Question

when I run a following code

    Runnable r = new Runnable() {

    @Override
    public void run() {

         final String urlString = "http://10.0.2.2/conn/s.png";
            // URL newurl = null;

                     try{   
                do
                {
                            if (ch==1)
                            {
                                //Thread.sleep(7000);
                                HttpGet httpRequest = new HttpGet(new URL(urlString).toURI());
                                HttpClient httpClient = new DefaultHttpClient();
                                HttpResponse response = (HttpResponse) httpClient.execute(httpRequest);
                                HttpEntity entity = response.getEntity();
                                BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity); 
                                    InputStream is = bufHttpEntity.getContent();
                                    Bitmap bitmap = BitmapFactory.decodeStream(is);
                                   im.destroyDrawingCache();
                                    im.setImageBitmap(bitmap);   
                                    bitmap=null;
                                   // Thread.sleep(3000);
                                    out.write(1);
                                   out.flush();




                                 }  
                }
                while(( ch=in.read()) == 1);
                     }
                     catch(IOException ex)
                     {

                     }
                    catch(URISyntaxException ex)
                    {}
    }
};

and the thread is initialized like this:

                  t = new Thread(r);
          t.start();

I am getting the following exception:

03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.ViewRoot.checkThread(ViewRoot.java:2683)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.ViewRoot.requestLayout(ViewRoot.java:557)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.View.requestLayout(View.java:7918)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.View.requestLayout(View.java:7918)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.View.requestLayout(View.java:7918)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.View.requestLayout(View.java:7918)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.view.View.requestLayout(View.java:7918)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.widget.ImageView.setImageDrawable(ImageView.java:306)
03-18 01:20:50.399: E/AndroidRuntime(305):  at android.widget.ImageView.setImageBitmap(ImageView.java:320)
03-18 01:20:50.399: E/AndroidRuntime(305):  at remote.presentation.rshare$1.run(rshare.java:124)
03-18 01:20:50.399: E/AndroidRuntime(305):  at java.lang.Thread.run(Thread.java:1096)

Answer 1

You are changing the UI from a thread, can’t do that in Android. It has to be done on the UI thread. I prefer AsyncTasks to using Threads. This AsyncTask will get an image from a url.

The class

private class GetImage extends AsyncTask<String,Void,Bitmap>{

    private ImageView view;

    public GetImage(ImageView iv){
         this.view = iv;
    }

    protected Bitmap doInBackground(String... params) {
                    //background thread
        try {

            return BitmapFactory.decodeStream((InputStream)new URL(params[0]).getContent());
        } catch (MalformedURLException e) {
            e.printStackTrace();

        } catch (IOException e) {
            e.printStackTrace();

        }

        return null;

    }
    @Override
    protected void onPostExecute(Bitmap b){
        if(b != null)
            this.view.setImageBitmap(b); 
    }
}

to use it

new GetImage(myImageView).execute(someURL);

EDIT (reason for edit, see comments) – the following code will repeatedly download the same image as the question asker wanted

Create a class variable for the GetImage class

GetImage getImageInstance = new GetImage(myImageView); 
getImageInstance.execute(url);

Modified class

private class GetImage extends AsyncTask<String,Bitmap,Void>{

    private ImageView view;
    Bitmap bitmap = null;
    long lastUpdateTimestamp = System.currentTimeMillis();
    public GetImage(ImageView iv){
         this.view = iv;
    }

    protected Bitmap doInBackground(String... params) {
                    //background thread
        while(running){
            try {
                //if more than 2 seconds have elapsed update the image
                if((System.currentTimeMillis() - lastUpdateTimestamp) > 2000){
                    bitmap = BitmapFactory.decodeStream((InputStream)new URL(params[0]).getContent());
                    pubilshProgress(bitmap);
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();

            } catch (IOException e) {
                 e.printStackTrace();

            }
        }
        return null;

    }
    //this method that will update the UI
    @Override
    protected void onProgressUpdate(Bitmap... images){
        if(images[0] != null)
            this.view.setImageBitmap(images[0]);
        lastUpdateTimestamp = System.currentTimeMillis();
    }
    @Override
    protected void onPostExecute(Void unused){
        bitmap.recycle();
    }
    public void stopDownloading(){
        running = false;
    }
}

To stop downloading

getImageInstance.stopDownloading();

I don’t know what your app does but users will not like downloading unnecessary images which eats into their data allowance, perhaps think about a better way to do what you want to do.