android - Keep an activity/activities alive while the app is open in the background -

hey guys i'm brand new site, know people put down lot asking duplicated questions hope isn't 1 of them.

as site, new android programming , have created simple app calculating price based on time.

this app has 3 activities use switch layouts 1. firstactivity - shows title page , button launch second activity 2. secondactivity - starts timer , calculates price based on seconds. 3. lastactivity - shows end results of time , price , allows user share other apps (email, sms)

everything working fine, when phone orientates current activity killed , restarted i've fixed forcing layout portrait - i've run problem again when move app background

so actual question: need secondactivity keep time, , lastactivity keep saved info if user switches apps. i'm not talking when app closed im talking when app switcher or home button activated , app still open in background.

thank in advance!

so in end needed more information on how implement data save features suggested , android has, found answer needed here: how make android app return last open activity when relaunched?

to solve problem needed add: |1| new activity |2| <action> , <category> tags activity |3| sharedpreference setters in each activity needed keep.

1. per @josefpfleger's intructions made new blank activity named restoreprevactivity , in android manifest set main , launcher , default removed intent filters in first activity defaulted there after creating app first time.

   <activity   android:name=".firstactivity"   android:label="@string/app_name"   android:screenorientation="portrait" > </activity> <activity   android:name=".secondactivity"   android:label="@string/title_activity_second"   android:screenorientation="portrait"   android:launchmode="standard"> </activity> <activity   android:name=".lastactivity"   android:label="@string/title_activity_last"   android:screenorientation="portrait"   android:launchmode="standard"> </activity> <activity   android:name=".restoreprevactivity"   android:label="@string/title_activity_main" >   <intent-filter>     <action android:name="android.intent.action.main" />     <category android:name="android.intent.category.launcher" />     <category android:name="android.intent.category.default" />   </intent-filter> </activity> 

2. after setting action , category of new activity needed add code activity. added oncreate() of recoverprevactivity

`

@override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      class<?> activityclass;      try {         sharedpreferences prefs = getsharedpreferences("x", mode_private);         activityclass = class.forname(                 prefs.getstring("lastactivity", fareactivity.class.getname()));     } catch(classnotfoundexception ex) {         activityclass = fareactivity.class;     }      startactivity(new intent(this, activityclass)); } 

where firstactivity replaced default activity run if no previous activity found.

3. finally went through activities , added onpause() saved activity name.

i added following code segment other activities , working flawlessly.

@override protected void onpause() {     super.onpause();      sharedpreferences prefs = getsharedpreferences("x", mode_private);     sharedpreferences.editor editor = prefs.edit();     editor.putstring("thisactivity", getclass().getname());     editor.commit(); } 

where thisactivity changed name of current activity.

result able launch app, start timer , press home button or app switcher safely switch apps or lock screen , upon return brought timer running uninterrupted! put test , ran clash of clans, memory heavy game , watched youtube videos 30 app running in background , came app see time correct , ran while gone.

thanks everyone's help! -stephen