android平台UniversalImageLoader(异步加载大量图片)

public class ImagePagerActivity extends BaseActivity
{

	private ViewPager pager;

	private DisplayImageOptions options;

	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);

		setContentView(R.layout.ac_image_pager);
		Bundle bundle = getIntent().getExtras();
		String[] imageUrls = bundle.getStringArray(Extra.IMAGES);
		int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);

		options = new DisplayImageOptions.Builder()
				.showImageForEmptyUri(R.drawable.image_for_empty_url)
				.cacheOnDisc().imageScaleType(ImageScaleType.EXACT).build();

		pager = (ViewPager) findViewById(R.id.pager);
		pager.setAdapter(new ImagePagerAdapter(imageUrls));
		pager.setCurrentItem(pagerPosition);
	}

	@Override
	protected void onStop()
	{
		imageLoader.stop();
		super.onStop();
	}

	private class ImagePagerAdapter extends PagerAdapter
	{

		private String[] images;
		private LayoutInflater inflater;

		ImagePagerAdapter(String[] images)
		{
			this.images = images;
			inflater = getLayoutInflater();
		}

		@Override
		public void destroyItem(View container, int position, Object object)
		{
			((ViewPager) container).removeView((View) object);
		}

		@Override
		public void finishUpdate(View container)
		{
		}

		@Override
		public int getCount()
		{
			return images.length;
		}

		@Override
		public Object instantiateItem(View view, int position)
		{
			final FrameLayout imageLayout = (FrameLayout) inflater.inflate(
					R.layout.item_pager_image, null);
			final ImageView imageView = (ImageView) imageLayout
					.findViewById(R.id.image);
			final ProgressBar spinner = (ProgressBar) imageLayout
					.findViewById(R.id.loading);

			imageLoader.displayImage(images[position], imageView, options,
					new ImageLoadingListener()
					{
						@Override
						public void onLoadingStarted()
						{
							spinner.setVisibility(View.VISIBLE);
						}

						@Override
						public void onLoadingFailed(FailReason failReason)
						{
							String message = null;
							switch (failReason)
							{
							case IO_ERROR:
								message = "Input/Output error";
								break;
							case OUT_OF_MEMORY:
								message = "Out Of Memory error";
								break;
							case UNKNOWN:
								message = "Unknown error";
								break;
							}
							Toast.makeText(ImagePagerActivity.this, message,
									Toast.LENGTH_SHORT).show();

							spinner.setVisibility(View.GONE);
							imageView
									.setImageResource(android.R.drawable.ic_delete);
						}

						@Override
						public void onLoadingComplete()
						{
							spinner.setVisibility(View.GONE);
							Animation anim = AnimationUtils.loadAnimation(
									ImagePagerActivity.this, R.anim.fade_in);
							imageView.setAnimation(anim);
							anim.start();
						}

						@Override
						public void onLoadingCancelled()
						{
							// Do nothing
						}
					});

			((ViewPager) view).addView(imageLayout, 0);
			return imageLayout;
		}

		@Override
		public boolean isViewFromObject(View view, Object object)
		{
			return view.equals(object);
		}

		@Override
		public void restoreState(Parcelable state, ClassLoader loader)
		{
		}

		@Override
		public Parcelable saveState()
		{
			return null;
		}

		@Override
		public void startUpdate(View container)
		{
		}
	}
}