Java tutorial
/* * 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 android.support.transition; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import android.animation.ObjectAnimator; import android.content.Context; import android.content.res.TypedArray; import android.content.res.XmlResourceParser; import android.support.annotation.NonNull; import android.support.v4.content.res.TypedArrayUtils; import android.support.v4.view.ViewCompat; import android.util.AttributeSet; import android.util.Log; import android.view.View; import android.view.ViewGroup; /** * This transition tracks changes to the visibility of target views in the * start and end scenes and fades views in or out when they become visible * or non-visible. Visibility is determined by both the * {@link View#setVisibility(int)} state of the view as well as whether it * is parented in the current view hierarchy. * * <p>The ability of this transition to fade out a particular view, and the * way that that fading operation takes place, is based on * the situation of the view in the view hierarchy. For example, if a view was * simply removed from its parent, then the view will be added into a {@link * android.view.ViewGroupOverlay} while fading. If a visible view is * changed to be {@link View#GONE} or {@link View#INVISIBLE}, then the * visibility will be changed to {@link View#VISIBLE} for the duration of * the animation. However, if a view is in a hierarchy which is also altering * its visibility, the situation can be more complicated. In general, if a * view that is no longer in the hierarchy in the end scene still has a * parent (so its parent hierarchy was removed, but it was not removed from * its parent), then it will be left alone to avoid side-effects from * improperly removing it from its parent. The only exception to this is if * the previous {@link Scene} was * {@link Scene#getSceneForLayout(android.view.ViewGroup, int, android.content.Context) * created from a layout resource file}, then it is considered safe to un-parent * the starting scene view in order to fade it out.</p> * * <p>A Fade transition can be described in a resource file by using the * tag <code>fade</code>, along with the standard * attributes of {@code Fade} and {@link Transition}.</p> */ public class Fade extends Visibility { private static final String PROPNAME_TRANSITION_ALPHA = "android:fade:transitionAlpha"; private static final String LOG_TAG = "Fade"; /** * Fading mode used in {@link #Fade(int)} to make the transition * operate on targets that are appearing. Maybe be combined with * {@link #OUT} to fade both in and out. */ public static final int IN = Visibility.MODE_IN; /** * Fading mode used in {@link #Fade(int)} to make the transition * operate on targets that are disappearing. Maybe be combined with * {@link #IN} to fade both in and out. */ public static final int OUT = Visibility.MODE_OUT; /** * Constructs a Fade transition that will fade targets in * and/or out, according to the value of fadingMode. * * @param fadingMode The behavior of this transition, a combination of * {@link #IN} and {@link #OUT}. */ public Fade(int fadingMode) { setMode(fadingMode); } /** * Constructs a Fade transition that will fade targets in and out. */ public Fade() { } public Fade(Context context, AttributeSet attrs) { super(context, attrs); TypedArray a = context.obtainStyledAttributes(attrs, Styleable.FADE); @Mode int fadingMode = TypedArrayUtils.getNamedInt(a, (XmlResourceParser) attrs, "fadingMode", Styleable.Fade.FADING_MODE, getMode()); setMode(fadingMode); a.recycle(); } @Override public void captureStartValues(@NonNull TransitionValues transitionValues) { super.captureStartValues(transitionValues); transitionValues.values.put(PROPNAME_TRANSITION_ALPHA, ViewUtils.getTransitionAlpha(transitionValues.view)); } /** * Utility method to handle creating and running the Animator. */ private Animator createAnimation(final View view, float startAlpha, float endAlpha) { if (startAlpha == endAlpha) { return null; } ViewUtils.setTransitionAlpha(view, startAlpha); final ObjectAnimator anim = ObjectAnimator.ofFloat(view, ViewUtils.TRANSITION_ALPHA, endAlpha); if (DBG) { Log.d(LOG_TAG, "Created animator " + anim); } FadeAnimatorListener listener = new FadeAnimatorListener(view); anim.addListener(listener); addListener(new TransitionListenerAdapter() { @Override public void onTransitionEnd(@NonNull Transition transition) { ViewUtils.setTransitionAlpha(view, 1); ViewUtils.clearNonTransitionAlpha(view); transition.removeListener(this); } }); return anim; } @Override public Animator onAppear(ViewGroup sceneRoot, View view, TransitionValues startValues, TransitionValues endValues) { if (DBG) { View startView = (startValues != null) ? startValues.view : null; Log.d(LOG_TAG, "Fade.onAppear: startView, startVis, endView, endVis = " + startView + ", " + view); } float startAlpha = getStartAlpha(startValues, 0); if (startAlpha == 1) { startAlpha = 0; } return createAnimation(view, startAlpha, 1); } @Override public Animator onDisappear(ViewGroup sceneRoot, final View view, TransitionValues startValues, TransitionValues endValues) { ViewUtils.saveNonTransitionAlpha(view); float startAlpha = getStartAlpha(startValues, 1); return createAnimation(view, startAlpha, 0); } private static float getStartAlpha(TransitionValues startValues, float fallbackValue) { float startAlpha = fallbackValue; if (startValues != null) { Float startAlphaFloat = (Float) startValues.values.get(PROPNAME_TRANSITION_ALPHA); if (startAlphaFloat != null) { startAlpha = startAlphaFloat; } } return startAlpha; } private static class FadeAnimatorListener extends AnimatorListenerAdapter { private final View mView; private boolean mLayerTypeChanged = false; FadeAnimatorListener(View view) { mView = view; } @Override public void onAnimationStart(Animator animation) { if (ViewCompat.hasOverlappingRendering(mView) && mView.getLayerType() == View.LAYER_TYPE_NONE) { mLayerTypeChanged = true; mView.setLayerType(View.LAYER_TYPE_HARDWARE, null); } } @Override public void onAnimationEnd(Animator animation) { ViewUtils.setTransitionAlpha(mView, 1); if (mLayerTypeChanged) { mView.setLayerType(View.LAYER_TYPE_NONE, null); } } } }