使用緩存來存儲位圖

Question

我正在使用LruCache來存儲位圖。

這是我運行的存儲位圖的異步任務。

new AsyncTask<Void, Void, Bitmap>() { 

     @Override 
     protected Bitmap doInBackground(Void... args) { 
      String url = d.getImageUrl(); 
      if (url != null && !url.equals("")) { 
       try { 
        LogUtils.log("getting image from cache"); 
        Bitmap image = imageCache.getBitmapFromMemCache(url); 
        if (image == null) { 

         image = BitmapFactory.decodeStream(new URL(url) 
           .openConnection().getInputStream()); 
         LogUtils.log("storing image to cache"); 
         imageCache.addBitmapToMemoryCache(url, image); 
        } else { 
         LogUtils.log("got image from cache"); 
        } 
        return image; 
       } catch (Exception e) { 
        e.printStackTrace(); 
       } 
      } 
      return null; 

     } 

     @Override 
     protected void onPostExecute(Bitmap image) { 
      if (holder.image != null) { 
       if (image != null) { 
        holder.image.setImageBitmap(image); 
        holder.image.setVisibility(View.VISIBLE); 
       } 
      } 

     } 

    }.execute(); 

這裏是我的緩存實現：

public class ImageCache { 

private static ImageCache instance; 

public static ImageCache getInstance(Context context) { 
    if (instance == null) 
     instance = new ImageCache(context); 
    return instance; 
} 

private LruCache<String, Bitmap> mMemoryCache; 

private ImageCache(Context context) { 
    // Get memory class of this device, exceeding this amount will throw an 
    // OutOfMemory exception. 
    final int memClass = ((ActivityManager) context 
      .getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass(); 

    final int cacheSize = (1024 * 1024 * memClass)/8; 


    mMemoryCache = new LruCache<String, Bitmap>(cacheSize) { 
     @Override 
     protected int sizeOf(String key, Bitmap bitmap) { 
      // The cache size will be measured in bytes rather than number 
      // of items. 
      return bitmap.getRowBytes() * bitmap.getHeight(); 
     } 
    }; 
} 

public void addBitmapToMemoryCache(String key, Bitmap bitmap) { 
    LogUtils.log("key: " + key); 
    if (getBitmapFromMemCache(key) == null) { 
     mMemoryCache.put(key, bitmap); 
    } 
} 

public Bitmap getBitmapFromMemCache(String key) { 
    return mMemoryCache.get(key); 
} 

} 

在我的表現我也有：

android:largeheap="true" 

的問題是，在我的ListView ...當我向下滾動.. ..圖像從URL重新加載和代碼到達此行：

LogUtils.log("storing image to cache"); 

什麼可能導致此問題？

Answer 1

感謝@Ascorbin我找到了答案！沒有必要重新發明輪子。 我用這個庫：

https://github.com/nostra13/Android-Universal-Image-Loader

如果任何人有同樣的問題，因爲我...這是...緩存圖片充分利用interwebs重新加載....然後使用該庫和這段程式設置你的圖像：

 DisplayImageOptions options = new DisplayImageOptions.Builder() 
     .showImageOnLoading(R.drawable.noimage) // resource or drawable 
     .showImageForEmptyUri(R.drawable.noimage) // resource or drawable 
     .resetViewBeforeLoading(true) 
     .delayBeforeLoading(0) 
     .cacheInMemory(true) 
     .cacheOnDisc(true) 
     .bitmapConfig(Bitmap.Config.ARGB_8888) 
     .build(); 


     String url = d.getImageUrl(); 
     ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(v.getContext()) 
       .defaultDisplayImageOptions(options) 
       .build(); 
     ImageLoader imageLoader = ImageLoader.getInstance(); 
     imageLoader.init(config); 
     imageLoader.displayImage("", holder.image); 
     imageLoader.displayImage(url, holder.image);