wearable/wear/WearAccessibilityApp/Wearable/src/main/java/com/example/android/wearable/wear/wearaccessibilityapp/ScalingScrollLayoutCallback.java

/*
 * Copyright (C) 2017 Google Inc. All Rights Reserved.
 *
 * 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.example.android.wearable.wear.wearaccessibilityapp;

import android.view.View;

import androidx.recyclerview.widget.RecyclerView;
import androidx.wear.widget.WearableLinearLayoutManager;

public class ScalingScrollLayoutCallback extends WearableLinearLayoutManager.LayoutCallback {

    /** How much should we scale the icon at most. */
    private static final float MAX_ICON_PROGRESS = 0.65f;

    @Override
    public void onLayoutFinished(View child, RecyclerView parent) {

        // Figure out % progress from top to bottom.
        float centerOffset = (child.getHeight() / 2.0f) / parent.getHeight();
        float yRelativeToCenterOffset = (child.getY() / parent.getHeight()) + centerOffset;

        // Normalize for center.
        float progressToCenter = Math.abs(0.5f - yRelativeToCenterOffset);

        // Adjust to the maximum scale.
        progressToCenter = Math.min(progressToCenter, MAX_ICON_PROGRESS);

        child.setScaleX(1 - progressToCenter);
        child.setScaleY(1 - progressToCenter);
    }
}