懶加載ImageLoader的應用

            建立一個方法類ImageLoader，構造函數含有三個參數：圖檔位址 Url、圖檔對象 ImageVIew、是否隻從緩存中擷取 fromCache；

           private ImageLoader mImageLoader;

       mImageLoader.DisplayImage(url, viewHolder.comment_item_img, false);

     public class ImageLoader {

     private MemoryCache memoryCache = new MemoryCache();

private AbstractFileCache fileCache;

private Map<ImageView, String> imageViews = Collections.synchronizedMap(new WeakHashMap<ImageView, String>());

// 線程池

private ExecutorService executorService;

public ImageLoader(Context context) {

fileCache = new FileCache(context);

//建立一個固定的線程池的大小

executorService = Executors.newFixedThreadPool(5);

}

    // 最主要的方法

public void DisplayImage(String url, ImageView imageView, boolean isLoadOnlyFromCache) {

imageViews.put(imageView, url);

// 先從記憶體緩存中查找

Bitmap bitmap = memoryCache.get(url);

if (bitmap != null)

imageView.setImageBitmap(bitmap);

else if (!isLoadOnlyFromCache) {

// 若沒有的話則開啟新線程加載圖檔

queuePhoto(url, imageView);

}

}

      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);

// 先從檔案緩存中查找是否有

Bitmap b = null;

if (f != null && f.exists()) {

b = decodeFile(f);

}

if (b != null) {

return b;

}

// 最後從指定的url中下載下傳圖檔

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);

CopyStream(is, os);

os.close();

bitmap = decodeFile(f);

return bitmap;

} catch (Exception ex) {

Log.e("", "getBitmap catch Exception...\nmessage = " + ex.getMessage());

return null;

}

}