Utils.java

/*
 * Copyright (C) 2013 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.tabcarousel;

import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.content.res.Resources.Theme;
import android.os.Build;
import android.util.TypedValue;
import android.view.View;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;

/**
 * Helpers
 */
public final class Utils {

    /* This class is never initiated */
    public Utils() {
    }

    /**
     * Used to determine if the device is running Honeycomb or greater
     * 
     * @return True if the device is running Honeycomb or greater, false
     *         otherwise
     */
    public static final boolean hasHoneycomb() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB;
    }

    /**
     * Used to determine if the device is running Jelly Bean or greater
     * 
     * @return True if the device is running Jelly Bean or greater, false
     *         otherwise
     */
    public static final boolean hasJellyBean() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN;
    }

    /**
     * Resolves the given attribute id of the theme to a resource id
     */
    public static int getAttribute(Theme theme, int attrId) {
        final TypedValue outValue = new TypedValue();
        theme.resolveAttribute(attrId, outValue, true);
        return outValue.resourceId;
    }

    /**
     * Returns the resource id of the background used for buttons to show
     * pressed and focused state
     */
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public static int getSelectableItemBackground(Theme theme) {
        if (hasHoneycomb()) {
            return getAttribute(theme, android.R.attr.selectableItemBackground);
        }
        return 0;
    }

    /**
     * Sets an alpha value on the view.
     */
    public static void setAlphaOnViewBackground(View view, float alpha) {
        if (view != null) {
            view.setBackgroundColor((int) (clamp(alpha, 0.0f, 1.0f) * 255) << 24);
        }
    }

    /**
     * If the input value lies outside of the specified range, return the nearer
     * bound. Otherwise, return the input value, unchanged.
     */
    public static float clamp(float input, float lowerBound, float upperBound) {
        if (input < lowerBound) {
            return lowerBound;
        } else if (input > upperBound) {
            return upperBound;
        }
        return input;
    }

    /**
     * Runs a piece of code after the next layout run
     * 
     * @param view The {@link View} used.
     * @param runnable The {@link Runnable} used after the next layout run
     */
    @SuppressLint("NewApi")
    public static void doAfterLayout(final View view, final Runnable runnable) {
        final OnGlobalLayoutListener listener = new OnGlobalLayoutListener() {
            @SuppressWarnings("deprecation")
            @Override
            public void onGlobalLayout() {
                /* Layout pass done, unregister for further events */
                if (hasJellyBean()) {
                    view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                } else {
                    view.getViewTreeObserver().removeGlobalOnLayoutListener(this);
                }
                runnable.run();
            }
        };
        view.getViewTreeObserver().addOnGlobalLayoutListener(listener);
    }
}