Gradle dependencies

compile group: 'androidx.transition', name: 'transition', version: '1.4.1'

• groupId: androidx.transition
• artifactId: transition
• version: 1.4.1

Artifact androidx.transition:transition:1.4.1 it located at Google repository (https://maven.google.com/)

Androidx artifact mapping:

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

Androidx class mapping:

androidx.transition.ChangeScroll android.support.transition.ChangeScroll

Overview

This transition captures the scroll properties of targets before and after the scene change and animates any changes.

Summary

Constructors

Methods

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)

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)

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.

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.

Source

/*
 * Copyright (C) 2017 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 android.animation.Animator;
import android.animation.ObjectAnimator;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;


/**
 * This transition captures the scroll properties of targets before and after
 * the scene change and animates any changes.
 */
public class ChangeScroll extends Transition {

    private static final String PROPNAME_SCROLL_X = "android:changeScroll:x";
    private static final String PROPNAME_SCROLL_Y = "android:changeScroll:y";

    private static final String[] PROPERTIES = {
            PROPNAME_SCROLL_X,
            PROPNAME_SCROLL_Y,
    };

    public ChangeScroll() {}

    public ChangeScroll(@NonNull Context context, @NonNull AttributeSet attrs) {
        super(context, attrs);
    }

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

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

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

    private void captureValues(TransitionValues transitionValues) {
        transitionValues.values.put(PROPNAME_SCROLL_X, transitionValues.view.getScrollX());
        transitionValues.values.put(PROPNAME_SCROLL_Y, transitionValues.view.getScrollY());
    }

    @Nullable
    @Override
    public Animator createAnimator(@NonNull ViewGroup sceneRoot,
            @Nullable TransitionValues startValues, @Nullable TransitionValues endValues) {
        if (startValues == null || endValues == null) {
            return null;
        }
        final View view = endValues.view;
        int startX = (Integer) startValues.values.get(PROPNAME_SCROLL_X);
        int endX = (Integer) endValues.values.get(PROPNAME_SCROLL_X);
        int startY = (Integer) startValues.values.get(PROPNAME_SCROLL_Y);
        int endY = (Integer) endValues.values.get(PROPNAME_SCROLL_Y);
        Animator scrollXAnimator = null;
        Animator scrollYAnimator = null;
        if (startX != endX) {
            view.setScrollX(startX);
            scrollXAnimator = ObjectAnimator.ofInt(view, "scrollX", startX, endX);
        }
        if (startY != endY) {
            view.setScrollY(startY);
            scrollYAnimator = ObjectAnimator.ofInt(view, "scrollY", startY, endY);
        }
        return TransitionUtils.mergeAnimators(scrollXAnimator, scrollYAnimator);
    }

}