Android Waiting progress bar Can't create handler inside thread that has not called Looper.prepare() error

Question

In my android application, I copy some data from server database to local database.It may take over 15 minutes. For slower connections, it may be exceeded. So I want to display a waiting progress bar.

The code is posted below.

refresh.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
final ProgressDialog progressDialog = ProgressDialog.show(login.this, "", "Please wait...");
new Thread() {
public void run() {
try{
mySQLiteAdapter.openToWrite();
mySQLiteAdapter.deleteAll();
radapter.openToWrite();
radapter.deleteAll();
uadapter.openToWrite();
uadapter.deleteAll();
        try
            {
                 HttpClient httpclient = new DefaultHttpClient();
                 HttpPost httppost = new HttpPost("http://xxxxxxxxxxxxxxxxxxxxx");
                 HttpResponse response = httpclient.execute(httppost);
                 HttpEntity entity = response.getEntity();
                  is = entity.getContent();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(
                        is, "iso-8859-1"), 8);
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                json = sb.toString();
            } catch (Exception e) {
            Toast.makeText(getBaseContext(), e.toString(), Toast.LENGTH_LONG).show();
            }

            try {
                jObj = new JSONObject(json);
                contacts = jObj.getJSONArray("get");
                for(int i = 0; i < contacts.length(); i++){
                JSONObject c = contacts.getJSONObject(i);
                    if(!c.isNull("rname"))// || c.getString("rcode").equals(null))
                    {
                        rname = c.getString("rname");
                        rcode = c.getString("rcode");
                        radapter.insert(rcode, rname);
                    }
                    else
                    {
                        rname = "";
                        rcode = c.getString("rcode");
                        radapter.insert(rcode, rname);
                    }
                }
                Toast.makeText(getBaseContext(), " Ryot BackUp completed", Toast.LENGTH_SHORT).show();

            } catch (JSONException e) {
                Toast.makeText(getBaseContext(), "Error"+e.toString(), Toast.LENGTH_LONG).show();
            }
                   progressDialog.dismiss();
               }
            }.start();
            adapter.deleteAll();
            oadapter.deleteAll();
            e2.setText("Back Up completed");
        }
            catch (Exception e) {
               Log.e("tag", e.getMessage());
               }
                   progressDialog.dismiss();
               }
            }.start();
       }

   });

When I'm running my application, the progress bar is displayed only for few seconds and the Catch block is executed, showing logcat error as

Logcat:

02-26 14:26:07.151: E/tag(301): Can't create handler inside thread that has not called Looper.prepare()

Can someone explain what is the mistake in my code and how to solve it

typical case of trying to access the ui from another thread. Solution is using an asynctask for background stuff and accessing the ui in onProgressUpdate and onPostExecute. — njzk2, Feb 26 '13 at 09:11

score 0 · Accepted Answer · edited May 23 '17 at 12:12

Toast.makeText(getBaseContext(), " Ryot BackUp completed", Toast.LENGTH_SHORT).show();

The problem is caused by the above code, this method will change UI, you can't update UI in a non-ui thread. So you need to call it from main ui thread.

Since it is a time-consuming work, I highly recommend you to use AsyncTask in Android.

But if you only want to make a little change in your existing code, try to use

context.runOnUiThread(new Runnable() {
  public void run() {
    Toast.makeText(...).show();
  }
});

or handler, you can take a look at How Handler Work in Android. A basic example:

public Handler mHandler = new Handler() {

    public void handleMessage(Message msg) {
           //show toast here
    }
}

protected void startLongRunningOperation() {

    Thread t = new Thread() {
        public void run() {
            //do something here
            //update the result
            mHandler.postDelayed(mUpdateResults, 200);}
            mHandler.post(mUpdateResults);
        }
    };
    t.start();
}

Where i should use this? for displaying toast only – Linga Feb 26 '13 at 09:12 — Linga, Feb 26 '13 at 09:12

score 0 · Answer 2 · answered Feb 26 '13 at 10:10

0

Instead of creating a new Thread make a HandlerThread - http://developer.android.com/reference/android/os/HandlerThread.html

Just replace "new Thread()" with "new HandlerThread("any string")" and it should work.

answered Feb 26 '13 at 10:10

azertiti

3,150
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Android Waiting progress bar Can't create handler inside thread that has not called Looper.prepare() error

2 Answers2