application est lente avec des images de android

Je devine que la plupart du temps de chargement est à cause de la grande quantité d'images combinées avec la taille des images.

Il y a 2 solutions possibles:

1. Redimensionner les images, ou réduire la qualité des images, de sorte que la taille est en dessous de 75 ko.

2. Utiliser le multi-threading pour récupérer plusieurs images à la fois. Cela pourrait ne pas aider si la connexion de l'utilisateur est vraiment lent, mais si vous combinez cela avec une assez petite taille, il peut juste aider suffisamment. Vous pourriez déterminer la largeur de bande actuelle de l'appareil de base et le nombre de threads que vous exécutez sur.

Par exemple: 20 images de 75 KO chacune et d'une connexion disponible de 200 KO/s = 3 ou 4 threads simultanés.

Espère que cette aide.

OriginalL'auteur Bram Vandenbussche

 public class clothImageLoader {
//the simplest in-memory cache implementation. This should be replaced with
//something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
//public static HashMap<String, Bitmap> cache = new HashMap<String,
//Bitmap>();
private static File cacheDir;
public clothImageLoader(Context context) {
//Make the background thead low priority. This way it will not affect
//the UI performance
photoLoaderThread.setPriority(Thread.NORM_PRIORITY - 1);
//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(),"LazyList");
cacheDir = new File(ConstValue.MY_ClothBitmap_DIR);
else
cacheDir = context.getCacheDir();
if (!cacheDir.exists())
cacheDir.mkdirs();
}
final int stub_id = R.drawable.icon;
public void DisplayImage(String url, Activity activity, ImageView imageView) {
if (ConstValue.ClothRoomcache.containsKey(url))
imageView.setImageBitmap(ConstValue.ClothRoomcache.get(url));
else {
queuePhoto(url, activity, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, Activity activity, ImageView imageView) {
//This ImageView may be used for other images before. So there may be
//some old tasks in the queue. We need to discard them.
photosQueue.Clean(imageView);
PhotoToLoad p = new PhotoToLoad(url, imageView);
synchronized (photosQueue.photosToLoad) {
photosQueue.photosToLoad.push(p);
photosQueue.photosToLoad.notifyAll();
}
//start thread if it's not started yet
if (photoLoaderThread.getState() == Thread.State.NEW)
photoLoaderThread.start();
}
private Bitmap getBitmap(String url) {
//I identify images by hashcode. Not a perfect solution, good for the
//demo.
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
//from SD cache
Bitmap b = decodeFile(f);
if (b != null)
return b;
//from web
try {
Bitmap bitmap = null;
/*
* InputStream is=new URL(url).openStream(); OutputStream os = new
* FileOutputStream(f); Utils.CopyStream(is, os); os.close();
*/
URL url1 = new URL(url);
bitmap = decodeFile(f);
/* Open a connection to that URL. */
URLConnection ucon = url1.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
//FlushedInputStream a = new FlushedInputStream(is);
BufferedInputStream bis = new BufferedInputStream(is);
/*
* Read bytes to the Buffer until there is nothing more to read(-1).
*/
ByteArrayBuffer baf = new ByteArrayBuffer(5000);
int current = 0;
while ((current = bis.read()) != -1) {
baf.append((byte) current);
}
/* Convert the Bytes read to a String. */
FileOutputStream fos = new FileOutputStream(f);
fos.write(baf.toByteArray());
fos.flush();
fos.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 = ConstValue.bmpSize;
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++;
}
//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;
}
}
PhotosQueue photosQueue = new PhotosQueue();
public void stopThread() {
photoLoaderThread.interrupt();
}
//stores list of photos to download
class PhotosQueue {
private Stack<PhotoToLoad> photosToLoad = new Stack<PhotoToLoad>();
//removes all instances of this ImageView
public void Clean(ImageView image) {
for (int j = 0; j < photosToLoad.size();) {
if (photosToLoad.get(j).imageView == image)
photosToLoad.remove(j);
else
++j;
}
}
}
class PhotosLoader extends Thread {
public void run() {
try {
while (true) {
//thread waits until there are any images to load in the
//queue
if (photosQueue.photosToLoad.size() == 0)
synchronized (photosQueue.photosToLoad) {
photosQueue.photosToLoad.wait();
}
if (photosQueue.photosToLoad.size() != 0) {
PhotoToLoad photoToLoad;
synchronized (photosQueue.photosToLoad) {
photoToLoad = photosQueue.photosToLoad.pop();
//photoToLoad=photosQueue.photosToLoad.get(0);
//photosQueue.photosToLoad.remove(photoToLoad);
}
Bitmap bmp = getBitmap(photoToLoad.url);
ConstValue.ClothRoomcache.put(photoToLoad.url, bmp);
if (((String) photoToLoad.imageView.getTag()).equals(photoToLoad.url)) {
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad.imageView);
Activity a = (Activity) photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
if (Thread.interrupted())
break;
}
} catch (InterruptedException e) {
//allow thread to exit
}
}
}
PhotosLoader photoLoaderThread = new PhotosLoader();
//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable {
Bitmap bitmap;
ImageView imageView;
public BitmapDisplayer(Bitmap b, ImageView i) {
bitmap = b;
imageView = i;
}
public void run() {
if (bitmap != null)
imageView.setImageBitmap(bitmap);
else
imageView.setImageResource(stub_id);
}
}
public static void clearCache() {
//clear memory cache
ConstValue.ClothRoomcache.clear();
//clear SD cache
File[] files = cacheDir.listFiles();
for (File f : files)
f.delete();
}
public class FlushedInputStream extends FilterInputStream {
public FlushedInputStream(InputStream inputStream) {
super(inputStream);
}
@Override
public long skip(long n) throws IOException {
long totalBytesSkipped = 0L;
while (totalBytesSkipped < n) {
long bytesSkipped = in.skip(n - totalBytesSkipped);
if (bytesSkipped == 0L) {
int a = read();
if (a < 0) {
break; //we reached EOF
} else {
bytesSkipped = 1; //we read one byte
}
}
totalBytesSkipped += bytesSkipped;
}
return totalBytesSkipped;
}
}
}

lorsque vous appelez la méthode ,dans le contrôle gridView méthode getView:

holder.image.setTag(ChoseInfo.get(position).getLink());
imageLoader.DisplayImage(ChoseInfo.get(position).getLink(), activity, holder.image);

ChoseInfo.get(position).getLink())

Ici getLink() est le lien internet.

OriginalL'auteur pengwang