Android 异步加载图片（扩展后）

import java.io.File;
import java.lang.ref.SoftReference;
import java.util.HashMap;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
import android.widget.ProgressBar;



public class AsyncBitmapLoader {
	/**
	 * 内存图片软引用缓冲
	 */

	private HashMap<String, SoftReference<Bitmap>> imageCache = null;
	private String localImagePath = "";

	public AsyncBitmapLoader(String localImagePath) {
		imageCache = new HashMap<String, SoftReference<Bitmap>>();
		this.localImagePath = localImagePath;

	}

	/**
	 * @param imageView
	 * @param progressBar
	 * @param imageURL
	 * @param imageCallBack
	 * @param position
	 *            list中第几项
	 * @param size
	 *            设定图片导出大小
	 * @param fromAct
	 *            "main"来自主界面， "detail"来自详情
	 * @return
	 */
	public Bitmap loadBitmap(final ImageView imageView, final ProgressBar progressBar, final String imageURL, final ImageCallBack imageCallBack,
			final int position, final int size, final String fromAct) {
		final String picName = imageURL.substring(imageURL.lastIndexOf("/") + 1);
		// 在内存缓存中，则返回Bitmap对象
		Bitmap bitmap = null;
		if (imageCache.containsKey(imageURL)) {
			SoftReference<Bitmap> reference = imageCache.get(imageURL);
			bitmap = reference.get();
			if (bitmap != null) {
				return bitmap;
			}
		}
		/**
		 * 加上一个对本地缓存的查找
		 */
		String bitmapName = picName;
		File cacheDir = new File(localImagePath);
		File[] cacheFiles = cacheDir.listFiles();
		int i = 0;
		for (; i < cacheFiles.length; i++) {
			if (bitmapName.equals(cacheFiles[i].getName())) {
				break;
			}
		}

		final Handler handler = new Handler() {
			@Override
			public void handleMessage(Message msg) {
				// TODO Auto-generated method stub
				if (msg.what == 0)
					imageCallBack.imageLoad(imageView, progressBar, (Bitmap) msg.obj, msg.arg1);
				else if (msg.what == 1) {
					imageCallBack.imageLoad(imageView, progressBar, msg.arg1, msg.arg2);
					// System.out.println(msg.arg1);
				}
			}
		};

		if (i < cacheFiles.length) {

			new Thread(new Runnable() {

				@Override
				public void run() {
					// TODO Auto-generated method stub
					Bitmap bitmap = null;
					BitmapFactory.Options options = new BitmapFactory.Options();
					options.inJustDecodeBounds = true;
					bitmap = BitmapFactory.decodeFile(localImagePath + picName, options); // 此时返回bm为空
					options.inJustDecodeBounds = false;
					int be = (int) (options.outHeight / (float) size);
					if (be <= 0)
						be = 1;

					if (fromAct.equals("detail")) {
						options.inSampleSize = be;
					} else {
						options.inSampleSize = be;
						options.inPurgeable = true;
						options.inInputShareable = true;
						options.inPreferredConfig = Bitmap.Config.ARGB_4444;
					}
					bitmap = BitmapFactory.decodeFile(localImagePath + picName, options);
					imageCache.put(imageURL, new SoftReference<Bitmap>(bitmap));
					imageCache.put(imageURL, new SoftReference<Bitmap>(bitmap));
					Message msg2 = handler.obtainMessage(0, position, position, bitmap);// 把自身位置传进去
					handler.sendMessage(msg2);
				}
			}).start();

			return null;
		}

		// 如果不在内存缓存中，也不在本地（被jvm回收掉），则开启线程下载图片
		new Thread() {
			@Override
			public void run() {
				// TODO Auto-generated method stub
				Bitmap bitmap = null;
				int i = 0;
				boolean downOk = false;
				handler.post(new Runnable() {
					@Override
					public void run() {
						Message msg = handler.obtainMessage(1, 0, position);
						handler.sendMessage(msg);
					}
				});
				// 下载
				while (i < 3) {
					if (MyHttpURLConnection_Util.downloadFile(imageURL, localImagePath + picName, null, new ProgressControl() {
						@Override
						public void messageControl(String str) {
						}

						@Override
						public void stepControl(final double j) {
							// TODO Auto-generated method stub
							Message msg = handler.obtainMessage(1, (int) j, position);
							handler.sendMessage(msg);
						}
					})) {
						downOk = true;
						break;
					}
					i++;
				}

				if (!downOk) {
					System.out.println("downFailed--" + imageURL);
					// Message msg1 = handler.obtainMessage(0, bitmap);
					// handler.sendMessage(msg1);
					return;
				}
				// 解码缩放
				BitmapFactory.Options options = new BitmapFactory.Options();
				options.inJustDecodeBounds = true;
				bitmap = BitmapFactory.decodeFile(localImagePath + picName, options); // 此时返回bm为空
				options.inJustDecodeBounds = false;
				int be = (int) (options.outHeight / (float) size);
				if (be <= 0)
					be = 1;
				if (fromAct.equals("detail")) {
					options.inSampleSize = be;
				} else {
					options.inSampleSize = be;
					options.inPurgeable = true;
					options.inInputShareable = true;
					options.inPreferredConfig = Bitmap.Config.ARGB_4444;
				}
				bitmap = BitmapFactory.decodeFile(localImagePath + picName, options);

				// 放入缓存
				imageCache.put(imageURL, new SoftReference<Bitmap>(bitmap));
				Message msg2 = handler.obtainMessage(0, position, position, bitmap);// 把自身位置传进去
				handler.sendMessage(msg2);

			}
		}.start();

		return null;
	}
}