/** 
   * 根据ImageView获适当的压缩的宽和高 
   * 
   * @param imageView 
   * @return 
   */ 
  public static ImageSize getImageViewSize(ImageView imageView) 
  { 
 
    ImageSize imageSize = new ImageSize(); 
    DisplayMetrics displayMetrics = imageView.getContext().getResources() 
        .getDisplayMetrics(); 
 
    LayoutParams lp = imageView.getLayoutParams(); 
 
    int width = imageView.getWidth();// 获取imageview的实际宽度 
    if (width <= 0) 
    { 
      width = lp.width;// 获取imageview在layout中声明的宽度 
    } 
    if (width <= 0) 
    { 
      // width = imageView.getMaxWidth();// 检查最大值 
      width = getImageViewFieldValue(imageView, "mMaxWidth"); 
    } 
    if (width <= 0) 
    { 
      width = displayMetrics.widthPixels; 
    } 
 
    int height = imageView.getHeight();// 获取imageview的实际高度 
    if (height <= 0) 
    { 
      height = lp.height;// 获取imageview在layout中声明的宽度 
    } 
    if (height <= 0) 
    { 
      height = getImageViewFieldValue(imageView, "mMaxHeight");// 检查最大值 
    } 
    if (height <= 0) 
    { 
      height = displayMetrics.heightPixels; 
    } 
    imageSize.width = width; 
    imageSize.height = height; 
 
    return imageSize; 
  } 
 
  public static class ImageSize 
  { 
    int width; 
    int height; 
  } 

// 获得图片的宽和高，并不把图片加载到内存中 
    BitmapFactory.Options options = new BitmapFactory.Options(); 
    options.inJustDecodeBounds = true; 
    BitmapFactory.decodeFile(path, options); 

/** 
   * 根据需求的宽和高以及图片实际的宽和高计算SampleSize 
   * 
   * @param options 
   * @param width 
   * @param height 
   * @return 
   */ 
  public static int caculateInSampleSize(Options options, int reqWidth, 
      int reqHeight) 
  { 
    int width = options.outWidth; 
    int height = options.outHeight; 
 
    int inSampleSize = 1; 
 
    if (width > reqWidth || height > reqHeight) 
    { 
      int widthRadio = Math.round(width * 1.0f / reqWidth); 
      int heightRadio = Math.round(height * 1.0f / reqHeight); 
 
      inSampleSize = Math.max(widthRadio, heightRadio); 
    } 
 
    return inSampleSize; 
  } 

options.inSampleSize = ImageSizeUtil.caculateInSampleSize(options, 
        width, height); 
 
    // 使用获得到的InSampleSize再次解析图片 
    options.inJustDecodeBounds = false; 
    Bitmap bitmap = BitmapFactory.decodeFile(path, options); 
    return bitmap; 

/** 
   * 根据url下载图片在指定的文件 
   * 
   * @param urlStr 
   * @param file 
   * @return 
   */ 
  public static Bitmap downloadImgByUrl(String urlStr, ImageView imageview) 
  { 
    FileOutputStream fos = null; 
    InputStream is = null; 
    try 
    { 
      URL url = new URL(urlStr); 
      HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
      is = new BufferedInputStream(conn.getInputStream()); 
      is.mark(is.available()); 
       
      Options opts = new Options(); 
      opts.inJustDecodeBounds = true; 
      Bitmap bitmap = BitmapFactory.decodeStream(is, null, opts); 
       
      //获取imageview想要显示的宽和高 
      ImageSize imageViewSize = ImageSizeUtil.getImageViewSize(imageview); 
      opts.inSampleSize = ImageSizeUtil.caculateInSampleSize(opts, 
          imageViewSize.width, imageViewSize.height); 
       
      opts.inJustDecodeBounds = false; 
      is.reset(); 
      bitmap = BitmapFactory.decodeStream(is, null, opts); 
 
      conn.disconnect(); 
      return bitmap; 
 
    } catch (Exception e) 
    { 
      e.printStackTrace(); 
    } finally 
    { 
      try 
      { 
        if (is != null) 
          is.close(); 
      } catch (IOException e) 
      { 
      } 
 
      try 
      { 
        if (fos != null) 
          fos.close(); 
      } catch (IOException e) 
      { 
      } 
    } 
 
    return null; 
 
  } 

public static ImageLoader getInstance(int threadCount, Type type) 
  { 
    if (mInstance == null) 
    { 
      synchronized (ImageLoader.class) 
      { 
        if (mInstance == null) 
        { 
          mInstance = new ImageLoader(threadCount, type); 
        } 
      } 
    } 
    return mInstance; 
  } 

/** 
 * 图片加载类 
 * 
 * @author zhy 
 * 
 */ 
public class ImageLoader 
{ 
  private static ImageLoader mInstance; 
 
  /** 
   * 图片缓存的核心对象 
   */ 
  private LruCache<String, Bitmap> mLruCache; 
  /** 
   * 线程池 
   */ 
  private ExecutorService mThreadPool; 
  private static final int DEAFULT_THREAD_COUNT = 1; 
  /** 
   * 队列的调度方式 
   */ 
  private Type mType = Type.LIFO; 
  /** 
   * 任务队列 
   */ 
  private LinkedList<Runnable> mTaskQueue; 
  /** 
   * 后台轮询线程 
   */ 
  private Thread mPoolThread; 
  private Handler mPoolThreadHandler; 
  /** 
   * UI线程中的Handler 
   */ 
  private Handler mUIHandler; 
 
  private Semaphore mSemaphorePoolThreadHandler = new Semaphore(0); 
  private Semaphore mSemaphoreThreadPool; 
 
  private boolean isDiskCacheEnable = true; 
 
  private static final String TAG = "ImageLoader"; 
 
  public enum Type 
  { 
    FIFO, LIFO; 
  } 
 
  private ImageLoader(int threadCount, Type type) 
  { 
    init(threadCount, type); 
  } 
 
  /** 
   * 初始化 
   * 
   * @param threadCount 
   * @param type 
   */ 
  private void init(int threadCount, Type type) 
  { 
    initBackThread(); 
 
    // 获取我们应用的最大可用内存 
    int maxMemory = (int) Runtime.getRuntime().maxMemory(); 
    int cacheMemory = maxMemory / 8; 
    mLruCache = new LruCache<String, Bitmap>(cacheMemory) 
    { 
      @Override 
      protected int sizeOf(String key, Bitmap value) 
      { 
        return value.getRowBytes() * value.getHeight(); 
      } 
 
    }; 
 
    // 创建线程池 
    mThreadPool = Executors.newFixedThreadPool(threadCount); 
    mTaskQueue = new LinkedList<Runnable>(); 
    mType = type; 
    mSemaphoreThreadPool = new Semaphore(threadCount); 
  } 
 
  /** 
   * 初始化后台轮询线程 
   */ 
  private void initBackThread() 
  { 
    // 后台轮询线程 
    mPoolThread = new Thread() 
    { 
      @Override 
      public void run() 
      { 
        Looper.prepare(); 
        mPoolThreadHandler = new Handler() 
        { 
          @Override 
          public void handleMessage(Message msg) 
          { 
            // 线程池去取出一个任务进行执行 
            mThreadPool.execute(getTask()); 
            try 
            { 
              mSemaphoreThreadPool.acquire(); 
            } catch (InterruptedException e) 
            { 
            } 
          } 
        }; 
        // 释放一个信号量 
        mSemaphorePoolThreadHandler.release(); 
        Looper.loop(); 
      }; 
    }; 
 
    mPoolThread.start(); 
  } 

/** 
   * 根据path为imageview设置图片 
   * 
   * @param path 
   * @param imageView 
   */ 
  public void loadImage(final String path, final ImageView imageView, 
      final boolean isFromNet) 
  { 
    imageView.setTag(path); 
    if (mUIHandler == null) 
    { 
      mUIHandler = new Handler() 
      { 
        public void handleMessage(Message msg) 
        { 
          // 获取得到图片，为imageview回调设置图片 
          ImgBeanHolder holder = (ImgBeanHolder) msg.obj; 
          Bitmap bm = holder.bitmap; 
          ImageView imageview = holder.imageView; 
          String path = holder.path; 
          // 将path与getTag存储路径进行比较 
          if (imageview.getTag().toString().equals(path)) 
          { 
            imageview.setImageBitmap(bm); 
          } 
        }; 
      }; 
    } 
 
    // 根据path在缓存中获取bitmap 
    Bitmap bm = getBitmapFromLruCache(path); 
 
    if (bm != null) 
    { 
      refreashBitmap(path, imageView, bm); 
    } else 
    { 
      addTask(buildTask(path, imageView, isFromNet)); 
    } 
 
  } 

private void refreashBitmap(final String path, final ImageView imageView, 
      Bitmap bm) 
  { 
    Message message = Message.obtain(); 
    ImgBeanHolder holder = new ImgBeanHolder(); 
    holder.bitmap = bm; 
    holder.path = path; 
    holder.imageView = imageView; 
    message.obj = holder; 
    mUIHandler.sendMessage(message); 
  } 

// 将path与getTag存储路径进行比较
   if (imageview.getTag().toString().equals(path))
   {
   imageview.setImageBitmap(bm);
   }

private synchronized void addTask(Runnable runnable) 
  { 
    mTaskQueue.add(runnable); 
    // if(mPoolThreadHandler==null)wait(); 
    try 
    { 
      if (mPoolThreadHandler == null) 
        mSemaphorePoolThreadHandler.acquire(); 
    } catch (InterruptedException e) 
    { 
    } 
    mPoolThreadHandler.sendEmptyMessage(0x110); 
  } 

mPoolThreadHandler = new Handler() 
        { 
          @Override 
          public void handleMessage(Message msg) 
          { 
            // 线程池去取出一个任务进行执行 
            mThreadPool.execute(getTask()); 

/** 
   * 从任务队列取出一个方法 
   * 
   * @return 
   */ 
  private Runnable getTask() 
  { 
    if (mType == Type.FIFO) 
    { 
      return mTaskQueue.removeFirst(); 
    } else if (mType == Type.LIFO) 
    { 
      return mTaskQueue.removeLast(); 
    } 
    return null; 
  } 

/** 
   * 根据传入的参数，新建一个任务 
   * 
   * @param path 
   * @param imageView 
   * @param isFromNet 
   * @return 
   */ 
  private Runnable buildTask(final String path, final ImageView imageView, 
      final boolean isFromNet) 
  { 
    return new Runnable() 
    { 
      @Override 
      public void run() 
      { 
        Bitmap bm = null; 
        if (isFromNet) 
        { 
          File file = getDiskCacheDir(imageView.getContext(), 
              md5(path)); 
          if (file.exists())// 如果在缓存文件中发现 
          { 
            Log.e(TAG, "find image :" + path + " in disk cache ."); 
            bm = loadImageFromLocal(file.getAbsolutePath(), 
                imageView); 
          } else 
          { 
            if (isDiskCacheEnable)// 检测是否开启硬盘缓存 
            { 
              boolean downloadState = DownloadImgUtils 
                  .downloadImgByUrl(path, file); 
              if (downloadState)// 如果下载成功 
              { 
                Log.e(TAG, 
                    "download image :" + path 
                        + " to disk cache . path is " 
                        + file.getAbsolutePath()); 
                bm = loadImageFromLocal(file.getAbsolutePath(), 
                    imageView); 
              } 
            } else 
            // 直接从网络加载 
            { 
              Log.e(TAG, "load image :" + path + " to memory."); 
              bm = DownloadImgUtils.downloadImgByUrl(path, 
                  imageView); 
            } 
          } 
        } else 
        { 
          bm = loadImageFromLocal(path, imageView); 
        } 
        // 3、把图片加入到缓存 
        addBitmapToLruCache(path, bm); 
        refreashBitmap(path, imageView, bm); 
        mSemaphoreThreadPool.release(); 
      } 
 
       
    }; 
  } 
   
  private Bitmap loadImageFromLocal(final String path, 
      final ImageView imageView) 
  { 
    Bitmap bm; 
    // 加载图片 
    // 图片的压缩 
    // 1、获得图片需要显示的大小 
    ImageSize imageSize = ImageSizeUtil.getImageViewSize(imageView); 
    // 2、压缩图片 
    bm = decodeSampledBitmapFromPath(path, imageSize.width, 
        imageSize.height); 
    return bm; 
  } 

/** 
   * 将图片加入LruCache 
   * 
   * @param path 
   * @param bm 
   */ 
  protected void addBitmapToLruCache(String path, Bitmap bm) 
  { 
    if (getBitmapFromLruCache(path) == null) 
    { 
      if (bm != null) 
        mLruCache.put(path, bm); 
    } 
  } 

package com.example.demo_zhy_18_networkimageloader; 
import android.content.Context; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.GridView; 
import android.widget.ImageView; 
 
import com.zhy.utils.ImageLoader; 
import com.zhy.utils.ImageLoader.Type; 
import com.zhy.utils.Images; 
 
public class ListImgsFragment extends Fragment 
{ 
  private GridView mGridView; 
  private String[] mUrlStrs = Images.imageThumbUrls; 
  private ImageLoader mImageLoader; 
 
  @Override 
  public void onCreate(Bundle savedInstanceState) 
  { 
    super.onCreate(savedInstanceState); 
    mImageLoader = ImageLoader.getInstance(3, Type.LIFO); 
  } 
 
  @Override 
  public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) 
  { 
    View view = inflater.inflate(R.layout.fragment_list_imgs, container, 
        false); 
    mGridView = (GridView) view.findViewById(R.id.id_gridview); 
    setUpAdapter(); 
    return view; 
  } 
 
  private void setUpAdapter() 
  { 
    if (getActivity() == null || mGridView == null) 
      return; 
 
    if (mUrlStrs != null) 
    { 
      mGridView.setAdapter(new ListImgItemAdaper(getActivity(), 0, 
          mUrlStrs)); 
    } else 
    { 
      mGridView.setAdapter(null); 
    } 
 
  } 
 
  private class ListImgItemAdaper extends ArrayAdapter<String> 
  { 
 
    public ListImgItemAdaper(Context context, int resource, String[] datas) 
    { 
      super(getActivity(), 0, datas); 
      Log.e("TAG", "ListImgItemAdaper"); 
    } 
 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) 
    { 
      if (convertView == null) 
      { 
        convertView = getActivity().getLayoutInflater().inflate( 
            R.layout.item_fragment_list_imgs, parent, false); 
      } 
      ImageView imageview = (ImageView) convertView 
          .findViewById(R.id.id_img); 
      imageview.setImageResource(R.drawable.pictures_no); 
      mImageLoader.loadImage(getItem(position), imageview, true); 
      return convertView; 
    } 
 
  } 
 
} 

<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:id="@+id/id_gridview" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  android:horizontalSpacing="3dp" 
  android:verticalSpacing="3dp" 
  android:numColumns="3" 
  > 
 
</GridView> 
item_fragment_list_imgs.xml

<ImageView xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:id="@+id/id_img" 
  android:layout_width="match_parent" 
  android:layout_height="120dp" 
  android:scaleType="centerCrop" > 
 
</ImageView>