listview异步加载sd卡图片

package com.example.gridview;

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

import android.annotation.SuppressLint;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.ImageView;


@SuppressLint("HandlerLeak")
public class AsyncBitmapLoader{

        /**
         * 内存图片软引用缓
         */
        @SuppressWarnings("rawtypes")
        private final HashMap<String, SoftReference> imageCache = new HashMap<String, SoftReference>();

        @SuppressWarnings("rawtypes")
        public Bitmap loadBitmap(final ImageView imageView, final String imageURL, final ImageCallBack imageCallBack){

                SoftReference reference = imageCache.get(imageURL);

                //在内存缓存中，则返回Bitmap对象
                if (null != reference && null != reference.get()) {
                        return (Bitmap) reference.get();
                } else {

                        if (null != reference) {
                                imageCache.remove(reference);
                        }
                        // 加上一个对本地缓存的查找
                        String bitmapName = toTransverseLine(imageURL.substring(imageURL.indexOf("//") + 2));

                        File cacheDir = new File("/mnt/sdcard/text/");
                        File[] cacheFiles = cacheDir.listFiles();
                        int i = 0;

                        if (null != cacheFiles) {
                                for (i = 0; i < cacheFiles.length;i++ ){
                                        if (bitmapName.equals(cacheFiles[i].getName())) {
                                                break;
                                        }
                                }

                                if (i < cacheFiles.length) {
                                        return BitmapFactory.decodeFile("/mnt/sdcard/text/" + bitmapName); 
                                }

                        }

                }

                final Handler handler = new Handler(){
                        public void handleMessage(Message msg){
                                imageCallBack.imageLoad(imageView, (Bitmap)msg.obj);
                        }
                };

                //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(){
                        public void run(){
                                InputStream bitmapIs = getStreamFromURL(imageURL);
                                Bitmap bitmap = BitmapFactory.decodeStream(bitmapIs);

                                if (bitmap == null ) {
                                        return ;
                                }

                                imageCache.put(imageURL, new SoftReference(bitmap));
                                Message msg = handler.obtainMessage(0, bitmap);
                                handler.sendMessage(msg);

                                File dir = new File("/mnt/sdcard/text/");

                                if (!dir.exists()) {
                                        dir.mkdirs();
                                }

                                // 下载图片保存到指定路径
                                String path = "/mnt/sdcard/text/" +
                                                toTransverseLine(imageURL.substring(imageURL.indexOf("//") + 2));

                                String path1 = "/mnt/sdcard/image/";

                                File bitmapFile = new File(path);
                                FileOutputStream fos = null;

                                if (!bitmapFile.exists()) {
                                        try{
                                                bitmapFile.createNewFile();
                                                fos = new FileOutputStream(bitmapFile);
                                                bitmap.compress(Bitmap.CompressFormat.PNG,100, fos);
                                        }catch (IOException e) {
                                                e.printStackTrace();
                                        }finally {
                                                try {
                                                        if (fos != null) {
                                                                fos.close();
                                                        }

                                                } catch (IOException e) {
                                                        e.printStackTrace();
                                                }
                                        }
                                }
                        }
                }.start();

                return null;
        }

        /**
         * 转换名称保存
         * @param url
         * @return
         */
        private String toTransverseLine(String url) {
                String name1 = url.replaceAll("/", "_");
                String name2 = name1.replaceAll("\\.", "_");
                String name3 = name2.replaceAll("\\:", "_");
                return name3;
        }

        public interface ImageCallBack{
                public void imageLoad(ImageView imageView, Bitmap bitmap);
        }
        
        
        /**
         * 通过url请求图片
         * @return
         */
        public static InputStream getStreamFromURL(String imageURL) { 
                InputStream in=null;
                try {
                        if (imageURL != null && !imageURL.equals("")) {
                                URL url=new URL(imageURL); 
                                HttpURLConnection connection=(HttpURLConnection) url.openConnection();   
                                in=connection.getInputStream();
                        }
                } catch (Exception e) {
                        e.printStackTrace(); 
                } 
                return in;
        }

        
        // =======================下边是调用 写在activity中========================
        private String mNewsPicUrl;        // 新闻图片的url
        private AsyncBitmapLoader asyncBitmapLoader;        // 异步加载
        private ImageView mHeadImage;
        
        /**
         * 显示图片
         * 
         */
        private void showImage() {

                if (mNewsPicUrl != null && !mNewsPicUrl.equals("")) {
                        Bitmap bitmap = asyncBitmapLoader.loadBitmap(mHeadImage, mNewsPicUrl, new ImageCallBack() {
                                public void imageLoad(ImageView imageView, Bitmap bitmap) {
                                        imageView.setImageBitmap(bitmap);
                                }
                        });

                        if (bitmap != null) {
                                mHeadImage.setImageBitmap(bitmap);
                        }else {
                                //                                mHeadImage.setVisibility(View.GONE);
                        }
                }else {
                        mHeadImage.setVisibility(View.GONE);
                }
        }
        
}