public abstract class

Visibility

extends Transition

 java.lang.Object

androidx.transition.Transition

↳androidx.transition.Visibility

Subclasses:

Slide, Fade, Explode

Gradle dependencies

compile group: 'androidx.transition', name: 'transition', version: '1.5.1'

  • groupId: androidx.transition
  • artifactId: transition
  • version: 1.5.1

Artifact androidx.transition:transition:1.5.1 it located at Google repository (https://maven.google.com/)

Androidx artifact mapping:

androidx.transition:transition com.android.support:transition

Androidx class mapping:

androidx.transition.Visibility android.support.transition.Visibility

Overview

This transition tracks changes to the visibility of target views in the start and end scenes. Visibility is determined not just by the View state of views, but also whether views exist in the current view hierarchy. The class is intended to be a utility for subclasses such as Fade, which use this visibility information to determine the specific animations to run when visibility changes occur. Subclasses should implement one or both of the methods Visibility.onAppear(ViewGroup, TransitionValues, int, TransitionValues, int), Visibility.onDisappear(ViewGroup, TransitionValues, int, TransitionValues, int) or Visibility.onAppear(ViewGroup, View, TransitionValues, TransitionValues), Visibility.onDisappear(ViewGroup, View, TransitionValues, TransitionValues).

Summary

Fields
public static final intMODE_IN

Mode used in Visibility.setMode(int) to make the transition operate on targets that are appearing.

public static final intMODE_OUT

Mode used in Visibility.setMode(int) to make the transition operate on targets that are disappearing.

from TransitionMATCH_ID, MATCH_INSTANCE, MATCH_ITEM_ID, MATCH_NAME
Constructors
publicVisibility()

publicVisibility(Context context, AttributeSet attrs)

Methods
public abstract voidcaptureEndValues(TransitionValues transitionValues)

Captures the values in the end scene for the properties that this transition monitors.

public abstract voidcaptureStartValues(TransitionValues transitionValues)

Captures the values in the start scene for the properties that this transition monitors.

public AnimatorcreateAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues)

This method creates an animation that will be run for this transition given the information in the startValues and endValues structures captured earlier for the start and end scenes.

public intgetMode()

Returns whether appearing and/or disappearing Views are supported.

public java.lang.StringgetTransitionProperties()

Returns the set of property names used stored in the TransitionValues object passed into Transition.captureStartValues(TransitionValues) that this transition cares about for the purposes of canceling overlapping animations.

public booleanisTransitionRequired(TransitionValues startValues, TransitionValues endValues)

Returns whether or not the transition should create an Animator, based on the values captured during Transition.captureStartValues(TransitionValues) and Transition.captureEndValues(TransitionValues).

public booleanisVisible(TransitionValues values)

Returns whether the view is 'visible' according to the given values object.

public AnimatoronAppear(ViewGroup sceneRoot, TransitionValues startValues, int startVisibility, TransitionValues endValues, int endVisibility)

The default implementation of this method does nothing.

public AnimatoronAppear(ViewGroup sceneRoot, View view, TransitionValues startValues, TransitionValues endValues)

The default implementation of this method returns a null Animator.

public AnimatoronDisappear(ViewGroup sceneRoot, TransitionValues startValues, int startVisibility, TransitionValues endValues, int endVisibility)

The default implementation of this method does nothing.

public AnimatoronDisappear(ViewGroup sceneRoot, View view, TransitionValues startValues, TransitionValues endValues)

The default implementation of this method returns a null Animator.

public voidsetMode(int mode)

Changes the transition to support appearing and/or disappearing Views, depending on mode.

from TransitionaddListener, addTarget, animate, cancel, clone, end, excludeChildren, excludeTarget, getDuration, getEpicenter, getEpicenterCallback, getInterpolator, getName, getPathMotion, getPropagation, getRootTransition, getStartDelay, getTargetIds, getTargetNames, getTargets, getTargetTypes, getTransitionValues, isSeekingSupported, pause, removeListener, removeTarget, resume, runAnimators, setDuration, setEpicenterCallback, setInterpolator, setMatchOrder, setPathMotion, setPropagation, setStartDelay, start, toString
from java.lang.Objectequals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Fields

public static final int MODE_IN

Mode used in Visibility.setMode(int) to make the transition operate on targets that are appearing. Maybe be combined with Visibility.MODE_OUT to target Visibility changes both in and out.

public static final int MODE_OUT

Mode used in Visibility.setMode(int) to make the transition operate on targets that are disappearing. Maybe be combined with Visibility.MODE_IN to target Visibility changes both in and out.

Constructors

public Visibility()

public Visibility(Context context, AttributeSet attrs)

Methods

public void setMode(int mode)

Changes the transition to support appearing and/or disappearing Views, depending on mode.

Parameters:

mode: The behavior supported by this transition, a combination of Visibility.MODE_IN and Visibility.MODE_OUT.

public int getMode()

Returns whether appearing and/or disappearing Views are supported.

Returns:

whether appearing and/or disappearing Views are supported. A combination of Visibility.MODE_IN and Visibility.MODE_OUT.

public java.lang.String getTransitionProperties()

Returns the set of property names used stored in the TransitionValues object passed into Transition.captureStartValues(TransitionValues) that this transition cares about for the purposes of canceling overlapping animations. When any transition is started on a given scene root, all transitions currently running on that same scene root are checked to see whether the properties on which they based their animations agree with the end values of the same properties in the new transition. If the end values are not equal, then the old animation is canceled since the new transition will start a new animation to these new values. If the values are equal, the old animation is allowed to continue and no new animation is started for that transition.

A transition does not need to override this method. However, not doing so will mean that the cancellation logic outlined in the previous paragraph will be skipped for that transition, possibly leading to artifacts as old transitions and new transitions on the same targets run in parallel, animating views toward potentially different end values.

Returns:

An array of property names as described in the class documentation for TransitionValues. The default implementation returns null.

public abstract void captureStartValues(TransitionValues transitionValues)

Captures the values in the start scene for the properties that this transition monitors. These values are then passed as the startValues structure in a later call to Transition.createAnimator(ViewGroup, 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 Transition.createAnimator(ViewGroup, TransitionValues, TransitionValues) method to determine what, if any, animations, should be run.

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.

Parameters:

transitionValues: The holder for any values that the Transition wishes to store. Values are stored in the values 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 transitionValues.values.put("appname:transitionname:rotation", view.getRotation()). The target view will already be stored in the transitionValues structure when this method is called.

See also: Transition.captureEndValues(TransitionValues), Transition.createAnimator(ViewGroup, TransitionValues, TransitionValues)

public abstract void captureEndValues(TransitionValues transitionValues)

Captures the values in the end scene for the properties that this transition monitors. These values are then passed as the endValues structure in a later call to Transition.createAnimator(ViewGroup, 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 Transition.createAnimator(ViewGroup, TransitionValues, TransitionValues) method to determine what, if any, animations, should be run.

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.

Parameters:

transitionValues: The holder for any values that the Transition wishes to store. Values are stored in the values 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 transitionValues.values.put("appname:transitionname:rotation", view.getRotation()). The target view will already be stored in the transitionValues structure when this method is called.

See also: Transition.captureStartValues(TransitionValues), Transition.createAnimator(ViewGroup, TransitionValues, TransitionValues)

public boolean isVisible(TransitionValues values)

Returns whether the view is 'visible' according to the given values object. This is determined by testing the same properties in the values object that are used to determine whether the object is appearing or disappearing in the Transition.createAnimator(ViewGroup, TransitionValues, TransitionValues) method. This method can be called by, for example, subclasses that want to know whether the object is visible in the same way that Visibility determines it for the actual animation.

Parameters:

values: The TransitionValues object that holds the information by which visibility is determined.

Returns:

True if the view reference by values is visible, false otherwise.

public Animator createAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues)

This method creates an animation that will be run for this transition given the information in the startValues and endValues structures captured earlier for the start and end scenes. Subclasses of Transition should override this method. The method should only be called by the transition system; it is not intended to be called from external classes.

This method is called by the transition's parent (all the way up to the topmost Transition in the hierarchy) with the sceneRoot and start/end values that the transition may need to set up initial target values and construct an appropriate animation. For example, if an overall Transition is a TransitionSet consisting of several child transitions in sequence, then some of the child transitions may want to set initial values on target views prior to the overall Transition commencing, to put them in an appropriate state for the delay between that start and the child Transition start time. For example, a transition that fades an item in may wish to set the starting alpha value to 0, to avoid it blinking in prior to the transition actually starting the animation. This is necessary because the scene change that triggers the Transition will automatically set the end-scene on all target views, so a Transition that wants to animate from a different value should set that value prior to returning from this method.

Additionally, a Transition can perform logic to determine whether the transition needs to run on the given target and start/end values. For example, a transition that resizes objects on the screen may wish to avoid running for views which are not present in either the start or end scenes.

If there is an animator created and returned from this method, the transition mechanism will apply any applicable duration, startDelay, and interpolator to that animation and start it. A return value of null indicates that no animation should run. The default implementation returns null.

The method is called for every applicable target object, which is stored in the TransitionValues.view field.

Parameters:

sceneRoot: The root of the transition hierarchy.
startValues: The values for a specific target in the start scene.
endValues: The values for the target in the end scene.

Returns:

A Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

public Animator onAppear(ViewGroup sceneRoot, TransitionValues startValues, int startVisibility, TransitionValues endValues, int endVisibility)

The default implementation of this method does nothing. Subclasses should override if they need to create an Animator when targets appear. The method should only be called by the Visibility class; it is not intended to be called from external classes.

Parameters:

sceneRoot: The root of the transition hierarchy
startValues: The target values in the start scene
startVisibility: The target visibility in the start scene
endValues: The target values in the end scene
endVisibility: The target visibility in the end scene

Returns:

An Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

public Animator onAppear(ViewGroup sceneRoot, View view, TransitionValues startValues, TransitionValues endValues)

The default implementation of this method returns a null Animator. Subclasses should override this method to make targets appear with the desired transition. The method should only be called from Visibility.onAppear(ViewGroup, TransitionValues, int, TransitionValues, int).

Parameters:

sceneRoot: The root of the transition hierarchy
view: The View to make appear. This will be in the target scene's View hierarchy and will be VISIBLE.
startValues: The target values in the start scene
endValues: The target values in the end scene

Returns:

An Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

public Animator onDisappear(ViewGroup sceneRoot, TransitionValues startValues, int startVisibility, TransitionValues endValues, int endVisibility)

The default implementation of this method does nothing. Subclasses should override if they need to create an Animator when targets disappear. The method should only be called by the Visibility class; it is not intended to be called from external classes.

Parameters:

sceneRoot: The root of the transition hierarchy
startValues: The target values in the start scene
startVisibility: The target visibility in the start scene
endValues: The target values in the end scene
endVisibility: The target visibility in the end scene

Returns:

An Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

public Animator onDisappear(ViewGroup sceneRoot, View view, TransitionValues startValues, TransitionValues endValues)

The default implementation of this method returns a null Animator. Subclasses should override this method to make targets disappear with the desired transition. The method should only be called from Visibility.onDisappear(ViewGroup, TransitionValues, int, TransitionValues, int).

Parameters:

sceneRoot: The root of the transition hierarchy
view: The View to make disappear. This will be in the target scene's View hierarchy or in an and will be VISIBLE.
startValues: The target values in the start scene
endValues: The target values in the end scene

Returns:

An Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

public boolean isTransitionRequired(TransitionValues startValues, TransitionValues endValues)

Returns whether or not the transition should create an Animator, based on the values captured during Transition.captureStartValues(TransitionValues) and Transition.captureEndValues(TransitionValues). The default implementation compares the property values returned from Transition.getTransitionProperties(), or all property values if getTransitionProperties() returns null. Subclasses may override this method to provide logic more specific to the transition implementation.

Parameters:

startValues: the values from captureStartValues, This may be null if the View did not exist in the start state.
endValues: the values from captureEndValues. This may be null if the View did not exist in the end state.

Source

/*
 * Copyright (C) 2016 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 androidx.transition;

import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.content.res.XmlResourceParser;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.IntDef;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.core.content.res.TypedArrayUtils;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

/**
 * This transition tracks changes to the visibility of target views in the
 * start and end scenes. Visibility is determined not just by the
 * {@link View#setVisibility(int)} state of views, but also whether
 * views exist in the current view hierarchy. The class is intended to be a
 * utility for subclasses such as {@link Fade}, which use this visibility
 * information to determine the specific animations to run when visibility
 * changes occur. Subclasses should implement one or both of the methods
 * {@link #onAppear(ViewGroup, TransitionValues, int, TransitionValues, int)},
 * {@link #onDisappear(ViewGroup, TransitionValues, int, TransitionValues, int)} or
 * {@link #onAppear(ViewGroup, View, TransitionValues, TransitionValues)},
 * {@link #onDisappear(ViewGroup, View, TransitionValues, TransitionValues)}.
 */
public abstract class Visibility extends Transition {

    static final String PROPNAME_VISIBILITY = "android:visibility:visibility";
    private static final String PROPNAME_PARENT = "android:visibility:parent";
    private static final String PROPNAME_SCREEN_LOCATION = "android:visibility:screenLocation";

    /**
     * Mode used in {@link #setMode(int)} to make the transition
     * operate on targets that are appearing. Maybe be combined with
     * {@link #MODE_OUT} to target Visibility changes both in and out.
     */
    public static final int MODE_IN = 0x1;

    /**
     * Mode used in {@link #setMode(int)} to make the transition
     * operate on targets that are disappearing. Maybe be combined with
     * {@link #MODE_IN} to target Visibility changes both in and out.
     */
    public static final int MODE_OUT = 0x2;

    @RestrictTo(LIBRARY_GROUP_PREFIX)
    @SuppressLint("UniqueConstants") // because MODE_IN and Fade.IN are aliases.
    @IntDef(flag = true, value = {MODE_IN, MODE_OUT, Fade.IN, Fade.OUT})
    @Retention(RetentionPolicy.SOURCE)
    public @interface Mode {
    }

    private static final String[] sTransitionProperties = {
            PROPNAME_VISIBILITY,
            PROPNAME_PARENT,
    };

    private static class VisibilityInfo {
        VisibilityInfo() {
        }

        boolean mVisibilityChange;
        boolean mFadeIn;
        int mStartVisibility;
        int mEndVisibility;
        ViewGroup mStartParent;
        ViewGroup mEndParent;
    }

    private int mMode = MODE_IN | MODE_OUT;

    public Visibility() {
    }

    public Visibility(@NonNull Context context, @NonNull AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.obtainStyledAttributes(attrs, Styleable.VISIBILITY_TRANSITION);
        @Mode
        int mode = TypedArrayUtils.getNamedInt(a, (XmlResourceParser) attrs,
                "transitionVisibilityMode",
                Styleable.VisibilityTransition.TRANSITION_VISIBILITY_MODE, 0);
        a.recycle();
        if (mode != 0) {
            setMode(mode);
        }
    }

    /**
     * Changes the transition to support appearing and/or disappearing Views, depending
     * on <code>mode</code>.
     *
     * @param mode The behavior supported by this transition, a combination of
     *             {@link #MODE_IN} and {@link #MODE_OUT}.
     */
    public void setMode(@Mode int mode) {
        if ((mode & ~(MODE_IN | MODE_OUT)) != 0) {
            throw new IllegalArgumentException("Only MODE_IN and MODE_OUT flags are allowed");
        }
        mMode = mode;
    }

    /**
     * Returns whether appearing and/or disappearing Views are supported.
     *
     * @return whether appearing and/or disappearing Views are supported. A combination of
     * {@link #MODE_IN} and {@link #MODE_OUT}.
     */
    @Mode
    public int getMode() {
        return mMode;
    }

    @Nullable
    @Override
    public String[] getTransitionProperties() {
        return sTransitionProperties;
    }

    private void captureValues(TransitionValues transitionValues) {
        int visibility = transitionValues.view.getVisibility();
        transitionValues.values.put(PROPNAME_VISIBILITY, visibility);
        transitionValues.values.put(PROPNAME_PARENT, transitionValues.view.getParent());
        int[] loc = new int[2];
        transitionValues.view.getLocationOnScreen(loc);
        transitionValues.values.put(PROPNAME_SCREEN_LOCATION, loc);
    }

    @Override
    public void captureStartValues(@NonNull TransitionValues transitionValues) {
        captureValues(transitionValues);
    }

    @Override
    public void captureEndValues(@NonNull TransitionValues transitionValues) {
        captureValues(transitionValues);
    }

    /**
     * Returns whether the view is 'visible' according to the given values
     * object. This is determined by testing the same properties in the values
     * object that are used to determine whether the object is appearing or
     * disappearing in the {@link
     * Transition#createAnimator(ViewGroup, TransitionValues, TransitionValues)}
     * method. This method can be called by, for example, subclasses that want
     * to know whether the object is visible in the same way that Visibility
     * determines it for the actual animation.
     *
     * @param values The TransitionValues object that holds the information by
     *               which visibility is determined.
     * @return True if the view reference by <code>values</code> is visible,
     * false otherwise.
     */
    public boolean isVisible(@Nullable TransitionValues values) {
        if (values == null) {
            return false;
        }
        int visibility = (Integer) values.values.get(PROPNAME_VISIBILITY);
        View parent = (View) values.values.get(PROPNAME_PARENT);

        return visibility == View.VISIBLE && parent != null;
    }

    private VisibilityInfo getVisibilityChangeInfo(TransitionValues startValues,
            TransitionValues endValues) {
        final VisibilityInfo visInfo = new VisibilityInfo();
        visInfo.mVisibilityChange = false;
        visInfo.mFadeIn = false;
        if (startValues != null && startValues.values.containsKey(PROPNAME_VISIBILITY)) {
            visInfo.mStartVisibility = (Integer) startValues.values.get(PROPNAME_VISIBILITY);
            visInfo.mStartParent = (ViewGroup) startValues.values.get(PROPNAME_PARENT);
        } else {
            visInfo.mStartVisibility = -1;
            visInfo.mStartParent = null;
        }
        if (endValues != null && endValues.values.containsKey(PROPNAME_VISIBILITY)) {
            visInfo.mEndVisibility = (Integer) endValues.values.get(PROPNAME_VISIBILITY);
            visInfo.mEndParent = (ViewGroup) endValues.values.get(PROPNAME_PARENT);
        } else {
            visInfo.mEndVisibility = -1;
            visInfo.mEndParent = null;
        }
        if (startValues != null && endValues != null) {
            if (visInfo.mStartVisibility == visInfo.mEndVisibility
                    && visInfo.mStartParent == visInfo.mEndParent) {
                return visInfo;
            } else {
                if (visInfo.mStartVisibility != visInfo.mEndVisibility) {
                    if (visInfo.mStartVisibility == View.VISIBLE) {
                        visInfo.mFadeIn = false;
                        visInfo.mVisibilityChange = true;
                    } else if (visInfo.mEndVisibility == View.VISIBLE) {
                        visInfo.mFadeIn = true;
                        visInfo.mVisibilityChange = true;
                    }
                    // no visibilityChange if going between INVISIBLE and GONE
                } else /* if (visInfo.mStartParent != visInfo.mEndParent) */ {
                    if (visInfo.mEndParent == null) {
                        visInfo.mFadeIn = false;
                        visInfo.mVisibilityChange = true;
                    } else if (visInfo.mStartParent == null) {
                        visInfo.mFadeIn = true;
                        visInfo.mVisibilityChange = true;
                    }
                }
            }
        } else if (startValues == null && visInfo.mEndVisibility == View.VISIBLE) {
            visInfo.mFadeIn = true;
            visInfo.mVisibilityChange = true;
        } else if (endValues == null && visInfo.mStartVisibility == View.VISIBLE) {
            visInfo.mFadeIn = false;
            visInfo.mVisibilityChange = true;
        }
        return visInfo;
    }

    @Nullable
    @Override
    public Animator createAnimator(@NonNull ViewGroup sceneRoot,
            @Nullable TransitionValues startValues, @Nullable TransitionValues endValues) {
        VisibilityInfo visInfo = getVisibilityChangeInfo(startValues, endValues);
        if (visInfo.mVisibilityChange
                && (visInfo.mStartParent != null || visInfo.mEndParent != null)) {
            if (visInfo.mFadeIn) {
                return onAppear(sceneRoot, startValues, visInfo.mStartVisibility,
                        endValues, visInfo.mEndVisibility);
            } else {
                return onDisappear(sceneRoot, startValues, visInfo.mStartVisibility,
                        endValues, visInfo.mEndVisibility
                );
            }
        }
        return null;
    }

    /**
     * The default implementation of this method does nothing. Subclasses
     * should override if they need to create an Animator when targets appear.
     * The method should only be called by the Visibility class; it is
     * not intended to be called from external classes.
     *
     * @param sceneRoot       The root of the transition hierarchy
     * @param startValues     The target values in the start scene
     * @param startVisibility The target visibility in the start scene
     * @param endValues       The target values in the end scene
     * @param endVisibility   The target visibility in the end scene
     * @return An Animator to be started at the appropriate time in the
     * overall transition for this scene change. A null value means no animation
     * should be run.
     */
    @Nullable
    @SuppressWarnings("UnusedParameters")
    public Animator onAppear(@NonNull ViewGroup sceneRoot, @Nullable TransitionValues startValues,
            int startVisibility, @Nullable TransitionValues endValues, int endVisibility) {
        if ((mMode & MODE_IN) != MODE_IN || endValues == null) {
            return null;
        }
        if (startValues == null) {
            View endParent = (View) endValues.view.getParent();
            TransitionValues startParentValues = getMatchedTransitionValues(endParent,
                    false);
            TransitionValues endParentValues = getTransitionValues(endParent, false);
            VisibilityInfo parentVisibilityInfo =
                    getVisibilityChangeInfo(startParentValues, endParentValues);
            if (parentVisibilityInfo.mVisibilityChange) {
                return null;
            }
        }
        return onAppear(sceneRoot, endValues.view, startValues, endValues);
    }

    /**
     * The default implementation of this method returns a null Animator. Subclasses should
     * override this method to make targets appear with the desired transition. The
     * method should only be called from
     * {@link #onAppear(ViewGroup, TransitionValues, int, TransitionValues, int)}.
     *
     * @param sceneRoot   The root of the transition hierarchy
     * @param view        The View to make appear. This will be in the target scene's View
     *                    hierarchy
     *                    and
     *                    will be VISIBLE.
     * @param startValues The target values in the start scene
     * @param endValues   The target values in the end scene
     * @return An Animator to be started at the appropriate time in the
     * overall transition for this scene change. A null value means no animation
     * should be run.
     */
    @Nullable
    public Animator onAppear(@NonNull ViewGroup sceneRoot, @NonNull View view,
            @Nullable TransitionValues startValues, @Nullable TransitionValues endValues) {
        return null;
    }

    /**
     * The default implementation of this method does nothing. Subclasses
     * should override if they need to create an Animator when targets disappear.
     * The method should only be called by the Visibility class; it is
     * not intended to be called from external classes.
     *
     * @param sceneRoot       The root of the transition hierarchy
     * @param startValues     The target values in the start scene
     * @param startVisibility The target visibility in the start scene
     * @param endValues       The target values in the end scene
     * @param endVisibility   The target visibility in the end scene
     * @return An Animator to be started at the appropriate time in the
     * overall transition for this scene change. A null value means no animation
     * should be run.
     */
    @Nullable
    @SuppressWarnings("UnusedParameters")
    public Animator onDisappear(@NonNull ViewGroup sceneRoot,
            @Nullable TransitionValues startValues, int startVisibility,
            @Nullable TransitionValues endValues, int endVisibility) {
        if ((mMode & MODE_OUT) != MODE_OUT) {
            return null;
        }

        if (startValues == null) {
            // startValues(and startView) will never be null for disappear transition.
            return null;
        }

        final View startView = startValues.view;
        final View endView = (endValues != null) ? endValues.view : null;
        View overlayView = null;
        View viewToKeep = null;
        boolean reusingOverlayView = false;

        View savedOverlayView = (View) startView.getTag(R.id.save_overlay_view);
        if (savedOverlayView != null) {
            // we've already created overlay for the start view.
            // it means that we are applying two visibility
            // transitions for the same view
            overlayView = savedOverlayView;
            reusingOverlayView = true;
        } else {
            boolean needOverlayForStartView = false;

            if (endView == null || endView.getParent() == null) {
                if (endView != null) {
                    // endView was removed from its parent - add it to the overlay
                    overlayView = endView;
                } else {
                    needOverlayForStartView = true;
                }
            } else {
                // visibility change
                if (endVisibility == View.INVISIBLE) {
                    viewToKeep = endView;
                } else {
                    // Becoming GONE
                    if (startView == endView) {
                        viewToKeep = endView;
                    } else {
                        needOverlayForStartView = true;
                    }
                }
            }

            if (needOverlayForStartView) {
                // endView does not exist. Use startView only under certain
                // conditions, because placing a view in an overlay necessitates
                // it being removed from its current parent
                if (startView.getParent() == null) {
                    // no parent - safe to use
                    overlayView = startView;
                } else if (startView.getParent() instanceof View) {
                    View startParent = (View) startView.getParent();
                    TransitionValues startParentValues = getTransitionValues(startParent, true);
                    TransitionValues endParentValues = getMatchedTransitionValues(startParent,
                            true);
                    VisibilityInfo parentVisibilityInfo =
                            getVisibilityChangeInfo(startParentValues, endParentValues);
                    if (!parentVisibilityInfo.mVisibilityChange) {
                        overlayView = TransitionUtils.copyViewImage(sceneRoot, startView,
                                startParent);
                    } else {
                        int id = startParent.getId();
                        if (startParent.getParent() == null && id != View.NO_ID
                                && sceneRoot.findViewById(id) != null && mCanRemoveViews) {
                            // no parent, but its parent is unparented  but the parent
                            // hierarchy has been replaced by a new hierarchy with the same id
                            // and it is safe to un-parent startView
                            overlayView = startView;
                        } else {
                            // TODO: Handle this case as well
                        }
                    }
                }
            }
        }

        if (overlayView != null) {
            if (!reusingOverlayView) {
                int[] screenLoc = (int[]) startValues.values.get(PROPNAME_SCREEN_LOCATION);
                int screenX = screenLoc[0];
                int screenY = screenLoc[1];
                int[] loc = new int[2];
                sceneRoot.getLocationOnScreen(loc);
                overlayView.offsetLeftAndRight((screenX - loc[0]) - overlayView.getLeft());
                overlayView.offsetTopAndBottom((screenY - loc[1]) - overlayView.getTop());
                sceneRoot.getOverlay().add(overlayView);
            }
            Animator animator = onDisappear(sceneRoot, overlayView, startValues, endValues);
            if (!reusingOverlayView) {
                if (animator == null) {
                    sceneRoot.getOverlay().remove(overlayView);
                } else {
                    startView.setTag(R.id.save_overlay_view, overlayView);

                    OverlayListener listener = new OverlayListener(sceneRoot, overlayView,
                            startView);

                    animator.addListener(listener);
                    animator.addPauseListener(listener);
                    getRootTransition().addListener(listener);
                }
            }
            return animator;
        }

        if (viewToKeep != null) {
            int originalVisibility = viewToKeep.getVisibility();
            ViewUtils.setTransitionVisibility(viewToKeep, View.VISIBLE);
            Animator animator = onDisappear(sceneRoot, viewToKeep, startValues, endValues);
            if (animator != null) {
                DisappearListener disappearListener = new DisappearListener(viewToKeep,
                        endVisibility, true);
                animator.addListener(disappearListener);
                getRootTransition().addListener(disappearListener);
            } else {
                ViewUtils.setTransitionVisibility(viewToKeep, originalVisibility);
            }
            return animator;
        }
        return null;
    }

    /**
     * The default implementation of this method returns a null Animator. Subclasses should
     * override this method to make targets disappear with the desired transition. The
     * method should only be called from
     * {@link #onDisappear(ViewGroup, TransitionValues, int, TransitionValues, int)}.
     *
     * @param sceneRoot   The root of the transition hierarchy
     * @param view        The View to make disappear. This will be in the target scene's View
     *                    hierarchy or in an {@link android.view.ViewGroupOverlay} and will be
     *                    VISIBLE.
     * @param startValues The target values in the start scene
     * @param endValues   The target values in the end scene
     * @return An Animator to be started at the appropriate time in the
     * overall transition for this scene change. A null value means no animation
     * should be run.
     */
    @Nullable
    public Animator onDisappear(@NonNull ViewGroup sceneRoot, @NonNull View view,
            @Nullable TransitionValues startValues, @Nullable TransitionValues endValues) {
        return null;
    }

    @Override
    public boolean isTransitionRequired(@Nullable TransitionValues startValues,
            @Nullable TransitionValues endValues) {
        if (startValues == null && endValues == null) {
            return false;
        }
        if (startValues != null && endValues != null
                && endValues.values.containsKey(PROPNAME_VISIBILITY)
                != startValues.values.containsKey(PROPNAME_VISIBILITY)) {
            // The transition wasn't targeted in either the start or end, so it couldn't
            // have changed.
            return false;
        }
        VisibilityInfo changeInfo = getVisibilityChangeInfo(startValues, endValues);
        return changeInfo.mVisibilityChange && (changeInfo.mStartVisibility == View.VISIBLE
                || changeInfo.mEndVisibility == View.VISIBLE);
    }

    private static class DisappearListener extends AnimatorListenerAdapter
            implements TransitionListener {

        private final View mView;
        private final int mFinalVisibility;
        private final ViewGroup mParent;
        private final boolean mSuppressLayout;

        private boolean mLayoutSuppressed;
        boolean mCanceled = false;

        DisappearListener(View view, int finalVisibility, boolean suppressLayout) {
            mView = view;
            mFinalVisibility = finalVisibility;
            mParent = (ViewGroup) view.getParent();
            mSuppressLayout = suppressLayout;
            // Prevent a layout from including mView in its calculation.
            suppressLayout(true);
        }

        @Override
        public void onAnimationCancel(Animator animation) {
            mCanceled = true;
        }

        @Override
        public void onAnimationRepeat(Animator animation) {
        }

        @Override
        public void onAnimationStart(Animator animation) {
        }

        @Override
        public void onAnimationEnd(Animator animation) {
            hideViewWhenNotCanceled();
        }

        @Override
        public void onAnimationStart(@NonNull Animator animation, boolean isReverse) {
            if (isReverse) {
                ViewUtils.setTransitionVisibility(mView, View.VISIBLE);
                if (mParent != null) {
                    mParent.invalidate();
                }
            }
        }

        @Override
        public void onAnimationEnd(@NonNull Animator animation, boolean isReverse) {
            if (!isReverse) {
                hideViewWhenNotCanceled();
            }
        }

        @Override
        public void onTransitionStart(@NonNull Transition transition) {
            // Do nothing
        }

        @Override
        public void onTransitionEnd(@NonNull Transition transition) {
            transition.removeListener(this);
        }

        @Override
        public void onTransitionCancel(@NonNull Transition transition) {
        }

        @Override
        public void onTransitionPause(@NonNull Transition transition) {
            suppressLayout(false);
            if (!mCanceled) {
                ViewUtils.setTransitionVisibility(mView, mFinalVisibility);
            }
        }

        @Override
        public void onTransitionResume(@NonNull Transition transition) {
            suppressLayout(true);
            if (!mCanceled) {
                ViewUtils.setTransitionVisibility(mView, View.VISIBLE);
            }
        }

        private void hideViewWhenNotCanceled() {
            if (!mCanceled) {
                // Recreate the parent's display list in case it includes mView.
                ViewUtils.setTransitionVisibility(mView, mFinalVisibility);
                if (mParent != null) {
                    mParent.invalidate();
                }
            }
            // Layout is allowed now that the View is in its final state
            suppressLayout(false);
        }

        private void suppressLayout(boolean suppress) {
            if (mSuppressLayout && mLayoutSuppressed != suppress && mParent != null) {
                mLayoutSuppressed = suppress;
                ViewGroupUtils.suppressLayout(mParent, suppress);
            }
        }
    }

    private class OverlayListener extends AnimatorListenerAdapter implements TransitionListener {
        private final ViewGroup mOverlayHost;
        private final View mOverlayView;
        private final View mStartView;
        private boolean mHasOverlay = true;

        OverlayListener(ViewGroup overlayHost, View overlayView, View startView) {
            mOverlayHost = overlayHost;
            mOverlayView = overlayView;
            mStartView = startView;
        }

        @Override
        public void onAnimationPause(Animator animation) {
            mOverlayHost.getOverlay().remove(mOverlayView);
        }

        @Override
        public void onAnimationResume(Animator animation) {
            if (mOverlayView.getParent() == null) {
                mOverlayHost.getOverlay().add(mOverlayView);
            } else {
                cancel();
            }
        }

        @Override
        public void onAnimationStart(@NonNull Animator animation, boolean isReverse) {
            if (isReverse) {
                mStartView.setTag(R.id.save_overlay_view, mOverlayView);
                mOverlayHost.getOverlay().add(mOverlayView);
                mHasOverlay = true;
            }
        }

        @Override
        public void onAnimationEnd(Animator animation) {
            removeFromOverlay();
        }

        @Override
        public void onAnimationEnd(@NonNull Animator animation, boolean isReverse) {
            if (!isReverse) {
                removeFromOverlay();
            }
        }

        @Override
        public void onTransitionEnd(@NonNull Transition transition) {
            transition.removeListener(this);
        }

        @Override
        public void onTransitionStart(@NonNull Transition transition) {
        }

        @Override
        public void onTransitionPause(@NonNull Transition transition) {
        }

        @Override
        public void onTransitionResume(@NonNull Transition transition) {
        }

        @Override
        public void onTransitionCancel(@NonNull Transition transition) {
            if (mHasOverlay) {
                removeFromOverlay();
            }
        }

        private void removeFromOverlay() {
            mStartView.setTag(R.id.save_overlay_view, null);
            mOverlayHost.getOverlay().remove(mOverlayView);
            mHasOverlay = false;
        }
    }
}