state for all elements in range. Not that callbacks can cancel
* selection of specific items, so some or even all items may not reflect the desired state
* after the update is complete.
*
* @param begin Adapter position for range start (inclusive).
* @param end Adapter position for range end (inclusive).
* @param selected New selection state.
*/
private void updateRange(
int begin, int end, boolean selected, @RangeType int type) {
mCallbacks.updateForRange(begin, end, selected, type);
}
@Override
public String toString() {
return "Range{begin=" + mBegin + ", end=" + mEnd + "}";
}
private void log(@RangeType int type, String message) {
String opType = type == TYPE_PRIMARY ? "PRIMARY" : "PROVISIONAL";
Log.d(TAG, String.valueOf(this) + ": " + message + " (" + opType + ")");
}
/*
* @see {@link DefaultSelectionTracker#updateForRange(int, int , boolean, int)}.
*/
abstract static class Callbacks {
abstract void updateForRange(
int begin, int end, boolean selected, @RangeType int type);
}
}
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