Problem: Android : CalledFromWrongThreadException;: Only the original thread that created a view hierarchy can touch its views

Avoid performing long-running operations (such as network I/O) directly in the UI thread — the main thread of an application where the UI is run — or your application may be blocked and become unresponsive. Here is a brief summary of the recommended approach for handling expensive operations:

1. Create a Handler object in your UI thread
2. Spawn off worker threads to perform any required expensive operations
3. Post results from a worker thread back to the UI thread's handler either through a Runnable or a Message
4. Update the views on the UI thread as needed

AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.

So Here is the best solutions:

ou have to move the portion of the background task that updates the ui onto the main thread. There is a simple piece of code for this:

runOnUiThread(new Runnable() {
     @Override
     public void run() {

//stuff that updates ui

    }
});

Documentation for Activity.runOnUiThread.


or you may use this:

Basically you would wrap //do whatever you wantin a Runnable and invoke it with a Handler instance.

Handler refresh = new Handler(Looper.getMainLooper());
refresh.post(new Runnable() {
    public void run()
    {
       //do whatever you want
    }
});

or simple do that:

you don't call directly the onProgressUpdate, you have to call publishProgress and let the AsynTask framework to handle the onProgressUpdate to be called back on the UI thread.

Finally, google it : Here is the best solutions that reach there. Gooogled

Happy Coding!!!

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How to lazy load of images in ListView or LazyList?

Lazy List is lazy loading of images from sd-card or from server using urls. It is like on demand loading images.

Images can be cached to local sd-card or phone memory. Url is considered the key. If the key is present in sd-card, display images from sd-card else display image by downloading from server and cache the same to location of your choice. The cache limit can set. You can also choose your own location to cache images. Cache can also be cleared.

Instead of user waiting to download large images and then displaying lazy list, loads images on demand. Since images are cached you can display images offline.

https://github.com/thest1/LazyList. Lazy List.

A simple library to display images in Android ListView. Images are being downloaded asynchronously in the background. Images are being cached on SD card and in memory. Can also be used for GridView and just to display images into an ImageView.

other examples:

James A Wilson give the best examles of highest vote on stackover.

package com.wilson.android.library;


import java.io.IOException;

public class DrawableManager {
    private final Map<String, Drawable> drawableMap;

    public DrawableManager() {
        drawableMap = new HashMap<String, Drawable>();
    }

    public Drawable fetchDrawable(String urlString) {
        if (drawableMap.containsKey(urlString)) {
            return drawableMap.get(urlString);
        }

        Log.d(this.getClass().getSimpleName(), "image url:" + urlString);
        try {
            InputStream is = fetch(urlString);
            Drawable drawable = Drawable.createFromStream(is, "src");


            if (drawable != null) {
                drawableMap.put(urlString, drawable);
                Log.d(this.getClass().getSimpleName(), "got a thumbnail drawable: " + drawable.getBounds() + ", "
                        + drawable.getIntrinsicHeight() + "," + drawable.getIntrinsicWidth() + ", "
                        + drawable.getMinimumHeight() + "," + drawable.getMinimumWidth());
            } else {
              Log.w(this.getClass().getSimpleName(), "could not get thumbnail");
            }

            return drawable;
        } catch (MalformedURLException e) {
            Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e);
            return null;
        } catch (IOException e) {
            Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e);
            return null;
        }
    }

    public void fetchDrawableOnThread(final String urlString, final ImageView imageView) {
        if (drawableMap.containsKey(urlString)) {
            imageView.setImageDrawable(drawableMap.get(urlString));
        }

        final Handler handler = new Handler() {
            @Override
            public void handleMessage(Message message) {
                imageView.setImageDrawable((Drawable) message.obj);
            }
        };

        Thread thread = new Thread() {
            @Override
            public void run() {
                //TODO : set imageView to a "pending" image
                Drawable drawable = fetchDrawable(urlString);
                Message message = handler.obtainMessage(1, drawable);
                handler.sendMessage(message);
            }
        };
        thread.start();
    }

    private InputStream fetch(String urlString) throws MalformedURLException, IOException {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet request = new HttpGet(urlString);
        HttpResponse response = httpClient.execute(request);
        return response.getEntity().getContent();
    }
}

Alternative of LazyList is:

open source instrument Universal Image Loader. It is originally based on Fedor Vlasov's project LazyList and has been vastly improved since then.

• Multithread image loading
• Possibility of wide tuning ImageLoader's configuration (thread executors, downlaoder, decoder, memory and disc cache, display image options, and others)
• Possibility of image caching in memory and/or on device's file sysytem (or SD card)
• Possibility to "listen" loading process
• Possibility to customize every display image call with separated options
• Widget support
• Android 2.0+ support

Finally, you may use this also,this is also best tutoiral for lazylist image loader.

I have followed this Android Training and I think it does an excellent job at downloading images without blocking the main UI. It also handles caching and dealing with scrolling through many images: Loading Large Bitmaps Efficiently

All sources from statckover.

Happy Coding!!!

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