android實現緩衝圖片等資料_Android

採用LinkedHashMap內建的LRU 演算法快取資料， 可檢測對象是否已被虛擬機器回收，並且重新計算當前緩衝大小，清除緩衝中無用的索引值對象(即已經被虛擬機器回收但未從緩衝清除的資料)；
 * 預設記憶體緩衝大小為: 4 * 1024 * 1024 可通過通過setMaxCacheSize重新設定緩衝大小，可手動清空記憶體緩衝
 * <br>支援記憶體緩衝和磁碟緩衝方式， 通過 {@link cc.util.cache.NetByteWrapper} 支援HTTP緩衝 （註：詳細參考cc.util.http包）； 註：使用JDK7

package cc.util.cache; import java.io.Serializable;import java.util.Objects; /**  封裝網路資料， 將資料的Etag、lastModified擷取到， 下次請求的時候提取出來到伺服器比對 * Help to wrap byte data which obtains from network, It will work with {@link cc.util.cache.NetChacheManager}  * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun 2014 */public class NetByteWrapper implements Serializable {   private final static long serialVersionUID = 1L;   /** data from network */  private byte[] data;  /** data size */  int contentLength;  /** latested modify time */  private long lastModified;  /** ETag： look up HTTP Protocol */  private String ETag;   public NetByteWrapper(byte[] data, long lastModified, String Etag) {    this.data = data;    this.lastModified = lastModified;    this.ETag = Etag;  }     public byte[] getData() {    return data;  }  public void setData(byte[] data) {    this.data = data;  }   public long getLastModified() {    return lastModified;  }  public void setLastModified(long lastModified) {    this.lastModified = lastModified;  }   public String getETag() {    return ETag;  }     public void setETag(String eTag) {    this.ETag = eTag;  }     public int getContentLength() {    return Objects.isNull(data) ? 0 : data.length;  }}  package cc.util.cache; import java.lang.ref.ReferenceQueue;import java.lang.ref.SoftReference; /**採用軟引用方式將資料存放起來 * enclose {@link cc.util.cache.NetByteWrapper} with {@link java.lang.ref.SoftReference}, In order to recycle the memory * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun. 2014 */public class NetByteSoftReference extends SoftReference<NetByteWrapper> {     private String key = "";  private long length = 0;   public NetByteSoftReference(String key, NetByteWrapper arg0) {    this(key, arg0, null);  }   public NetByteSoftReference(String key, NetByteWrapper arg0,      ReferenceQueue<? super NetByteWrapper> arg1) {    super(arg0, arg1);    // TODO Auto-generated constructor stub    this.key = key;    this.length = arg0.getContentLength();  }     public String getKey() {    return key;  }     public long getLength() {    return length;  } }  package cc.util.cache; import java.lang.ref.ReferenceQueue;import java.lang.ref.SoftReference;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.util.Iterator;import java.util.LinkedHashMap;import java.util.Objects; /** * 採用LinkedHashMap內建的LRU 演算法快取資料， 可檢測對象是否已被虛擬機器回收，並且重新計算當前緩衝大小，清除緩衝中無用的索引值對象(即已經被虛擬機器回收但未從緩衝清除的資料)； * 預設記憶體緩衝大小為: 4 * 1024 * 1024 可通過通過setMaxCacheSize重新設定緩衝大小，可手動清空記憶體緩衝，支援採用記憶體映射方式讀取緩衝 * <br>支援記憶體緩衝和磁碟緩衝方式， 通過 {@link cc.util.cache.NetByteWrapper} 支援HTTP緩衝 （註：詳細參考cc.util.http包） * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun 2014 */public class NetCacheManager {   /** max cache size */  private long MAX_CACHE_SIZE = 4 * 1024 * 1024;  private long cacheSize = 0;    private static NetCacheManager instance = null;     private final ReferenceQueue<NetByteWrapper> referenceQueue;  private final LinkedHashMap<String, NetByteSoftReference> cacheMap;     private NetCacheManager(){    referenceQueue = new ReferenceQueue<NetByteWrapper>();    cacheMap = new LinkedHashMap<String, NetByteSoftReference>(16, 0.75f, true) {       private static final long serialVersionUID = -8378285623387632829L;      @Override      protected boolean removeEldestEntry(          java.util.Map.Entry<String, NetByteSoftReference> eldest) {        // TODO Auto-generated method stub        boolean shouldRemove = cacheSize > MAX_CACHE_SIZE;        if (shouldRemove) {          cacheSize -= eldest.getValue().getLength();          System.gc();        }        return shouldRemove;      }    };  }     /** singleton model */  public static synchronized NetCacheManager newInstance(){    if (Objects.isNull(instance)) {      instance = new NetCacheManager();    }    return instance;  }     /**   * reset the memory cache size   * @param cacheSize   */  public void setMaxCacheSize(long cacheSize) {    this.MAX_CACHE_SIZE = cacheSize;  }     /**   * 擷取當前記憶體緩衝大小   * @return   */  public long getCacheSize() {    return cacheSize;  }     /**   * 將資料緩衝至記憶體， 如果http返回的資料<b>不支援</b>緩衝則採用此方法，緩衝的key一般為請求的url   * @param key   * @param value   */  public void cacheInMemory(String key, byte[] value) {    this.cacheInMemory(key, value, 0, null);  }     /**   * 將資料緩衝至記憶體， 如果http返回的資料<b>支援</b>緩衝則採用此方法   * @param key   * @param value   * @param lastModified   */  public void cacheInMemory(String key, byte[] value, long lastModified) {    this.cacheInMemory(key, value, lastModified, null);  }     /**   * 將資料緩衝至記憶體， 如果http返回的資料<b>支援</b>緩衝則採用此方法   * @param key   * @param value   * @param Etags   */  public void cacheInMemory(String key, byte[] value, String Etags) {    this.cacheInMemory(key, value, 0, Etags);  }     /**   * 將資料緩衝至記憶體， 如果http返回的資料<b>支援</b>緩衝則採用此方法   * @param key   * @param value   * @param lastModified   * @param Etags   */  private void cacheInMemory(String key, byte[] value, long lastModified, String Etags) {    Objects.requireNonNull(key, "key must not be null");    clearRecycledObject();    NetByteWrapper wrapper = new NetByteWrapper(value, lastModified, Etags);    NetByteSoftReference byteRef = new NetByteSoftReference(key, wrapper, referenceQueue);    cacheMap.put(key, byteRef);    value = null;    wrapper = null;  }     /**   * 緩衝至磁碟, 預設不首先緩衝到記憶體   * @param key   * @param value   * @param path   */  public void cacheInDisk(String key, byte[] value, String path) {    cacheInDisk(key, value, path, false);  }     /**   *    * @param key   * @param value   * @param path   * @param cacheInMemory   */  public void cacheInDisk(String key, byte[] value, String path, boolean cacheInMemory) {    this.cacheInDisk(key, value, 0, null, path, cacheInMemory);  }     /**   *    * @param key   * @param value   * @param lastModified   * @param Etags   * @param path   * @param cacheInMemory   */  private void cacheInDisk(String key, byte[] value, long lastModified, String Etags, String path, boolean cacheInMemory) {    if (cacheInMemory) cacheInMemory(key, value, lastModified, Etags);    try (FileOutputStream fos = new FileOutputStream(path);        ObjectOutputStream oos = new ObjectOutputStream(fos)) {        NetByteWrapper wrapper = new NetByteWrapper(value, lastModified, Etags);        oos.writeObject(wrapper);    } catch (Exception e) {        // TODO: handle exception      e.printStackTrace();    }  }     /**   * get {@link cc.util.cache.NetByteWrapper} from memory according to key   * @param key   * @return {@link cc.util.cache.NetByteWrapper}   */  public NetByteWrapper getFromMemory(String key) {    SoftReference<NetByteWrapper> softReference = cacheMap.get(key);    return Objects.nonNull(softReference) ? softReference.get() : null;  }     /**   * get byte[] from memory according to key   * @param context   * @param key   * @return   */  public byte[] getByteFromMemory(String key) {    NetByteWrapper wrapper = getFromMemory(key);    return Objects.nonNull(wrapper) ? wrapper.getData() : null;  }     /**   * 從磁碟擷取資料   * @param path   * @return {@link cc.util.cache.NetByteWrapper}   */  public NetByteWrapper getFromDisk(String path) {    try (FileInputStream fis = new FileInputStream(path);        ObjectInputStream ois = new ObjectInputStream(fis)) {      NetByteWrapper wrapper = (NetByteWrapper) ois.readObject();      return wrapper;    } catch (Exception e) {      // TODO: handle exception      e.printStackTrace();      return null;    }  }     /**   * 採用記憶體映射的方式從磁碟擷取資料（加快讀取緩衝的大檔案）   * @param path   * @return   */  public NetByteWrapper getFromDiskByMapped(String path) {    try (FileInputStream fis = new FileInputStream(path);        FileChannel channel= fis.getChannel();        ByteArrayOutputStream baos = new ByteArrayOutputStream()){      MappedByteBuffer mbb = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());      byte[] bts = new byte[1024];       int len = (int) channel.size();      for (int offset = 0; offset < len; offset += 1024) {         if (len - offset > 1024) mbb.get(bts);        else mbb.get((bts = new byte[len - offset]));         baos.write(bts);      }       ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());      ObjectInputStream ois = new ObjectInputStream(bais);      NetByteWrapper wrapper = (NetByteWrapper) ois.readObject();      bais.close();      ois.close();      return wrapper;    } catch (Exception e) {      // TODO: handle exception      e.printStackTrace();      return null;    }  }     /**   * 從磁碟擷取緩衝的byte[] 資料   * @param path   * @return   */  public byte[] getByteFromDisk(String path) {    NetByteWrapper wrapper = getFromDisk(path);    return Objects.isNull(wrapper) ? null : wrapper.getData();  }     /**   * 通過記憶體映射放射從磁碟擷取緩衝的byte[] 資料   * @param path   * @return   */  public byte[] getByteFromDiskByMapped(String path) {    NetByteWrapper wrapper = getFromDiskByMapped(path);    return Objects.isNull(wrapper) ? null : wrapper.getData();  }     /**   * calculate the size of the cache memory   */  private void clearRecycledObject() {    NetByteSoftReference ref = null;    //檢測對象是否被回收，如果被回收則從緩衝中移除死項    while (Objects.nonNull((ref = (NetByteSoftReference) referenceQueue.poll()))) {      cacheMap.remove(ref.getKey());    }    cacheSize = 0;    Iterator<String> keys = cacheMap.keySet().iterator();    while (keys.hasNext()) {      cacheSize += cacheMap.get(keys.next()).getLength();    }  }     /**   * clear the memory cache   */  public void clearCache() {    clearRecycledObject();    cacheMap.clear();    System.gc();    System.runFinalization();  }   }

以上所述就是本文的全部內容了，希望大家能夠喜歡。