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      1 /*
      2  * Copyright (C) 2014 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 package android.transition;
     17 
     18 import android.graphics.Rect;
     19 import android.transition.Slide.GravityFlag;
     20 import android.view.Gravity;
     21 import android.view.View;
     22 import android.view.ViewGroup;
     23 
     24 /**
     25  * A <code>TransitionPropagation</code> that propagates based on the distance to the side
     26  * and, orthogonally, the distance to epicenter. If the transitioning View is visible in
     27  * the start of the transition, then it will transition sooner when closer to the side and
     28  * later when farther. If the view is not visible in the start of the transition, then
     29  * it will transition later when closer to the side and sooner when farther from the edge.
     30  * This is the default TransitionPropagation used with {@link android.transition.Slide}.
     31  */
     32 public class SidePropagation extends VisibilityPropagation {
     33     private static final String TAG = "SlidePropagation";
     34 
     35     private float mPropagationSpeed = 3.0f;
     36     private int mSide = Gravity.BOTTOM;
     37 
     38     /**
     39      * Sets the side that is used to calculate the transition propagation. If the transitioning
     40      * View is visible in the start of the transition, then it will transition sooner when
     41      * closer to the side and later when farther. If the view is not visible in the start of
     42      * the transition, then it will transition later when closer to the side and sooner when
     43      * farther from the edge. The default is {@link Gravity#BOTTOM}.
     44      *
     45      * @param side The side that is used to calculate the transition propagation. Must be one of
     46      *             {@link Gravity#LEFT}, {@link Gravity#TOP}, {@link Gravity#RIGHT},
     47      *             {@link Gravity#BOTTOM}, {@link Gravity#START}, or {@link Gravity#END}.
     48      */
     49     public void setSide(@GravityFlag int side) {
     50         mSide = side;
     51     }
     52 
     53     /**
     54      * Sets the speed at which transition propagation happens, relative to the duration of the
     55      * Transition. A <code>propagationSpeed</code> of 1 means that a View centered at the side
     56      * set in {@link #setSide(int)} and View centered at the opposite edge will have a difference
     57      * in start delay of approximately the duration of the Transition. A speed of 2 means the
     58      * start delay difference will be approximately half of the duration of the transition. A
     59      * value of 0 is illegal, but negative values will invert the propagation.
     60      *
     61      * @param propagationSpeed The speed at which propagation occurs, relative to the duration
     62      *                         of the transition. A speed of 4 means it works 4 times as fast
     63      *                         as the duration of the transition. May not be 0.
     64      */
     65     public void setPropagationSpeed(float propagationSpeed) {
     66         if (propagationSpeed == 0) {
     67             throw new IllegalArgumentException("propagationSpeed may not be 0");
     68         }
     69         mPropagationSpeed = propagationSpeed;
     70     }
     71 
     72     @Override
     73     public long getStartDelay(ViewGroup sceneRoot, Transition transition,
     74             TransitionValues startValues, TransitionValues endValues) {
     75         if (startValues == null && endValues == null) {
     76             return 0;
     77         }
     78         int directionMultiplier = 1;
     79         Rect epicenter = transition.getEpicenter();
     80         TransitionValues positionValues;
     81         if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
     82             positionValues = startValues;
     83             directionMultiplier = -1;
     84         } else {
     85             positionValues = endValues;
     86         }
     87 
     88         int viewCenterX = getViewX(positionValues);
     89         int viewCenterY = getViewY(positionValues);
     90 
     91         int[] loc = new int[2];
     92         sceneRoot.getLocationOnScreen(loc);
     93         int left = loc[0] + Math.round(sceneRoot.getTranslationX());
     94         int top = loc[1] + Math.round(sceneRoot.getTranslationY());
     95         int right = left + sceneRoot.getWidth();
     96         int bottom = top + sceneRoot.getHeight();
     97 
     98         int epicenterX;
     99         int epicenterY;
    100         if (epicenter != null) {
    101             epicenterX = epicenter.centerX();
    102             epicenterY = epicenter.centerY();
    103         } else {
    104             epicenterX = (left + right) / 2;
    105             epicenterY = (top + bottom) / 2;
    106         }
    107 
    108         float distance = distance(sceneRoot, viewCenterX, viewCenterY, epicenterX, epicenterY,
    109                 left, top, right, bottom);
    110         float maxDistance = getMaxDistance(sceneRoot);
    111         float distanceFraction = distance/maxDistance;
    112 
    113         long duration = transition.getDuration();
    114         if (duration < 0) {
    115             duration = 300;
    116         }
    117 
    118         return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
    119     }
    120 
    121     private int distance(View sceneRoot, int viewX, int viewY, int epicenterX, int epicenterY,
    122             int left, int top, int right, int bottom) {
    123         final int side;
    124         if (mSide == Gravity.START) {
    125             final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
    126             side = isRtl ? Gravity.RIGHT : Gravity.LEFT;
    127         } else if (mSide == Gravity.END) {
    128             final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
    129             side = isRtl ? Gravity.LEFT : Gravity.RIGHT;
    130         } else {
    131             side = mSide;
    132         }
    133         int distance = 0;
    134         switch (side) {
    135             case Gravity.LEFT:
    136                 distance = right - viewX + Math.abs(epicenterY - viewY);
    137                 break;
    138             case Gravity.TOP:
    139                 distance = bottom - viewY + Math.abs(epicenterX - viewX);
    140                 break;
    141             case Gravity.RIGHT:
    142                 distance = viewX - left + Math.abs(epicenterY - viewY);
    143                 break;
    144             case Gravity.BOTTOM:
    145                 distance = viewY - top + Math.abs(epicenterX - viewX);
    146                 break;
    147         }
    148         return distance;
    149     }
    150 
    151     private int getMaxDistance(ViewGroup sceneRoot) {
    152         switch (mSide) {
    153             case Gravity.LEFT:
    154             case Gravity.RIGHT:
    155             case Gravity.START:
    156             case Gravity.END:
    157                 return sceneRoot.getWidth();
    158             default:
    159                 return sceneRoot.getHeight();
    160         }
    161     }
    162 }
    163