CircleListView.java

/*
 ********************************************************************************
 * Copyright (c) 2012 Samsung Electronics, Inc.
 * All rights reserved.
 *
 * This software is a confidential and proprietary information of Samsung
 * Electronics, Inc. ("Confidential Information"). You shall not disclose such
 * Confidential Information and shall use it only in accordance with the terms
 * of the license agreement you entered into with Samsung Electronics.
 ********************************************************************************
 */

package com.sprc.circlelauncher.view;

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
import android.widget.TextView;

import com.sprc.circlelauncher.BuildConfig;
import com.sprc.circlelauncher.R;

public class CircleListView extends ListView implements OnScrollListener {

	private static final String TAG = CircleListView.class.getSimpleName();
	private static final boolean DEBUG = BuildConfig.DEBUG && false;

	private static final int DEFAULT_SCROLL_DURATION = 200;

	public static final int DEFAULT_SELECTION = Integer.MAX_VALUE / 2;

	private boolean mIsForceCentering;

	private ViewModifier mViewModifier;

	private final CenterRunnable mCenterRunnable = new CenterRunnable();
	private int mScrollDuration = DEFAULT_SCROLL_DURATION;
	private OnItemCenteredListener mOnItemCenteredListener;

	public CircleListView(Context context, AttributeSet attrs) {
		super(context, attrs);

		super.setOnScrollListener(this);

		setOverscrollFooter(null);
		setOverscrollHeader(null);
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		super.onLayout(changed, l, t, r, b);

		setSelection(DEFAULT_SELECTION);
	}

	@Override
	protected void onScrollChanged(int l, int t, int oldl, int oldt) {
		super.onScrollChanged(l, t, oldl, oldt);

		if (mViewModifier != null) {

			final int count = getChildCount();
			for (int i = 0; i < count; ++i) {
				View v = getChildAt(i);

				mViewModifier.applyToView(v, this);
			}
		}
	}

	/**
	 * Sets the current {@link ViewModifier} for this list.
	 *
	 * @param modifier
	 *            implementation of the {@link ViewModifier} class
	 *
	 * @see ViewModifier
	 */
	public void setViewModifier(ViewModifier modifier) {
		mViewModifier = modifier;
	}

	/**
	 * Sets the smooth scroll duration.
	 *
	 * @param duration
	 *            the number of milliseconds the scrolling animation will take
	 */
	public void setScrollDuration(int duration) {
		mScrollDuration = duration;
	}

	/**
	 * Sets the listener object that will be notified when the list centers on an item.
	 *
	 * @param listener
	 *            the {@link OnItemCenteredListener} implementation
	 */
	public void setOnItemCenteredListener(OnItemCenteredListener listener) {
		mOnItemCenteredListener = listener;
	}

	/**
	 * Smoothly scrolls the {@link CircleListView} so the {@link View} v is in the middle.
	 *
	 * @param v
	 *            the {@link View} that should be in the center after the scroll
	 * @param scrollDuration
	 *            how long will the scroll take
	 */
	public void smoothScrollToView(View v) {
		final float y = v.getY() + v.getHeight() * 0.5f;
		final float halfHeight = getHeight() * 0.5f;
		final int distance = (int) (y - halfHeight);

		smoothScrollBy(distance, mScrollDuration);
	}

	@Override
	public void setOnScrollListener(OnScrollListener l) {
		throw new UnsupportedOperationException();
	}

	public void onScrollStateChanged(AbsListView view, int scrollState) {
		if (scrollState == SCROLL_STATE_IDLE) {

			if (!mIsForceCentering) {
				// Start centering the view

				mIsForceCentering = true;

				final View childView = findViewAtCenter();

				if (childView != null) {
					if (DEBUG) {
						TextView tv = (TextView) childView.findViewById(R.id.label_app_name);
						Log.d(TAG, "Application in center: " + tv.getText().toString());
					}

					if (mOnItemCenteredListener != null) {
						mOnItemCenteredListener.onItemCentered(childView);
					}

					mCenterRunnable.setView(childView);
					ViewCompat.postOnAnimation(this, mCenterRunnable);
				}
			}
		}
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {

		removeCallbacks(mCenterRunnable);

		mIsForceCentering = false;

		return super.onTouchEvent(ev);
	}

	public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

	}

	/**
	 * Finds a View located at the specified point.
	 *
	 * @param x
	 *            x-coordinate of the point
	 * @param y
	 *            y-coordinate of the point
	 * @return {@link View} located at (x, y) or <code>null</code> if not found
	 */
	public View findViewAt(int x, int y) {
		final int count = getChildCount();
		for (int i = 0; i < count; ++i) {
			final View v = getChildAt(i);
			final int x0 = v.getLeft();
			final int y0 = v.getTop();
			final int x1 = v.getWidth() - x0;
			final int y1 = v.getHeight() + y0;

			if (x >= x0 && x <= x1 && y >= y0 && y <= y1) {
				return v;
			}
		}

		return null;
	}

	/**
	 * Finds a {@link View} located in the center of the {@link CircleListView}.
	 *
	 * @return the {@link View} at the center of the {@link CircleListView}
	 */
	public View findViewAtCenter() {
		return findViewAt(0, getHeight() / 2);
	}

	public class CenterRunnable implements Runnable {

		private View mView;

		public void setView(View v) {
			mView = v;
		}

		public void run() {
			smoothScrollToView(mView);

			mIsForceCentering = true;
		}
	}

	/**
	 * Handles the event occurring when the list centers on an item.
	 *
	 * @see CircleListView#setOnItemCenteredListener(OnItemCenteredListener)
	 */
	public interface OnItemCenteredListener {
		public void onItemCentered(View v);
	}
}