java - Edit ViewGroup outside onCreate -

i create viewgroup programatically. add 2 views, game , seekbar. however, if try change seekbar properties within game (which has pointer androidadapter) using, example, parent.seekbar.setvisibility(view.visible) app crashes.

the parent filed set follows, inside game class:

public class simulation extends applicationadapter implements gesturedetector.gesturelistener{      androidlauncher parent=null;      public void setparent( androidlauncher nparent ){        parent = nparent;     }      public void something(){         if( parent != null ) parent.layout.removeview( parent.seekbar );     } } 

i'm missing permission change view? have set/change before editing seekbar? thanks!

public class androidlauncher extends androidapplication {      simulation simul;     viewgroup layout;      seekbar seekbar;     shapedrawable thumb;     layoutparams lp;      @override     protected void oncreate (bundle savedinstancestate) {         simul = new simulation();         simul.setparent(this);         super.oncreate(savedinstancestate);          setcontentview( r.layout.main );         layout = (viewgroup) findviewbyid( r.id.panel );          androidapplicationconfiguration config = new androidapplicationconfiguration();         config.usewakelock = true;         config.useaccelerometer = false;         config.usecompass = false;         layout.addview(initializeforview(simul, config));           seekbar = new seekbar(this);         seekbar.setmax(100);         thumb = new shapedrawable(new ovalshape());         thumb.setintrinsicheight(50);         thumb.setintrinsicwidth(50);         seekbar.setthumb(thumb);         seekbar.setprogress(1);         seekbar.setbackground(new colordrawable(android.r.color.transparent));         lp = new layoutparams(600, 50);         seekbar.setlayoutparams(lp);         seekbar.setonseekbarchangelistener(new onseekbarchangelistener() {             public void onstoptrackingtouch(seekbar arg0) {                 // todo auto-generated method stub                 system.out.println(".....111.......");             }              public void onstarttrackingtouch(seekbar arg0) {                 // todo auto-generated method stub                 system.out.println(".....222.......");             }              public void onprogresschanged(seekbar arg0, int arg1, boolean arg2) {                 // todo auto-generated method stub                 system.out.println(".....333......." + arg1);             }         });          layout.addview(seekbar);     } } 

only main thread can edit views. edit views other classes, must pass reference main thread class using setparent(this). callback method should set in main thread class, method called when wish edit views. in method, must guarantee instructions executed main/ui thread, can using runonuithread(...).

check following example:

public class androidlauncher extends androidapplication {  simulation simul; viewgroup layout;  seekbar seekbar;  @override protected void oncreate (bundle savedinstancestate) {     super.oncreate(savedinstancestate);     simul = new simulation();     simul.setparent(this);       setcontentview(r.layout.main);     layout = (viewgroup) findviewbyid( r.id.panel );      androidapplicationconfiguration config = new androidapplicationconfiguration();     config.usewakelock = true;     config.useaccelerometer = false;     config.usecompass = false;     layout.addview(initializeforview(simul, config));      seekbar = (seekbar) findviewbyid(r.id.seekbar);     seekbar.setonseekbarchangelistener(new onseekbarchangelistener() {         @override         public void onprogresschanged(seekbar seekbar, int progress, boolean fromuser) {             system.out.println( progress );         }          @override         public void onstarttrackingtouch(seekbar seekbar) {          }          @override         public void onstoptrackingtouch(seekbar seekbar) {          }     });  }  public void showseekbar(){     runonuithread(new runnable() {         @override         public void run() {             seekbar.setvisibility( view.visible );         }     });  }   public void hideseekbar(){     runonuithread(new runnable() {         @override         public void run() {             seekbar.setvisibility( view.gone );         }     });  } 

the xml file set follows:

<?xml version="1.0" encoding="utf-8"?> <framelayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/main" android:orientation="vertical">    <framelayout     android:id="@+id/panel"     android:layout_width="match_parent"     android:layout_height="match_parent">  </framelayout>   <seekbar     android:layout_width="406dp"     android:layout_height="wrap_content"     android:id="@+id/seekbar"     android:layout_gravity="top|center_horizontal"     android:progress="50"     android:max="200"     android:visibility="gone"     android:layout_margintop="30dp" />