content: /*
   * Copyright 2016 Google Inc. All Rights Reserved.
   *
   * 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.google.samples.apps.ourstreets.transition;
  
  import android.animation.Animator;
  import android.animation.ObjectAnimator;
  import android.content.Context;
  import android.transition.Transition;
  import android.transition.TransitionValues;
  import android.util.AttributeSet;
  import android.view.View;
  import android.view.ViewGroup;
  
  
  /**
   * Transitions target {@link View}s elevation property to/from zero
   * when it's entering/exiting a scene.
   */
  public class Elevation extends Transition {
  
      private static final String PROP_ELEVATION = "ourstreets:elevation";
  
      private static final String[] PROPERTIES = {PROP_ELEVATION};
  
      /**
       * Constructs an Elevation object with no target objects.
       */
      public Elevation() {
          super();
      }
  
      /**
       * Perform inflation from XML and apply a class-specific base style
       * from a theme attribute or style resource.
       *
       * @param context The Context the transition is running in, through which it can
       * access the current theme, resources, etc.
       * @param attrs The attributes of the XML tag that is inflating the transition.
       */
      public Elevation(Context context, AttributeSet attrs) {
          super(context, attrs);
      }
  
      @Override
      public void captureStartValues(TransitionValues transitionValues) {
          captureValues(transitionValues);
      }
  
      @Override
      public void captureEndValues(TransitionValues transitionValues) {
          captureValues(transitionValues);
      }
  
      private void captureValues(TransitionValues transitionValues) {
          transitionValues.values.put(PROP_ELEVATION, transitionValues.view.getElevation());
      }
  
      @Override
      public String[] getTransitionProperties() {
          return PROPERTIES;
      }
  
      @Override
      public Animator createAnimator(ViewGroup sceneRoot, TransitionValues startValues,
                                     TransitionValues endValues) {
          if (startValues == null && endValues == null) {
              return null; // nothing to do here
          }
  
          boolean isEntering = startValues == null;
  
          TransitionValues values = isEntering ? endValues : startValues;
          View target = values.view;
  
          float targetElevation = (float) values.values.get(PROP_ELEVATION);
          float startElevation = isEntering ? 0f : targetElevation;
          float endElevation = isEntering ? targetElevation : 0f;
  
          //noinspection ResourceType
          target.setElevation(startElevation);
  
          return ObjectAnimator.ofFloat(target, View.TRANSLATION_Z, endElevation);
      }
  
  }
  