android - Why does Apps Main Activity not take new values of variables after they are changed when the activity starts? -

hi know why though ive created methods change co-ordinate values (which executed before main method). main method still taking default values gave co-ordinate variables @ start of activity?

here code:

for first activity shown on app (start activity) allows change lat , long co-ordinates typing in alert dialog, starting main map activity:

    public class startviewactivity extends activity {  mainactivity longlat = new mainactivity();  @override public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.startview);      button button = (button) findviewbyid(r.id.button1);     button button1 = (button) findviewbyid(r.id.button2);     button button2 = (button) findviewbyid(r.id.button3);      button.setonclicklistener(new onclicklistener() {          public void onclick(view v) {              alertdialog.builder alert = new alertdialog.builder(startviewactivity.this);             alert.settitle("longitude");             alert.setmessage("input longitude");              final edittext input = new edittext(startviewactivity.this);             alert.setview(input);              alert.setpositivebutton( "continue..", new dialoginterface.onclicklistener() {                         public void onclick(dialoginterface dialog,                                 int which) {                             string lng1 = input.gettext().tostring();                             longlat.lngsetter(lng1);                         }                     });             alert.show();          }      });      button1.setonclicklistener(new onclicklistener() {          public void onclick(view v) {              alertdialog.builder alert = new alertdialog.builder(startviewactivity.this);             alert.settitle("latitude");             alert.setmessage("input latitude");              final edittext input = new edittext(startviewactivity.this);             alert.setview(input);              alert.setpositivebutton( "continue..", new dialoginterface.onclicklistener() {                         public void onclick(dialoginterface dialog, int which) {                             string lat1 = input.gettext().tostring();                             longlat.latsetter(lat1);                         }                     });             alert.show();         }});          button2.setonclicklistener(new onclicklistener() {              public void onclick(view v) {                  intent intent = new    intent(startviewactivity.this,mainactivity.class);                 startactivity(intent);              }});         }} 

this code main activity, contains methods called in start activity should change lat , lng values (but takes original lat , lng values every time activity starts) :

    package com.example.workinggooglemaps;  import java.util.random;  import android.app.activity; import android.os.bundle; import android.view.menu;  import com.google.android.gms.maps.cameraupdatefactory; import com.google.android.gms.maps.googlemap; import com.google.android.gms.maps.mapfragment; import com.google.android.gms.maps.model.circleoptions; import com.google.android.gms.maps.model.latlng; import com.google.android.gms.maps.model.markeroptions; import com.google.android.gms.maps.model.polylineoptions;  public class mainactivity extends activity {  double[] tokens = new double[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,         13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,         30, 31 }; private double lat = 50.597636; private double lng = -2.447766; private googlemap themap; private random number = new random(); private int counter = 0;   public void lngsetter(string f){     lng = double.parsedouble(f);      system.out.println(lng);     } public void latsetter(string g){     lat = double.parsedouble(g);      system.out.println(lat);     }  public void polylinedrawer() {      themap.addpolyline(new polylineoptions()             .add(new latlng(tokens[0], tokens[1]))             .add(new latlng(tokens[2], tokens[3]))             .add(new latlng(tokens[4], tokens[5]))             .add(new latlng(tokens[6], tokens[7]))             .add(new latlng(tokens[8], tokens[9]))             .add(new latlng(tokens[10], tokens[11]))             .add(new latlng(tokens[12], tokens[13]))             .add(new latlng(tokens[14], tokens[15]))             .add(new latlng(tokens[16], tokens[17]))             .add(new latlng(tokens[18], tokens[19]))             .add(new latlng(tokens[20], tokens[21]))             .add(new latlng(tokens[22], tokens[23]))             .add(new latlng(tokens[24], tokens[25]))             .add(new latlng(tokens[26], tokens[27]))             .add(new latlng(tokens[28], tokens[29])).width(3)             .color(0xffff0000).zindex(0));  }  public void drawer() {     (; counter < 30; counter = counter + 2)         tokens[0] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[1] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[2] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[3] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[4] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[5] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[6] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[7] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[8] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[9] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[10] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[11] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[12] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[13] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[14] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[15] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[16] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[17] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[18] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[19] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[20] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[21] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[22] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[23] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[24] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[25] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[26] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[27] = (((number.nextdouble()) / 250) + lng) - 0.002;     tokens[28] = (((number.nextdouble()) / 250) + lat) - 0.002;     tokens[29] = (((number.nextdouble()) / 250) + lng) - 0.002; }   protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     if (themap == null) {         themap = ((mapfragment) getfragmentmanager().findfragmentbyid(                 r.id.the_map)).getmap();     }     if (themap != null) {      }      latlng co_ords = new latlng(lat, lng);     themap.setmaptype(googlemap.map_type_hybrid);     themap.addcircle(new circleoptions().center(co_ords).radius(200)             .strokewidth(3).zindex(1));     themap.addcircle(new circleoptions().center(co_ords).radius(150)             .strokewidth(3).zindex(1));     themap.addcircle(new circleoptions().center(co_ords).radius(100)             .strokewidth(3).zindex(1));     themap.addcircle(new circleoptions().center(co_ords).radius(50)             .strokewidth(3).zindex(1));     themap.addmarker(new markeroptions().position(co_ords)             .title("cerberus"));     themap.animatecamera(cameraupdatefactory.newlatlngzoom(co_ords, 17));     drawer();     polylinedrawer(); }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.main, menu);     return true; }  } 

i'm not sure if matter ill include manifest file , xml files both activities well:

here manifest:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="com.example.workinggooglemaps"     android:versioncode="1"     android:versionname="1.0" >      <uses-sdk         android:minsdkversion="11"         android:targetsdkversion="17" />      <permission         android:name="com.example.workinggooglemaps.permission.maps_receive"         android:protectionlevel="signature" />      <uses-permission android:name="com.example.workinggooglemaps.permission.maps_receive" />     <uses-permission android:name="android.permission.internet" />     <uses-permission android:name="android.permission.access_network_state" />     <uses-permission android:name="android.permission.write_external_storage" />     <uses-permission android:name="com.google.android.providers.gsf.permission.read_gservices" />     <uses-permission android:name="android.permission.access_coarse_location" />     <uses-permission android:name="android.permission.access_fine_location" />      <uses-feature         android:glesversion="0x00020000"         android:required="true" />      <application         android:allowbackup="true"         android:icon="@drawable/ic_launcher"         android:label="@string/app_name"         android:theme="@style/apptheme" >         <activity             android:name="com.example.workinggooglemaps.startviewactivity"             android:label="@string/app_name" >             <intent-filter>                 <action android:name="android.intent.action.main" />                  <category android:name="android.intent.category.launcher" />             </intent-filter>         </activity>         <activity             android:name="com.example.workinggooglemaps.mainactivity"             android:label="@string/app_name" >           </activity>         <meta-data             android:name="com.google.android.maps.v2.api_key"             android:value="aizasyagtm2ztsmeveqyljdvnkosyxadlu2j_rc" />     </application>  </manifest> 

here start activity xml:

<?xml version="1.0" encoding="utf-8"?> <relativelayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent" >      <button         android:id="@+id/button2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignleft="@+id/button1"         android:layout_alignright="@+id/button1"         android:layout_below="@+id/button1"         android:text="set latitude" />      <button         android:id="@+id/button1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignparenttop="true"         android:layout_centerhorizontal="true"         android:layout_margintop="72dp"         android:text="set longitude" />      <button         android:id="@+id/button3"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignparentbottom="true"         android:layout_alignright="@+id/button2"         android:layout_marginbottom="83dp"         android:text="show on map" />  </relativelayout>  here main activity xml:  <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:orientation="vertical" >      <fragment         android:id="@+id/the_map"         android:name="com.google.android.gms.maps.mapfragment"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_weight="0.49" />  </linearlayout> 

here main activity xml:

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:orientation="vertical" >      <fragment         android:id="@+id/the_map"         android:name="com.google.android.gms.maps.mapfragment"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_weight="0.49" />  </linearlayout> 

any appreciated :)

remove:

mainactivity longlat = new mainactivity(); 

you don't need create object of activity inside another. take user input value 1 activity , start activity using intent.

intent intent = new intent(currentactivity.this, newactivity.class); startactivity(intent); 

if want pass data between them, can pass parameters new activity using putextra function.

intent.putextra("param1", paramvalue); 

see how pass data between activities in android application? more.