LinearLayout-based CardView

LinearCardView.java

/*
 * Copyright (C) 2014 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.v7.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Rect;
import android.os.Build;
import android.support.v7.cardview.R;
import android.util.AttributeSet;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

/**
 * A FrameLayout with a rounded corner background and shadow.
 * <p>
 * CardView uses <code>elevation</code> property on L for shadows and falls back to a custom shadow
 * implementation on older platforms.
 * <p>
 * Due to expensive nature of rounded corner clipping, on platforms before L, CardView does not
 * clip its children that intersect with rounded corners. Instead, it adds padding to avoid such
 * intersection (See {@link #setPreventCornerOverlap(boolean)} to change this behavior).
 * <p>
 * Before L, CardView adds padding to its content and draws shadows to that area. This padding
 * amount is equal to <code>maxCardElevation + (1 - cos45) * cornerRadius</code> on the sides and
 * <code>maxCardElevation * 1.5 + (1 - cos45) * cornerRadius</code> on top and bottom.
 * <p>
 * Since padding is used to offset content for shadows, you cannot set padding on CardView.
 * Instead,
 * you can use content padding attributes in XML or {@link #setContentPadding(int, int, int, int)}
 * in code to set the padding between the edges of the Card and children of CardView.
 * <p>
 * Note that, if you specify exact dimensions for the CardView, because of the shadows, its content
 * area will be different between platforms before L and after L. By using api version specific
 * resource values, you can avoid these changes. Alternatively, If you want CardView to add inner
 * padding on platforms L and after as well, you can set {@link #setUseCompatPadding(boolean)} to
 * <code>true</code>.
 * <p>
 * To change CardView's elevation in a backward compatible way, use
 * {@link #setCardElevation(float)}. CardView will use elevation API on L and before L, it will
 * change the shadow size. To avoid moving the View while shadow size is changing, shadow size is
 * clamped by {@link #getMaxCardElevation()}. If you want to change elevation dynamically, you
 * should call {@link #setMaxCardElevation(float)} when CardView is initialized.
 *
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardBackgroundColor
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardCornerRadius
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardElevation
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardMaxElevation
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardUseCompatPadding
 * @attr ref android.support.v7.cardview.R.styleable#CardView_cardPreventCornerOverlap
 * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPadding
 * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingLeft
 * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingTop
 * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingRight
 * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingBottom
 */
public class LinearCardView extends LinearLayout implements CardViewDelegate {

    private static final CardViewImpl IMPL;

    static {
        if (Build.VERSION.SDK_INT >= 21) {
            IMPL = new CardViewApi21();
        } else if (Build.VERSION.SDK_INT >= 17) {
            IMPL = new CardViewJellybeanMr1();
        } else {
            IMPL = new CardViewEclairMr1();
        }
        IMPL.initStatic();
    }

    private boolean mCompatPadding;

    private boolean mPreventCornerOverlap;

    private final Rect mContentPadding = new Rect();

    private final Rect mShadowBounds = new Rect();


    public LinearCardView(Context context) {
        super(context);
        initialize(context, null, 0);
    }

    public LinearCardView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initialize(context, attrs, 0);
    }

    public LinearCardView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initialize(context, attrs, defStyleAttr);
    }

    @Override
    public void setPadding(int left, int top, int right, int bottom) {
        // NO OP
    }

    public void setPaddingRelative(int start, int top, int end, int bottom) {
        // NO OP
    }

    /**
     * Returns whether CardView will add inner padding on platforms L and after.
     *
     * @return True CardView adds inner padding on platforms L and after to have same dimensions
     * with platforms before L.
     */
    @Override
    public boolean getUseCompatPadding() {
        return mCompatPadding;
    }

    /**
     * CardView adds additional padding to draw shadows on platforms before L.
     * <p>
     * This may cause Cards to have different sizes between L and before L. If you need to align
     * CardView with other Views, you may need api version specific dimension resources to account
     * for the changes.
     * As an alternative, you can set this flag to <code>true</code> and CardView will add the same
     * padding values on platforms L and after.
     * <p>
     * Since setting this flag to true adds unnecessary gaps in the UI, default value is
     * <code>false</code>.
     *
     * @param useCompatPadding True if CardView should add padding for the shadows on platforms L
     *                         and above.
     * @attr ref android.support.v7.cardview.R.styleable#CardView_cardUseCompatPadding
     */
    public void setUseCompatPadding(boolean useCompatPadding) {
        if (mCompatPadding == useCompatPadding) {
            return;
        }
        mCompatPadding = useCompatPadding;
        IMPL.onCompatPaddingChanged(this);
    }

    /**
     * Sets the padding between the Card's edges and the children of CardView.
     * <p>
     * Depending on platform version or {@link #getUseCompatPadding()} settings, CardView may
     * update these values before calling {@link android.view.View#setPadding(int, int, int, int)}.
     *
     * @param left   The left padding in pixels
     * @param top    The top padding in pixels
     * @param right  The right padding in pixels
     * @param bottom The bottom padding in pixels
     * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPadding
     * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingLeft
     * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingTop
     * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingRight
     * @attr ref android.support.v7.cardview.R.styleable#CardView_contentPaddingBottom
     */
    public void setContentPadding(int left, int top, int right, int bottom) {
        mContentPadding.set(left, top, right, bottom);
        IMPL.updatePadding(this);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (IMPL instanceof CardViewApi21 == false) {
            final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
            switch (widthMode) {
                case MeasureSpec.EXACTLY:
                case MeasureSpec.AT_MOST:
                    final int minWidth = (int) Math.ceil(IMPL.getMinWidth(this));
                    widthMeasureSpec = MeasureSpec.makeMeasureSpec(Math.max(minWidth,
                            MeasureSpec.getSize(widthMeasureSpec)), widthMode);
                    break;
            }

            final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
            switch (heightMode) {
                case MeasureSpec.EXACTLY:
                case MeasureSpec.AT_MOST:
                    final int minHeight = (int) Math.ceil(IMPL.getMinHeight(this));
                    heightMeasureSpec = MeasureSpec.makeMeasureSpec(Math.max(minHeight,
                            MeasureSpec.getSize(heightMeasureSpec)), heightMode);
                    break;
            }
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        } else {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    }

    private void initialize(Context context, AttributeSet attrs, int defStyleAttr) {
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CardView, defStyleAttr,
                R.style.CardView_Light);
        int backgroundColor = a.getColor(R.styleable.CardView_cardBackgroundColor, 0);
        float radius = a.getDimension(R.styleable.CardView_cardCornerRadius, 0);
        float elevation = a.getDimension(R.styleable.CardView_cardElevation, 0);
        float maxElevation = a.getDimension(R.styleable.CardView_cardMaxElevation, 0);
        mCompatPadding = a.getBoolean(R.styleable.CardView_cardUseCompatPadding, false);
        mPreventCornerOverlap = a.getBoolean(R.styleable.CardView_cardPreventCornerOverlap, true);
        int defaultPadding = a.getDimensionPixelSize(R.styleable.CardView_contentPadding, 0);
        mContentPadding.left = a.getDimensionPixelSize(R.styleable.CardView_contentPaddingLeft,
                defaultPadding);
        mContentPadding.top = a.getDimensionPixelSize(R.styleable.CardView_contentPaddingTop,
                defaultPadding);
        mContentPadding.right = a.getDimensionPixelSize(R.styleable.CardView_contentPaddingRight,
                defaultPadding);
        mContentPadding.bottom = a.getDimensionPixelSize(R.styleable.CardView_contentPaddingBottom,
                defaultPadding);
        if (elevation > maxElevation) {
            maxElevation = elevation;
        }
        a.recycle();
        IMPL.initialize(this, context, backgroundColor, radius, elevation, maxElevation);
    }

    /**
     * Returns the inner padding after the Card's left edge
     *
     * @return the inner padding after the Card's left edge
     */
    public int getContentPaddingLeft() {
        return mContentPadding.left;
    }

    /**
     * Returns the inner padding before the Card's right edge
     *
     * @return the inner padding before the Card's right edge
     */
    public int getContentPaddingRight() {
        return mContentPadding.right;
    }

    /**
     * Returns the inner padding after the Card's top edge
     *
     * @return the inner padding after the Card's top edge
     */
    public int getContentPaddingTop() {
        return mContentPadding.top;
    }

    /**
     * Returns the inner padding before the Card's bottom edge
     *
     * @return the inner padding before the Card's bottom edge
     */
    public int getContentPaddingBottom() {
        return mContentPadding.bottom;
    }

    /**
     * Updates the corner radius of the CardView.
     *
     * @param radius The radius in pixels of the corners of the rectangle shape
     * @attr ref android.support.v7.cardview.R.styleable#CardView_cardCornerRadius
     * @see #setRadius(float)
     */
    public void setRadius(float radius) {
        IMPL.setRadius(this, radius);
    }

    /**
     * Returns the corner radius of the CardView.
     *
     * @return Corner radius of the CardView
     * @see #getRadius()
     */
    public float getRadius() {
        return IMPL.getRadius(this);
    }

    /**
     * Internal method used by CardView implementations to update the padding.
     *
     * @hide
     */
    @Override
    public void setShadowPadding(int left, int top, int right, int bottom) {
        mShadowBounds.set(left, top, right, bottom);
        super.setPadding(left + mContentPadding.left, top + mContentPadding.top,
                right + mContentPadding.right, bottom + mContentPadding.bottom);
    }

    /**
     * Updates the backward compatible elevation of the CardView.
     *
     * @param radius The backward compatible elevation in pixels.
     * @attr ref android.support.v7.cardview.R.styleable#CardView_cardElevation
     * @see #getCardElevation()
     * @see #setMaxCardElevation(float)
     */
    public void setCardElevation(float radius) {
        IMPL.setElevation(this, radius);
    }

    /**
     * Returns the backward compatible elevation of the CardView.
     *
     * @return Elevation of the CardView
     * @see #setCardElevation(float)
     * @see #getMaxCardElevation()
     */
    public float getCardElevation() {
        return IMPL.getElevation(this);
    }

    /**
     * Updates the backward compatible elevation of the CardView.
     * <p>
     * Calling this method has no effect if device OS version is L or newer and
     * {@link #getUseCompatPadding()} is <code>false</code>.
     *
     * @param radius The backward compatible elevation in pixels.
     * @attr ref android.support.v7.cardview.R.styleable#CardView_cardElevation
     * @see #setCardElevation(float)
     * @see #getMaxCardElevation()
     */
    public void setMaxCardElevation(float radius) {
        IMPL.setMaxElevation(this, radius);
    }

    /**
     * Returns the backward compatible elevation of the CardView.
     *
     * @return Elevation of the CardView
     * @see #setMaxCardElevation(float)
     * @see #getCardElevation()
     */
    public float getMaxCardElevation() {
        return IMPL.getMaxElevation(this);
    }

    /**
     * Returns whether CardView should add extra padding to content to avoid overlaps with rounded
     * corners on API versions 20 and below.
     *
     * @return True if CardView prevents overlaps with rounded corners on platforms before L.
     *         Default value is <code>true</code>.
     */
    @Override
    public boolean getPreventCornerOverlap() {
        return mPreventCornerOverlap;
    }

    /**
     * On API 20 and before, CardView does not clip the bounds of the Card for the rounded corners.
     * Instead, it adds padding to content so that it won't overlap with the rounded corners.
     * You can disable this behavior by setting this field to <code>false</code>.
     * <p>
     * Setting this value on API 21 and above does not have any effect unless you have enabled
     * compatibility padding.
     *
     * @param preventCornerOverlap Whether CardView should add extra padding to content to avoid
     *                             overlaps with the CardView corners.
     * @attr ref android.support.v7.cardview.R.styleable#CardView_cardPreventCornerOverlap
     * @see #setUseCompatPadding(boolean)
     */
    public void setPreventCornerOverlap(boolean preventCornerOverlap) {
        if (preventCornerOverlap == mPreventCornerOverlap) {
            return;
        }
        mPreventCornerOverlap = preventCornerOverlap;
        IMPL.onPreventCornerOverlapChanged(this);
    }
}