/**
  * 注意: 次构造器不支持下载进度提示功能
  * @param context
  * @param withCache 是否支持缓存
  *     false--不带缓存
  *     true--支持缓存功能，默认缓存路径在外置存储缓冲目录中的picasso-big-cache文件夹中
  */
 public ImageLoader(Context context, boolean withCache) {
  this(context, null, withCache);
 }

 /**
  * 支持下载进度提示，以及设置缓存路径
  * @param context
  * @param listener 下载进度监听器
  * @param cachePath 缓存路径字符串
  */
 public ImageLoader(Context context, ProgressListener listener, String cachePath) {
  // TODO extend to support multiple libraries as Glide
  // TODO must be initialized and kept as an member instance to avoid losing cache
  Picasso.Builder builder = setupLoaderClientWithCachePath(context, listener, cachePath);
  setupListener(builder);

  picasso = builder.build();
  picasso.setIndicatorsEnabled(BuildConfig.DEBUG);
  picasso.setLoggingEnabled(BuildConfig.DEBUG);
 }

 /**
  * 支持下载进度提示，以及设置缓存路径为默认路径picasso-big-cache
  * @param context
  * @param listener 下载进度监听器
  * @param withCache 是否支持缓存
  */
 public ImageLoader(Context context, ProgressListener listener, boolean withCache) {
  // TODO extend to support multiple libraries as Glide
  // TODO must be initialized and kept as an member instance to avoid losing cache
  Picasso.Builder builder = setupLoaderClient(context, listener, withCache);
  setupListener(builder);

  picasso = builder.build();
  picasso.setIndicatorsEnabled(BuildConfig.DEBUG);
  picasso.setLoggingEnabled(BuildConfig.DEBUG);
 }

public void shutdown() {
  if (picasso == null) return;

  Logger.d(Logger.TAG, "Image loader has been shutdown");
  picasso.shutdown();
  callback = null;
 }

public ImageLoader cancelRequest(ImageView imageView) {
  picasso.cancelRequest(imageView);
  return this;
 }

public ImageLoader load(final int resourceId) {
  cleanResources();
  this.imageResourceId = resourceId;
  return this;
 }

public ImageLoader load(final String imageUri) {
  cleanResources();
  this.imageUri = imageUri;
  return this;
 }

public ImageLoader withPlaceholder(final int placeholder) {
  this.placeholder = placeholder;
  return this;
 }

public ImageLoader withErrorImage(final int errorImage) {
  this.errorImage = errorImage;
  return this;
 }

public ImageLoader withTag(final String tag) {
  this.tag = tag;
  return this;
 }

public void pause(final String tag) {
  if (picasso == null) return;

  picasso.pauseTag(tag);
 }

public void resume(final String tag) {
  if (picasso == null) return;

  picasso.resumeTag(tag);
 }

public ImageLoader withCallback(final Callback callback) {
  this.callback = callback;
  return this;
 }

public ImageLoader fit() {
  this.fit = true;
  return this;
 }

 public ImageLoader centerCrop() {
  this.centerCrop = true;
  return this;
 }

 public ImageLoader centerInside() {
  this.centerInside = true;
  return this;
 }

 public ImageLoader resize(final int widthResId, final int heightResId) {
  this.widthResId = widthResId;
  this.heigthResId = heightResId;
  return this;
 }

public void into(final ImageView imageView) {
  run(imageView);
 }