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Android

Posted by Daniel Vido
Daniel Vido
4,824 Points

Fun Facts has stopped - please help

Hello,

This is my logcat:

06-25 13:34:03.996 4165-4165/hu.russmedia.mokastenyek10 E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: hu.russmedia.mokastenyek10, PID: 4165 java.lang.RuntimeException: Unable to start activity ComponentInfo{hu.russmedia.mokastenyek10/hu.russmedia.mokastenyek10.MTActivity}: 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:2325) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5257) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at hu.russmedia.mokastenyek10.MTActivity.onCreate(MTActivity.java:32) at android.app.Activity.performCreate(Activity.java:5990) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)             at android.app.ActivityThread.access$800(ActivityThread.java:151)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)             at android.os.Handler.dispatchMessage(Handler.java:102)             at android.os.Looper.loop(Looper.java:135)             at android.app.ActivityThread.main(ActivityThread.java:5257)             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:903)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Can you please help?

1 Answer

Daniel Hartin
Daniel Hartin
18,106 Points
Daniel Hartin
Daniel Hartin
18,106 Points

Hi Daniel

You are getting a Null pointer exception when the code tries to execute the setOnClickListener(). Have you declared the button in your onCreate() method like

mButton = (Button) findViewById(R.id.button1); //obviously your id's and variable names maybe different.

Hope this helps

Daniel

Daniel Vido
Daniel Vido
4,824 Points

Hi Daniel,

Yes, this is my onCreate code, same as it was presented in the video (at least I hope :))

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_mt);

    // Declare our View variables and assign the Views from the layout file
    final TextView factlabel = (TextView) findViewById(R.id.factTextview);
    final Button showFactButton = (Button) findViewById(R.id.showFactButton);
    View.OnClickListener listener = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            // The button was clicked so update the fact label with a new fact
            String fact = "Ostrices can run faster than horses.";
            factlabel.setText(fact);

        }
    };
    showFactButton.setOnClickListener(listener);
}