FloatingImageButton.java

package com.roboo.like.google.view.floatingbutton;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.LayerDrawable;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.StateListDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.os.Build;
import android.os.Handler;
import android.os.Message;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;
import android.widget.AbsListView;
import android.widget.ImageButton;

import com.roboo.like.google.R;

/**
 * Android Google+ like floating action button which reacts on the attached list view scrolling events.
 * 
 * @author Oleksandr Melnykov
 */
public class FloatingImageButton extends ImageButton
{

	public static final int TYPE_NORMAL = 0;
	public static final int TYPE_MINI = 1;

	private StateListDrawable mDrawable;
	private AbsListView mListView;

	private int mScrollY;
	private boolean mVisible;

	private int mColorNormal;
	private int mColorPressed;
	private boolean mShadow;
	private int mType;

	private final ScrollSettleHandler mScrollSettleHandler = new ScrollSettleHandler();
	private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();

	public FloatingImageButton(Context context)
	{
		super(context);
		init(context, null);
	}

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

	public FloatingImageButton(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
		init(context, attrs);
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
	{
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		int size = getDimension(mType == TYPE_NORMAL ? R.dimen.fab_size_normal : R.dimen.fab_size_mini);
		if (mShadow)
		{
			int shadowSize = getDimension(R.dimen.fab_shadow_size);
			size += shadowSize * 2;
		}
		setMeasuredDimension(size, size);
	}

	@Override
	public Parcelable onSaveInstanceState()
	{
		Parcelable superState = super.onSaveInstanceState();
		SavedState savedState = new SavedState(superState);
		savedState.mScrollY = mScrollY;

		return savedState;
	}

	@Override
	public void onRestoreInstanceState(Parcelable state)
	{
		if (state instanceof SavedState)
		{
			SavedState savedState = (SavedState) state;
			mScrollY = savedState.mScrollY;
			super.onRestoreInstanceState(savedState.getSuperState());
		}
		else
		{
			super.onRestoreInstanceState(state);
		}
	}

	private void init(Context context, AttributeSet attributeSet)
	{
		mVisible = true;
		mColorNormal = getColor(android.R.color.holo_blue_dark);
		mColorPressed = getColor(android.R.color.holo_blue_light);
		mType = TYPE_NORMAL;
		mShadow = true;
		if (attributeSet != null)
		{
			initAttributes(context, attributeSet);
		}
		updateBackground();
	}

	private void initAttributes(Context context, AttributeSet attributeSet)
	{
		TypedArray attr = getTypedArray(context, attributeSet, R.styleable.FloatingImageButton);
		if (attr != null)
		{
			try
			{
				mColorNormal = attr.getColor(R.styleable.FloatingImageButton_fab_colorNormal, getColor(android.R.color.holo_blue_dark));
				mColorPressed = attr.getColor(R.styleable.FloatingImageButton_fab_colorPressed, getColor(android.R.color.holo_blue_light));
				mShadow = attr.getBoolean(R.styleable.FloatingImageButton_fab_shadow, true);
				mType = attr.getInt(R.styleable.FloatingImageButton_fab_type, TYPE_NORMAL);
			}
			finally
			{
				attr.recycle();
			}
		}
	}

	private void updateBackground()
	{
		mDrawable = new StateListDrawable();
		mDrawable.addState(new int[] { android.R.attr.state_pressed }, createDrawable(mColorPressed));
		mDrawable.addState(new int[] {}, createDrawable(mColorNormal));
		setBackgroundCompat(mDrawable);
	}

	private Drawable createDrawable(int color)
	{
		OvalShape ovalShape = new OvalShape();
		ShapeDrawable shapeDrawable = new ShapeDrawable(ovalShape);
		shapeDrawable.getPaint().setColor(color);

		if (mShadow)
		{
			LayerDrawable layerDrawable = new LayerDrawable(new Drawable[] { getResources().getDrawable(R.drawable.ic_shadow), shapeDrawable });
			int shadowSize = getDimension(mType == TYPE_NORMAL ? R.dimen.fab_shadow_size : R.dimen.fab_mini_shadow_size);
			layerDrawable.setLayerInset(1, shadowSize, shadowSize, shadowSize, shadowSize);
			return layerDrawable;
		}
		else
		{
			return shapeDrawable;
		}
	}

	private TypedArray getTypedArray(Context context, AttributeSet attributeSet, int[] attr)
	{
		return context.obtainStyledAttributes(attributeSet, attr, 0, 0);
	}

	private int getColor(int id)
	{
		return getResources().getColor(id);
	}

	private int getDimension(int id)
	{
		return getResources().getDimensionPixelSize(id);
	}

	@SuppressWarnings("deprecation")
	@SuppressLint("NewApi")
	private void setBackgroundCompat(Drawable drawable)
	{
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
		{
			setBackground(drawable);
		}
		else
		{
			setBackgroundDrawable(drawable);
		}
	}

	private int getListViewScrollY()
	{
		View topChild = mListView.getChildAt(0);
		return topChild == null ? 0 : mListView.getFirstVisiblePosition() * topChild.getHeight() - topChild.getTop();
	}

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

	private class ScrollSettleHandler extends Handler
	{
		private static final int TRANSLATE_DURATION_MILLIS = 200;

		private int mSettledScrollY;

		public void onScroll(int scrollY)
		{
			if (mSettledScrollY != scrollY)
			{
				mSettledScrollY = scrollY;
				removeMessages(0);
				sendEmptyMessage(0);
			}
		}

		@Override
		public void handleMessage(Message msg)
		{
			animate().setInterpolator(mInterpolator).setDuration(TRANSLATE_DURATION_MILLIS).translationY(mSettledScrollY);
		}
	}

	public void setColorNormal(int color)
	{
		if (color != mColorNormal)
		{
			mColorNormal = color;
			updateBackground();
		}
	}

	public int getColorNormal()
	{
		return mColorNormal;
	}

	public void setColorPressed(int color)
	{
		if (color != mColorPressed)
		{
			mColorPressed = color;
			updateBackground();
		}
	}

	public int getColorPressed()
	{
		return mColorPressed;
	}

	public void setShadow(boolean shadow)
	{
		if (shadow != mShadow)
		{
			mShadow = shadow;
			updateBackground();
		}
	}

	public boolean hasShadow()
	{
		return mShadow;
	}

	public void setType(int type)
	{
		if (type != mType)
		{
			mType = type;
			updateBackground();
		}
	}

	public int getType()
	{
		return mType;
	}

	public void attachToListView(AbsListView listView)
	{
		if (listView == null)
		{
			throw new NullPointerException("AbsListView cannot be null.");
		}
		mListView = listView;
		mListView.setOnScrollListener(new AbsListView.OnScrollListener()
		{
			@Override
			public void onScrollStateChanged(AbsListView view, int scrollState)
			{}

			@Override
			public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
			{
				int newScrollY = getListViewScrollY();
				if (newScrollY == mScrollY)
				{
					return;
				}

				if (newScrollY > mScrollY && mVisible)
				{
					// Scrolling up
					mVisible = false;
					mScrollSettleHandler.onScroll(getHeight() + getMarginBottom());
				}
				else if (newScrollY < mScrollY && !mVisible)
				{
					// Scrolling down
					mVisible = true;
					mScrollSettleHandler.onScroll(0);
				}
				mScrollY = newScrollY;
			}
		});
	}

	/**
	 * A {@link android.os.Parcelable} representing the {@link com.FloatingImageButton.fab.FloatingActionButton}'s state.
	 */
	public static class SavedState extends BaseSavedState
	{

		private int mScrollY;

		public SavedState(Parcelable parcel)
		{
			super(parcel);
		}

		private SavedState(Parcel in)
		{
			super(in);
			mScrollY = in.readInt();
		}

		@Override
		public void writeToParcel(Parcel out, int flags)
		{
			super.writeToParcel(out, flags);
			out.writeInt(mScrollY);
		}

		public static final Creator<SavedState> CREATOR = new Creator<SavedState>()
		{

			@Override
			public SavedState createFromParcel(Parcel in)
			{
				return new SavedState(in);
			}

			@Override
			public SavedState[] newArray(int size)
			{
				return new SavedState[size];
			}
		};
	}
}