android - Application Crashes while changing activities -

i've been working on support multiple screens in app. however, when screen detected 480x800 screen, switches activity resolution, @ point crashes...

this detect.java, makes decision based on screen resolution:

package com.example.mywallpapers;  import android.app.activity; import android.content.intent; import android.graphics.point; import android.os.build; import android.os.bundle; import android.view.display; import android.view.windowmanager;  public class detect extends activity {      @suppresswarnings("deprecation")     @override     protected void oncreate(bundle savedinstancestate) {         // todo auto-generated method stub         super.oncreate(savedinstancestate);         int width = 0;         point size = new point();         windowmanager w = getwindowmanager();          if (build.version.sdk_int >= build.version_codes.honeycomb_mr2) {              w.getdefaultdisplay().getsize(size);              width = size.x;         } else {             display d = w.getdefaultdisplay();             width = d.getwidth();         }         if (width == 480) {                 startactivity(new intent(detect.this, seventwentyone.class));            } else if (width == 720) {             startactivity(new intent("com.example.mywallpapers.foureightone"));         } else {             startactivity(new intent("com.example.mywallpapers.foureightone"));         }      }        } 

this seventwentyone class (which isn't 1280x720 resolution, 480x800)

package com.example.mywallpapers;  import java.io.ioexception; import android.app.activity; import android.graphics.bitmap; import android.graphics.bitmapfactory; import android.media.mediaplayer; import android.os.bundle; import android.view.gravity; import android.view.view; import android.widget.button; import android.widget.imageview; import android.widget.toast;  import com.mopub.mobileads.mopubview;  public class seventwentyone extends activity {      imageview display;     int tophone;     private mopubview madview;     mediaplayer knopje;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.foureightyeighthundredeen);          madview = (mopubview) findviewbyid(r.id.adview);         madview.setadunitid("e95a36beb72611e281c11231392559e4"); // enter                                                                     // ad unit                                                                     // id         // www.mopub.com         madview.loadad();          display = (imageview) findviewbyid(r.id.wap49);         button image1 = (button) findviewbyid(r.id.wap50);         button image2 = (button) findviewbyid(r.id.wap51);         button image3 = (button) findviewbyid(r.id.wap52);         button image4 = (button) findviewbyid(r.id.wap53);         button image5 = (button) findviewbyid(r.id.wap54);         button image6 = (button) findviewbyid(r.id.wap55);         button image7 = (button) findviewbyid(r.id.wap56);         button image8 = (button) findviewbyid(r.id.wap57);         button image9 = (button) findviewbyid(r.id.wap58);         button image10 = (button) findviewbyid(r.id.wap59);         button image11 = (button) findviewbyid(r.id.wap60);         button image12 = (button) findviewbyid(r.id.wap61);         button image13 = (button) findviewbyid(r.id.wap62);         button image14 = (button) findviewbyid(r.id.wap63);         button image15 = (button) findviewbyid(r.id.wap64);         button image16 = (button) findviewbyid(r.id.wap65);         button image17 = (button) findviewbyid(r.id.wap66);         button image18 = (button) findviewbyid(r.id.wap67);         button image19 = (button) findviewbyid(r.id.wap68);         button image20 = (button) findviewbyid(r.id.wap69);         button image21 = (button) findviewbyid(r.id.wap70);         button image22 = (button) findviewbyid(r.id.wap71);         button image23 = (button) findviewbyid(r.id.wap72);         button image24 = (button) findviewbyid(r.id.wap73);         button image25 = (button) findviewbyid(r.id.wap74);         button image26 = (button) findviewbyid(r.id.wap75);         button image27 = (button) findviewbyid(r.id.wap76);         button image28 = (button) findviewbyid(r.id.wap77);         button image29 = (button) findviewbyid(r.id.wap78);         button image30 = (button) findviewbyid(r.id.wap79);         button image31 = (button) findviewbyid(r.id.wap80);         button image32 = (button) findviewbyid(r.id.wap81);         button image33 = (button) findviewbyid(r.id.wap82);         button image34 = (button) findviewbyid(r.id.wap83);         button image35 = (button) findviewbyid(r.id.wap84);         button image36 = (button) findviewbyid(r.id.wap85);         button image37 = (button) findviewbyid(r.id.wap86);         button image38 = (button) findviewbyid(r.id.wap87);         button image39 = (button) findviewbyid(r.id.wap88);         button image40 = (button) findviewbyid(r.id.wap89);         button image41 = (button) findviewbyid(r.id.wap90);         button image42 = (button) findviewbyid(r.id.wap91);         button image43 = (button) findviewbyid(r.id.wap92);         button image44 = (button) findviewbyid(r.id.wap93);         button image45 = (button) findviewbyid(r.id.wap94);         button image46 = (button) findviewbyid(r.id.wap95);         button image47 = (button) findviewbyid(r.id.wap96);         button setwall = (button) findviewbyid(r.id.setwallpaperbutton);          tophone = r.drawable.a_aardbeien;         knopje = mediaplayer.create(getapplicationcontext(), r.raw.button);           image1.setonclicklistener(new view.onclicklistener() { // line 90              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.aardmannetje);                 tophone = r.drawable.a_aardmannetje;                 knopje.start();             }         });         image2.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.aardbeien);                 tophone = r.drawable.a_aardbeien;                 knopje.start();             }         });         image3.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.android);                 tophone = r.drawable.a_android;                 knopje.start();             }         });         image4.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.batman);                 tophone = r.drawable.a_batman;                 knopje.start();             }         });         image5.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.bij);                 tophone = r.drawable.a_bij;                 knopje.start();             }         });         image6.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.blaadjes);                 tophone = r.drawable.a_blaadjes;                 knopje.start();             }         });         image7.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.bliksem);                 tophone = r.drawable.a_bliksem;                 knopje.start();             }         });         image8.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.bloemblaadjes);                 tophone = r.drawable.a_bloemblaadjes;                 knopje.start();             }         });         image9.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.bloemetjes);                 tophone = r.drawable.a_bloemetjes;                 knopje.start();             }         });         image10.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.blokjes);                 tophone = r.drawable.a_blokjes;                 knopje.start();             }         });         image11.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.bubbels);                 tophone = r.drawable.a_bubbels;                 knopje.start();             }         });         image12.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.chocolade);                 tophone = r.drawable.a_chocolade;                 knopje.start();             }         });         image13.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.closeuproos);                 tophone = r.drawable.a_closeuproos;                 knopje.start();             }         });         image14.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.druppels);                 tophone = r.drawable.a_druppels;                 knopje.start();             }         });         image15.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.duinen);                 tophone = r.drawable.a_duinen;                 knopje.start();             }         });         image16.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.frambozen);                 tophone = r.drawable.a_frambozen;                 knopje.start();             }         });         image17.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.gekleurdeblokjes);                 tophone = r.drawable.a_gekleurdeblokjes;                 knopje.start();             }         });         image18.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.gekleurdeballetjes);                 tophone = r.drawable.a_gekleurderondjes;                 knopje.start();             }         });         image19.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.gekleurderoos);                 tophone = r.drawable.a_gekleurderoos;                 knopje.start();             }         });         image20.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.geld);                 tophone = r.drawable.a_geld;                 knopje.start();             }         });         image21.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.gitaar);                 tophone = r.drawable.a_gitaar;                 knopje.start();             }         });         image22.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.graslucht);                 tophone = r.drawable.a_luchtgras;                 knopje.start();             }         });         image23.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.hartjes);                 tophone = r.drawable.a_hartjes;                 knopje.start();             }         });         image24.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.hartjesdruppel);                 tophone = r.drawable.a_hartjesdruppel;                 knopje.start();             }         });         image25.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.ijsjes);                 tophone = r.drawable.a_ijsjes;                 knopje.start();             }         });         image26.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.jellybeans);                 tophone = r.drawable.a_jellybeans;                 knopje.start();             }         });         image27.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.kerstballen);                 tophone = r.drawable.a_kerstballen;                 knopje.start();             }         });         image28.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.kleurenspiraal);                 tophone = r.drawable.a_kleurenspiraal;                 knopje.start();             }         });         image29.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.kleurenhout);                 tophone = r.drawable.a_kleurhout;                 knopje.start();             }         });         image30.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.kleurstrepen);                 tophone = r.drawable.a_kleurstrepen;                 knopje.start();             }         });         image31.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.kunst);                 tophone = r.drawable.a_kunst;                 knopje.start();             }         });         image32.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.lente);                 tophone = r.drawable.a_lente;                 knopje.start();             }         });         image33.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.muziek);                 tophone = r.drawable.a_muziek;                 knopje.start();             }         });         image34.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.panterprint);                 tophone = r.drawable.a_panterprint;                 knopje.start();             }         });          image35.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.parijs);                 tophone = r.drawable.a_parijs;                 knopje.start();             }         });         image36.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.piano);                 tophone = r.drawable.a_piano;                 knopje.start();             }         });         image37.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.rozen);                 tophone = r.drawable.a_rozen;                 knopje.start();             }         });         image38.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.rozepaarsebloemetjes);                 tophone = r.drawable.a_rozepaarsebloemetjes;                 knopje.start();             }         });         image39.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.stenen);                 tophone = r.drawable.a_stenen;                 knopje.start();             }         });         image40.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.strand);                 tophone = r.drawable.a_strand;                 knopje.start();             }         });         image41.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.streepjes);                 tophone = r.drawable.a_streepjes;                 knopje.start();             }         });         image42.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.struik);                 tophone = r.drawable.a_struik;                 knopje.start();             }         });         image43.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.tjahoezullenwehetnoemen);                 tophone = r.drawable.a_tjahoezullenwehetnoemen;                 knopje.start();             }         });         image44.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.tulpen);                 tophone = r.drawable.a_tulpen;                 knopje.start();             }         });         image45.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.veren);                 tophone = r.drawable.a_veren;                 knopje.start();             }         });         image46.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.watermannetje);                 tophone = r.drawable.a_watermannetje;                 knopje.start();             }         });         image47.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view arg0) {                 display.setimageresource(r.drawable.zwartwit);                 tophone = r.drawable.a_zwartwit;                 knopje.start();             }         });         setwall.setonclicklistener(new view.onclicklistener() {              @suppresswarnings("deprecation")             @override             public void onclick(view arg0) {                 bitmap whatever = bitmapfactory.decodestream(getresources()                         .openrawresource(tophone));                 try {                      getapplicationcontext().setwallpaper(whatever);                 } catch (ioexception e) {                     e.printstacktrace();                 } {knopje.start();                     toast my_toast = toast.maketext(getapplicationcontext(), "wallpaper set!", toast.length_short);                     my_toast.setgravity(gravity.center, 0, 0);                     my_toast.show();;                 }               }          });     };      @override     protected void onpause() {         // todo auto-generated method stub         super.onpause();         madview.destroy();     }      @override     protected void ondestroy() {         super.ondestroy();         madview.destroy();     }      @override     protected void onresume() {         // todo auto-generated method stub         super.onresume();         madview = (mopubview) findviewbyid(r.id.adview);         madview.setadunitid("e95a36beb72611e281c11231392559e4"); // enter                                                                     // ad unit                                                                     // id         // www.mopub.com         madview.loadad();     }  } 

whenever test app on 480x800 phone, crashes nullpointerexeption. idea 1 might come from?

this logcat:

05-15 11:27:47.600: e/androidruntime(31642): fatal exception: main 05-15 11:27:47.600: e/androidruntime(31642): java.lang.runtimeexception: unable start activity componentinfo{com.example.mywallpapers/com.example.mywallpapers.seventwentyone}: java.lang.nullpointerexception 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread.performlaunchactivity(activitythread.java:2100) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread.handlelaunchactivity(activitythread.java:2125) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread.access$600(activitythread.java:140) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread$h.handlemessage(activitythread.java:1227) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.os.handler.dispatchmessage(handler.java:99) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.os.looper.loop(looper.java:137) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread.main(activitythread.java:4898) 05-15 11:27:47.600: e/androidruntime(31642):    @ java.lang.reflect.method.invokenative(native method) 05-15 11:27:47.600: e/androidruntime(31642):    @ java.lang.reflect.method.invoke(method.java:511) 05-15 11:27:47.600: e/androidruntime(31642):    @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:1008) 05-15 11:27:47.600: e/androidruntime(31642):    @ com.android.internal.os.zygoteinit.main(zygoteinit.java:775) 05-15 11:27:47.600: e/androidruntime(31642):    @ dalvik.system.nativestart.main(native method) 05-15 11:27:47.600: e/androidruntime(31642): caused by: java.lang.nullpointerexception 05-15 11:27:47.600: e/androidruntime(31642):    @ com.example.mywallpapers.seventwentyone.oncreate(seventwentyone.java:90) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activity.performcreate(activity.java:5206) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1094) 05-15 11:27:47.600: e/androidruntime(31642):    @ android.app.activitythread.performlaunchactivity(activitythread.java:2064) 05-15 11:27:47.600: e/androidruntime(31642):    ... 11 more