Bonjour,

Je télécharge des données grâce à un webservice que je met dans une ListView.

Chaque item de ma ListView est composée d'une miniature que je charge dans mon ImageView correspondante grâce à ma classe ImageLoader (voir ci-dessous).

Mon pproblème est le suivant :

Lorque je scrolle ma Listview certaines images se superposent sur d'autres pendant un certain moment pour ensuite afficher la bonne.

Existe-il un moyen pour éviter celà ?

Mon Adapter

Code : Sélectionner tout - Visualiser dans une fenêtre à part
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package com.xxxxxxxxxx;
 
import java.util.ArrayList;
import java.util.HashMap;
 
import com.utils.ImageLoader;
 
 
import android.app.Activity;
import android.content.Context;
import android.graphics.Typeface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
 
public class ActualiteAdapter extends BaseAdapter
{
	ArrayList<HashMap<String, String>> mylist;
	LayoutInflater	inflater;
	public Typeface arial_bold, arial;
	public Activity activity;
	public ImageLoader imageLoader; 
 
	public ActualiteAdapter (Context context, Activity a, ArrayList<HashMap<String, String>> myList)
	{
 
		inflater = LayoutInflater.from (context);
		this.mylist = myList;
		activity = a;
		imageLoader=new ImageLoader(activity.getApplicationContext());
 
 
	}
 
 
	public int getCount ()
	{
		return mylist.size ();
	}
 
	public Object getItem (int position)
	{
		return mylist.get (position);
	}
 
	public long getItemId (int position)
	{
		// TODO Auto-generated method stub
		return position;
	}
 
	public View getView (int position, View convertView, ViewGroup parent)
	{
		ViewHolder holder;
		if (convertView == null)
		{
			holder = new ViewHolder ();
 
 
			convertView = inflater.inflate (R.layout.actualite_item, null);
 
 
			holder.titre = (TextView) convertView.findViewById (R.id.titre);
			holder.extrait = (TextView) convertView.findViewById (R.id.extrait);
			holder.miniature = (ImageView) convertView.findViewById (R.id.miniature);	
			convertView.setTag (holder);
		}
		else
		{
			holder = (ViewHolder) convertView.getTag ();
		}
 
 
 
	    holder.titre.setText (mylist.get (position).get("titre").toString ().trim());	
	    holder.extrait.setText (mylist.get (position).get("detail").toString ().trim().replace("[saut]", ""));
 
	    imageLoader.DisplayImage(mylist.get(position).get("miniature").toString ().trim(), activity, holder.miniature);
 
		return convertView;
 
	}
 
	public class ViewHolder
	{
		ImageView   miniature;
		TextView	titre;
		TextView extrait;
 
	}
 
 
}
Ma classe permettant de télécharger les images

Code : Sélectionner tout - Visualiser dans une fenêtre à part
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package com.utils;
 
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Stack;
 
import com.xxxxxx.R;
 
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;
 
public class ImageLoader {
 
    //the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
    private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();
 
    private File cacheDir;
 
    public ImageLoader(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(),"dirproject");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }
 
 
    final int stub_id = R.drawable.stub;
 
 
 
    public void DisplayImage(String url, Activity activity, ImageView imageView)
    {
        if(cache.containsKey(url))
        {
 
            imageView.setImageBitmap(cache.get(url));
 
        }
        else
        {
              queuePhoto(url, activity, imageView);
              imageView.setBackgroundResource(R.drawable.draw_imageloading);
 
 
 
        }    
    }
 
    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();
            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=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++;
            }
 
            //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();
                        }
                        Bitmap bmp=getBitmap(photoToLoad.url);
                        cache.put(photoToLoad.url, bmp);
                            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 void clearCache() {
        //clear memory cache
        cache.clear();
 
        //clear SD cache
        File[] files=cacheDir.listFiles();
        for(File f:files)
            f.delete();
    }
 
 
 // Retourne la taille du Cache
    public String GetSizeOfDirectory()
    {
    	return formatSize(getFolderSize(cacheDir));
    }
 
 
 // Retourne la taille du dossier en Bytes
 	private static long getFolderSize(File dir) {
 	    long size = 0;
 	    for (File file : dir.listFiles()) {
 	        if (file.isFile()) {
 	            System.out.println(file.getName() + " " + file.length());
 	            size += file.length();
 	        }
 	        else
 	            size += getFolderSize(file);
 	    }
 	    return size;
 	}
 
 
 	private static String formatSize(long size) {
 		String suffix = null;
 
 		if(size == 0)
 		suffix = " KiB";
 
 		if (size >= 1024 && size != 0) {
 			suffix = " KiB";
 			size /= 1024;
 			if (size >= 1024) {
 				suffix = " MiB";
 				size /= 1024;
 			}
 		}
 		StringBuilder resultBuffer = new StringBuilder(Long.toString(size));
 
 		int commaOffset = resultBuffer.length() - 3;
 		while (commaOffset > 0) {
 			resultBuffer.insert(commaOffset, ',');
 			commaOffset -= 3;
 		}
 
 		if (suffix != null)
 			resultBuffer.append(suffix);
 		return resultBuffer.toString();
 	}
 
}