/*
* Copyright (C) 2014 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.transition;
import android.view.ViewGroup;
/**
* Extend <code>TransitionPropagation</code> to customize start delays for Animators created
* in {@link android.transition.Transition#createAnimator(ViewGroup,
* TransitionValues, TransitionValues)}. A Transition such as {@link android.transition.Explode}
* defaults to using {@link android.transition.CircularPropagation} and Views closer to the
* epicenter will move out of the scene later and into the scene sooner than Views farther
* from the epicenter, giving the appearance of inertia. With no TransitionPropagation, all
* Views will react simultaneously to the start of the transition.
*
* @see Transition#setPropagation(TransitionPropagation)
* @see Transition#getEpicenter()
*/
public abstract class TransitionPropagation {
/**
* Called by Transition to alter the Animator start delay. All start delays will be adjusted
* such that the minimum becomes zero.
* @param sceneRoot The root of the View hierarchy running the transition.
* @param transition The transition that created the Animator
* @param startValues The values for a specific target in the start scene.
* @param endValues The values for the target in the end scene.
* @return A start delay to use with the Animator created by <code>transition</code>. The
* delay will be offset by the minimum delay of all <code>TransitionPropagation</code>s
* used in the Transition so that the smallest delay will be 0. Returned values may be
* negative.
*/
public abstract long getStartDelay(ViewGroup sceneRoot, Transition transition,
TransitionValues startValues, TransitionValues endValues);
/**
* Captures the values in the start or end scene for the properties that this
* transition propagation monitors. These values are then passed as the startValues
* or endValues structure in a later call to
* {@link #getStartDelay(ViewGroup, Transition, TransitionValues, TransitionValues)}.
* The main concern for an implementation is what the
* properties are that the transition cares about and what the values are
* for all of those properties. The start and end values will be compared
* later during the
* {@link #getStartDelay(ViewGroup, Transition, TransitionValues, TransitionValues)}.
* method to determine the start delay.
*
* <p>Subclasses must implement this method. The method should only be called by the
* transition system; it is not intended to be called from external classes.</p>
*
* @param transitionValues The holder for any values that the Transition
* wishes to store. Values are stored in the <code>values</code> field
* of this TransitionValues object and are keyed from
* a String value. For example, to store a view's rotation value,
* a transition might call
* <code>transitionValues.values.put("appname:transitionname:rotation",
* view.getRotation())</code>. The target view will already be stored in
* the transitionValues structure when this method is called.
*/
public abstract void captureValues(TransitionValues transitionValues);
/**
* Returns the set of property names stored in the {@link TransitionValues}
* object passed into {@link #captureValues(TransitionValues)} that
* this transition propagation cares about for the purposes of preventing
* duplicate capturing of property values.
* <p>A <code>TransitionPropagation</code> must override this method to prevent
* duplicate capturing of values and must contain at least one </p>
*
* @return An array of property names as described in the class documentation for
* {@link TransitionValues}.
*/
public abstract String[] getPropagationProperties() ;
}