[Android]startActivity() Intent in einem AsnycTask mit ProgressDialog benutzen:

	@Override
	protected void onListItemClick(ListView l, View v, int position, long id) {
		super.onListItemClick(l, v, position, id);
		// Get the item that was clicked
		Object o = this.getListAdapter().getItem(position);
		String keyword = o.toString();
		
		if (keyword.startsWith("Map")) {
//			Intent launch_traismap_Intent = new Intent(Trais.this, TraisMap.class);
//			Trais.this.startActivity(launch_traismap_Intent);
			new BackgroundWorker().execute(keyword);
		}


....

}

    private class BackgroundWorker extends AsyncTask<String, Void, Boolean> { 
    	
    	private ProgressDialog pd;
    	    	    	
		protected Boolean doInBackground(String... params) {
			if(params[0].startsWith("Map")) {
				Intent launch_traismap_Intent = new Intent(Trais.this, TraisMap.class);
				Trais.this.startActivity(launch_traismap_Intent);
			}else if(params[0].startsWith("POIs")) {
				Intent launch_pois_own_Intent = new Intent(Trais.this, PoisOwn.class);
				Trais.this.startActivity(launch_pois_own_Intent);
			}
			
			
			return true;
		}		
		
		
		/* (non-Javadoc)
		 * @see android.os.AsyncTask#onPreExecute()
		 */		
		protected void onPreExecute() {
			// Things to be done before execution of long running operation. For example showing ProgessDialog
			pd = ProgressDialog.show(Trais.this, "Bitte warten...", "Downloading Data...", true, false);
		}		
		
		
		/* (non-Javadoc)
		 * @see android.os.AsyncTask#onPostExecute(java.lang.Object)
		 */		
		protected void onPostExecute(Boolean result) {
			// execution of result of Long time consuming operation
			pd.dismiss();
		}		
    }

            		//-ProgressDialog starten, da Daten heruntergeladen werden
                    progressDialog.show();
              
                    //-Intent erstellen
            		startActivity(new Intent(this, Category.class));

            //-Thread starten um GUI Thread nicht zum hängen zu bringen
            Thread t = new Thread() {
            	
            	//-Thread starten
                public void run() {
                	
                	//-Schleife vorbereiten
                    Looper.prepare();
                    
            		//-ProgressDialog starten, da Daten heruntergeladen werden
                    progressDialog.show();
              
                    //-Intent erstellen
            		startActivity(new Intent(Main.this, Category.class));
                    
                    Looper.loop();                
                }
            };
            
            //-Thread starten
            t.start();

        //-ProgressDialog vorbereiten, welcher geöffnet wird, wenn Daten heruntergeladen werden
        progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Bitte warten...");
        progressDialog.setIndeterminate(true);
        progressDialog.setCancelable(false);

//-ProgressDialog erstellen
	public static ProgressDialog progressDialog;