android - Fragments and Activities -- where do I put my application logic? -

i have created view how want look. has 1 images, input box, , button. want load activity when button clicked. confused why there fragments , activities. new android world (coming ios).

my understanding activities similar viewcontrollers, not sure understand fragment is.

where put event handling?

package com.phppointofsale.phppointofsale;  import android.support.v7.app.actionbaractivity; import android.support.v7.app.actionbar; import android.support.v4.app.fragment; import android.os.bundle; import android.view.layoutinflater; import android.view.menu; import android.view.menuitem; import android.view.view; import android.view.viewgroup; import android.os.build;  public class storeurlactivity extends actionbaractivity {      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_store_url);          if (savedinstancestate == null) {             getsupportfragmentmanager().begintransaction()                     .add(r.id.container, new storeurlfragement()).commit();         }     }      @override     public boolean oncreateoptionsmenu(menu menu) {          // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.menu.store_url, menu);         return true;     }      @override     public boolean onoptionsitemselected(menuitem item) {         // handle action bar item clicks here. action bar         // automatically handle clicks on home/up button, long         // specify parent activity in androidmanifest.xml.         int id = item.getitemid();         if (id == r.id.action_settings) {             return true;         }         return super.onoptionsitemselected(item);     }      /**      * placeholder fragment containing simple view.      */     public static class storeurlfragement extends fragment {          public storeurlfragement() {         }          @override         public view oncreateview(layoutinflater inflater, viewgroup container,                 bundle savedinstancestate) {             view rootview = inflater.inflate(r.layout.fragment_store_url,                     container, false);             return rootview;         }     }  } 

firstly recommend reading fragments . pay particular attention created fragment section, includes fragment life-cycle diagram. second download , compile sample app,the effective navigation app understand how different fragments work in tandem, , implements action bar.

to answer question more or less fragment can thought of separate class. once call upon particular fragment can call functions within class.

fragment case-switch

this sample code show mean.

 public fragment getitem(int i){     switch (i) {         case 0:             // first section of app interesting -- offers             // launchpad other demonstrations in example application.             return new launchpadsectionfragment();          case 1:             return new bluetoothclass();          default:             // gps section of app .             fragment fragment = new dummysectionfragment();             bundle args = new bundle();             args.putint(dummysectionfragment.arg_section_number, + 1);             fragment.setarguments(args);             return fragment;         } } 

in case each fragment me represented class, implemented in separate tab , each tab had separate functionality. 1 of key advantages of fragments can run separate activities without first letting 1 activity complete.

furthermore each fragment extension of java.lang.object library. has functions + additional ones. read this well. lastly idea have separate xml files each fragment can display separately when fragment invoked.

some more code

each fragment will/could have this

public void onactivitycreated(bundle savedinstancestate){         super.onactivitycreated(savedinstancestate);             // stuff on creation. add bulk of code. clicklistners          view rootview = inflater.inflate(r.layout.xml_the_fragment_uses container,false);         rootview.findviewbyid(r.id.your_id).setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             //do          }     }); }       public void onstart(){         super.onstart();         toast.maketext(getactivity(), "fragment started",toast.length_short).show();     }             public void onresume(){         super.onstart();         toast.maketext(getactivity(), "fragment resumed",toast.length_short).show();      }      public void onstop(){         super.onstart();         toast.maketext(getactivity(), "fragment stoped",toast.length_short).show();         disablebt();     } 

remember these functions fragment life-cycle mentioned earlier.

hopefully gave idea on fragments. remember read this lot of functionality uses v7 app compat library. including fragment manager.