Android Image loader

Question

请在我的图像加载器中帮助它加载图像需要几秒钟，那时我需要在图像视图的中间显示进度条，请帮助我

请参阅代码

在我的课程中，我正在以这种方式调用图像加载器

    public ImageLoader imageLoader = new ImageLoader(this);     
    imageLoader.DisplayImage1(imagepath, image_view); 





   public class ImageLoader {

MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService; 
private int stub_id=R.drawable.head_icon;
public ImageLoader(Context context){
    fileCache=new FileCache(context);
    executorService=Executors.newFixedThreadPool(5);
}


public void DisplayImage(String url, ImageView imageView)
{
    imageViews.put(imageView, url);
    Bitmap bitmap=memoryCache.get(url);
    if(bitmap!=null)
        imageView.setImageBitmap((getRoundedCornerImage(bitmap)));
    else
    {
        queuePhoto(url, imageView);
        imageView.setImageResource(stub_id);
    }
}


public void DisplayImage1(String url, ImageView imageView)
{
    imageViews.put(imageView, url);
    Bitmap bitmap=memoryCache.get(url);
    if(bitmap!=null)
        imageView.setImageBitmap(((bitmap)));
    else
    {
        queuePhoto(url, imageView);
        imageView.setImageResource(stub_id);
    }
}



private void queuePhoto(String url, ImageView imageView)
{
    PhotoToLoad p=new PhotoToLoad(url, imageView);
    executorService.submit(new PhotosLoader(p));
}

private Bitmap getBitmap(String url) 
{
    File f=fileCache.getFile(url);

    //from SD cache
    Bitmap b = decodeFile(f);
    if(b!=null)
        return b;

    //from web
    try {
        Bitmap bitmap=null;
        URL imageUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
        conn.setConnectTimeout(30000);
        conn.setReadTimeout(30000);
        conn.setInstanceFollowRedirects(true);
        InputStream is=conn.getInputStream();
        OutputStream os = new FileOutputStream(f);
        Utils.CopyStream(is, os);
        os.close();
        bitmap = decodeFile(f);
        return bitmap;
    } catch (Exception ex){
       ex.printStackTrace();
       return null;
    }
}

//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){
    try {
        //decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f),null,o);

        //Find the correct scale value. It should be the power of 2.
        final int REQUIRED_SIZE=70;
        int width_tmp=o.outWidth, height_tmp=o.outHeight;
        int scale=1;
        while(true){
            if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                break;
            width_tmp/=2;
            height_tmp/=2;
            scale*=2;
        }

        //decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize=scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
    return null;
}

//Task for the queue
private class PhotoToLoad
{
    public String url;
    public ImageView imageView;
    public PhotoToLoad(String u, ImageView i){
        url=u; 
        imageView=i;
    }
}

class PhotosLoader implements Runnable {
    PhotoToLoad photoToLoad;
    PhotosLoader(PhotoToLoad photoToLoad){
        this.photoToLoad=photoToLoad;
    }

    @Override
    public void run() {
        if(imageViewReused(photoToLoad))
            return;
        Bitmap bmp=getBitmap(photoToLoad.url);
        memoryCache.put(photoToLoad.url, bmp);
        if(imageViewReused(photoToLoad))
            return;
        BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
        Activity a=(Activity)photoToLoad.imageView.getContext();
        a.runOnUiThread(bd);
    }
}

boolean imageViewReused(PhotoToLoad photoToLoad){
    String tag=imageViews.get(photoToLoad.imageView);
    if(tag==null || !tag.equals(photoToLoad.url))
        return true;
    return false;
}

//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
    Bitmap bitmap;
    PhotoToLoad photoToLoad;
    public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
    @Override
    public void run()
    {
        if(imageViewReused(photoToLoad))
            return;
        if(bitmap!=null)
            photoToLoad.imageView.setImageBitmap(((bitmap)));
        else
            photoToLoad.imageView.setImageResource(stub_id);
    }
}

public void clearCache() {
    memoryCache.clear();
    fileCache.clear();
}



  }

Answer 1

不要重新发明轮子。例如，使用AQuery：

String imageUrl = "http://farm6.static.flickr.com/5035/5802797131_a729dac808_b.jpg";    

aq.id(R.id.image).progress(R.id.progress).image(imageUrl, false, false);

http://code.google.com/p/android-query/wiki/ImageLoading