android - 从解析加载后图像变得模糊。 com

Question

我的应用从 parse.com 加载图像。所以我创建了一个 imageloader.jàva 类来下载和显示图像。但是即使我在 parse.com 中添加 xxxhdpi，加载的图像也很模糊。我在图像加载器类中做错了吗

这是我的代码

图像加载器

public class ImageLoader {

MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews = Collections
.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
// Handler to display images in UI thread
Handler handler = new Handler();

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

final int stub_id = R.drawable.temp_img;

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);

    Bitmap b = decodeFile(f);
    if (b != null)
        return b;

    // Download Images from the Internet
    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();
        conn.disconnect();
        bitmap = decodeFile(f);
        return bitmap;
    } catch (Throwable ex) {
        ex.printStackTrace();
        if (ex instanceof OutOfMemoryError)
            memoryCache.clear();
        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;
        FileInputStream stream1 = new FileInputStream(f);
        BitmapFactory.decodeStream(stream1, null, o);
        stream1.close();

        // 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;
        FileInputStream stream2 = new FileInputStream(f);
        Bitmap bitmap = BitmapFactory.decodeStream(stream2, null, o2);
        stream2.close();
        return bitmap;
    } catch (FileNotFoundException e) {
    } catch (IOException e) {
        e.printStackTrace();
    }
    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() {
        try {
            if (imageViewReused(photoToLoad))
                return;
            Bitmap bmp = getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if (imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad);
            handler.post(bd);
        } catch (Throwable th) {
            th.printStackTrace();
        }
    }
}

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();
}

}

内存缓存

public class MemoryCache {

private static final String TAG = "MemoryCache";

// Last argument true for LRU ordering
private Map<String, Bitmap> cache = Collections
.synchronizedMap(new LinkedHashMap<String, Bitmap>(10, 1.5f, true));

// Current allocated size
private long size = 0;

// Max memory in bytes
private long limit = 1000000;

public MemoryCache() {
    // Use 25% of available heap size
    setLimit(Runtime.getRuntime().maxMemory() / 4);
}

public void setLimit(long new_limit) {
    limit = new_limit;
    Log.i(TAG, "MemoryCache will use up to " + limit / 1024. / 1024. + "MB");
}

public Bitmap get(String id) {
    try {
        if (!cache.containsKey(id))
            return null;
        return cache.get(id);
    } catch (NullPointerException ex) {
        ex.printStackTrace();
        return null;
    }
}

public void put(String id, Bitmap bitmap) {
    try {
        if (cache.containsKey(id))
            size -= getSizeInBytes(cache.get(id));
        cache.put(id, bitmap);
        size += getSizeInBytes(bitmap);
        checkSize();
    } catch (Throwable th) {
        th.printStackTrace();
    }
}

private void checkSize() {
    Log.i(TAG, "cache size=" + size + " length=" + cache.size());
    if (size > limit) {
        // Least recently accessed item will be the first one iterated
        Iterator<Entry<String, Bitmap>> iter = cache.entrySet().iterator();
        while (iter.hasNext()) {
            Entry<String, Bitmap> entry = iter.next();
            size -= getSizeInBytes(entry.getValue());
            iter.remove();
            if (size <= limit)
                break;
        }
        Log.i(TAG, "Clean cache. New size " + cache.size());
    }
}

public void clear() {
    try {
        cache.clear();
        size = 0;
    } catch (NullPointerException ex) {
        ex.printStackTrace();
    }
}

long getSizeInBytes(Bitmap bitmap) {
    if (bitmap == null)
        return 0;
    return bitmap.getRowBytes() * bitmap.getHeight();
}
}

文件缓存

public class FileCache {

private File cacheDir;

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(
            android.os.Environment.getExternalStorageDirectory(),
            "ImgTxt");
    else
        cacheDir = context.getCacheDir();
    if (!cacheDir.exists())
        cacheDir.mkdirs();
}

public File getFile(String url) {
    String filename = String.valueOf(url.hashCode());
    // 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 1

REQUIRED_SCALE 的值设置为 70，其中设置了比例类型。 最终 int REQUIRED_SIZE = 70; 根据图像清晰度的要求，将值从 70 增加到 200 或更多。