java - Cannot add function "OnClickListener" to ImageButton -

here java code:

public class mainpage extends appcompatactivity implements navigationview.onnavigationitemselectedlistener {  tablayout tablayout; viewpageadapter viewpageadapter; viewpager viewpager; imagebutton pfp; bitmap bitmap_one;  private string upload_url = "http://.php"; private int pick_image_request = 1; private string key_image = "image";  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.main_page);     inittypeface();       //id's     pfp = (imagebutton) findviewbyid(r.id.imagebutton_one);     pfp.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             if (v == pfp){                 showfilechooser();             }         }     });       //searchintent     intent searchi = getintent();     if (intent.action_search.equals(searchi.getaction())) {          string query = searchi.getstringextra(searchmanager.query);         toast.maketext(mainpage.this, query, toast.length_short).show();     }      //toolbar     toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar);     setsupportactionbar(toolbar);     getsupportactionbar().settitle(null);      //tabs     tablayout = (tablayout) findviewbyid(r.id.tablayout_two);     viewpager = (viewpager) findviewbyid(r.id.viewpager_two);     viewpageadapter = new viewpageadapter(getsupportfragmentmanager());     viewpageadapter.addfragments(new feedfragment(), "feed");     viewpageadapter.addfragments(new messagesfragment(), "messages");     viewpageadapter.addfragments(new notificationsfragment(), "notifications");     viewpager.setadapter(viewpageadapter);     tablayout.setupwithviewpager(viewpager);       //floatingactionbutton     floatingactionbutton fab = (floatingactionbutton) findviewbyid(r.id.fab);     fab.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view view) {         }     });       //navigationdrawer     drawerlayout drawer = (drawerlayout) findviewbyid(r.id.drawer_layout);     actionbardrawertoggle toggle = new actionbardrawertoggle(             this, drawer, toolbar, r.string.navigation_drawer_open, r.string.navigation_drawer_close);     drawer.setdrawerlistener(toggle);     toggle.syncstate();      navigationview navigationview = (navigationview) findviewbyid(r.id.nav_view);     navigationview.setnavigationitemselectedlistener(this); }  @override public void onbackpressed() {     drawerlayout drawer = (drawerlayout) findviewbyid(r.id.drawer_layout);     if (drawer.isdraweropen(gravitycompat.start)) {         drawer.closedrawer(gravitycompat.start);     } else {         super.onbackpressed();     } }  @override public boolean onnavigationitemselected(menuitem item) {     int id = item.getitemid();      if (id == r.id.profile) {          intent = new intent(this, profile.class);         startactivity(i);      } else if (id == r.id.whatshot) {          intent = new intent(this, whatshot.class);         startactivity(i);      } else if (id == r.id.trending) {          intent = new intent(this, trending.class);         startactivity(i);      } else if (id == r.id.radioplayer) {          intent = new intent(this, radio.class);         startactivity(i);      } else if (id == r.id.musicplayer) {          intent = new intent(this, musicplayer.class);         startactivity(i);      } else if (id == r.id.settings) {          intent = new intent(this, settings.class);         startactivity(i);      } else if (id == r.id.info) {          intent = new intent(this, info.class);         startactivity(i);      }      drawerlayout drawer = (drawerlayout) findviewbyid(r.id.drawer_layout);     drawer.closedrawer(gravitycompat.start);     return true; }  @override public boolean oncreateoptionsmenu(menu menu) {      getmenuinflater().inflate(r.menu.main_menu, menu);      searchview searchview = (searchview) menu.finditem(r.id.search_view).getactionview();     searchmanager searchmanager = (searchmanager) getsystemservice(search_service);     searchview.setsearchableinfo(searchmanager.getsearchableinfo(getcomponentname()));      return super.oncreateoptionsmenu(menu); }   //imageinfo private void showfilechooser() {     intent intent = new intent();     intent.settype("image/*");     intent.setaction(intent.action_get_content);     startactivityforresult(intent.createchooser(intent, "select picture"), pick_image_request); }  @override protected void onactivityresult(int requestcode, int resultcode, intent data) {     super.onactivityresult(requestcode, resultcode, data);      if (requestcode == pick_image_request && resultcode == result_ok && data != null && data.getdata() != null) {         uri filepath = data.getdata();         try {              bitmap_one = mediastore.images.media.getbitmap(getcontentresolver(), filepath);             pfp.setimagebitmap(bitmap_one);         } catch (ioexception e) {             e.printstacktrace();         }     } }    //typeface private void inittypeface() {      typeface mytypeface = typeface.createfromasset(getassets(), "fonts/amble-regular.ttf");     textview text = (textview) findviewbyid(r.id.toolbartitle);     text.settypeface(mytypeface);  } } 

here xml code:

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="@dimen/nav_header_height" android:background="@drawable/side_nav_bar" android:gravity="bottom" android:orientation="vertical" android:paddingbottom="@dimen/activity_vertical_margin" android:paddingleft="@dimen/activity_horizontal_margin" android:paddingright="@dimen/activity_horizontal_margin" android:paddingtop="@dimen/activity_vertical_margin" android:theme="@style/themeoverlay.appcompat.dark">  <imagebutton     android:id="@+id/imagebutton_one"     android:layout_width="90dp"     android:background="#2a363b"     android:onclick="pfpclick"     android:layout_height="90dp"     android:paddingtop="@dimen/nav_header_vertical_spacing" />  <textview     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:paddingtop="@dimen/nav_header_vertical_spacing"     android:text=""     android:textappearance="@style/textappearance.appcompat.body1" />  <textview     android:id="@+id/textview"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="" />  </linearlayout> 

what trying accomplish onclick of imagebutton, can choose file , add it. keep getting error:

attempt invoke virtual method 'void android.widget.imagebutton.setonclicklistener(android.view.view$onclicklistener)' on null object reference

p.s imagebutton in navigation drawer.

you should either this:

android:onclick="pfpclick" 

but need define method in class name pfpclick, , not there

or this

pfp.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             if (v == pfp){                 showfilechooser();             }         }     }); 

both @ same time bad practice , second option not necessary:

if (v == pfp){  

because listener implementing anonymous

i suggest remove in layout:

 android:onclick="pfpclick" 

and clean/modify listener snippet:

pfp.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             showfilechooser();          }     });