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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package androidx.transition;
     18 
     19 import android.graphics.Rect;
     20 import android.view.Gravity;
     21 import android.view.View;
     22 import android.view.ViewGroup;
     23 
     24 import androidx.core.view.ViewCompat;
     25 
     26 /**
     27  * A <code>TransitionPropagation</code> that propagates based on the distance to the side
     28  * and, orthogonally, the distance to epicenter. If the transitioning View is visible in
     29  * the start of the transition, then it will transition sooner when closer to the side and
     30  * later when farther. If the view is not visible in the start of the transition, then
     31  * it will transition later when closer to the side and sooner when farther from the edge.
     32  * This is the default TransitionPropagation used with {@link android.transition.Slide}.
     33  */
     34 public class SidePropagation extends VisibilityPropagation {
     35 
     36     private float mPropagationSpeed = 3.0f;
     37     private int mSide = Gravity.BOTTOM;
     38 
     39     /**
     40      * Sets the side that is used to calculate the transition propagation. If the transitioning
     41      * View is visible in the start of the transition, then it will transition sooner when
     42      * closer to the side and later when farther. If the view is not visible in the start of
     43      * the transition, then it will transition later when closer to the side and sooner when
     44      * farther from the edge. The default is {@link Gravity#BOTTOM}.
     45      *
     46      * @param side The side that is used to calculate the transition propagation. Must be one of
     47      *             {@link Gravity#LEFT}, {@link Gravity#TOP}, {@link Gravity#RIGHT},
     48      *             {@link Gravity#BOTTOM}, {@link Gravity#START}, or {@link Gravity#END}.
     49      */
     50     public void setSide(@Slide.GravityFlag int side) {
     51         mSide = side;
     52     }
     53 
     54     /**
     55      * Sets the speed at which transition propagation happens, relative to the duration of the
     56      * Transition. A <code>propagationSpeed</code> of 1 means that a View centered at the side
     57      * set in {@link #setSide(int)} and View centered at the opposite edge will have a difference
     58      * in start delay of approximately the duration of the Transition. A speed of 2 means the
     59      * start delay difference will be approximately half of the duration of the transition. A
     60      * value of 0 is illegal, but negative values will invert the propagation.
     61      *
     62      * @param propagationSpeed The speed at which propagation occurs, relative to the duration
     63      *                         of the transition. A speed of 4 means it works 4 times as fast
     64      *                         as the duration of the transition. May not be 0.
     65      */
     66     public void setPropagationSpeed(float propagationSpeed) {
     67         if (propagationSpeed == 0) {
     68             throw new IllegalArgumentException("propagationSpeed may not be 0");
     69         }
     70         mPropagationSpeed = propagationSpeed;
     71     }
     72 
     73     @Override
     74     public long getStartDelay(ViewGroup sceneRoot, Transition transition,
     75             TransitionValues startValues, TransitionValues endValues) {
     76         if (startValues == null && endValues == null) {
     77             return 0;
     78         }
     79         int directionMultiplier = 1;
     80         Rect epicenter = transition.getEpicenter();
     81         TransitionValues positionValues;
     82         if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
     83             positionValues = startValues;
     84             directionMultiplier = -1;
     85         } else {
     86             positionValues = endValues;
     87         }
     88 
     89         int viewCenterX = getViewX(positionValues);
     90         int viewCenterY = getViewY(positionValues);
     91 
     92         int[] loc = new int[2];
     93         sceneRoot.getLocationOnScreen(loc);
     94         int left = loc[0] + Math.round(sceneRoot.getTranslationX());
     95         int top = loc[1] + Math.round(sceneRoot.getTranslationY());
     96         int right = left + sceneRoot.getWidth();
     97         int bottom = top + sceneRoot.getHeight();
     98 
     99         int epicenterX;
    100         int epicenterY;
    101         if (epicenter != null) {
    102             epicenterX = epicenter.centerX();
    103             epicenterY = epicenter.centerY();
    104         } else {
    105             epicenterX = (left + right) / 2;
    106             epicenterY = (top + bottom) / 2;
    107         }
    108 
    109         float distance = distance(sceneRoot, viewCenterX, viewCenterY, epicenterX, epicenterY,
    110                 left, top, right, bottom);
    111         float maxDistance = getMaxDistance(sceneRoot);
    112         float distanceFraction = distance / maxDistance;
    113 
    114         long duration = transition.getDuration();
    115         if (duration < 0) {
    116             duration = 300;
    117         }
    118 
    119         return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
    120     }
    121 
    122     private int distance(View sceneRoot, int viewX, int viewY, int epicenterX, int epicenterY,
    123             int left, int top, int right, int bottom) {
    124         final int side;
    125         if (mSide == Gravity.START) {
    126             final boolean isRtl = ViewCompat.getLayoutDirection(sceneRoot)
    127                     == ViewCompat.LAYOUT_DIRECTION_RTL;
    128             side = isRtl ? Gravity.RIGHT : Gravity.LEFT;
    129         } else if (mSide == Gravity.END) {
    130             final boolean isRtl = ViewCompat.getLayoutDirection(sceneRoot)
    131                     == ViewCompat.LAYOUT_DIRECTION_RTL;
    132             side = isRtl ? Gravity.LEFT : Gravity.RIGHT;
    133         } else {
    134             side = mSide;
    135         }
    136         int distance = 0;
    137         switch (side) {
    138             case Gravity.LEFT:
    139                 distance = right - viewX + Math.abs(epicenterY - viewY);
    140                 break;
    141             case Gravity.TOP:
    142                 distance = bottom - viewY + Math.abs(epicenterX - viewX);
    143                 break;
    144             case Gravity.RIGHT:
    145                 distance = viewX - left + Math.abs(epicenterY - viewY);
    146                 break;
    147             case Gravity.BOTTOM:
    148                 distance = viewY - top + Math.abs(epicenterX - viewX);
    149                 break;
    150         }
    151         return distance;
    152     }
    153 
    154     private int getMaxDistance(ViewGroup sceneRoot) {
    155         switch (mSide) {
    156             case Gravity.LEFT:
    157             case Gravity.RIGHT:
    158             case Gravity.START:
    159             case Gravity.END:
    160                 return sceneRoot.getWidth();
    161             default:
    162                 return sceneRoot.getHeight();
    163         }
    164     }
    165 
    166 }
    167