开源项目之UniversalImageLoader(异步加载大量图片)

UniversalImageLoader是实现异步加载大量图片的源码和例子，包括缓存、硬盘缓存、容错机制等技术。

项目如图：





测试效果如图：



总共有四种格式效果！

第一种ImageList，效果如图：



关键测试代码如下：

public class ImageListActivity extends BaseActivity
{

	private String[] imageUrls;

	private DisplayImageOptions options;

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.ac_image_list);

		Bundle bundle = getIntent().getExtras();
		imageUrls = bundle.getStringArray(Extra.IMAGES);

		options = new DisplayImageOptions.Builder()
				.showStubImage(R.drawable.stub_image).cacheInMemory()
				.cacheOnDisc().build();

		ListView listView = (ListView) findViewById(android.R.id.list);
		listView.setAdapter(new ItemAdapter());
		listView.setOnItemClickListener(new OnItemClickListener()
		{
			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id)
			{
				startImageGalleryActivity(position);
			}
		});
	}

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

	private void startImageGalleryActivity(int position)
	{
		Intent intent = new Intent(this, ImagePagerActivity.class);
		intent.putExtra(Extra.IMAGES, imageUrls);
		intent.putExtra(Extra.IMAGE_POSITION, position);
		startActivity(intent);
	}

	class ItemAdapter extends BaseAdapter
	{

		private class ViewHolder
		{
			public TextView text;
			public ImageView image;
		}

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

		@Override
		public Object getItem(int position)
		{
			return position;
		}

		@Override
		public long getItemId(int position)
		{
			return position;
		}

		@Override
		public View getView(final int position, View convertView,
				ViewGroup parent)
		{
			View view = convertView;
			final ViewHolder holder;
			if (convertView == null)
			{
				view = getLayoutInflater().inflate(R.layout.item_list_image,
						null);
				holder = new ViewHolder();
				holder.text = (TextView) view.findViewById(R.id.text);
				holder.image = (ImageView) view.findViewById(R.id.image);
				view.setTag(holder);
			} else
				holder = (ViewHolder) view.getTag();

			holder.text.setText("Item " + position);

			imageLoader
					.displayImage(imageUrls[position], holder.image, options);

			return view;
		}
	}
}

第二种ImageGrid效果！如图：



测试关键代码如下：

public class ImageGridActivity extends BaseActivity
{

	private String[] imageUrls;

	private DisplayImageOptions options;

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.ac_image_grid);

		Bundle bundle = getIntent().getExtras();
		imageUrls = bundle.getStringArray(Extra.IMAGES);

		options = new DisplayImageOptions.Builder()
				.showStubImage(R.drawable.stub_image)
				.showImageForEmptyUri(R.drawable.image_for_empty_url)
				.cacheInMemory().cacheOnDisc().build();

		GridView gridView = (GridView) findViewById(R.id.gridview);
		gridView.setAdapter(new ImageAdapter());
		gridView.setOnItemClickListener(new OnItemClickListener()
		{
			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id)
			{
				startImageGalleryActivity(position);
			}
		});
	}

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

	private void startImageGalleryActivity(int position)
	{
		Intent intent = new Intent(this, ImagePagerActivity.class);
		intent.putExtra(Extra.IMAGES, imageUrls);
		intent.putExtra(Extra.IMAGE_POSITION, position);
		startActivity(intent);
	}

	public class ImageAdapter extends BaseAdapter
	{
		@Override
		public int getCount()
		{
			return imageUrls.length;
		}

		@Override
		public Object getItem(int position)
		{
			return null;
		}

		@Override
		public long getItemId(int position)
		{
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent)
		{
			final ImageView imageView;
			if (convertView == null)
			{
				imageView = (ImageView) getLayoutInflater().inflate(
						R.layout.item_grid_image, parent, false);
			} else
			{
				imageView = (ImageView) convertView;
			}

			imageLoader.displayImage(imageUrls[position], imageView, options,
					new SimpleImageLoadingListener()
					{
						@Override
						public void onLoadingComplete()
						{
							Animation anim = AnimationUtils.loadAnimation(
									ImageGridActivity.this, R.anim.fade_in);
							imageView.setAnimation(anim);
							anim.start();
						}
					});

			return imageView;
		}
	}
}

第三种ImagePager效果，如图：



测试关键实现如下：

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)
		{
		}
	}
}

第四种ImageGallery效果如图：



测试关键代码：

public class ImageGalleryActivity extends BaseActivity
{

	private Gallery gallery;

	private DisplayImageOptions options;

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

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

		options = new DisplayImageOptions.Builder()
				.showImageForEmptyUri(R.drawable.image_for_empty_url)
				.showStubImage(R.drawable.stub_image).cacheInMemory()
				.cacheOnDisc().build();

		gallery = (Gallery) findViewById(R.id.gallery);
		gallery.setAdapter(new ImagePagerAdapter(imageUrls));
		gallery.setSelection(galleryPosition);
	}

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

	private class ImagePagerAdapter extends BaseAdapter
	{

		private String[] images;
		private LayoutInflater inflater;

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

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

		@Override
		public Object getItem(int position)
		{
			return position;
		}

		@Override
		public long getItemId(int position)
		{
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent)
		{
			ImageView imageView = (ImageView) convertView;
			if (imageView == null)
			{
				imageView = (ImageView) inflater.inflate(
						R.layout.item_gallery_image, parent, false);
			}
			imageLoader.displayImage(images[position], imageView, options);
			return imageView;
		}
	}
}

实例中通过imageLoader成员负责图片操作！初始化如下：

protected ImageLoader imageLoader = ImageLoader.getInstance();

此处主要是围绕UniversalImageLoader使用的介绍！~代码不难。

学习的目标是成熟！~

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