android - Interface NullPointerException - Sending Listener w/ Data to MainActivity on Button Click within Fragment -
been working on sending string data mainactivity on button click within fragment. doesn't seem difficult procedure, i'm getting tied somewhere , receiving nullpointerexception. i'm assuming has way i'm using interface. new android, suggestions , comments appreciated. thanks!
interface code:
public interface btninterface { public void btnclicked(string x, string y, string z, string w); } main activity snippet:
public class mainactivity extends activity implements btninterface{ fragment_x frag; fragmenttransaction ft; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); frag = new fragment_x(); frag.setinterface(this); ft = getfragmentmanager().begintransaction(); ft.add(r.id._frag_container, frag); ft.commit(); } @override public void btnclicked(string x, string y,string z, string w) { log.d("data-check", x); } fragment snippet:
public class fragment_x extends fragment { view v; button btn; btninterface buttoninterface; string x, y, z, w; string choices1 = {"random", "values"} string choices2 = {"random", "values"} string choices3 = {"random", "values"} string choices4 = {"random", "values"} public void setinterface(btninterface buttoninterface) { this.buttoninterface = buttoninterface; } public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) { v = inflater.inflate(r.layout.frag_layout, container, false); spin1 = (spinner) v.findviewbyid(r.id.spin1); arrayadapter<string> adapter = new arrayadapter<string>(getactivity(), r.layout.spinner_layout, choices1); adapter.setdropdownviewresource(r.layout.spinner_dropdown); spinsomewhere.setadapter(adapter); spin2 = (spinner) v.findviewbyid(r.id.spin2); arrayadapter<string> adapter1 = new arrayadapter<string>(getactivity(), r.layout.spinner_layout, choices2); adapter1.setdropdownviewresource(r.layout.spinner_dropdown); spinfor.setadapter(adapter1); spin3 = (spinner) v.findviewbyid(r.id.spin3); arrayadapter<string> adapter2 = new arrayadapter<string>(getactivity(), r.layout.spinner_layout, choices4); adapter2.setdropdownviewresource(r.layout.spinner_dropdown); spinxp.setadapter(adapter2); spin4 = (spinner) v.findviewbyid(r.id.spin4); arrayadapter<string> adapter3 = new arrayadapter<string>(getactivity(), r.layout.spinner_layout, choices4); adapter3.setdropdownviewresource(r.layout.spinner_dropdown); spinwith.setadapter(adapter3); btn.setonclicklistener(new onclicklistener() { @override public void onclick(view v) { x = spin1.getselecteditem().tostring(); y = spin2.getselecteditem().tostring(); z = spin3.getselecteditem().tostring(); w = spin4.getselecteditem().tostring(); buttoninterface.btnclicked(x,y,z,w); } }); return v; } } error log:
05-30 21:27:35.230: e/androidruntime(3016): fatal exception: main 05-30 21:27:35.230: e/androidruntime(3016): process: com.ex.app, pid: 3016 05-30 21:27:35.230: e/androidruntime(3016): java.lang.runtimeexception: unable start activity componentinfo{com.ex.app/com.ex.app.mainactivity}: java.lang.nullpointerexception 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread.performlaunchactivity(activitythread.java:2195) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread.handlelaunchactivity(activitythread.java:2245) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread.access$800(activitythread.java:135) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread$h.handlemessage(activitythread.java:1196) 05-30 21:27:35.230: e/androidruntime(3016): @ android.os.handler.dispatchmessage(handler.java:102) 05-30 21:27:35.230: e/androidruntime(3016): @ android.os.looper.loop(looper.java:136) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread.main(activitythread.java:5017) 05-30 21:27:35.230: e/androidruntime(3016): @ java.lang.reflect.method.invokenative(native method) 05-30 21:27:35.230: e/androidruntime(3016): @ java.lang.reflect.method.invoke(method.java:515) 05-30 21:27:35.230: e/androidruntime(3016): @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:779) 05-30 21:27:35.230: e/androidruntime(3016): @ com.android.internal.os.zygoteinit.main(zygoteinit.java:595) 05-30 21:27:35.230: e/androidruntime(3016): @ dalvik.system.nativestart.main(native method) 05-30 21:27:35.230: e/androidruntime(3016): caused by: java.lang.nullpointerexception 05-30 21:27:35.230: e/androidruntime(3016): @ com.ex.app.fragment_x.oncreateview(fragment_x.java:75) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.fragment.performcreateview(fragment.java:1700) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:890) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:1062) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.backstackrecord.run(backstackrecord.java:684) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.fragmentmanagerimpl.execpendingactions(fragmentmanager.java:1447) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activity.performstart(activity.java:5240) 05-30 21:27:35.230: e/androidruntime(3016): @ android.app.activitythread.performlaunchactivity(activitythread.java:2168) 05-30 21:27:35.230: e/androidruntime(3016): ... 11 more
it null because forgot set btninterface fragment_x after instantiate it.
solution:
frag = new fragment_x(); frag.setinterface(this); ft = getfragmentmanager().begintransaction(); ft.add(r.id._frag_container, frag); ft.commit();
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