本文为大家分享了Android图片加载的缓存类，供大家参考，具体内容如下

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.lang.ref.SoftReference; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import java.util.LinkedHashMap; 
import java.util.concurrent.ConcurrentHashMap; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.Build; 
import android.os.Handler; 
import android.text.TextUtils; 
 
/** 
 * 图片加载器,主要功能是从网络中下载图片并缓存。这里之所以另写一个功能类似重复的原因是 之前旧的图片加载逻辑感觉非常复杂，我这里写个轻量级的 
 * 
 * @author H3c 
 * 
 */ 
public class ImageLoaderEngine { 
  public static final int LOAD_IMG_SUCCESS = 2010; 
  private final int MAX_CAPACITY = Build.VERSION.SDK_INT > Build.VERSION_CODES.GINGERBREAD_MR1 ? 50 : 10;// 一级缓存缓存图片数 
 
  private static ImageLoaderEngine instance; 
  private static Handler mHandler; 
  private ExecutorService pool;// 后台线程池 
  // 这里用LinkedHashMap不用LruCache的原因是LruCache直接申请内存大小而不是图片个数。此App已经有一个全局的LruCache了，重复申请内存大小对应用不利 
  private LinkedHashMap<String, Bitmap> mFirstLevelCache;// <momentId>一级缓存，硬链接bitmap，只保留最近用的图片。 
  private ConcurrentHashMap<String, SoftReference<Bitmap>> mSecondLevelCache;// <momentId> 
 
  public static ImageLoaderEngine getInstance(Handler handler) { 
    if (instance == null) { 
      instance = new ImageLoaderEngine(); 
    } 
    if(handler != null) { 
      mHandler = handler; 
    } 
    return instance; 
  } 
 
  private ImageLoaderEngine() { 
    pool = Executors.newFixedThreadPool(4);// 默认线程池大小为6 
    initCache(); 
  } 
 
  private void initCache() { 
    mFirstLevelCache = new LinkedHashMap<String, Bitmap>(MAX_CAPACITY / 2, 
        0.75f, true) { 
      private static final long serialVersionUID = 1L; 
 
      protected boolean removeEldestEntry(Entry<String, Bitmap> eldest) { 
        if (size() > MAX_CAPACITY) {// 超过一级缓存大小后会挪到二级缓存中 
          mSecondLevelCache.put(eldest.getKey(), 
              new SoftReference<Bitmap>(eldest.getValue())); 
          return true; 
        } 
        return false; 
      }; 
    }; 
    mSecondLevelCache = new ConcurrentHashMap<String, SoftReference<Bitmap>>();// <momentId> 
  } 
   
  /** 
   * 移除缓存 
   * @param key 
   */ 
  public void deleteCacheByKey(String key) { 
    String sdCacheingPath = IOHelper.getCachedPicturePath( 
        Global.packageName, key); 
    String sdCacheedPath = sdCacheingPath +".png"; 
    File file = new File(sdCacheingPath); 
    if(file.exists()) { 
      file.delete(); 
    } 
    file = new File(sdCacheedPath); 
    if(file.exists()) { 
      file.delete(); 
    } 
     
    mFirstLevelCache.remove(key); 
    mSecondLevelCache.remove(key); 
  } 
 
  /** 
   * 释放资源 
   */ 
  public void recycleImageLoader() { 
    new Thread(new Runnable() { 
      @Override 
      public void run() { 
        if (pool != null) { 
          pool.shutdownNow(); 
        } 
        if (mFirstLevelCache != null) { 
          for (Bitmap bmp : mFirstLevelCache.values()) { 
            if (bmp != null) { 
              bmp.recycle(); 
              bmp = null; 
            } 
          } 
          mFirstLevelCache.clear(); 
          mFirstLevelCache = null; 
        } 
        if (mSecondLevelCache != null) { 
          mSecondLevelCache.clear(); 
        } 
        mHandler = null; 
      } 
    }).start(); 
  } 
 
  /** 
   * 后台请求图片 
   * 
   * @param item 
   */ 
  public void loadImageByMoment(final NMoment moment,String photoTag) { 
    if (moment.isPicture() 
        || moment.isVideo()) { 
      String id = moment.id + photoTag; 
      loadImageByUrl(id+"", moment.getPicture(Global.widthPixels/3*2),moment.orientation); 
    } 
  } 
   
  /** 
   * 后台请求图片 
   * @param key 
   * @param url 
   */ 
  public void loadImageByUrl(final String key,final String url,final int orientation) { 
      pool.submit(new Runnable() { 
        public void run() { 
          LogHelper.e("ImageLoaderEngine","从网络中下载"); 
          // 如果内存中有就算了 
          if (mFirstLevelCache.get(key) != null 
              || mSecondLevelCache.get(key) != null) {// 如果图片已经缓存了 
            LogHelper.e("ImageLoaderEngine","下载图片错误 1"); 
            return; 
          } 
 
          // 如果SD卡缓存中有就算了 
          final String sdCacheingPath = IOHelper.getCachedPicturePath( 
              Global.packageName, key); 
          File cacheingFile = new File(sdCacheingPath); 
          if (cacheingFile.exists()) {// 如果正在缓存就算了 
            long currentTime = System.currentTimeMillis(); 
            if((currentTime - cacheingFile.lastModified()) >2 * 60 * 1000) { 
              LogHelper.e("ImageLoaderEngine","2分钟都还没下载完，准备删除它.."+currentTime+"="+cacheingFile.lastModified()); 
              cacheingFile.delete(); 
            } else { 
              getBitmapFromNetworkAndAddToMemory(url, key, orientation); 
              LogHelper.e("ImageLoaderEngine","第二次进来应该走这里.."); 
              return; 
            } 
          } 
           
          String sdCacheedPath = sdCacheingPath + ".png";// 缓存完成后会改名字，否则会导致缓存错误，图片变黑 
          File cacheedFile = new File(sdCacheedPath); 
          if (cacheedFile.exists()) {// 如果缓存了就算了 
            LogHelper.e("ImageLoaderEngine","下载图片错误 2"); 
            return; 
          } 
           
          getBitmapFromNetworkAndAddToMemory(url, key, orientation); 
        } 
      }); 
  } 
   
  private void getBitmapFromNetworkAndAddToMemory(String url,String key,int orientation) { 
    Bitmap bmp = getBitmapFromUrl(url); 
    if(bmp!= null) { 
      LogHelper.e("ImageLoaderEngine","下载网络图片成功"); 
       
      if(key.endsWith("_DetailDaily")) { 
        bmp = scaledBitmap(bmp, Global.getThumbWidth()); 
      } 
       
      if(orientation != 0) { 
        mFirstLevelCache.put(key, ViewHelper.rotateBitmap(orientation, bmp));// 从网络下载后直接显示 
      } else { 
        mFirstLevelCache.put(key, bmp);// 从网络下载后直接显示 
      } 
     
      if (mHandler != null) { 
        mHandler.removeMessages(LOAD_IMG_SUCCESS); 
        mHandler.sendEmptyMessageDelayed( 
            LOAD_IMG_SUCCESS, 600);// 延时提示没有数据了 
      } 
       
      final String sdCacheingPath = IOHelper.getCachedPicturePath( 
          Global.packageName, key); 
      saveBitmapToFile(sdCacheingPath, bmp); 
    } else { 
      LogHelper.e("ImageLoaderEngine","下载网络图片失败..."); 
    } 
  } 
   
  /** 
   * 直接从网络中获取 
   * @param url 
   * @return 
   */ 
  public Bitmap getBitmapFromUrl(String url) { 
    URL myFileUrl = null; 
    Bitmap bitmap = null; 
    InputStream is = null; 
    try { 
      if (!UIUtils.isNetworkAvailable(MyApplication.getInstance())) { 
        return null; 
      } 
      myFileUrl = new URL(url); 
      HttpURLConnection conn = (HttpURLConnection) myFileUrl 
          .openConnection(); 
      conn.setDoInput(true); 
      conn.connect(); 
      is = conn.getInputStream(); 
      bitmap = BitmapFactory.decodeStream(is); 
    } catch (Exception e) { 
      try { 
        if(is != null) { 
          is.close(); 
        } 
      } catch (IOException e1) { 
        e1.printStackTrace(); 
      } 
      e.printStackTrace(); 
    } 
    return bitmap; 
  } 
   
  public Bitmap getImageInMemory(NMoment moment) { 
    return getImageInMemory(moment, ""); 
  } 
   
  /** 
   * 新增接口，可以根据tag重新标识Moment，这样可以扩展应用场景，比如首页需要大图，进入相集页需要小图 
   * @param moment 
   * @param photoTag 
   * @return 
   */ 
  public Bitmap getImageInMemory(NMoment moment, String photoTag) { 
    String id = moment.id + photoTag; 
     
    Bitmap bmp = null; 
    // 1. 从一级缓存中获取 
    bmp = getFromFirstLevelCache(id); 
    if (bmp != null && !bmp.isRecycled()) { 
      LogHelper.e("ImageLoaderEngine","一级缓存获取:"+id); 
      return bmp; 
    } 
    // 2. 从二级缓存中获取 
    bmp = getFromSecondLevelCache(id); 
    if (bmp != null && !bmp.isRecycled()) { 
      LogHelper.e("ImageLoaderEngine","二级缓存获取:"+id); 
      return bmp; 
    } 
     
    if(bmp != null && bmp.isRecycled()) { 
      return null; 
    } else { 
      return bmp; 
    } 
  } 
   
  public void setImage(String key,Bitmap picture) { 
    mFirstLevelCache.put(key, picture); 
  } 
   
  /** 
   * 获取图片 
   */ 
  public Bitmap getImage(NMoment moment) { 
    return getImage(moment, ""); 
  } 
   
  public Bitmap getImage(NMoment moment, String photoTag) { 
    String id = moment.id + photoTag; 
    Bitmap bmp = null; 
    // 1. 从一级缓存中获取 
    bmp = getFromFirstLevelCache(id); 
    if (bmp != null && !bmp.isRecycled()) { 
      LogHelper.e("ImageLoaderEngine","一级缓存获取:"+id); 
      return bmp; 
    } 
    // 2. 从二级缓存中获取 
    bmp = getFromSecondLevelCache(id); 
    if (bmp != null && !bmp.isRecycled()) { 
      LogHelper.e("ImageLoaderEngine","二级缓存获取:"+id); 
      return bmp; 
    } 
    // 3. 从SD卡缓存中获取 
    bmp = getFromSDCache(moment, photoTag); 
    if (bmp != null && !bmp.isRecycled()) { 
      LogHelper.e("ImageLoaderEngine","SD卡缓存获取:"+id); 
      return bmp; 
    } 
    // 4. 从网络中获取 
    loadImageByMoment(moment, photoTag);  
//    LogHelper.e("ImageLoaderEngine","本地获取图片失败:"+moment.id+"="+moment.getPicture()); 
     
    if(bmp != null && bmp.isRecycled()) { 
      return null; 
    } else { 
      return bmp; 
    } 
  } 
 
  public Bitmap getImage(String key,String url) { 
    Bitmap bmp = null; 
    // 1. 从一级缓存中获取 
    bmp = getFromFirstLevelCache(key); 
    if (bmp != null && !bmp.isRecycled()) { 
      return bmp; 
    } 
    // 2. 从二级缓存中获取 
    bmp = getFromSecondLevelCache(key); 
    if (bmp != null && !bmp.isRecycled()) { 
      return bmp; 
    } 
    // 3. 从SD卡缓存中获取 
    bmp = getFromSDCacheByKey(key,0); 
    if (bmp != null && !bmp.isRecycled()) { 
      return bmp; 
    } 
    // 4. 从网络中获取 
    loadImageByUrl(key, url,0); 
     
    if(bmp != null && bmp.isRecycled()) { 
      return null; 
    } else { 
      return bmp; 
    } 
  } 
   
  /** 
   * 一级缓存获取图片 
   * 
   * @param imgId 
   * @return 
   */ 
  private Bitmap getFromFirstLevelCache(String imgId) { 
    Bitmap bitmap = null; 
    synchronized (mFirstLevelCache) { 
      bitmap = mFirstLevelCache.get(imgId); 
      if (bitmap != null) { 
        mFirstLevelCache.remove(imgId); 
        mFirstLevelCache.put(imgId, bitmap); 
      } 
    } 
    return bitmap; 
  } 
 
  /** 
   * 二级缓存获取图片 
   * 
   * @param url 
   * @return 
   */ 
  private Bitmap getFromSecondLevelCache(String imgId) { 
    Bitmap bitmap = null; 
    SoftReference<Bitmap> softReference = mSecondLevelCache.get(imgId); 
    if (softReference != null) { 
      bitmap = softReference.get(); 
      if (bitmap == null) { 
        mSecondLevelCache.remove(imgId); 
      } 
    } 
    return bitmap; 
  } 
 
  /** 
   * 从SD卡缓存获取图片，并放入一级缓存中 
   * 
   * @param moment 
   * @return 
   * @throws IOException 
   */ 
  private Bitmap getFromSDCache(final NMoment moment,final String photoTag) { 
    Bitmap drawable = null; 
    String id = moment.id + photoTag; 
     
    String sdCacheingPath = IOHelper.getCachedPicturePath(Global.packageName, 
        id); 
     
    String sdCacheedPath = sdCacheingPath + ".png"; 
    if(moment.isLocal){ 
      if(moment.isVideo()) { 
        //获取本地路径 
        sdCacheedPath = moment.getPicture(Global.widthPixels/3*2); 
      } else { 
        sdCacheedPath = moment.local_res_path; 
      } 
    } 
     
    File cacheFile = new File(sdCacheedPath); 
    if (!cacheFile.exists()) {// 如果没有缓存完成就退出 
      LogHelper.e("ImageLoaderEngine","找不到缓存文件:"+sdCacheedPath); 
      if(!TextUtils.isEmpty(moment.local_res_path)) {// 如果本地有图片，就先用本地图片代替 
        sdCacheedPath = moment.local_res_path; 
        cacheFile = new File(sdCacheedPath); 
        if (cacheFile.exists() && !GlobalData.PHONE_MANUFACTURER.equalsIgnoreCase("samsung")) { 
          LogHelper.e("ImageLoaderEngine","AK47...:"+GlobalData.PHONE_MANUFACTURER);// 先从本地找替代图片.. 
          new Thread(new Runnable() {// 从网络下载 
            @Override 
            public void run() { 
              loadImageByMoment(moment, photoTag);  
            } 
          }).start(); 
          return getFitPhoto(sdCacheedPath, moment, cacheFile); 
        } else { 
          return null; 
        } 
      } else { 
        return null; 
      } 
    } 
     
    drawable = getFitPhoto(sdCacheedPath, moment, cacheFile); 
 
    if (drawable != null) { 
      if (moment.orientation != 0) { 
        drawable = ViewHelper 
            .rotateBitmap(moment.orientation, drawable); 
      } 
      if(mFirstLevelCache != null) { 
        mFirstLevelCache.put(id, drawable); 
      } 
    } else { 
      cacheFile.delete(); 
    } 
    return drawable; 
  } 
   
  private Bitmap getFitPhoto(String sdCacheedPath,NMoment moment,File cacheFile) { 
    FileInputStream fs = null; 
    Bitmap result; 
    try { 
      BitmapFactory.Options options = new BitmapFactory.Options(); 
      options.inJustDecodeBounds = true; 
      BitmapFactory.decodeFile(sdCacheedPath, options); 
      int hRatio = (int) Math.ceil(options.outHeight 
          / (float) moment.picture_height); // 算高度 
      int wRatio = (int) Math.ceil(options.outWidth 
          / (float) Global.widthPixels); // 算宽度 
 
      if (hRatio > 1 || wRatio > 1) { 
        if (hRatio > wRatio) { 
          options.inSampleSize = hRatio; 
        } else 
          options.inSampleSize = wRatio; 
      } 
 
      options.inPurgeable = true; 
      options.inInputShareable = true; 
      options.inDither = false; 
      options.inJustDecodeBounds = false; 
 
      try { 
        fs = new FileInputStream(cacheFile); 
      } catch (FileNotFoundException e) { 
        e.printStackTrace(); 
      } 
 
      result = BitmapFactory.decodeFileDescriptor(fs.getFD(), null, 
          options); 
    } catch (Exception e) { 
      throw new RuntimeException(e); 
    } finally { 
      if (fs != null) { 
        try { 
          fs.close(); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        } 
      } 
    } 
    return result; 
  } 
   
  private Bitmap getFromSDCacheByKey(String key,int orientation) { 
    Bitmap drawable = null; 
    FileInputStream fs = null; 
     
    String sdCacheedPath = IOHelper.getCachedPicturePath( 
        Global.packageName, key) + ".png"; 
     
    File cacheFile = new File(sdCacheedPath); 
    if (!cacheFile.exists()) {// 如果没有缓存完成就退出 
      return null; 
    } 
 
    try { 
      BitmapFactory.Options options = new BitmapFactory.Options(); 
      options.inJustDecodeBounds = true; 
      BitmapFactory.decodeFile(sdCacheedPath, options); 
      int wRatio = (int) Math.ceil(options.outWidth 
          / (float) Global.widthPixels); // 算宽度 
      options.inSampleSize = wRatio; 
      options.inPurgeable = true; 
      options.inInputShareable = true; 
      options.inDither = false; 
      options.inJustDecodeBounds = false; 
 
      try { 
        fs = new FileInputStream(cacheFile); 
      } catch (FileNotFoundException e) { 
        e.printStackTrace(); 
      } 
       
      drawable = BitmapFactory.decodeFileDescriptor(fs.getFD(), null, 
          options); 
 
      if (drawable != null) { 
        if(orientation != 0) { 
          drawable = ViewHelper.rotateBitmap(orientation, drawable); 
        } 
        mFirstLevelCache.put(key, drawable); 
      } else { 
        cacheFile.delete(); 
      } 
    } catch (Exception e) { 
      throw new RuntimeException(e); 
    } finally { 
      if (fs != null) { 
        try { 
          fs.close(); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        } 
      } 
    } 
    return drawable; 
  } 
 
  /** 
   * 创建一个灰色的默认图 
   * @param moment 
   * @return 
   */ 
  public Bitmap getDefaultBitmap(NMoment moment) { 
    return ImageHelper.createBitmap(moment.picture_width, moment.picture_height, 
        R.color.image_bg_daily); 
  } 
   
  /** 
   * 保存Bitmap文件到sd卡，传入jpg结尾的路径 
   * @param filePath 
   * @param mBitmap 
   */ 
  public void saveBitmapToFile(String filePath, Bitmap mBitmap) { 
    try { 
      File file = new File(filePath); 
 
      if (!file.getParentFile().exists()) { 
        file.getParentFile().mkdirs(); 
      } 
 
      if (file.exists() && file.length() > 0) { 
        long currentTime = System.currentTimeMillis(); 
        if ((currentTime - file.lastModified()) > 2 * 60 * 1000) { 
          LogHelper.e("ImageLoaderEngine", 
              "2分钟都还没下载完，准备删除它.." + currentTime + "=" 
                  + file.lastModified()); 
          file.delete(); 
        } else { 
          return; 
        } 
      } else { 
        file.createNewFile(); 
      } 
 
      FileOutputStream fOut = null; 
      fOut = new FileOutputStream(file); 
      mBitmap.compress(Bitmap.CompressFormat.JPEG, 80, fOut); 
      fOut.flush(); 
      fOut.close(); 
       
      file.renameTo(new File(filePath+".png")); 
    } catch (Exception e) { 
      e.printStackTrace(); 
      LogHelper.e("ImageLoaderEngine","保存图片错误:"+e); 
    } 
    LogHelper.e("ImageLoaderEngine","保存网络图片成功"+filePath+".png"); 
  } 
 
  /** 
   * 保存文件至缓存，这里重写而不用IOHelper里面的原因是IOHelper里面过于复杂 
   * 
   * @param url 
   * @param filePath 
   * @return 
   */ 
  public boolean saveUrlBitmapToFile(String url, String filePath) { 
      if (TextUtils.isEmpty(filePath)) { 
        return false; 
      } 
    File iconFile = new File(filePath); 
    if (iconFile.getParentFile() == null) { 
        return false; 
    } 
    if (!iconFile.getParentFile().exists()) { 
      iconFile.getParentFile().mkdirs(); 
    } 
 
    if (iconFile.exists() && iconFile.length() > 0) { 
      long currentTime = System.currentTimeMillis(); 
      if((currentTime - iconFile.lastModified()) >2 * 60 * 1000) { 
        LogHelper.e("ImageLoaderEngine","2分钟都还没下载完，准备删除它.."+currentTime+"="+iconFile.lastModified()); 
        iconFile.delete(); 
      } else { 
        return true; 
      } 
    } 
 
    FileOutputStream fos = null; 
    InputStream is = null; 
    try { 
      fos = new FileOutputStream(filePath); 
      is = new URL(url).openStream(); 
 
      int data = is.read(); 
      while (data != -1) { 
        fos.write(data); 
        data = is.read(); 
      } 
    } catch (IOException e) { 
      LogHelper.e("ImageLoaderEngine", "ImageLoaderEngine 下载图片错误" + e); 
      iconFile.delete(); 
      e.printStackTrace(); 
      return false; 
    } finally { 
      try { 
        if (is != null) { 
          is.close(); 
        } 
        if (fos != null) { 
          fos.close(); 
        } 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
    iconFile.renameTo(new File(filePath+".png")); 
    return true; 
  } 
   
  /** 
   * 缩放bitmap 
   * @param bmp 
   * @param scaledValue缩放值 
   * @return 
   */ 
  public Bitmap scaledBitmap(Bitmap bmp,int scaledValue) { 
    int bmpWidth = bmp.getWidth(); 
    int bmpHeight = bmp.getHeight(); 
     
    if(bmpWidth >= bmpHeight) {// 横图 
      bmpWidth = (bmpWidth * scaledValue / bmpHeight); 
      bmpHeight = scaledValue; 
    } else { 
      bmpHeight = (bmpHeight * scaledValue / bmpWidth); 
      bmpWidth = scaledValue; 
    } 
     
    Bitmap scaledBmp = Bitmap.createScaledBitmap(bmp,bmpWidth,bmpHeight,true); 
    bmp.recycle(); 
    bmp = null; 
     
    return scaledBmp; 
  } 
} 

以上就是一个完整的Android图片加载缓存类，希望对大家的学习有所帮助。

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