android 加载图片轻松避免OOM(out of memory)

在使用android加载图片的时候,经常会出现内存溢出,主要是由于android可使用的内存太小,而通过代码加载进来的图片,并不会被GC回收,于是我写了一个工具类用来加载图片,并且建立缓存,轻松避免内存溢出,废话不多说,上代码

package l.test1.util;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.util.HashMap;import java.util.HashSet;import java.util.LinkedList;import java.util.Map;import java.util.Queue;import java.util.Set;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.BitmapFactory.Options;/** * Bitmap工具类,缓存用过的指定数量的图片,使用此工具类,不再需要手动管理Bitmap内存 原理: * 用一个队列保存使用Bitmap的顺序,每次使用Bitmap将对象移动到队列头 当内存不够,或者达到制定的缓存数量的时候,回收队列尾部图片 * 保证当前使用最多的图片得到最长时间的缓存,提高速度 *  * @author liaoxingliao *  */public final class BitMapUtil {private static final Size ZERO_SIZE = new Size(0, 0);private static final Options OPTIONS_GET_SIZE = new Options();private static final Options OPTIONS_DECODE = new Options();private static final byte[] LOCKED = new byte[0];private static final LinkedList<String> CACHE_ENTRIES = new LinkedList<String>(); // 此对象用来保持Bitmap的回收顺序,保证最后使用的图片被回收private static final Queue<QueueEntry> TASK_QUEUE = new LinkedList<QueueEntry>(); // 线程请求创建图片的队列private static final Set<String> TASK_QUEUE_INDEX = new HashSet<String>(); // 保存队列中正在处理的图片的key,有效防止重复添加到请求创建队列private static final Map<String, Bitmap> IMG_CACHE_INDEX = new HashMap<String, Bitmap>(); // 缓存Bitmap// 通过图片路径,图片大小private static int CACHE_SIZE = 200; // 缓存图片数量static {OPTIONS_GET_SIZE.inJustDecodeBounds = true;// 初始化创建图片线程,并等待处理new Thread() {{setDaemon(true);}public void run() {while (true) {synchronized (TASK_QUEUE) {if (TASK_QUEUE.isEmpty()) {try {TASK_QUEUE.wait();} catch (InterruptedException e) {e.printStackTrace();}}}QueueEntry entry = TASK_QUEUE.poll();String key = createKey(entry.path, entry.width,entry.height);TASK_QUEUE_INDEX.remove(key);//createBitmap(entry.path, entry.width, entry.height);//修正过的代码getBitmap(entry.path,entry.width,entry.height);}}}.start();}/** * 创建一张图片 如果缓存中已经存在,则返回缓存中的图,否则创建一个新的对象,并加入缓存 * 宽度,高度,为了缩放原图减少内存的,如果输入的宽,高,比原图大,返回原图 *  * @param path图片物理路径 (必须是本地路径,不能是网络路径) * @param width需要的宽度 * @param height需要的高度 * @return */public static Bitmap getBitmap(String path, int width, int height) {Bitmap bitMap = null;try {if (CACHE_ENTRIES.size() >= CACHE_SIZE) {destoryLast();}bitMap = useBitmap(path, width, height);if (bitMap != null && !bitMap.isRecycled()) {return bitMap;}bitMap = createBitmap(path, width, height);String key = createKey(path, width, height);synchronized (LOCKED) {IMG_CACHE_INDEX.put(key, bitMap);CACHE_ENTRIES.addFirst(key);}} catch (OutOfMemoryError err) {destoryLast();System.out.println(CACHE_SIZE);//return createBitmap(path, width, height);//修正过的代码return getBitmap(path, width, height);}return bitMap;}/** * 设置缓存图片数量 如果输入负数,会产生异常 *  * @param size */public static void setCacheSize(int size) {if (size <= 0) {throw new RuntimeException("size :" + size);}while (size < CACHE_ENTRIES.size()) {destoryLast();}CACHE_SIZE = size;}/** * 加入一个图片处理请求到图片创建队列 *  * @param path *            图片路径(本地) * @param width *            图片宽度 * @param height *            图片高度 */public static void addTask(String path, int width, int height) {QueueEntry entry = new QueueEntry();entry.path = path;entry.width = width;entry.height = height;synchronized (TASK_QUEUE) {String key = createKey(path, width, height);if (!TASK_QUEUE_INDEX.contains(key)&& !IMG_CACHE_INDEX.containsKey(key)) {TASK_QUEUE.add(entry);TASK_QUEUE_INDEX.add(key);TASK_QUEUE.notify();}}}/** * 通过图片路径返回图片实际大小 * @param path图片物理路径 * @return */public static Size getBitMapSize(String path) {File file = new File(path);if (file.exists()) {InputStream in = null;try {in = new FileInputStream(file);BitmapFactory.decodeStream(in, null, OPTIONS_GET_SIZE);return new Size(OPTIONS_GET_SIZE.outWidth,OPTIONS_GET_SIZE.outHeight);} catch (FileNotFoundException e) {return ZERO_SIZE;} finally {closeInputStream(in);}}return ZERO_SIZE;}// ------------------------------------------------------------------ private Methods// 将图片加入队列头private static Bitmap useBitmap(String path, int width, int height) {Bitmap bitMap = null;String key = createKey(path, width, height);synchronized (LOCKED) {bitMap = IMG_CACHE_INDEX.get(key);if (null != bitMap) {if (CACHE_ENTRIES.remove(key)) {CACHE_ENTRIES.addFirst(key);}}}return bitMap;}// 回收最后一张图片private static void destoryLast() {synchronized (LOCKED) {String key = CACHE_ENTRIES.removeLast();if (key.length() > 0) {Bitmap bitMap = IMG_CACHE_INDEX.remove(key);if (bitMap != null && !bitMap.isRecycled()) {bitMap.recycle();bitMap = null;}}}}// 创建键private static String createKey(String path, int width, int height) {if (null == path || path.length() == 0) {return "";}return path + "_" + width + "_" + height;}// 通过图片路径,宽度高度创建一个Bitmap对象private static Bitmap createBitmap(String path, int width, int height) {File file = new File(path);if (file.exists()) {InputStream in = null;try {in = new FileInputStream(file);Size size = getBitMapSize(path);if (size.equals(ZERO_SIZE)) {return null;}int scale = 1;int a = size.getWidth() / width;int b = size.getHeight() / height;scale = Math.max(a, b);synchronized (OPTIONS_DECODE) {OPTIONS_DECODE.inSampleSize = scale;Bitmap bitMap = BitmapFactory.decodeStream(in, null,OPTIONS_DECODE);return bitMap;}} catch (FileNotFoundException e) {e.printStackTrace();} finally {closeInputStream(in);}}return null;}// 关闭输入流private static void closeInputStream(InputStream in) {if (null != in) {try {in.close();} catch (IOException e) {e.printStackTrace();}}}// 图片大小static class Size {private int width, height;Size(int width, int height) {this.width = width;this.height = height;}public int getWidth() {return width;}public int getHeight() {return height;}}// 队列缓存参数对象static class QueueEntry {public String path;public int width;public int height;}}

测试代码使用android1.6完成,需要的可移步下载,地址为:http://download.csdn.net/detail/liaoxingliao/3756187 (这个工程内部的这个工具类由于我的疏忽有几个地方写错了,现在但是那个资源上传完以后,既不能修改,又不能删除.有谁知道怎么改的,希望告诉我一下)

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