Integrate band selection into the files app. (62a7fd0e) · Commits · e / os / android_packages_apps_DocumentsUI

src/com/android/documentsui/BandSelectManager.java

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		/*
		* Copyright (C) 2015 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 com.android.documentsui;

		import static com.android.documentsui.Events.isMouseEvent;
		import static com.android.internal.util.Preconditions.checkState;

		import android.graphics.Point;
		import android.graphics.Rect;
		import android.graphics.drawable.Drawable;
		import android.support.v7.widget.RecyclerView;
		import android.support.v7.widget.RecyclerView.ViewHolder;
		import android.util.Log;
		import android.util.SparseBooleanArray;
		import android.view.MotionEvent;
		import android.view.View;

		/**
		* Provides mouse driven band-select support when used in conjuction with {@link RecyclerView} and
		* {@link MultiSelectManager}. This class is responsible for rendering the band select overlay and
		* selecting overlaid items via MultiSelectManager.
		*/
		public class BandSelectManager extends RecyclerView.SimpleOnItemTouchListener {

		private static final int NOT_SELECTED = -1;
		private static final int NOT_SET = -1;

		// For debugging purposes.
		private static final String TAG = "BandSelectManager";
		private static final boolean DEBUG = false;

		private final RecyclerView mRecyclerView;
		private final MultiSelectManager mSelectManager;
		private final Drawable mRegionSelectorDrawable;
		private final SparseBooleanArray mSelectedByBand = new SparseBooleanArray();

		private boolean mIsBandSelectActive = false;
		private Point mOrigin;
		private Point mPointer;
		private Rect mBounds;

		// Maintain the last selection made by band, so if bounds shrink back, we can deselect
		// the respective items.
		private int mCursorDeltaY = 0;
		private int mFirstSelected = NOT_SELECTED;

		// The time at which the current band selection-induced scroll began. If no scroll is in
		// progress, the value is NOT_SET.
		private long mScrollStartTime = NOT_SET;
		private final Runnable mScrollRunnable = new Runnable() {
		/**
		* The number of milliseconds of scrolling at which scroll speed continues to increase. At
		* first, the scroll starts slowly; then, the rate of scrolling increases until it reaches
		* its maximum value at after this many milliseconds.
		*/
		private static final long SCROLL_ACCELERATION_LIMIT_TIME_MS = 2000;

		@Override
		public void run() {
		// Compute the number of pixels the pointer's y-coordinate is past the view. Negative
		// values mean the pointer is at or before the top of the view, and positive values mean
		// that the pointer is at or after the bottom of the view. Note that one additional
		// pixel is added here so that the view still scrolls when the pointer is exactly at the
		// top or bottom.
		int pixelsPastView = 0;
		if (mPointer.y <= 0) {
		pixelsPastView = mPointer.y - 1;
		} else if (mPointer.y >= mRecyclerView.getHeight() - 1) {
		pixelsPastView = mPointer.y - mRecyclerView.getHeight() + 1;
		}

		if (!mIsBandSelectActive \|\| pixelsPastView == 0) {
		// If band selection is inactive, or if it is active but not at the edge of the
		// view, no scrolling is necessary.
		mScrollStartTime = NOT_SET;
		return;
		}

		if (mScrollStartTime == NOT_SET) {
		// If the pointer was previously not at the edge of the view but now is, set the
		// start time for the scroll.
		mScrollStartTime = System.currentTimeMillis();
		}

		// Compute the number of pixels to scroll, and scroll that many pixels.
		final int numPixels = computeNumPixelsToScroll(
		pixelsPastView, System.currentTimeMillis() - mScrollStartTime);
		mRecyclerView.scrollBy(0, numPixels);

		// Adjust the y-coordinate of the origin the opposite number of pixels so that the
		// origin remains in the same place relative to the view's items.
		mOrigin.y -= numPixels;
		resizeBandSelectRectangle();

		mRecyclerView.removeCallbacks(mScrollRunnable);
		mRecyclerView.postOnAnimation(this);
		}

		/**
		* Computes the number of pixels to scroll based on how far the pointer is past the end of
		* the view and how long it has been there. Roughly based on ItemTouchHelper's algorithm for
		* computing the number of pixels to scroll when an item is dragged to the end of a
		* {@link RecyclerView}.
		* @param pixelsPastView
		* @param scrollDuration
		* @return
		*/
		private int computeNumPixelsToScroll(int pixelsPastView, long scrollDuration) {
		final int maxScrollStep = computeMaxScrollStep(mRecyclerView);
		final int direction = (int) Math.signum(pixelsPastView);
		final int absPastView = Math.abs(pixelsPastView);

		// Calculate the ratio of how far out of the view the pointer currently resides to the
		// entire height of the view.
		final float outOfBoundsRatio = Math.min(
		1.0f, (float) absPastView / mRecyclerView.getHeight());
		// Interpolate this ratio and use it to compute the maximum scroll that should be
		// possible for this step.
		final float cappedScrollStep =
		direction * maxScrollStep * smoothOutOfBoundsRatio(outOfBoundsRatio);

		// Likewise, calculate the ratio of the time spent in the scroll to the limit.
		final float timeRatio = Math.min(
		1.0f, (float) scrollDuration / SCROLL_ACCELERATION_LIMIT_TIME_MS);
		// Interpolate this ratio and use it to compute the final number of pixels to scroll.
		final int numPixels = (int) (cappedScrollStep * smoothTimeRatio(timeRatio));

		// If the final number of pixels to scroll ends up being 0, the view should still scroll
		// at least one pixel.
		return numPixels != 0 ? numPixels : direction;
		}

		/**
		* Computes the maximum scroll allowed for a given animation frame. Currently, this
		* defaults to the height of the view, but this could be tweaked if this results in scrolls
		* that are too fast or too slow.
		* @param rv
		* @return
		*/
		private int computeMaxScrollStep(RecyclerView rv) {
		return rv.getHeight();
		}

		/**
		* Interpolates the given out of bounds ratio on a curve which starts at (0,0) and ends at
		* (1,1) and quickly approaches 1 near the start of that interval. This ensures that drags
		* that are at the edge or barely past the edge of the view still cause sufficient
		* scrolling. The equation y=(x-1)^5+1 is used, but this could also be tweaked if needed.
		* @param ratio A ratio which is in the range [0, 1].
		* @return A "smoothed" value, also in the range [0, 1].
		*/
		private float smoothOutOfBoundsRatio(float ratio) {
		return (float) Math.pow(ratio - 1.0f, 5) + 1.0f;
		}

		/**
		* Interpolates the given time ratio on a curve which starts at (0,0) and ends at (1,1) and
		* stays close to 0 for most input values except those very close to 1. This ensures that
		* scrolls start out very slowly but speed up drastically after the scroll has been in
		* progress close to SCROLL_ACCELERATION_LIMIT_TIME_MS. The equation y=x^5 is used, but this
		* could also be tweaked if needed.
		* @param ratio A ratio which is in the range [0, 1].
		* @return A "smoothed" value, also in the range [0, 1].
		*/
		private float smoothTimeRatio(float ratio) {
		return (float) Math.pow(ratio, 5);
		}
		};

		/**
		* @param recyclerView
		* @param multiSelectManager
		*/
		public BandSelectManager(RecyclerView recyclerView, MultiSelectManager multiSelectManager) {
		mRecyclerView = recyclerView;
		mSelectManager = multiSelectManager;
		mRegionSelectorDrawable =
		mRecyclerView.getContext().getTheme().getDrawable(R.drawable.band_select_overlay);

		mRecyclerView.addOnItemTouchListener(this);
		}

		@Override
		public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
		// Only intercept the event if it was triggered by a mouse. If band select is inactive,
		// do not intercept ACTION_UP events as they will not be processed.
		return isMouseEvent(e) &&
		(mIsBandSelectActive \|\| e.getActionMasked() != MotionEvent.ACTION_UP);
		}

		@Override
		public void onTouchEvent(RecyclerView rv, MotionEvent e) {
		checkState(isMouseEvent(e));
		processMotionEvent(e);
		}

		/**
		* Processes a MotionEvent by starting, ending, or resizing the band select overlay.
		* @param e
		*/
		private void processMotionEvent(MotionEvent e) {
		if (mIsBandSelectActive && e.getActionMasked() == MotionEvent.ACTION_UP) {
		endBandSelect();
		return;
		}

		mPointer = new Point((int) e.getX(), (int) e.getY());
		if (!mIsBandSelectActive) {
		startBandSelect();
		}

		scrollViewIfNecessary();
		resizeBandSelectRectangle();
		selectChildrenCoveredBySelection();
		}

		/**
		* Starts band select by adding the drawable to the RecyclerView's overlay.
		*/
		private void startBandSelect() {
		if (DEBUG) Log.d(TAG, "Starting band select from (" + mPointer.x + "," + mPointer.y + ").");
		mIsBandSelectActive = true;
		mOrigin = mPointer;
		mRecyclerView.getOverlay().add(mRegionSelectorDrawable);
		}

		/**
		* Scrolls the view if necessary.
		*/
		private void scrollViewIfNecessary() {
		mRecyclerView.removeCallbacks(mScrollRunnable);
		mScrollRunnable.run();
		mRecyclerView.invalidate();
		}

		/**
		* Resizes the band select rectangle by using the origin and the current pointer positoin as
		* two opposite corners of the selection.
		*/
		private void resizeBandSelectRectangle() {
		if (mBounds != null) {
		mCursorDeltaY = mPointer.y - mBounds.bottom;
		}

		mBounds = new Rect(Math.min(mOrigin.x, mPointer.x),
		Math.min(mOrigin.y, mPointer.y),
		Math.max(mOrigin.x, mPointer.x),
		Math.max(mOrigin.y, mPointer.y));

		mRegionSelectorDrawable.setBounds(mBounds);
		}

		/**
		* Selects the children covered by the band select overlay by delegating to MultiSelectManager.
		* TODO: Provide a finished implementation. This is down and dirty, proof of concept code.
		* Final optimized implementation, with support for managing offscreen selection to come.
		*/
		private void selectChildrenCoveredBySelection() {

		// track top and bottom selections. Details on why this is useful below.
		int first = NOT_SELECTED;
		int last = NOT_SELECTED;

		for (int i = 0; i < mRecyclerView.getChildCount(); i++) {

		View child = mRecyclerView.getChildAt(i);
		ViewHolder holder = mRecyclerView.getChildViewHolder(child);
		Rect childRect = new Rect();
		child.getHitRect(childRect);

		boolean shouldSelect = Rect.intersects(childRect, mBounds);
		int position = holder.getAdapterPosition();

		// This also allows us to clear the selection of elements
		// that only temporarily entered the bounds of the band.
		if (mSelectedByBand.get(position) && !shouldSelect) {
		mSelectManager.setItemSelected(position, false);
		mSelectedByBand.delete(position);
		}

		// We need to keep track of the first and last items selected.
		// We'll use this information along with cursor direction
		// to determine the starting point of the selection.
		// We provide this information to selection manager
		// to enable more natural user interaction when working
		// with Shift+Click and multiple contiguous selection ranges.
		if (shouldSelect) {
		if (first == NOT_SELECTED) {
		first = position;
		} else {
		last = position;
		}
		mSelectManager.setItemSelected(position, true);
		mSelectedByBand.put(position, true);
		}
		}

		// Remember which is the last selected item, so we can
		// share that with selection manager when band select ends.
		// It'll use that as it's begin selection point when
		// user SHIFT+Clicks.
		if (mCursorDeltaY < 0 && last != NOT_SELECTED) {
		mFirstSelected = last;
		} else if (mCursorDeltaY > 0 && first != NOT_SELECTED) {
		mFirstSelected = first;
		}
		}

		/**
		* Ends band select by removing the overlay.
		*/
		private void endBandSelect() {
		if (DEBUG) Log.d(TAG, "Ending band select.");
		mIsBandSelectActive = false;
		mSelectedByBand.clear();
		mRecyclerView.getOverlay().remove(mRegionSelectorDrawable);
		if (mFirstSelected != NOT_SELECTED) {
		mSelectManager.setSelectionFocusBegin(mFirstSelected);
		}
		}
		}