我正在使用此代码BaseAdapter为画廊创建一个：
private class ImageAdapter extends BaseAdapter {
/** The parent context */
private Context myContext;
/** URL-Strings to some remote images. */
public String[] mImageURLs = {
urlImage1,
urlImage2,urlImage3,urlImage4,urlImage5,urlImage6,urlImage7};
String [] myRemoteImages = {imageUrl,imageUrl2,imageUrl3,imageUrl4,imageUrl5,imageUrl6,imageUrl7};
/** Simple Constructor saving the 'parent' context. */
public ImageAdapter(Context c) { this.myContext = c; }
/** Returns the amount of images we have defined. */
public int getCount() {
return this.myRemoteImages.length;
}
/* Use the array-Positions as unique IDs */
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
/** Returns a new ImageView to
* be displayed, depending on
* the position passed. */
public View getView(int position, View convertView, ViewGroup parent) {
ImageView i = new ImageView(this.myContext);
try {
URL aURL = new URL(myRemoteImages[position]);
Log.v("ImageLoader", "Remote images set");
i.setTag(mImageURLs[position]);
URI imageUri = null;
SharedPreferences myPrefs = getSharedPreferences("imageUri", 0);
SharedPreferences.Editor myPrefsEdit = myPrefs.edit();
//Setting the Uri of aURL to imageUri.
try {
imageUri = aURL.toURI();
myPrefsEdit.putString("uris", imageUri.toString());
myPrefsEdit.commit();
} catch (URISyntaxException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
//Testing to see if images are already in cache, if not then we load the images from the web and save them to the cache.
if (new File(new File(myContext.getCacheDir(), "thumbnails"), "" + imageUri.hashCode()).exists()) {
Log.v("Loader", "File exists in cache. Now pulling from the cache");
String cachFile = myContext.getCacheDir() +"/thumbnails/"+imageUri.hashCode();
FileInputStream fis;
try {
fis = new FileInputStream(cachFile);
Bitmap bm = BitmapFactory.decodeStream(fis);
i.setImageBitmap(bm);
i.setScaleType(ImageView.ScaleType.FIT_CENTER);
Log.v("Loader", "Image loaded from cache");
/* Set the Width/Height of the ImageView. */
if (Build.VERSION.SDK_INT >= 11) {
i.setLayoutParams(new Gallery.LayoutParams(450, 300));
} else {
i.setLayoutParams(new Gallery.LayoutParams(200, 200));
}
} catch (FileNotFoundException e) {
Log.e("DEBUGTAG", "Remtoe Image Exception", e);
}
//If images are not in cache... Here we download the images from the URL, and save them to cache.
} else {
Log.v("Loader", "Images are not in cache, Downloading images now....");
URLConnection conn = aURL.openConnection();
conn.setUseCaches(true);
conn.connect();
InputStream is = conn.getInputStream();
/* Buffered is always good for a performance plus. */
BufferedInputStream bis = new BufferedInputStream(is);
/* Decode url-data to a bitmap. */
Bitmap bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
Log.v(imageUrl, "Retrieving image");
/* Apply the Bitmap to the ImageView that will be returned. */
i.setImageBitmap(bm);
putBitmapInDiskCache(imageUri, bm);
Log.v("Loader", "Image saved to cache");
/* Set the Width/Height of the ImageView. */
if (Build.VERSION.SDK_INT >= 11) {
i.setLayoutParams(new Gallery.LayoutParams(450, 300));
}
我想要做的是对图库使用延迟加载，而不是在此处下载图像，然后将它们设置到图库。这是迟缓和太昂贵。
如您所见，我有上面的入门代码。我该如何使用 LazyLoading 呢？