ProgressDialog在 AsyncTaskTask 中的单独使用

public class AsyncClass extends AsyncTask<Void, String, Void> { 
    private Context context; 
    ProgressDialog dialog; 
 
        public AsyncClass(Context cxt) { 
            context = cxt; 
            dialog = new ProgressDialog(context); 
        } 
 
        @Override 
        protected void onPreExecute() { 
            dialog.setTitle("Please wait"); 
            dialog.show(); 
        } 
 
        @Override 
        protected Void doInBackground(Void... unused) { 
            SystemClock.sleep(2000); 
            return (null); 
        } 
 
        @Override 
        protected void onPostExecute(Void unused) { 
            dialog.dismiss(); 
        } 
    } 2.使用
private class PrepareAdapter1 extends AsyncTask<Void,Void,ContactsListCursorAdapter > { 
    ProgressDialog dialog; 
    @Override 
    protected void onPreExecute() { 
        dialog = new ProgressDialog(viewContacts.this); 
        dialog.setMessage(getString(R.string.please_wait_while_loading)); 
        dialog.setIndeterminate(true); 
        dialog.setCancelable(false); 
        dialog.show(); 
    } 
    /* (non-Javadoc) 
     * @see android.os.AsyncTask#doInBackground(Params[]) 
     */ 
    @Override 
    protected ContactsListCursorAdapter doInBackground(Void... params) { 
        cur1 = objItem.getContacts(); 
        startManagingCursor(cur1); 
 
        adapter1 = new ContactsListCursorAdapter (viewContacts.this, 
                R.layout.contact_for_listitem, cur1, new String[] {}, new int[] {}); 
 
        return adapter1; 
    } 
 
    protected void onPostExecute(ContactsListCursorAdapter result) { 
        list.setAdapter(result); 
        dialog.dismiss(); 
    } 
}