Utility class to calculate paddings and set margins on CardViews to correctly align them in a layout

CardViewUtils.java

package de.twoid.widget.util;

/*
 * Copyright 2015 Johannes Homeier, Florian Reifschneider
 *
 * 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.
 *
 *
 * Modified by Florian Reifschneider <[email protected]> to use the padding
 * calculation from the support library.
 */


import android.support.v7.widget.CardView;
import android.view.ViewGroup;

/**
 * A utility-class providing methods to easily align a {@link android.support.v7.widget.CardView} in a layout by using margins
 */
public class CardViewUtils {

    // used to calculate content padding
    final static double COS_45 = Math.cos(Math.toRadians(45));

    final static float SHADOW_MULTIPLIER = 1.5f;

    /**
     * Computes the compatPadding for the passed {@link CardView}
     *
     * @param cardView     the CardView to generate the compatPadding from
     * @return a array of integers with paddingLeft (position 0), paddingTop (position 1) ,paddingRight (position 2) and paddingBottom (position 3)
     */
    public static int[] getCompatPadding(CardView cardView) {
        int[] compatPadding = new int[4];

        float elevation = cardView.getMaxCardElevation();
        float radius = cardView.getRadius();
        boolean addPaddingForCorners = cardView.getPreventCornerOverlap();

        compatPadding[0] = compatPadding[2] = (int) Math.ceil(calculateHorizontalPadding(elevation, radius,
                addPaddingForCorners));
        compatPadding[1] = compatPadding[3] = (int) Math.ceil(calculateVerticalPadding(elevation, radius,
                addPaddingForCorners));

        return compatPadding;
    }

    private static float calculateVerticalPadding(float maxShadowSize, float cornerRadius,
                                          boolean addPaddingForCorners) {
        if (addPaddingForCorners) {
            return (float) (maxShadowSize * SHADOW_MULTIPLIER + (1 - COS_45) * cornerRadius);
        } else {
            return maxShadowSize * SHADOW_MULTIPLIER;
        }
    }

    private static float calculateHorizontalPadding(float maxShadowSize, float cornerRadius,
                                            boolean addPaddingForCorners) {
        if (addPaddingForCorners) {
            return (float) (maxShadowSize + (1 - COS_45) * cornerRadius);
        } else {
            return maxShadowSize;
        }
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side
     *
     * @param child                the CardView to set the compatMargin to
     * @param compatMarginLeft     the compatMargin from the left of the cardviews content
     * @param compatMarginTop      the compatMargin from the top of the cardviews content
     * @param compatMarginRight    the compatMargin from the right of the cardviews content
     * @param compatMarginBottom   the compatMargin from the bottom of the cardviews content
     * @param allowNegativePadding if true, the compatMargins can be negative (in case the computed compatPadding of the cardView is bigger than the compatMargin on the same side; otherwise, the compatMargin will be clamped to 0
     */
    public static void setCompatMargin(CardView child, int compatMarginLeft, int compatMarginTop, int compatMarginRight, int compatMarginBottom, boolean allowNegativePadding) {
        int[] compatPadding = getCompatPadding(child);

        ViewGroup.MarginLayoutParams params = (ViewGroup.MarginLayoutParams) child.getLayoutParams();
        params.leftMargin = allowNegativePadding ? compatMarginLeft - compatPadding[0] : Math.max(0, compatMarginLeft - compatPadding[0]);
        params.topMargin = allowNegativePadding ? compatMarginTop - compatPadding[1] : Math.max(0, compatMarginTop - compatPadding[1]);
        params.rightMargin = allowNegativePadding ? compatMarginRight - compatPadding[2] : Math.max(0, compatMarginRight - compatPadding[2]);
        params.bottomMargin = allowNegativePadding ? compatMarginBottom - compatPadding[3] : Math.max(0, compatMarginBottom - compatPadding[3]);
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side;
     * If the resulting margin for a side is negative, it will be set to 0.
     *
     * @param child              the CardView to set the compatMargin to
     * @param compatMarginLeft   the compatMargin from the left of the cardviews content
     * @param compatMarginTop    the compatMargin from the top of the cardviews content
     * @param compatMarginRight  the compatMargin from the right of the cardviews content
     * @param compatMarginBottom the compatMargin from the bottom of the cardviews content
     */
    public static void setCompatMargin(CardView child, int compatMarginLeft, int compatMarginTop, int compatMarginRight, int compatMarginBottom) {
        setCompatMargin(child, compatMarginLeft, compatMarginTop, compatMarginRight, compatMarginBottom, false);
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side;
     *
     * @param child                 the CardView to set the compatMargin to
     * @param compatMarginLeftRight the compatMargin from the left and right of the cardviews content
     * @param compatMarginTopBottom the compatMargin from the top and bottom of the cardviews content
     * @param allowNegativePadding  if true, the compatMargins can be negative (in case the computed compatPadding of the cardView is bigger than the compatMargin on the same side; otherwise, the compatMargin will be clamped to 0
     */
    public static void setCompatMargin(CardView child, int compatMarginLeftRight, int compatMarginTopBottom, boolean allowNegativePadding) {
        setCompatMargin(child, compatMarginLeftRight, compatMarginTopBottom, compatMarginLeftRight, compatMarginTopBottom, allowNegativePadding);
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side;
     * If the resulting margin for a side is negative, it will be set to 0.
     *
     * @param child                 the CardView to set the compatMargin to
     * @param compatMarginLeftRight the compatMargin from the left and right of the cardviews content
     * @param compatMarginTopBottom the compatMargin from the top and bottom of the cardviews content
     */
    public static void setCompatMargin(CardView child, int compatMarginLeftRight, int compatMarginTopBottom) {
        setCompatMargin(child, compatMarginLeftRight, compatMarginTopBottom, compatMarginLeftRight, compatMarginTopBottom);
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side;
     *
     * @param child                the CardView to set the compatMargin to
     * @param compatMargin         the compatMargin from the left, top, right and bottom of the cardviews content
     * @param allowNegativePadding if true, the compatMargins can be negative (in case the computed compatPadding of the cardView is bigger than the compatMargin on the same side; otherwise, the compatMargin will be clamped to 0
     */
    public static void setCompatMargin(CardView child, int compatMargin, boolean allowNegativePadding) {
        setCompatMargin(child, compatMargin, compatMargin, compatMargin, compatMargin, allowNegativePadding);
    }

    /**
     * Sets a compatMargin to the cardView so that the sum of compatMargin and compatPadding on either side sum up to the passed compatMargin for that side;
     * If the resulting margin for a side is negative, it will be set to 0.
     *
     * @param child        the CardView to set the compatMargin to
     * @param compatMargin the compatMargin from the left, top, right and bottom of the cardviews content
     */
    public static void setCompatMargin(CardView child, int compatMargin) {
        setCompatMargin(child, compatMargin, compatMargin, compatMargin, compatMargin);
    }

    /**
     * Computes the dimension of the CardViews content
     *
     * @param cardView
     * @return a array of integers with width (position 0) and height (position 1) of the CardViews content
     */
    public static int[] getContentDimension(CardView cardView) {
        int[] compatPadding = getCompatPadding(cardView);

        return new int[]{
                cardView.getWidth() - compatPadding[0] - compatPadding[2]
                , cardView.getHeight() - compatPadding[1] - compatPadding[3]
        };
    }
}

I wonder if the additional padding from preventCornerOverlap is correct.. i thought it was used to inset the content in the card from the borders of the card, not the borders of the view.

Besides that a welcomed refinement =)