Question

I am a noob to android trying to learn how to properly implement a progress dialog. I started with some code that queried and parsed twitter results before populating a listview during OnCreate. this worked perfectly. I wanted to to add a progress bar since it takes a few seconds, but ever since i added the progress bar my code has stopped working. I get nullpointer errors during parsing and my app crashes due to an error saying ” Only the original thread that created a view hierarchy can touch its views. ” Any help to resolve this is greatly appreciated.

 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    dialog = new ProgressDialog (MainActivity.this);
    dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    dialog.setMessage("Loading... please wait");
    dialog.setIndeterminate(false);
    dialog.setMax(100);
    dialog.setProgress(0);
    dialog.show();

    Runnable runnable = new Runnable() {
        @Override
        public void run() {

    tweets = new ArrayList<Tweet>();

    try {           
        JSONObject jArray = JSONfunctions.getJSONfromURL("http://search.twitter.com/search.json?q=gold%20silver%20news&rpp=15");
        JSONArray parsedTwitter = jArray.getJSONArray("results");       
        if(parsedTwitter.equals("") ){
            Toast.makeText(MainActivity.this, "No nearby locations", Toast.LENGTH_LONG).show();
        }else{
            for (int i = 0; i < parsedTwitter.length(); i++) {
            JSONObject parsedspecific = parsedTwitter.getJSONObject(i);             
        if (i == 0){                
            String from_user = parsedspecific.getString("from_user");
            String text = parsedspecific.getString("text"); 
            String profile_image_url = parsedspecific.getString("profile_image_url");  
            Tweet tweet0 = new Tweet(from_user, text, profile_image_url );
            tweets.add(tweet0);                 
            }
dialog.setProgress(50);
        if (i == 1){                
            String from_user = parsedspecific.getString("from_user");
            String text = parsedspecific.getString("text"); 
            String profile_image_url = parsedspecific.getString("profile_image_url");  
            Tweet tweet1 = new Tweet(from_user, text, profile_image_url );
            tweets.add(tweet1);                 
            }

      }
            }

    } catch (Exception e) {
        Log.e("log_tag", "Error parsing data "+ e.toString());
    }

    ListView listView = (ListView) findViewById(R.id.ListViewId);      
    listView.setAdapter(new UserItemAdapter(MainActivity.this, R.layout.listitem, tweets));


    dialog.setProgress(100);
    dialog.dismiss();
        }
    };

    new Thread(runnable).start();


}

Answer 1

This means the Dialog is in a different Thread and you need a handler to mess with it, try adding the next line before the OnCreate() method:

Handler handler;

Then on the OnCreate method, instantiate the handler so it is in the same thread as the dialog

handler = new Handler();

Last, to update the dialog from a different thread you need to use the handler like this:

handler.post(new Runnable(){
public void run(){
//Do here whatever you want to do to the dialog
dialog.setProgress("whatever integer");
}
});

Hope this helps