FloatingActionButton.java

package com.github.tibolte.agendacalendarview.widgets;

import android.content.Context;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;

/**
 * Floating action button helping to scroll back to the current date.
 */
public class FloatingActionButton extends android.support.design.widget.FloatingActionButton {
    private static final int TRANSLATE_DURATION_MILLIS = 200;

    private boolean mVisible = true;

    private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();

    // region Constructors

    public FloatingActionButton(Context context) {
        super(context);
    }

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

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

    // endregion

    // region Overrides

    @Override
    public void show() {
        show(true);
    }

    @Override
    public void hide() {
        hide(true);
    }

    // endregion

    // region Public methods

    public void show(boolean animate) {
        toggle(true, animate, false);
    }

    public void hide(boolean animate) {
        toggle(false, animate, false);
    }

    public boolean isVisible() {
        return mVisible;
    }

    // endregion

    // region Private methods

    private void toggle(final boolean visible, final boolean animate, boolean force) {
        if (mVisible != visible || force) {
            mVisible = visible;
            int height = getHeight();
            if (height == 0 && !force) {
                ViewTreeObserver vto = getViewTreeObserver();
                if (vto.isAlive()) {
                    vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
                        @Override
                        public boolean onPreDraw() {
                            ViewTreeObserver currentVto = getViewTreeObserver();
                            if (currentVto.isAlive()) {
                                currentVto.removeOnPreDrawListener(this);
                            }
                            toggle(visible, animate, true);
                            return true;
                        }
                    });
                    return;
                }
            }
            int translationY = visible ? 0 : height + getMarginBottom();
            if (animate) {
                animate().setInterpolator(mInterpolator)
                        .setDuration(TRANSLATE_DURATION_MILLIS)
                        .translationY(translationY);
            } else {
                setTranslationY(translationY);
            }
        }
    }

    private int getMarginBottom() {
        int marginBottom = 0;
        final ViewGroup.LayoutParams layoutParams = getLayoutParams();
        if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
            marginBottom = ((ViewGroup.MarginLayoutParams) layoutParams).bottomMargin;
        }
        return marginBottom;
    }

    // endregion
}