我正在尝试等待advertisingidclient.getadvertisingidinfo（活动）的响应，但没有成功。在主线程完成之前，此方法不会响应。

import android.app.Activity;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
import com.google.android.gms.ads.identifier.AdvertisingIdClient;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesNotAvailableException;
import com.google.android.gms.common.GooglePlayServicesUtil;
import java.io.IOException;

public class MyActivity extends Activity {

    private Activity m_activity = null;
    private AdvertisingIdClient.Info m_info = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // start the thread with the getAdvertisingIdInfo()
        startGoogleAdvertisingIdRequest(this);

        // simulate a waiting loop, others app init, ...
        for (int i=0; i<20; i++) {
            SystemClock.sleep(100);
        }

        // get the uuid
        String uuid = getGoogleAdvertisingId();

        // call a method who need the uuid
        Log.i("UUID", "receive uuid: " + uuid);
    }

    public String getGoogleAdvertisingId() {
        String uuid = null;
        if (m_info != null) {
            if (!m_info.isLimitAdTrackingEnabled()) {
                uuid = m_info.getId();
            } else {
                uuid = "another uuid";
            }
        } else {
            uuid = "another uuid";
        }

        return uuid;
    }

    public void startGoogleAdvertisingIdRequest(final Activity activity) {
        m_activity = activity;
        if (GooglePlayServicesUtil.isGooglePlayServicesAvailable(activity) == ConnectionResult.SUCCESS) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    AdvertisingIdClient.Info adInfo = null;
                    try {
                        Log.i("UUID", "before google request");
                        adInfo = AdvertisingIdClient.getAdvertisingIdInfo(activity);
                        Log.i("UUID", "after google request");
                    } catch (IOException e) {
                        Log.w("UUID", "getAdvertisingIdInfo IOException: " + e.getMessage());
                    } catch (GooglePlayServicesNotAvailableException e) {
                        Log.w("UUID", "GooglePlayServicesNotAvailableException: " + e.getMessage());
                    } catch (Exception e) {
                        Log.w("UUID", "GooglePlayServicesException: " + e.getMessage());
                    } finally {
                        finished(adInfo);
                    }
                }
            }).start();
        }
    }

    private void finished(final AdvertisingIdClient.Info adInfo){
        if(adInfo != null){
            m_activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    m_info = adInfo;
                    Log.i("UUID", "runOnUiThread id: " + adInfo.getId());
                }
            });
        }
    }
}

此代码的logcat

11:29:52.103  30810-30828/com.example.testuuid I/UUID﹕ before google request
11:29:54.107  30810-30810/com.example.testuuid I/UUID﹕ receive uuid: another uuid
11:29:54.127  30810-30828/com.example.testuuid I/UUID﹕ after google request
11:29:54.151  30810-30810/com.example.testuuid I/UUID﹕ runOnUiThread id: d5dc3bfb-4756-490c-8f8e-2bedfb5e827a

相同的logcat，等待时间更长（5s）

11:36:14.215  31413-31436/com.example.testuuid I/UUID﹕ before google request
11:36:19.225  31413-31413/com.example.testuuid I/UUID﹕ receive uuid: another uuid
11:36:19.293  31413-31436/com.example.testuuid I/UUID﹕ after google request
11:36:19.315  31413-31413/com.example.testuuid I/UUID﹕ runOnUiThread id: d5dc3bfb-4756-490c-8f8e-2bedfb5e827a

每次主线程阻止另一个线程中的getadvertisingidinfo（）时。
原因是什么？如何做到这一点？