Android编程图片加载类ImageLoader定义与用法实例分析

/** * @描述 图片加载类 * @项目名称 App_News * @包名 com.android.news.tools * @类名 ImageLoader * @author chenlin * @date 2015-3-7 下午7:35:28 * @version 1.0 */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();  }  public static ImageLoader getInstance() {    if (mInstance == null) {      synchronized (ImageLoader.class) {        if (mInstance == null) {          mInstance = new ImageLoader(DEAFULT_THREAD_COUNT, Type.LIFO);        }      }    }    return mInstance;  }  public static ImageLoader getInstance(int threadCount, Type type) {    if (mInstance == null) {      synchronized (ImageLoader.class) {        if (mInstance == null) {          mInstance = new ImageLoader(threadCount, type);        }      }    }    return mInstance;  }  /**   * 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));    }  }  /**   * 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;  }  /**   * 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;  }  /**   * 利用签名辅助类，将字符串字节数组   *   * @param str   * @return   */  public String md5(String str) {    byte[] digest = null;    try {      MessageDigest md = MessageDigest.getInstance("md5");      digest = md.digest(str.getBytes());      return bytes2hex02(digest);    } catch (NoSuchAlgorithmException e) {      e.printStackTrace();    }    return null;  }  /**   * 方式二   *   * @param bytes   * @return   */  public String bytes2hex02(byte[] bytes) {    StringBuilder sb = new StringBuilder();    String tmp = null;    for (byte b : bytes) {      // 将每个字节与0xFF进行与运算，然后转化为10进制，然后借助于Integer再转化为16进制      tmp = Integer.toHexString(0xFF & b);      if (tmp.length() == 1)// 每个字节8为，转为16进制标志，2个16进制位      {        tmp = "0" + tmp;      }      sb.append(tmp);    }    return sb.toString();  }  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);    }  }  /**   * 根据图片需要显示的宽和高对图片进行压缩   *   * @param path   * @param width   * @param height   * @return   */  protected Bitmap decodeSampledBitmapFromPath(String path, 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);    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;  }  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);  }  /**   * 获得缓存图片的地址   *   * @param context   * @param uniqueName   * @return   */  public File getDiskCacheDir(Context context, String uniqueName) {    String cachePath;    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {      cachePath = context.getExternalCacheDir().getPath();    } else {      cachePath = context.getCacheDir().getPath();    }    return new File(cachePath + File.separator + uniqueName);  }  /**   * 根据path在缓存中获取bitmap   *   * @param key   * @return   */  private Bitmap getBitmapFromLruCache(String key) {    return mLruCache.get(key);  }  private class ImgBeanHolder {    Bitmap bitmap;    ImageView imageView;    String path;  }}

/** * @描述 获取图片大小工具类s * @项目名称 App_News * @包名 com.android.news.util * @类名 ImageSizeUtil * @author chenlin * @date 2014-3-7 下午7:37:50 * @version 1.0 */public class ImageSizeUtil {  /**   * 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;  }  /**   * 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 (lp != null) {      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 (lp != null) {      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 {    public int width;    public int height;  }  /**   * 通过反射获取imageview的某个属性值   *   * @param object   * @param fieldName   * @return   */  private static int getImageViewFieldValue(Object object, String fieldName) {    int value = 0;    try {      Field field = ImageView.class.getDeclaredField(fieldName);      field.setAccessible(true);      int fieldValue = field.getInt(object);      if (fieldValue > 0 && fieldValue < Integer.MAX_VALUE) {        value = fieldValue;      }    } catch (Exception e) {    }    return value;  }}