MemoryCache.java

/*
 * The MIT License (MIT)
 * 
 * Copyright � 2013 Clover Studio Ltd. All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.cloverstudio.spikademo.lazy;

import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import android.graphics.Bitmap;
import android.util.Log;

/*
 * MemoryCache
 * 
 * Used for managing files from application's memory cache directory.
 */

public class MemoryCache {

	private static final String TAG = "MemoryCache";
	private Map<String, Bitmap> cache = Collections
			.synchronizedMap(new LinkedHashMap<String, Bitmap>(10, 1.5f, true));// Last
																				// argument
																				// true
																				// for
																				// LRU
																				// ordering
	private long size = 0;// current allocated size
	private long limit = 1000000;// max memory in bytes

	public MemoryCache() {
		// use 25% of available heap size
		setLimit(Runtime.getRuntime().maxMemory() / 4);
	}

	public void setLimit(long new_limit) {
		limit = new_limit;
		Log.i(TAG, "MemoryCache will use up to " + limit / 1024. / 1024. + "MB");
	}

	public Bitmap get(String id) {
		try {
			if (!cache.containsKey(id))
				return null;
			// NullPointerException sometimes happen here
			// http://code.google.com/p/osmdroid/issues/detail?id=78
			return cache.get(id);
		} catch (NullPointerException ex) {
			ex.printStackTrace();
			return null;
		}
	}

	public void put(String id, Bitmap bitmap) {
		try {
			if (cache.containsKey(id))
				size -= getSizeInBytes(cache.get(id));
			cache.put(id, bitmap);
			size += getSizeInBytes(bitmap);
			checkSize();
		} catch (Throwable th) {
			th.printStackTrace();
		}
	}

	private void checkSize() {
		Log.i(TAG, "cache size=" + size + " length=" + cache.size());
		if (size > limit) {
			/* // least recently accessed item will be the first one iterated */
			Iterator<Entry<String, Bitmap>> iter = cache.entrySet().iterator();
			while (iter.hasNext()) {
				Entry<String, Bitmap> entry = iter.next();
				size -= getSizeInBytes(entry.getValue());
				iter.remove();
				if (size <= limit)
					break;
			}
			Log.i(TAG, "Clean cache. New size " + cache.size());
		}
	}

	public void clear() {
		try {
			// NullPointerException sometimes happen here
			// http://code.google.com/p/osmdroid/issues/detail?id=78
			cache.clear();
			size = 0;
		} catch (NullPointerException ex) {
			ex.printStackTrace();
		}
	}

	long getSizeInBytes(Bitmap bitmap) {
		if (bitmap == null)
			return 0;
		return bitmap.getRowBytes() * bitmap.getHeight();
	}
}