异步的图片加载代码,Java代码库,德仔网

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【Java】异步的图片加载
作者:fuweiping / 发布于2012/11/27/ 671
package com.ejoy.adpter;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;

import com.ejoy.utils.BitmapUtils;

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

public class AsyncBitmapLoader {
	/**
	 * 内存图片软引用缓冲
	 */
	private HashMap<String, SoftReference<Bitmap>> imageCache = null;

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

	protected String GetDatabasePath(String name) {
		String EXTERN_PATH = null;
		if (com.ejoy.FileServer.SDCardOperation.CanSdCardUse()) {
			EXTERN_PATH = android.os.Environment.getExternalStorageDirectory()
					.getAbsolutePath() + "/ejoy/cache/";
			File f = new File(EXTERN_PATH);
			if (!f.exists()) {
				f.mkdirs();
			}
		}
		if (name.trim() == "") {
			return EXTERN_PATH;
		} else {
			return EXTERN_PATH + name;
		}
	}

	public Bitmap loadBitmap(final ImageView imageView, final String imageURL,
			final ImageCallBack imageCallBack) {

		final Handler handler = new Handler() {
			@Override
			public void handleMessage(Message msg) {
				imageCallBack.imageLoad(imageView, (Bitmap) msg.obj);
			}
		};
		if (imageURL.trim() == "") {
			handler.sendMessage(handler.obtainMessage(0, null));
		}
		final String FileName = imageURL
				.substring(imageURL.lastIndexOf("/") + 1);

		// 在内存缓存中，则返回Bitmap对象
		if (imageCache.containsKey(imageURL)) {
			SoftReference<Bitmap> reference = imageCache.get(imageURL);
			Bitmap bitmap = reference.get();
			if (bitmap != null) {
				handler.sendMessage(handler.obtainMessage(0, bitmap));
				return bitmap;
			}
		} else {
			/**
			 * 加上一个对本地缓存的查找
			 */
			File cacheDir = new File(GetDatabasePath(""));
			File[] cacheFiles = cacheDir.listFiles();
			int i = 0;
			int j = cacheFiles.length;
			for (; i < j; i++) {
				if (FileName.equals(cacheFiles[i].getName())
						&& cacheFiles[i].length() > 0) {
					break;
				}
			}
			if (i < cacheFiles.length) {
				String path = GetDatabasePath(FileName);
				Bitmap bitmap;
				try {
					bitmap = BitmapUtils.getBitmapByPath(path,
							BitmapUtils.getOptions(path), 90, 90);
				} catch (FileNotFoundException e) {
					bitmap = null;
				}
				handler.sendMessage(handler.obtainMessage(0, bitmap));
				return bitmap;
			}
		}

		// 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() {
				URL url;
				Bitmap bitmap = null;
				try {
					if (imageURL.trim() != "" && FileName.trim() != "") {
						url = new URL(imageURL);
						URLConnection conn = url.openConnection();
						conn.setDoInput(true);
						conn.connect();
						InputStream bitmapIs = conn.getInputStream();
						bitmap = BitmapFactory.decodeStream(bitmapIs);
						imageCache.put(imageURL, new SoftReference<Bitmap>(
								bitmap));
						File bitmapFile = new File(GetDatabasePath(FileName));
						if (!bitmapFile.isDirectory()) {
							if (!bitmapFile.exists()) {
								bitmapFile.createNewFile();
							} else {
								if (bitmapFile.length() == 0) {
									bitmapFile.delete();
									bitmapFile.createNewFile();
								}
							}
							FileOutputStream fos;
							try {
								fos = new FileOutputStream(bitmapFile);
								if (fos != null) {
									bitmap.compress(Bitmap.CompressFormat.JPEG,
											100, fos);
									fos.close();
								}
							} catch (FileNotFoundException e) {
							} catch (IOException e) {
								e.printStackTrace();
							}
						}
						bitmapIs.close();
					} else {
					}
				} catch (FileNotFoundException e) {
				} catch (Exception e1) {
					e1.printStackTrace();
				}
				Message msg = handler.obtainMessage(0, bitmap);
				handler.sendMessage(msg);
			}
		}.start();

		return null;
	}

	/**
	 * 回调接口
	 * 
	 * @author onerain
	 * 
	 */
	public interface ImageCallBack {
		public void imageLoad(ImageView imageView, Bitmap bitmap);
	}
}
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