Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Android Build a Simple Android App (2014) Basic Android Programming Adding the onClick() Method

Santino Mirarchi
Santino Mirarchi
276 Points
Posted by Santino Mirarchi
Santino Mirarchi
276 Points

Fatal error! The app crashes when it runs in the emulator

Hello guys when I try to run the app unfortunately it crashes as soon I run the emulator. I copy and paste the logcat here.

04-22 19:59:11.385 2246-2246/com.santinomirarchi.fanfacts I/art﹕ Not late-enabling -Xcheck:jni (already on) 04-22 19:59:11.649 2246-2246/com.santinomirarchi.fanfacts D/AndroidRuntime﹕ Shutting down VM 04-22 19:59:11.724 2246-2246/com.santinomirarchi.fanfacts E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.santinomirarchi.fanfacts, PID: 2246 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.santinomirarchi.fanfacts/com.santinomirarchi.fanfacts.FunFactsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.santinomirarchi.fanfacts.FunFactsActivity.onCreate(FunFactsActivity.java:30) at android.app.Activity.performCreate(Activity.java:5937) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)             at android.app.ActivityThread.access$800(ActivityThread.java:144)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:135)             at android.app.ActivityThread.main(ActivityThread.java:5221)             at java.lang.reflect.Method.invoke(Native Method)             at java.lang.reflect.Method.invoke(Method.java:372)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 04-22 19:59:44.530 2246-2246/com.santinomirarchi.fanfacts I/Process﹕ Sending signal. PID: 2246 SIG: 9 04-22 19:59:53.440 2712-2712/com.santinomirarchi.fanfacts D/AndroidRuntime﹕ Shutting down VM 04-22 19:59:53.440 2712-2712/com.santinomirarchi.fanfacts E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.santinomirarchi.fanfacts, PID: 2712 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.santinomirarchi.fanfacts/com.santinomirarchi.fanfacts.FunFactsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.santinomirarchi.fanfacts.FunFactsActivity.onCreate(FunFactsActivity.java:30) at android.app.Activity.performCreate(Activity.java:5937) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)             at android.app.ActivityThread.access$800(ActivityThread.java:144)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:135)             at android.app.ActivityThread.main(ActivityThread.java:5221)             at java.lang.reflect.Method.invoke(Native Method)             at java.lang.reflect.Method.invoke(Method.java:372)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 04-22 20:07:13.696 2817-2817/com.santinomirarchi.fanfacts I/art﹕ Not late-enabling -Xcheck:jni (already on) 04-22 20:07:14.387 2817-2817/com.santinomirarchi.fanfacts D/AndroidRuntime﹕ Shutting down VM 04-22 20:07:14.463 2817-2817/com.santinomirarchi.fanfacts E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.santinomirarchi.fanfacts, PID: 2817 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.santinomirarchi.fanfacts/com.santinomirarchi.fanfacts.FunFactsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.santinomirarchi.fanfacts.FunFactsActivity.onCreate(FunFactsActivity.java:30) at android.app.Activity.performCreate(Activity.java:5937) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)             at android.app.ActivityThread.access$800(ActivityThread.java:144)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:135)             at android.app.ActivityThread.main(ActivityThread.java:5221)             at java.lang.reflect.Method.invoke(Native Method)             at java.lang.reflect.Method.invoke(Method.java:372)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 04-22 20:07:35.449 2817-2817/com.santinomirarchi.fanfacts I/Process﹕ Sending signal. PID: 2817 SIG: 9

Santino Mirarchi
Santino Mirarchi
276 Points
Santino Mirarchi
Santino Mirarchi
276 Points

Guys thanks to a friend of mine I found the solution to the problem. It was just a capital letter matter in the java code that was different from the one one in the xml file. It was the ID ShowFactButton...in the java code I wrote "showFactButton"