What is the best way to keep an android application's thread (other than the UI thread) running even after the application is closed?

Make it a Service. .. which is like a daemon process in Unix.

I think "services" is your answer. In android, if you want anything to run in background even after closing the activity, you should do it as a ser

Make it a service and it will run in background.... you may refer to foll. tutorial : http://www.vogella.com/articles/AndroidServices/article.html

You can use BroadcastReceiver to achive your requriment . check following code. activity_alarm_manager.xml <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical">     <Button         android:id="@+id/btStart"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:padding="@dimen/padding_medium"         android:text="@string/btStart"         android:onClick="startRepeatingTimer"         tools:context=".WidgetAlarmManagerActivity" />     <Button         android:id="@+id/btCancel"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:padding="@dimen/padding_medium"         android:text="@string/btCancel"         android:onClick="cancelRepeatingTimer"          /> <Button         android:id="@+id/btOneTime"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:padding="@dimen/padding_medium"         android:text="@string/btOneTime"         android:onClick="onetimeTimer"          /> </LinearLayout> AlarmManagerActivity.java public class AlarmManagerActivity extends Activity { private AlarmManagerBroadcastReceiver alarm;     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_alarm_manager);         alarm = new AlarmManagerBroadcastReceiver();     }         @Override protected void onStart() { super.onStart(); }     public void startRepeatingTimer(View view) {     Context context = this.getApplicationContext();     if(alarm != null){     alarm.SetAlarm(context);     }else{     Toast.makeText(context, "Alarm is null", Toast.LENGTH_SHORT).show();     }     }         public void cancelRepeatingTimer(View view){     Context context = this.getApplicationContext();     if(alarm != null){     alarm.CancelAlarm(context);     }else{     Toast.makeText(context, "Alarm is null", Toast.LENGTH_SHORT).show();     }     }         public void onetimeTimer(View view){     Context context = this.getApplicationContext();     if(alarm != null){     alarm.setOnetimeTimer(context);     }else{     Toast.makeText(context, "Alarm is null", Toast.LENGTH_SHORT).show();     }     }     @Override     public boolean onCreateOptionsMenu(Menu menu) {         getMenuInflater().inflate(R.menu.activity_widget_alarm_manager, menu);         return true;     }     }   AlarmManagerBroadcastReceiver.java public class AlarmManagerBroadcastReceiver extends BroadcastReceiver { final public static String ONE_TIME = "onetime"; @Override public void onReceive(Context context, Intent intent) { PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);          PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "YOUR TAG");          //Acquire the lock          wl.acquire();          //You can do the processing here update the widget/remote views.          Bundle extras = intent.getExtras();          StringBuilder msgStr = new StringBuilder();                   if(extras != null && extras.getBoolean(ONE_TIME, Boolean.FALSE)){         msgStr.append("One time Timer : ");          }          Format formatter = new SimpleDateFormat("hh:mm:ss a");          msgStr.append(formatter.format(new Date()));          Toast.makeText(context, msgStr, Toast.LENGTH_LONG).show();                   //Release the lock          wl.release();          } public void SetAlarm(Context context)     {         AlarmManager am=(AlarmManager)context.getSystemService(Context.ALARM_SERVICE);         Intent intent = new Intent(context, AlarmManagerBroadcastReceiver.class);         intent.putExtra(ONE_TIME, Boolean.FALSE);         PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, 0);         //After after 30 seconds         am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000 * 5 , pi);     }     public void CancelAlarm(Context context)     {         Intent intent = new Intent(context, AlarmManagerBroadcastReceiver.class);         PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);         AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);         alarmManager.cancel(sender);     }     public void setOnetimeTimer(Context context){     AlarmManager am=(AlarmManager)context.getSystemService(Context.ALARM_SERVICE);         Intent intent = new Intent(context, AlarmManagerBroadcastReceiver.class);         intent.putExtra(ONE_TIME, Boolean.TRUE);         PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, 0);         am.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), pi);     } } Manifest.xml  <uses-sdk         android:minSdkVersion="10"         android:targetSdkVersion="15" />     <!-- Permissions --> <uses-permission android:name="android.permission.WAKE_LOCK"/>     <application         android:icon="@drawable/ic_launcher"         android:label="@string/app_name"         >         <activity             android:name=".AlarmManagerActivity"             android:label="@string/title_activity_alarm_manager" >             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                 <category android:name="android.intent.category.LAUNCHER" />             </intent-filter>         </activity>         <!-- Broadcast receiver -->         <receiver   android:name=".AlarmManagerBroadcastReceiver"></receiver>     </application>

Use Android's services! U can't have the UI thread run in the background for ever since android closes apps when they run out of memory!! Using services u can run apps which doesn't have to have a UI! See android documentation for more details