src/com/android/deskclock/widget/EmptyViewController.java

/*
 * Copyright (C) 2015 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 com.android.deskclock.widget;

import android.transition.Fade;
import android.transition.Transition;
import android.transition.TransitionManager;
import android.transition.TransitionSet;
import android.view.View;
import android.view.ViewGroup;

import com.android.deskclock.Utils;

/**
 * Controller that displays empty view and handles animation appropriately.
 */
public final class EmptyViewController {

    private static final int ANIMATION_DURATION = 300;
    private static final boolean USE_TRANSITION_FRAMEWORK = Utils.isLOrLater();

    private final Transition mEmptyViewTransition;
    private final ViewGroup mMainLayout;
    private final View mContentView;
    private final View mEmptyView;
    private boolean mIsEmpty;

    /**
     * Constructor of the controller.
     *
     * @param contentView  The view that should be displayed when empty view is hidden.
     * @param emptyView The view that should be displayed when main view is empty.
     */
    public EmptyViewController(ViewGroup mainLayout, View contentView, View emptyView) {
        mMainLayout = mainLayout;
        mContentView = contentView;
        mEmptyView = emptyView;
        if (USE_TRANSITION_FRAMEWORK) {
            mEmptyViewTransition = new TransitionSet()
                    .setOrdering(TransitionSet.ORDERING_SEQUENTIAL)
                    .addTarget(contentView)
                    .addTarget(emptyView)
                    .addTransition(new Fade(Fade.OUT))
                    .addTransition(new Fade(Fade.IN))
                    .setDuration(ANIMATION_DURATION);
        } else {
            mEmptyViewTransition = null;
        }
    }

    /**
     * Sets the state for the controller. If it's empty, it will display the empty view.
     *
     * @param isEmpty Whether or not the controller should transition into empty state.
     */
    public void setEmpty(boolean isEmpty) {
        if (mIsEmpty == isEmpty) {
            return;
        }
        mIsEmpty = isEmpty;
        // State changed, perform transition.
        if (USE_TRANSITION_FRAMEWORK) {
            TransitionManager.beginDelayedTransition(mMainLayout, mEmptyViewTransition);
        }
        mEmptyView.setVisibility(mIsEmpty ? View.VISIBLE : View.GONE);
        mContentView.setVisibility(mIsEmpty ? View.GONE : View.VISIBLE);
    }
}