xref: /frameworks/support/design/src/android/support/design/widget/FloatingActionButton.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 android.support.design.widget;

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.ColorStateList;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.PorterDuff;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.support.annotation.ColorInt;
import android.support.annotation.DrawableRes;
import android.support.annotation.IntDef;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.R;
import android.support.design.widget.FloatingActionButtonImpl.InternalVisibilityChangedListener;
import android.support.v4.content.res.ConfigurationHelper;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.AppCompatDrawableManager;
import android.support.v7.widget.AppCompatImageHelper;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;

/**
 * Floating action buttons are used for a special type of promoted action. They are distinguished
 * by a circled icon floating above the UI and have special motion behaviors related to morphing,
 * launching, and the transferring anchor point.
 *
 * <p>Floating action buttons come in two sizes: the default and the mini. The size can be
 * controlled with the {@code fabSize} attribute.</p>
 *
 * <p>As this class descends from {@link ImageView}, you can control the icon which is displayed
 * via {@link #setImageDrawable(Drawable)}.</p>
 *
 * <p>The background color of this view defaults to the your theme's {@code colorAccent}. If you
 * wish to change this at runtime then you can do so via
 * {@link #setBackgroundTintList(ColorStateList)}.</p>
 */
@CoordinatorLayout.DefaultBehavior(FloatingActionButton.Behavior.class)
public class FloatingActionButton extends VisibilityAwareImageButton {

    private static final String LOG_TAG = "FloatingActionButton";

    /**
     * Callback to be invoked when the visibility of a FloatingActionButton changes.
     */
    public abstract static class OnVisibilityChangedListener {
        /**
         * Called when a FloatingActionButton has been
         * {@link #show(OnVisibilityChangedListener) shown}.
         *
         * @param fab the FloatingActionButton that was shown.
         */
        public void onShown(FloatingActionButton fab) {}

        /**
         * Called when a FloatingActionButton has been
         * {@link #hide(OnVisibilityChangedListener) hidden}.
         *
         * @param fab the FloatingActionButton that was hidden.
         */
        public void onHidden(FloatingActionButton fab) {}
    }

    // These values must match those in the attrs declaration

    /**
     * The mini sized button. Will always been smaller than {@link #SIZE_NORMAL}.
     *
     * @see #setSize(int)
     */
    public static final int SIZE_MINI = 1;

    /**
     * The normal sized button. Will always been larger than {@link #SIZE_MINI}.
     *
     * @see #setSize(int)
     */
    public static final int SIZE_NORMAL = 0;

    /**
     * Size which will change based on the window size. For small sized windows
     * (largest screen dimension < 470dp) this will select a small sized button, and for
     * larger sized windows it will select a larger size.
     *
     * @see #setSize(int)
     */
    public static final int SIZE_AUTO = -1;

    /**
     * The switch point for the largest screen edge where SIZE_AUTO switches from mini to normal.
     */
    private static final int AUTO_MINI_LARGEST_SCREEN_WIDTH = 470;

    /** @hide */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef({SIZE_MINI, SIZE_NORMAL, SIZE_AUTO})
    public @interface Size {}

    private ColorStateList mBackgroundTint;
    private PorterDuff.Mode mBackgroundTintMode;

    private int mBorderWidth;
    private int mRippleColor;
    private int mSize;
    private int mImagePadding;
    private int mMaxImageSize;

    private boolean mCompatPadding;
    private final Rect mShadowPadding = new Rect();
    private final Rect mTouchArea = new Rect();

    private AppCompatImageHelper mImageHelper;

    private FloatingActionButtonImpl mImpl;

    public FloatingActionButton(Context context) {
        this(context, null);
    }

    public FloatingActionButton(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        ThemeUtils.checkAppCompatTheme(context);

        TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.FloatingActionButton, defStyleAttr,
                R.style.Widget_Design_FloatingActionButton);
        mBackgroundTint = a.getColorStateList(R.styleable.FloatingActionButton_backgroundTint);
        mBackgroundTintMode = parseTintMode(a.getInt(
                R.styleable.FloatingActionButton_backgroundTintMode, -1), null);
        mRippleColor = a.getColor(R.styleable.FloatingActionButton_rippleColor, 0);
        mSize = a.getInt(R.styleable.FloatingActionButton_fabSize, SIZE_AUTO);
        mBorderWidth = a.getDimensionPixelSize(R.styleable.FloatingActionButton_borderWidth, 0);
        final float elevation = a.getDimension(R.styleable.FloatingActionButton_elevation, 0f);
        final float pressedTranslationZ = a.getDimension(
                R.styleable.FloatingActionButton_pressedTranslationZ, 0f);
        mCompatPadding = a.getBoolean(R.styleable.FloatingActionButton_useCompatPadding, false);
        a.recycle();

        mImageHelper = new AppCompatImageHelper(this, AppCompatDrawableManager.get());
        mImageHelper.loadFromAttributes(attrs, defStyleAttr);

        mMaxImageSize = (int) getResources().getDimension(R.dimen.design_fab_image_size);

        getImpl().setBackgroundDrawable(mBackgroundTint, mBackgroundTintMode,
                mRippleColor, mBorderWidth);
        getImpl().setElevation(elevation);
        getImpl().setPressedTranslationZ(pressedTranslationZ);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int preferredSize = getSizeDimension();

        mImagePadding = (preferredSize - mMaxImageSize) / 2;
        getImpl().updatePadding();

        final int w = resolveAdjustedSize(preferredSize, widthMeasureSpec);
        final int h = resolveAdjustedSize(preferredSize, heightMeasureSpec);

        // As we want to stay circular, we set both dimensions to be the
        // smallest resolved dimension
        final int d = Math.min(w, h);

        // We add the shadow's padding to the measured dimension
        setMeasuredDimension(
                d + mShadowPadding.left + mShadowPadding.right,
                d + mShadowPadding.top + mShadowPadding.bottom);
    }

    /**
     * Set the ripple color for this {@link FloatingActionButton}.
     * <p>
     * When running on devices with KitKat or below, we draw a fill rather than a ripple.
     *
     * @param color ARGB color to use for the ripple.
     *
     * @attr ref android.support.design.R.styleable#FloatingActionButton_rippleColor
     */
    public void setRippleColor(@ColorInt int color) {
        if (mRippleColor != color) {
            mRippleColor = color;
            getImpl().setRippleColor(color);
        }
    }

    /**
     * Return the tint applied to the background drawable, if specified.
     *
     * @return the tint applied to the background drawable
     * @see #setBackgroundTintList(ColorStateList)
     */
    @Nullable
    @Override
    public ColorStateList getBackgroundTintList() {
        return mBackgroundTint;
    }

    /**
     * Applies a tint to the background drawable. Does not modify the current tint
     * mode, which is {@link PorterDuff.Mode#SRC_IN} by default.
     *
     * @param tint the tint to apply, may be {@code null} to clear tint
     */
    public void setBackgroundTintList(@Nullable ColorStateList tint) {
        if (mBackgroundTint != tint) {
            mBackgroundTint = tint;
            getImpl().setBackgroundTintList(tint);
        }
    }

    /**
     * Return the blending mode used to apply the tint to the background
     * drawable, if specified.
     *
     * @return the blending mode used to apply the tint to the background
     *         drawable
     * @see #setBackgroundTintMode(PorterDuff.Mode)
     */
    @Nullable
    @Override
    public PorterDuff.Mode getBackgroundTintMode() {
        return mBackgroundTintMode;
    }

    /**
     * Specifies the blending mode used to apply the tint specified by
     * {@link #setBackgroundTintList(ColorStateList)}} to the background
     * drawable. The default mode is {@link PorterDuff.Mode#SRC_IN}.
     *
     * @param tintMode the blending mode used to apply the tint, may be
     *                 {@code null} to clear tint
     */
    public void setBackgroundTintMode(@Nullable PorterDuff.Mode tintMode) {
        if (mBackgroundTintMode != tintMode) {
            mBackgroundTintMode = tintMode;
            getImpl().setBackgroundTintMode(tintMode);
        }
    }

    @Override
    public void setBackgroundDrawable(Drawable background) {
        Log.i(LOG_TAG, "Setting a custom background is not supported.");
    }

    @Override
    public void setBackgroundResource(int resid) {
        Log.i(LOG_TAG, "Setting a custom background is not supported.");
    }

    @Override
    public void setBackgroundColor(int color) {
        Log.i(LOG_TAG, "Setting a custom background is not supported.");
    }

    @Override
    public void setImageResource(@DrawableRes int resId) {
        // Intercept this call and instead retrieve the Drawable via the image helper
        mImageHelper.setImageResource(resId);
    }

    /**
     * Shows the button.
     * <p>This method will animate the button show if the view has already been laid out.</p>
     */
    public void show() {
        show(null);
    }

    /**
     * Shows the button.
     * <p>This method will animate the button show if the view has already been laid out.</p>
     *
     * @param listener the listener to notify when this view is shown
     */
    public void show(@Nullable final OnVisibilityChangedListener listener) {
        show(listener, true);
    }

    private void show(OnVisibilityChangedListener listener, boolean fromUser) {
        getImpl().show(wrapOnVisibilityChangedListener(listener), fromUser);
    }

    /**
     * Hides the button.
     * <p>This method will animate the button hide if the view has already been laid out.</p>
     */
    public void hide() {
        hide(null);
    }

    /**
     * Hides the button.
     * <p>This method will animate the button hide if the view has already been laid out.</p>
     *
     * @param listener the listener to notify when this view is hidden
     */
    public void hide(@Nullable OnVisibilityChangedListener listener) {
        hide(listener, true);
    }

    private void hide(@Nullable OnVisibilityChangedListener listener, boolean fromUser) {
        getImpl().hide(wrapOnVisibilityChangedListener(listener), fromUser);
    }

    /**
     * Set whether FloatingActionButton should add inner padding on platforms Lollipop and after,
     * to ensure consistent dimensions on all platforms.
     *
     * @param useCompatPadding true if FloatingActionButton is adding inner padding on platforms
     *                         Lollipop and after, to ensure consistent dimensions on all platforms.
     *
     * @attr ref android.support.design.R.styleable#FloatingActionButton_useCompatPadding
     * @see #getUseCompatPadding()
     */
    public void setUseCompatPadding(boolean useCompatPadding) {
        if (mCompatPadding != useCompatPadding) {
            mCompatPadding = useCompatPadding;
            getImpl().onCompatShadowChanged();
        }
    }

    /**
     * Returns whether FloatingActionButton will add inner padding on platforms Lollipop and after.
     *
     * @return true if FloatingActionButton is adding inner padding on platforms Lollipop and after,
     * to ensure consistent dimensions on all platforms.
     *
     * @attr ref android.support.design.R.styleable#FloatingActionButton_useCompatPadding
     * @see #setUseCompatPadding(boolean)
     */
    public boolean getUseCompatPadding() {
        return mCompatPadding;
    }

    /**
     * Sets the size of the button.
     *
     * <p>The options relate to the options available on the material design specification.
     * {@link #SIZE_NORMAL} is larger than {@link #SIZE_MINI}. {@link #SIZE_AUTO} will choose
     * an appropriate size based on the screen size.</p>
     *
     * @param size one of {@link #SIZE_NORMAL}, {@link #SIZE_MINI} or {@link #SIZE_AUTO}
     *
     * @attr ref android.support.design.R.styleable#FloatingActionButton_fabSize
     */
    public void setSize(@Size int size) {
        if (size != mSize) {
            mSize = size;
            requestLayout();
        }
    }

    /**
     * Returns the chosen size for this button.
     *
     * @return one of {@link #SIZE_NORMAL}, {@link #SIZE_MINI} or {@link #SIZE_AUTO}
     * @see #setSize(int)
     */
    @Size
    public int getSize() {
        return mSize;
    }

    @Nullable
    private InternalVisibilityChangedListener wrapOnVisibilityChangedListener(
            @Nullable final OnVisibilityChangedListener listener) {
        if (listener == null) {
            return null;
        }

        return new InternalVisibilityChangedListener() {
            @Override
            public void onShown() {
                listener.onShown(FloatingActionButton.this);
            }

            @Override
            public void onHidden() {
                listener.onHidden(FloatingActionButton.this);
            }
        };
    }

    private int getSizeDimension() {
        return getSizeDimension(mSize);
    }

    private int getSizeDimension(@Size final int size) {
        final Resources res = getResources();
        switch (size) {
            case SIZE_AUTO:
                // If we're set to auto, grab the size from resources and refresh
                final int width = ConfigurationHelper.getScreenWidthDp(res);
                final int height = ConfigurationHelper.getScreenHeightDp(res);
                return Math.max(width, height) < AUTO_MINI_LARGEST_SCREEN_WIDTH
                        ? getSizeDimension(SIZE_MINI)
                        : getSizeDimension(SIZE_NORMAL);
            case SIZE_MINI:
                return res.getDimensionPixelSize(R.dimen.design_fab_size_mini);
            case SIZE_NORMAL:
            default:
                return res.getDimensionPixelSize(R.dimen.design_fab_size_normal);
        }
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        getImpl().onAttachedToWindow();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        getImpl().onDetachedFromWindow();
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        getImpl().onDrawableStateChanged(getDrawableState());
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    public void jumpDrawablesToCurrentState() {
        super.jumpDrawablesToCurrentState();
        getImpl().jumpDrawableToCurrentState();
    }

    /**
     * Return in {@code rect} the bounds of the actual floating action button content in view-local
     * coordinates. This is defined as anything within any visible shadow.
     *
     * @return true if this view actually has been laid out and has a content rect, else false.
     */
    public boolean getContentRect(@NonNull Rect rect) {
        if (ViewCompat.isLaidOut(this)) {
            rect.set(0, 0, getWidth(), getHeight());
            rect.left += mShadowPadding.left;
            rect.top += mShadowPadding.top;
            rect.right -= mShadowPadding.right;
            rect.bottom -= mShadowPadding.bottom;
            return true;
        } else {
            return false;
        }
    }

    /**
     * Returns the FloatingActionButton's background, minus any compatible shadow implementation.
     */
    @NonNull
    public Drawable getContentBackground() {
        return getImpl().getContentBackground();
    }

    private static int resolveAdjustedSize(int desiredSize, int measureSpec) {
        int result = desiredSize;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
        switch (specMode) {
            case MeasureSpec.UNSPECIFIED:
                // Parent says we can be as big as we want. Just don't be larger
                // than max size imposed on ourselves.
                result = desiredSize;
                break;
            case MeasureSpec.AT_MOST:
                // Parent says we can be as big as we want, up to specSize.
                // Don't be larger than specSize, and don't be larger than
                // the max size imposed on ourselves.
                result = Math.min(desiredSize, specSize);
                break;
            case MeasureSpec.EXACTLY:
                // No choice. Do what we are told.
                result = specSize;
                break;
        }
        return result;
    }

    static PorterDuff.Mode parseTintMode(int value, PorterDuff.Mode defaultMode) {
        switch (value) {
            case 3:
                return PorterDuff.Mode.SRC_OVER;
            case 5:
                return PorterDuff.Mode.SRC_IN;
            case 9:
                return PorterDuff.Mode.SRC_ATOP;
            case 14:
                return PorterDuff.Mode.MULTIPLY;
            case 15:
                return PorterDuff.Mode.SCREEN;
            default:
                return defaultMode;
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if(getContentRect(mTouchArea) && !mTouchArea.contains((int) ev.getX(), (int) ev.getY())) {
            return false;
        }

        return super.onTouchEvent(ev);
    }

    /**
     * Behavior designed for use with {@link FloatingActionButton} instances. Its main function
     * is to move {@link FloatingActionButton} views so that any displayed {@link Snackbar}s do
     * not cover them.
     */
    public static class Behavior extends CoordinatorLayout.Behavior<FloatingActionButton> {
        // We only support the FAB <> Snackbar shift movement on Honeycomb and above. This is
        // because we can use view translation properties which greatly simplifies the code.
        private static final boolean SNACKBAR_BEHAVIOR_ENABLED = Build.VERSION.SDK_INT >= 11;

        private ValueAnimatorCompat mFabTranslationYAnimator;
        private float mFabTranslationY;
        private Rect mTmpRect;

        @Override
        public boolean layoutDependsOn(CoordinatorLayout parent,
                FloatingActionButton child, View dependency) {
            // We're dependent on all SnackbarLayouts (if enabled)
            return SNACKBAR_BEHAVIOR_ENABLED && dependency instanceof Snackbar.SnackbarLayout;
        }

        @Override
        public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child,
                View dependency) {
            if (dependency instanceof Snackbar.SnackbarLayout) {
                updateFabTranslationForSnackbar(parent, child, true);
            } else if (dependency instanceof AppBarLayout) {
                // If we're depending on an AppBarLayout we will show/hide it automatically
                // if the FAB is anchored to the AppBarLayout
                updateFabVisibility(parent, (AppBarLayout) dependency, child);
            }
            return false;
        }

        @Override
        public void onDependentViewRemoved(CoordinatorLayout parent, FloatingActionButton child,
                View dependency) {
            if (dependency instanceof Snackbar.SnackbarLayout) {
                updateFabTranslationForSnackbar(parent, child, true);
            }
        }

        private boolean updateFabVisibility(CoordinatorLayout parent,
                AppBarLayout appBarLayout, FloatingActionButton child) {
            final CoordinatorLayout.LayoutParams lp =
                    (CoordinatorLayout.LayoutParams) child.getLayoutParams();
            if (lp.getAnchorId() != appBarLayout.getId()) {
                // The anchor ID doesn't match the dependency, so we won't automatically
                // show/hide the FAB
                return false;
            }

            if (child.getUserSetVisibility() != VISIBLE) {
                // The view isn't set to be visible so skip changing its visibility
                return false;
            }

            if (mTmpRect == null) {
                mTmpRect = new Rect();
            }

            // First, let's get the visible rect of the dependency
            final Rect rect = mTmpRect;
            ViewGroupUtils.getDescendantRect(parent, appBarLayout, rect);

            if (rect.bottom <= appBarLayout.getMinimumHeightForVisibleOverlappingContent()) {
                // If the anchor's bottom is below the seam, we'll animate our FAB out
                child.hide(null, false);
            } else {
                // Else, we'll animate our FAB back in
                child.show(null, false);
            }
            return true;
        }

        private void updateFabTranslationForSnackbar(CoordinatorLayout parent,
                final FloatingActionButton fab, boolean animationAllowed) {
            final float targetTransY = getFabTranslationYForSnackbar(parent, fab);
            if (mFabTranslationY == targetTransY) {
                // We're already at (or currently animating to) the target value, return...
                return;
            }

            final float currentTransY = ViewCompat.getTranslationY(fab);

            // Make sure that any current animation is cancelled
            if (mFabTranslationYAnimator != null && mFabTranslationYAnimator.isRunning()) {
                mFabTranslationYAnimator.cancel();
            }

            if (animationAllowed && fab.isShown()
                    && Math.abs(currentTransY - targetTransY) > (fab.getHeight() * 0.667f)) {
                // If the FAB will be travelling by more than 2/3 of its height, let's animate
                // it instead
                if (mFabTranslationYAnimator == null) {
                    mFabTranslationYAnimator = ViewUtils.createAnimator();
                    mFabTranslationYAnimator.setInterpolator(
                            AnimationUtils.FAST_OUT_SLOW_IN_INTERPOLATOR);
                    mFabTranslationYAnimator.setUpdateListener(
                            new ValueAnimatorCompat.AnimatorUpdateListener() {
                                @Override
                                public void onAnimationUpdate(ValueAnimatorCompat animator) {
                                    ViewCompat.setTranslationY(fab,
                                            animator.getAnimatedFloatValue());
                                }
                            });
                }
                mFabTranslationYAnimator.setFloatValues(currentTransY, targetTransY);
                mFabTranslationYAnimator.start();
            } else {
                // Now update the translation Y
                ViewCompat.setTranslationY(fab, targetTransY);
            }

            mFabTranslationY = targetTransY;
        }

        private float getFabTranslationYForSnackbar(CoordinatorLayout parent,
                FloatingActionButton fab) {
            float minOffset = 0;
            final List<View> dependencies = parent.getDependencies(fab);
            for (int i = 0, z = dependencies.size(); i < z; i++) {
                final View view = dependencies.get(i);
                if (view instanceof Snackbar.SnackbarLayout && parent.doViewsOverlap(fab, view)) {
                    minOffset = Math.min(minOffset,
                            ViewCompat.getTranslationY(view) - view.getHeight());
                }
            }

            return minOffset;
        }

        @Override
        public boolean onLayoutChild(CoordinatorLayout parent, FloatingActionButton child,
                int layoutDirection) {
            // First, let's make sure that the visibility of the FAB is consistent
            final List<View> dependencies = parent.getDependencies(child);
            for (int i = 0, count = dependencies.size(); i < count; i++) {
                final View dependency = dependencies.get(i);
                if (dependency instanceof AppBarLayout
                        && updateFabVisibility(parent, (AppBarLayout) dependency, child)) {
                    break;
                }
            }
            // Now let the CoordinatorLayout lay out the FAB
            parent.onLayoutChild(child, layoutDirection);
            // Now offset it if needed
            offsetIfNeeded(parent, child);
            // Make sure we translate the FAB for any displayed Snackbars (without an animation)
            updateFabTranslationForSnackbar(parent, child, false);
            return true;
        }

        /**
         * Pre-Lollipop we use padding so that the shadow has enough space to be drawn. This method
         * offsets our layout position so that we're positioned correctly if we're on one of
         * our parent's edges.
         */
        private void offsetIfNeeded(CoordinatorLayout parent, FloatingActionButton fab) {
            final Rect padding = fab.mShadowPadding;

            if (padding != null && padding.centerX() > 0 && padding.centerY() > 0) {
                final CoordinatorLayout.LayoutParams lp =
                        (CoordinatorLayout.LayoutParams) fab.getLayoutParams();

                int offsetTB = 0, offsetLR = 0;

                if (fab.getRight() >= parent.getWidth() - lp.rightMargin) {
                    // If we're on the left edge, shift it the right
                    offsetLR = padding.right;
                } else if (fab.getLeft() <= lp.leftMargin) {
                    // If we're on the left edge, shift it the left
                    offsetLR = -padding.left;
                }
                if (fab.getBottom() >= parent.getBottom() - lp.bottomMargin) {
                    // If we're on the bottom edge, shift it down
                    offsetTB = padding.bottom;
                } else if (fab.getTop() <= lp.topMargin) {
                    // If we're on the top edge, shift it up
                    offsetTB = -padding.top;
                }

                fab.offsetTopAndBottom(offsetTB);
                fab.offsetLeftAndRight(offsetLR);
            }
        }
    }

    /**
     * Returns the backward compatible elevation of the FloatingActionButton.
     *
     * @return the backward compatible elevation in pixels.
     * @attr ref android.support.design.R.styleable#FloatingActionButton_elevation
     * @see #setCompatElevation(float)
     */
    public float getCompatElevation() {
        return getImpl().getElevation();
    }

    /**
     * Updates the backward compatible elevation of the FloatingActionButton.
     *
     * @param elevation The backward compatible elevation in pixels.
     * @attr ref android.support.design.R.styleable#FloatingActionButton_elevation
     * @see #getCompatElevation()
     * @see #setUseCompatPadding(boolean)
     */
    public void setCompatElevation(float elevation) {
        getImpl().setElevation(elevation);
    }

    private FloatingActionButtonImpl getImpl() {
        if (mImpl == null) {
            mImpl = createImpl();
        }
        return mImpl;
    }

    private FloatingActionButtonImpl createImpl() {
        final int sdk = Build.VERSION.SDK_INT;
        if (sdk >= 21) {
            return new FloatingActionButtonLollipop(this, new ShadowDelegateImpl());
        } else if (sdk >= 14) {
            return new FloatingActionButtonIcs(this, new ShadowDelegateImpl());
        } else {
            return new FloatingActionButtonEclairMr1(this, new ShadowDelegateImpl());
        }
    }

    private class ShadowDelegateImpl implements ShadowViewDelegate {
        @Override
        public float getRadius() {
            return getSizeDimension() / 2f;
        }

        @Override
        public void setShadowPadding(int left, int top, int right, int bottom) {
            mShadowPadding.set(left, top, right, bottom);
            setPadding(left + mImagePadding, top + mImagePadding,
                    right + mImagePadding, bottom + mImagePadding);
        }

        @Override
        public void setBackgroundDrawable(Drawable background) {
            FloatingActionButton.super.setBackgroundDrawable(background);
        }

        @Override
        public boolean isCompatPaddingEnabled() {
            return mCompatPadding;
        }
    }
}