ERROR/AndroidRuntime(29693): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

I'm new to Android. i'm trying to use this class I've downloaded.

public class BatchImageDownloader extends AsyncTask<Void, Void, Void> {

List<String> imgUrls = new ArrayList<String>();
BaseAdapter adapter;
HashMap<String, Drawable> imageCache;
Context ctxt;

public BatchImageDownloader(BaseAdapter adapter, HashMap<String, Drawable> imageCache, Context ctxt) {
    this.adapter = adapter;
    this.imageCache = imageCache;
    this.ctxt = ctxt;
}

public void addUrl(String url) {
    imgUrls.add(url);
    Log.i("imgDownloader", "url ADDED!");
}

@Override
protected Void doInBackground(Void... params) {
    for (String url : imgUrls) {
        if (!imageCache.containsKey(url)) {
            Drawable bm = downloadImage(url);
            if (null != bm) {
                imageCache.put(url, bm);
                publishProgress();
            }
        }
    }
    return null;
}

@Override
protected void onProgressUpdate(Void... values) {
    adapter.notifyDataSetChanged();
}

@Override
protected void onPostExecute(Void result) {
    adapter.notifyDataSetChanged(); 
}

public Drawable downloadImage(String url) {

    DefaultHttpClient httpClient = new DefaultHttpClient();
    HttpGet request = new HttpGet(url);
    try {           
        HttpResponse response = httpClient.execute(request);
        InputStream stream = response.getEntity().getContent();
        Drawable drawable = Drawable.createFromStream(stream, "src");
        //Log.i("imgDownloader", "image DOWNLOADED!");
        //int duration = Toast.LENGTH_LONG;
        //Toast.makeText(ctxt, "Inizio scaricamento", duration).show();
        return drawable;
    } catch (ClientProtocolException e) {
        e.printStackTr开发者_开发百科ace();
        return null;
    } catch (IllegalStateException e) {
        e.printStackTrace();
        return null;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    } catch (NullPointerException e){
        e.printStackTrace();
        return null;            
    }

}

}

Well, when I try to execute it by: batchDownloader.execute(); I get this:

05-13 16:13:22.750: ERROR/AndroidRuntime(29693): FATAL EXCEPTION: AsyncTask #1
05-13 16:13:22.750: ERROR/AndroidRuntime(29693): java.lang.RuntimeException: An error   occured while executing doInBackground()
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.lang.Thread.run(Thread.java:1096)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at android.os.Handler.<init>(Handler.java:121)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at android.widget.Toast.<init>(Toast.java:68)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at android.widget.Toast.makeText(Toast.java:231)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at com.apps.EveryEyeFeedReader.BatchImageDownloader.downloadImage(BatchImageDownloader.java:73)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at com.apps.EveryEyeFeedReader.BatchImageDownloader.doInBackground(BatchImageDownloader.java:43)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at com.apps.EveryEyeFeedReader.BatchImageDownloader.doInBackground(BatchImageDownloader.java:1)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-13 16:13:22.750: ERROR/AndroidRuntime(29693):     ... 4 more

Anyone can help me? Thx

You can't interact with the UI in the doInBackground() method, move your UI logic to the onPostExecute(). That's why (presumably) you had to comment out the Toast lines.

in your exception , there is something related to the Toast ,

note that anyThing which have relation with UI, the only thread who can touch it is the UIThread

so i think u should do something like this :

Ctx.runOnUIThread(new Runnable()
{@override
public void run(){ Toast.makeText(.............).show();
}
});

hope it helps :)

he means that , any instructions which has a relation with changing or modification of the UI Components, you should put it in the method onPostExecute()

so don't call for Example Toast.show() in your method doInBackground(...);