UniversalImageLoader

GitHub社区开源项目，图片加载工具，该项目的地址为：

https://github.com/nostra13/Android-Universal-Image-Loader

该项目实现了内存缓存和磁盘缓存两种方式保存和加载图片，可以用来处理图片过多时导致的内存溢出问题。

该项目的基本结构：

在使用ImageLoader之前先通过ImageLoaderConfiguration配置：

// This configuration tuning is custom. You can tune every option, you
		// may tune some of them,
		// or you can create default configuration by
		// ImageLoaderConfiguration.createDefault(this);
		// method.
		ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(
				context).threadPriority(Thread.NORM_PRIORITY - 2)
				.denyCacheImageMultipleSizesInMemory()
				.discCacheFileNameGenerator(new Md5FileNameGenerator())
				.tasksProcessingOrder(QueueProcessingType.LIFO)
				.writeDebugLogs() // Remove for release app
				.build();
		// Initialize ImageLoader with configuration.
		ImageLoader.getInstance().init(config);

然后设置图片显示选项：

options = new DisplayImageOptions.Builder()
				.showImageOnLoading(R.drawable.ic_stub)
				.showImageForEmptyUri(R.drawable.ic_empty)
				.showImageOnFail(R.drawable.ic_error).cacheInMemory(true)
				.cacheOnDisc(true).bitmapConfig(Bitmap.Config.RGB_565).build();

显示图片：

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

总体代码如下：

package com.sun.uidemo;

import android.annotation.TargetApi;
import android.app.Application;
import android.content.Context;
import android.os.Build;
import android.os.StrictMode;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;
import com.sun.uidemo.Constants.Config;

/**
 * @author Sergey Tarasevich (nostra13[at]gmail[dot]com)
 */
public class UILApplication extends Application {
	@TargetApi(Build.VERSION_CODES.GINGERBREAD)
	@SuppressWarnings("unused")
	@Override
	public void onCreate() {
		if (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) {
		// This configuration tuning is custom. You can tune every option, you
		// may tune some of them,
		// or you can create default configuration by
		// ImageLoaderConfiguration.createDefault(this);
		// method.
		ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(
				context).threadPriority(Thread.NORM_PRIORITY - 2)
				.denyCacheImageMultipleSizesInMemory()
				.discCacheFileNameGenerator(new Md5FileNameGenerator())
				.tasksProcessingOrder(QueueProcessingType.LIFO)
				.writeDebugLogs() // Remove for release app
				.build();
		// Initialize ImageLoader with configuration.
		ImageLoader.getInstance().init(config);
	}
}

package com.sun.uidemo;

import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class ImageActivity extends Activity {
	private ImageLoader imageLoader = ImageLoader.getInstance();
	private DisplayImageOptions options;
	private GridView gv;
	private String[] imageUrls;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.image_layout);

		gv = (GridView) this.findViewById(R.id.imageDisplay);
		imageUrls = Constants.IMAGES;
		options = new DisplayImageOptions.Builder()
				.showImageOnLoading(R.drawable.ic_stub)
				.showImageForEmptyUri(R.drawable.ic_empty)
				.showImageOnFail(R.drawable.ic_error).cacheInMemory(true)
				.cacheOnDisc(true).bitmapConfig(Bitmap.Config.RGB_565).build();
		gv.setAdapter(new ImageAdapter());
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		getMenuInflater().inflate(R.menu.image_menu, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		switch (item.getItemId()) {
		case R.id.item_clear_memory_cache:
			imageLoader.clearMemoryCache();
			return true;
		case R.id.item_clear_disc_cache:
			imageLoader.clearDiscCache();
			return true;
		default:
			return false;
		}
	}

	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;
			}
			//为指定的ImageView设置图片
			imageLoader.displayImage(imageUrls[position], imageView, options);
			return imageView;
		}
	}
}

效果如下：

基本的使用方法就是这样，如果想了解更多，可以具体去分析一下源代码。