Error while Retriving files from google drive using drive API. “Calling this from your main thread can lead to deadlock

Error while Retriving files from google drive using drive API. "Calling
this from your main thread can lead to deadlock

Hi this is what i am trying to do to get the text files.I tried same with
New thread
also when i create new thread its not coming inside the getfiles(Drive
services) method only. Please give me solution i am not getting this.
Error is runnung with main may lead to deadlock
public class MainActivity extends Activity {
static final int REQUEST_ACCOUNT_PICKER = 1;
private static Uri fileUri;
private static Drive service;
private GoogleAccountCredential credential;
Button b;
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b = (Button)findViewById(R.id.b1);
credential = GoogleAccountCredential.usingOAuth2(this,
DriveScopes.DRIVE);
startActivityForResult(credential.newChooseAccountIntent(),
REQUEST_ACCOUNT_PICKER);
Toast.makeText(getApplicationContext(), "case1",
Toast.LENGTH_LONG).show();
}
protected void onActivityResult(final int requestCode, final int
resultCode, final Intent data)
{
if(requestCode==REQUEST_ACCOUNT_PICKER)
{
if (resultCode == RESULT_OK && data != null && data.getExtras()
!= null)
{
Toast.makeText(getApplicationContext(), "case2",
Toast.LENGTH_LONG).show();
String accountName =
data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
if (accountName != null)
{
credential.setSelectedAccountName(accountName);
service = getDriveService(credential);
Toast.makeText(getApplicationContext(), "Got the E mail
id", Toast.LENGTH_LONG).show();
b.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Toast.makeText(getApplicationContext(), "case4",
Toast.LENGTH_LONG).show();
getfiles(service);
}
});
}
}
}
}
public void getfiles(final Drive service)
{
Toast.makeText(getApplicationContext(), "case5",
Toast.LENGTH_LONG).show();
String TEXT_PLAIN = "TEXT/PLAIN";
try
{
Files.List request = service.files().list().setQ("mimeType = '" +
TEXT_PLAIN +"'");
Toast.makeText(getApplicationContext(), "case",
Toast.LENGTH_LONG).show();
Map<String, File> textFiles = new HashMap<String, File>();
do {
Toast.makeText(getApplicationContext(), "case6",
Toast.LENGTH_LONG).show();
FileList files = request.execute(); //this is error line
Toast.makeText(getApplicationContext(), "case7",
Toast.LENGTH_LONG).show();
for (File file : files.getItems())
{
textFiles.put(file.getId(), file);
}
request.setPageToken(files.getNextPageToken());
} while (request.getPageToken() != null &&
request.getPageToken().length() > 0);
}
catch(Exception e)
{
Toast.makeText(getApplicationContext(),e.toString(),
Toast.LENGTH_LONG).show();
}
}
private Drive getDriveService(GoogleAccountCredential credential) {
return new Drive.Builder(AndroidHttp.newCompatibleTransport(), new
GsonFactory(), credential)
.build();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}