Androidの開源架構ImageLoader的完美使用

Androidの開源架構ImageLoader的完美使用 1.  很多人都在讨論如何讓圖檔能在異步加載更加流暢，可以顯示大量圖檔，在拖動ListView的時候不會出現卡的現象。 關于ImageLoader這個開源架構的使用有很多網友都介紹過，不過還不夠清楚，這裡有一個關于這個開源項目的完美例子，ListView的圖檔加載、GridView的圖檔加載、ViewPager的圖檔加載、Gallery畫廊的圖檔加載、Widget的使用。很完善的一個例子，在這裡我把所有界面效果做出部落格分享出來，需要源碼的朋友到我的資源頁下載下傳

2. 實作ListView 圖檔加載    首先加載一個application 類 ，主要加載ImageLoader

public class UILApplication extends Application {
	@TargetApi(Build.VERSION_CODES.GINGERBREAD)
	@SuppressWarnings("unused")
	@Override
	public void onCreate() {
		if (Constants.Config.DEVELOPER_MODE && Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
			StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectAll().penaltyDialog().build());
			StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectAll().penaltyDeath().build());
		}
		super.onCreate();
		initImageLoader(getApplicationContext());
	}

	public static void initImageLoader(Context context) {
		ImageLoaderConfiguration.Builder config = new ImageLoaderConfiguration.Builder(context);
		config.threadPriority(Thread.NORM_PRIORITY - 2);
		config.denyCacheImageMultipleSizesInMemory();
		config.diskCacheFileNameGenerator(new Md5FileNameGenerator());
		config.diskCacheSize(50 * 1024 * 1024); // 50 MiB
		config.tasksProcessingOrder(QueueProcessingType.LIFO);
		config.writeDebugLogs(); // Remove for release app
		// Initialize ImageLoader with configuration.
		ImageLoader.getInstance().init(config.build());
	}
}
           

  然後在listview中主類加載圖檔，如下

public class MainActivity extends Activity {

	String[] imageUrls = new String[] { };

	DisplayImageOptions options;
	private ListView listView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	
		//imageLoader.init(ImageLoaderConfiguration.createDefault(MainActivity.this));
		options = new DisplayImageOptions.Builder()
				.showImageOnLoading(R.drawable.ic_stub)
				.showImageForEmptyUri(R.drawable.ic_empty)
				.showImageOnFail(R.drawable.ic_error).cacheInMemory(true)
				.cacheOnDisk(true).considerExifParams(true)
				.displayer(new RoundedBitmapDisplayer(20)).build();

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

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

	class ImageAdapter extends BaseAdapter {
		private LayoutInflater inflater;
		private ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();

		ImageAdapter() {
			inflater = LayoutInflater.from(MainActivity.this);
		}

		@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 = inflater
						.inflate(R.layout.item_list_image, parent, false);
				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 + 1));
			ImageLoader.getInstance().displayImage(imageUrls[position],
					holder.image, options, animateFirstListener);
			return view;
		}
	}

	private static class AnimateFirstDisplayListener extends
			SimpleImageLoadingListener {

		static final List<String> displayedImages = Collections
				.synchronizedList(new LinkedList<String>());

		@Override
		public void onLoadingComplete(String imageUri, View view,
				Bitmap loadedImage) {
			if (loadedImage != null) {
				ImageView imageView = (ImageView) view;
				boolean firstDisplay = !displayedImages.contains(imageUri);
				if (firstDisplay) {
					FadeInBitmapDisplayer.animate(imageView, 500);
					displayedImages.add(imageUri);
				}
			}
		}
	}

}
           

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