NULL POINTER EXCEPTION in android application -
this simple activity takes message user , displays in second activity. getting java.lang null pointer exception. data in file follows : // activity_main.xml // xml file main activity
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingbottom="@dimen/activity_vertical_margin" android:paddingleft="@dimen/activity_horizontal_margin" android:paddingright="@dimen/activity_horizontal_margin" android:paddingtop="@dimen/activity_vertical_margin" tools:context=".mainactivity" > <textview android:id="@+id/textview1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignparentleft="true" android:layout_alignparenttop="true" android:layout_margintop="29dp" android:text="enter message" android:textsize="18dp" /> <edittext android:id="@+id/edittext1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignparentleft="true" android:layout_alignparentright="true" android:layout_below="@+id/textview1" android:layout_margintop="38dp" android:ems="10" > <requestfocus /> </edittext> <button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/edittext1" android:layout_centerhorizontal="true" android:layout_margintop="96dp" android:text="send" android:onclick="sendmessage" /> </relativelayout> // mainactivity.java // code main activity creates intent , pass value entered display activity
package com.example.simpleactivity; import android.os.bundle; import android.app.activity; import android.content.intent; import android.view.menu; import android.view.view; import android.widget.edittext; public class mainactivity extends activity { public final static string extra_message = "com.example.simpleactivity.message"; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); } public void sendmessage(view view) { edittext textmessage = (edittext) findviewbyid(r.id.edittext1); string message = textmessage.gettext().tostring(); intent intent = new intent(this, displaymessageactivity.class); intent.putextra(extra_message, message); startactivity(intent); } @override public boolean oncreateoptionsmenu(menu menu) { // inflate menu; adds items action bar if present. getmenuinflater().inflate(r.menu.main, menu); return true; } } // activity_display_message.xml // xml file display activity
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingbottom="@dimen/activity_vertical_margin" android:paddingleft="@dimen/activity_horizontal_margin" android:paddingright="@dimen/activity_horizontal_margin" android:paddingtop="@dimen/activity_vertical_margin" tools:context=".displaymessageactivity" > <textview android:id="@+id/textview2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignparentleft="true" android:layout_alignparenttop="true" android:layout_marginleft="58dp" android:layout_margintop="110dp" android:text="large text" android:textappearance="?android:attr/textappearancelarge" /> </relativelayout> // displaymessageactivity.java // display activity gets , intent , displays message
package com.example.simpleactivity; import android.app.activity; import android.content.intent; import android.os.bundle; import android.view.menu; import android.widget.textview; public class displaymessageactivity extends activity { textview tv; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); //setcontentview(r.layout.activity_display_message); intent intent = getintent(); string message = intent.getstringextra(mainactivity.extra_message); tv = (textview) findviewbyid(r.id.textview2); tv.settext(message); setcontentview(tv); } @override public boolean oncreateoptionsmenu(menu menu) { // inflate menu; adds items action bar if present. getmenuinflater().inflate(r.menu.display_message, menu); return true; } } // logcat follows:
08-09 18:23:08.812: i/choreographer(1520): skipped 37 frames! application may doing work on main thread. 08-09 18:23:08.942: d/gralloc_goldfish(1520): emulator without gpu emulation detected. 08-09 18:23:13.262: d/androidruntime(1520): shutting down vm 08-09 18:23:13.262: w/dalvikvm(1520): threadid=1: thread exiting uncaught exception (group=0x414c4700) 08-09 18:23:13.402: e/androidruntime(1520): fatal exception: main 08-09 18:23:13.402: e/androidruntime(1520): java.lang.runtimeexception: unable start activity componentinfo{com.example.simpleactivity/com.example.simpleactivity.displaymessageactivity}: java.lang.nullpointerexception 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread.performlaunchactivity(activitythread.java:2211) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread.handlelaunchactivity(activitythread.java:2261) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread.access$600(activitythread.java:141) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread$h.handlemessage(activitythread.java:1256) 08-09 18:23:13.402: e/androidruntime(1520): @ android.os.handler.dispatchmessage(handler.java:99) 08-09 18:23:13.402: e/androidruntime(1520): @ android.os.looper.loop(looper.java:137) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread.main(activitythread.java:5103) 08-09 18:23:13.402: e/androidruntime(1520): @ java.lang.reflect.method.invokenative(native method) 08-09 18:23:13.402: e/androidruntime(1520): @ java.lang.reflect.method.invoke(method.java:525) 08-09 18:23:13.402: e/androidruntime(1520): @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:737) 08-09 18:23:13.402: e/androidruntime(1520): @ com.android.internal.os.zygoteinit.main(zygoteinit.java:553) 08-09 18:23:13.402: e/androidruntime(1520): @ dalvik.system.nativestart.main(native method) 08-09 18:23:13.402: e/androidruntime(1520): caused by: java.lang.nullpointerexception 08-09 18:23:13.402: e/androidruntime(1520): @ com.example.simpleactivity.displaymessageactivity.oncreate(displaymessageactivity.java:20) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activity.performcreate(activity.java:5133) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1087) 08-09 18:23:13.402: e/androidruntime(1520): @ android.app.activitythread.performlaunchactivity(activitythread.java:2175) 08-09 18:23:13.402: e/androidruntime(1520): ... 11 more 08-09 18:23:17.812: i/process(1520): sending signal. pid: 1520 sig: 9
in displaymessageactivity oncreate() method :
@override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); //setcontentview(r.layout.activity_display_message); intent intent = getintent(); string message = intent.getstringextra(mainactivity.extra_message); tv = (textview) findviewbyid(r.id.textview2); tv.settext(message); setcontentview(tv); } uncomment first setcontentview() , comment last setcontentview() below :
@override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_display_message); intent intent = getintent(); string message = intent.getstringextra(mainactivity.extra_message); tv = (textview) findviewbyid(r.id.textview2); tv.settext(message); //setcontentview(tv); }
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