Question

我正在使用imageLoader类从url加载图片。但是那些所有图像都通过名为LazyList的文件夹名称存储在库中。它需要高达40 -100 MB的内存。但我不想加载图像，因为用户可能会感到不适。抱歉英语不好。

一切正常，但它会在图库中创建一个文件夹，并显示我的应用使用的所有图片。所以我觉得用户会觉得用户不舒服。

这是我的imageloader代码，它甚至与其他几个类链接

public class ImageLoader {
MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews = Collections
        .synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;

public ImageLoader(Context context) {
    fileCache = new FileCache(context);
    executorService = Executors.newFixedThreadPool(5);
}

final int stub_id = R.drawable.abs__ab_bottom_transparent_light_holo;

public void DisplayImage(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 = 100;
        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;
    }

    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

我通过更改FileCache类及其目标文件夹

来获得解决方案

public class FileCache {
    private File cacheDir;
    private File nomediaFile;
    String NOMEDIA = " .nomedia";
public FileCache(Context context) {
    // Find the dir to save cached images
    if (android.os.Environment.getExternalStorageState().equals(
            android.os.Environment.MEDIA_MOUNTED)) {
        cacheDir = new File(Environment.getExternalStorageDirectory()
                + "/mydir");
        if (cacheDir.mkdir()) {
            nomediaFile = new File(
                    Environment.getExternalStorageDirectory() + "/mydir/"
                            + NOMEDIA);
            if (!nomediaFile.exists()) {
                try {
                    nomediaFile.createNewFile();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    } else {
        cacheDir = context.getCacheDir();
    }
    if (!cacheDir.exists())
        cacheDir.mkdirs();
}

public File getFile(String url) {
    // I identify images by hashcode. Not a perfect solution, good for the
    // demo.
    // String filename=String.valueOf(url.hashCode());
    // Another possible solution (thanks to grantland)
    @SuppressWarnings("deprecation")
    String filename = URLEncoder.encode(url);
    File f = new File(cacheDir, filename);
    return f;

}

public void clear() {
    File[] files = cacheDir.listFiles();
    if (files == null)
        return;
    for (File f : files)
        f.delete();
}
}

Answer 2

您可以使用droidQuery库延迟从URL加载图像，然后基于每个会话缓存它们。您还可以处理自己的缓存，例如SharedPreferences或SQLite数据库。要下载图像，请使用长手法：

$.ajax(new AjaxOptions().url("http://www.example.com")
                        .type("GET")
                        .dataType("image")
                        .timeout(30000)
                        .cache(true)
                        .cacheTimeout(600000)//milliseconds
                        //consider using .imageWidth() or .imageHeight() methods to control output size
                        .success(new Function() {
                            @Override
                            public void invoke($ droidQuery, Object... params) {
                                myImageView.setImageBitmap((Bitmap) params[0]);
                                //save raw bitmap across sessions, maybe.
                            }
                        });

要将数据保存到数据库或 SharedPreferences ，请仔细阅读文档：http://developer.android.com/guide/topics/data/data-storage.html

Imageloader类在库中创建lazylist文件夹。如何避免它

2 个答案: