/*
* Copyright (C) 2007 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 android.view;
import android.graphics.Rect;
import java.util.ArrayList;
/**
* The algorithm used for finding the next focusable view in a given direction
* from a view that currently has focus.
*/
public class FocusFinder {
private static ThreadLocal<FocusFinder> tlFocusFinder =
new ThreadLocal<FocusFinder>() {
protected FocusFinder initialValue() {
return new FocusFinder();
}
};
/**
* Get the focus finder for this thread.
*/
public static FocusFinder getInstance() {
return tlFocusFinder.get();
}
Rect mFocusedRect = new Rect();
Rect mOtherRect = new Rect();
Rect mBestCandidateRect = new Rect();
// enforce thread local access
private FocusFinder() {}
/**
* Find the next view to take focus in root's descendants, starting from the view
* that currently is focused.
* @param root Contains focused
* @param focused Has focus now.
* @param direction Direction to look.
* @return The next focusable view, or null if none exists.
*/
public final View findNextFocus(ViewGroup root, View focused, int direction) {
if (focused != null) {
// check for user specified next focus
View userSetNextFocus = focused.findUserSetNextFocus(root, direction);
if (userSetNextFocus != null &&
userSetNextFocus.isFocusable() &&
(!userSetNextFocus.isInTouchMode() ||
userSetNextFocus.isFocusableInTouchMode())) {
return userSetNextFocus;
}
// fill in interesting rect from focused
focused.getFocusedRect(mFocusedRect);
root.offsetDescendantRectToMyCoords(focused, mFocusedRect);
} else {
// make up a rect at top left or bottom right of root
switch (direction) {
case View.FOCUS_RIGHT:
case View.FOCUS_DOWN:
final int rootTop = root.getScrollY();
final int rootLeft = root.getScrollX();
mFocusedRect.set(rootLeft, rootTop, rootLeft, rootTop);
break;
case View.FOCUS_LEFT:
case View.FOCUS_UP:
final int rootBottom = root.getScrollY() + root.getHeight();
final int rootRight = root.getScrollX() + root.getWidth();
mFocusedRect.set(rootRight, rootBottom,
rootRight, rootBottom);
break;
}
}
return findNextFocus(root, focused, mFocusedRect, direction);
}
/**
* Find the next view to take focus in root's descendants, searching from
* a particular rectangle in root's coordinates.
* @param root Contains focusedRect.
* @param focusedRect The starting point of the search.
* @param direction Direction to look.
* @return The next focusable view, or null if none exists.
*/
public View findNextFocusFromRect(ViewGroup root, Rect focusedRect, int direction) {
return findNextFocus(root, null, focusedRect, direction);
}
private View findNextFocus(ViewGroup root, View focused, Rect focusedRect, int direction) {
ArrayList<View> focusables = root.getFocusables(direction);
// initialize the best candidate to something impossible
// (so the first plausible view will become the best choice)
mBestCandidateRect.set(focusedRect);
switch(direction) {
case View.FOCUS_LEFT:
mBestCandidateRect.offset(focusedRect.width() + 1, 0);
break;
case View.FOCUS_RIGHT:
mBestCandidateRect.offset(-(focusedRect.width() + 1), 0);
break;
case View.FOCUS_UP:
mBestCandidateRect.offset(0, focusedRect.height() + 1);
break;
case View.FOCUS_DOWN:
mBestCandidateRect.offset(0, -(focusedRect.height() + 1));
}
View closest = null;
int numFocusables = focusables.size();
for (int i = 0; i < numFocusables; i++) {
View focusable = focusables.get(i);
// only interested in other non-root views
if (focusable == focused || focusable == root) continue;
// get visible bounds of other view in same coordinate system
focusable.getDrawingRect(mOtherRect);
root.offsetDescendantRectToMyCoords(focusable, mOtherRect);
if (isBetterCandidate(direction, focusedRect, mOtherRect, mBestCandidateRect)) {
mBestCandidateRect.set(mOtherRect);
closest = focusable;
}
}
return closest;
}
/**
* Is rect1 a better candidate than rect2 for a focus search in a particular
* direction from a source rect? This is the core routine that determines
* the order of focus searching.
* @param direction the direction (up, down, left, right)
* @param source The source we are searching from
* @param rect1 The candidate rectangle
* @param rect2 The current best candidate.
* @return Whether the candidate is the new best.
*/
boolean isBetterCandidate(int direction, Rect source, Rect rect1, Rect rect2) {
// to be a better candidate, need to at least be a candidate in the first
// place :)
if (!isCandidate(source, rect1, direction)) {
return false;
}
// we know that rect1 is a candidate.. if rect2 is not a candidate,
// rect1 is better
if (!isCandidate(source, rect2, direction)) {
return true;
}
// if rect1 is better by beam, it wins
if (beamBeats(direction, source, rect1, rect2)) {
return true;
}
// if rect2 is better, then rect1 cant' be :)
if (beamBeats(direction, source, rect2, rect1)) {
return false;
}
// otherwise, do fudge-tastic comparison of the major and minor axis
return (getWeightedDistanceFor(
majorAxisDistance(direction, source, rect1),
minorAxisDistance(direction, source, rect1))
< getWeightedDistanceFor(
majorAxisDistance(direction, source, rect2),
minorAxisDistance(direction, source, rect2)));
}
/**
* One rectangle may be another candidate than another by virtue of being
* exclusively in the beam of the source rect.
* @return Whether rect1 is a better candidate than rect2 by virtue of it being in src's
* beam
*/
boolean beamBeats(int direction, Rect source, Rect rect1, Rect rect2) {
final boolean rect1InSrcBeam = beamsOverlap(direction, source, rect1);
final boolean rect2InSrcBeam = beamsOverlap(direction, source, rect2);
// if rect1 isn't exclusively in the src beam, it doesn't win
if (rect2InSrcBeam || !rect1InSrcBeam) {
return false;
}
// we know rect1 is in the beam, and rect2 is not
// if rect1 is to the direction of, and rect2 is not, rect1 wins.
// for example, for direction left, if rect1 is to the left of the source
// and rect2 is below, then we always prefer the in beam rect1, since rect2
// could be reached by going down.
if (!isToDirectionOf(direction, source, rect2)) {
return true;
}
// for horizontal directions, being exclusively in beam always wins
if ((direction == View.FOCUS_LEFT || direction == View.FOCUS_RIGHT)) {
return true;
}
// for vertical directions, beams only beat up to a point:
// now, as long as rect2 isn't completely closer, rect1 wins
// e.g for direction down, completely closer means for rect2's top
// edge to be closer to the source's top edge than rect1's bottom edge.
return (majorAxisDistance(direction, source, rect1)
< majorAxisDistanceToFarEdge(direction, source, rect2));
}
/**
* Fudge-factor opportunity: how to calculate distance given major and minor
* axis distances. Warning: this fudge factor is finely tuned, be sure to
* run all focus tests if you dare tweak it.
*/
int getWeightedDistanceFor(int majorAxisDistance, int minorAxisDistance) {
return 13 * majorAxisDistance * majorAxisDistance
+ minorAxisDistance * minorAxisDistance;
}
/**
* Is destRect a candidate for the next focus given the direction? This
* checks whether the dest is at least partially to the direction of (e.g left of)
* from source.
*
* Includes an edge case for an empty rect (which is used in some cases when
* searching from a point on the screen).
*/
boolean isCandidate(Rect srcRect, Rect destRect, int direction) {
switch (direction) {
case View.FOCUS_LEFT:
return (srcRect.right > destRect.right || srcRect.left >= destRect.right)
&& srcRect.left > destRect.left;
case View.FOCUS_RIGHT:
return (srcRect.left < destRect.left || srcRect.right <= destRect.left)
&& srcRect.right < destRect.right;
case View.FOCUS_UP:
return (srcRect.bottom > destRect.bottom || srcRect.top >= destRect.bottom)
&& srcRect.top > destRect.top;
case View.FOCUS_DOWN:
return (srcRect.top < destRect.top || srcRect.bottom <= destRect.top)
&& srcRect.bottom < destRect.bottom;
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* Do the "beams" w.r.t the given direcition's axos of rect1 and rect2 overlap?
* @param direction the direction (up, down, left, right)
* @param rect1 The first rectangle
* @param rect2 The second rectangle
* @return whether the beams overlap
*/
boolean beamsOverlap(int direction, Rect rect1, Rect rect2) {
switch (direction) {
case View.FOCUS_LEFT:
case View.FOCUS_RIGHT:
return (rect2.bottom >= rect1.top) && (rect2.top <= rect1.bottom);
case View.FOCUS_UP:
case View.FOCUS_DOWN:
return (rect2.right >= rect1.left) && (rect2.left <= rect1.right);
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* e.g for left, is 'to left of'
*/
boolean isToDirectionOf(int direction, Rect src, Rect dest) {
switch (direction) {
case View.FOCUS_LEFT:
return src.left >= dest.right;
case View.FOCUS_RIGHT:
return src.right <= dest.left;
case View.FOCUS_UP:
return src.top >= dest.bottom;
case View.FOCUS_DOWN:
return src.bottom <= dest.top;
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* @return The distance from the edge furthest in the given direction
* of source to the edge nearest in the given direction of dest. If the
* dest is not in the direction from source, return 0.
*/
static int majorAxisDistance(int direction, Rect source, Rect dest) {
return Math.max(0, majorAxisDistanceRaw(direction, source, dest));
}
static int majorAxisDistanceRaw(int direction, Rect source, Rect dest) {
switch (direction) {
case View.FOCUS_LEFT:
return source.left - dest.right;
case View.FOCUS_RIGHT:
return dest.left - source.right;
case View.FOCUS_UP:
return source.top - dest.bottom;
case View.FOCUS_DOWN:
return dest.top - source.bottom;
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* @return The distance along the major axis w.r.t the direction from the
* edge of source to the far edge of dest. If the
* dest is not in the direction from source, return 1 (to break ties with
* {@link #majorAxisDistance}).
*/
static int majorAxisDistanceToFarEdge(int direction, Rect source, Rect dest) {
return Math.max(1, majorAxisDistanceToFarEdgeRaw(direction, source, dest));
}
static int majorAxisDistanceToFarEdgeRaw(int direction, Rect source, Rect dest) {
switch (direction) {
case View.FOCUS_LEFT:
return source.left - dest.left;
case View.FOCUS_RIGHT:
return dest.right - source.right;
case View.FOCUS_UP:
return source.top - dest.top;
case View.FOCUS_DOWN:
return dest.bottom - source.bottom;
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* Find the distance on the minor axis w.r.t the direction to the nearest
* edge of the destination rectange.
* @param direction the direction (up, down, left, right)
* @param source The source rect.
* @param dest The destination rect.
* @return The distance.
*/
static int minorAxisDistance(int direction, Rect source, Rect dest) {
switch (direction) {
case View.FOCUS_LEFT:
case View.FOCUS_RIGHT:
// the distance between the center verticals
return Math.abs(
((source.top + source.height() / 2) -
((dest.top + dest.height() / 2))));
case View.FOCUS_UP:
case View.FOCUS_DOWN:
// the distance between the center horizontals
return Math.abs(
((source.left + source.width() / 2) -
((dest.left + dest.width() / 2))));
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
/**
* Find the nearest touchable view to the specified view.
*
* @param root The root of the tree in which to search
* @param x X coordinate from which to start the search
* @param y Y coordinate from which to start the search
* @param direction Direction to look
* @param deltas Offset from the <x, y> to the edge of the nearest view. Note that this array
* may already be populated with values.
* @return The nearest touchable view, or null if none exists.
*/
public View findNearestTouchable(ViewGroup root, int x, int y, int direction, int[] deltas) {
ArrayList<View> touchables = root.getTouchables();
int minDistance = Integer.MAX_VALUE;
View closest = null;
int numTouchables = touchables.size();
int edgeSlop = ViewConfiguration.get(root.mContext).getScaledEdgeSlop();
Rect closestBounds = new Rect();
Rect touchableBounds = mOtherRect;
for (int i = 0; i < numTouchables; i++) {
View touchable = touchables.get(i);
// get visible bounds of other view in same coordinate system
touchable.getDrawingRect(touchableBounds);
root.offsetRectBetweenParentAndChild(touchable, touchableBounds, true, true);
if (!isTouchCandidate(x, y, touchableBounds, direction)) {
continue;
}
int distance = Integer.MAX_VALUE;
switch (direction) {
case View.FOCUS_LEFT:
distance = x - touchableBounds.right + 1;
break;
case View.FOCUS_RIGHT:
distance = touchableBounds.left;
break;
case View.FOCUS_UP:
distance = y - touchableBounds.bottom + 1;
break;
case View.FOCUS_DOWN:
distance = touchableBounds.top;
break;
}
if (distance < edgeSlop) {
// Give preference to innermost views
if (closest == null ||
closestBounds.contains(touchableBounds) ||
(!touchableBounds.contains(closestBounds) && distance < minDistance)) {
minDistance = distance;
closest = touchable;
closestBounds.set(touchableBounds);
switch (direction) {
case View.FOCUS_LEFT:
deltas[0] = -distance;
break;
case View.FOCUS_RIGHT:
deltas[0] = distance;
break;
case View.FOCUS_UP:
deltas[1] = -distance;
break;
case View.FOCUS_DOWN:
deltas[1] = distance;
break;
}
}
}
}
return closest;
}
/**
* Is destRect a candidate for the next touch given the direction?
*/
private boolean isTouchCandidate(int x, int y, Rect destRect, int direction) {
switch (direction) {
case View.FOCUS_LEFT:
return destRect.left <= x && destRect.top <= y && y <= destRect.bottom;
case View.FOCUS_RIGHT:
return destRect.left >= x && destRect.top <= y && y <= destRect.bottom;
case View.FOCUS_UP:
return destRect.top <= y && destRect.left <= x && x <= destRect.right;
case View.FOCUS_DOWN:
return destRect.top >= y && destRect.left <= x && x <= destRect.right;
}
throw new IllegalArgumentException("direction must be one of "
+ "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT}.");
}
}
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