[java] Can't create handler inside thread that has not called Looper.prepare() inside AsyncTask for ProgressDialog

I don't understand why I'm getting this error. I'm using AsyncTask to run some processes in the background.

I have:

protected void onPreExecute() 
{
    connectionProgressDialog = new ProgressDialog(SetPreference.this);
    connectionProgressDialog.setCancelable(true);
    connectionProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    connectionProgressDialog.setMessage("Connecting to site...");
    connectionProgressDialog.show();

    downloadSpinnerProgressDialog = new ProgressDialog(SetPreference.this);
    downloadSpinnerProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    downloadSpinnerProgressDialog.setMessage("Downloading wallpaper...");
}

When I get into doInBackground() depending on a condition I:

[...]    
connectionProgressDialog.dismiss();
downloadSpinnerProgressDialog.show();
[...]

Whenever I try downloadSpinnerProgressDialog.show() I receive the error.

Any ideas guys?

final Handler handler = new Handler() {
        @Override
        public void handleMessage(final Message msgs) {
        //write your code hear which give error
        }
        }

new Thread(new Runnable() {
    @Override
    public void run() {
    handler.sendEmptyMessage(1);
        //this will call handleMessage function and hendal all error
    }
    }).start();

I had a similar issue but from reading this question I figured I could run on UI thread:

YourActivity.this.runOnUiThread(new Runnable() {
    public void run() {
        alertDialog.show();
    }
});

Seems to do the trick for me.

I had a hard time making this work too, the solution for me was to use both hyui and konstantin answers,

class ExampleTask extends AsyncTask<String, String, String> {

// Your onPreExecute method.

@Override
protected String doInBackground(String... params) {
    // Your code.
    if (condition_is_true) {
        this.publishProgress("Show the dialog");
    }
    return "Result";
}

@Override
protected void onProgressUpdate(String... values) {

    super.onProgressUpdate(values);
    YourActivity.this.runOnUiThread(new Runnable() {
       public void run() {
           alertDialog.show();
       }
     });
 }

}