Android java.lang.RuntimeException: Unable to instantiate activity ComponentInfo ... java.lang.NullPointerException

Question

For some reason, I keep on getting the following error every time I try to launch my application:

Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}:java.lang.NullPointerException

I checked my manifest file and every activity has been added.

The only method I use when I start the application up is:

private void logIn(){
    Button logIn = (Button) findViewById(R.id.login);
    logIn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Intent loginIntent = new Intent(MainActivity.this, HomeActivity.class);
            loginIntent.putExtra("cmUN", cmUN);
            loginIntent.putExtra("cmPW", cmPW);
            startActivity(loginIntent);
        }
    });
}

Here's the onCreate:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

    logIn();
}

Full log:

E

/AndroidRuntime(1607): FATAL EXCEPTION: main
E/AndroidRuntime(1607): Process: com.example.lifeahead, PID: 1607
E/AndroidRuntime(1607): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}: java.lang.NullPointerException
E/AndroidRuntime(1607):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
E/AndroidRuntime(1607):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
E/AndroidRuntime(1607):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
E/AndroidRuntime(1607):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
E/AndroidRuntime(1607):     at android.os.Handler.dispatchMessage(Handler.java:102)
E/AndroidRuntime(1607):     at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime(1607):     at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime(1607):     at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(1607):     at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime(1607):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
E/AndroidRuntime(1607):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
E/AndroidRuntime(1607):     at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(1607): Caused by: java.lang.NullPointerException
E/AndroidRuntime(1607):     at android.app.Activity.findViewById(Activity.java:1884)
E/AndroidRuntime(1607):     at com.example.lifeahead.MainActivity.<init>(MainActivity.java:22)
E/AndroidRuntime(1607):     at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(1607):     at java.lang.Class.newInstance(Class.java:1208)
E/AndroidRuntime(1607):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
E/AndroidRuntime(1607):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
E/AndroidRuntime(1607):     ... 11 more

I appreciate all the help I can get!

and the code of the activity, not just the function, where are you calling to that function? — Guillermo Merino
– Guillermo Merino, Commented Mar 17, 2014 at 13:59

Blackbelt · Accepted Answer · 2014-03-17 13:58:48Z

10

the stacktrace is telling you that

  Button logIn = (Button) findViewById(R.id.login);

the object returned by findViewById is null, since the only method that you have is logIn(). The only reason why findViewById returns null is because you are looking for a view that does not belongs to the current activity's view hierarchy

answered Mar 17, 2014 at 13:58

Blackbelt

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2 Comments

Guillermo Merino Over a year ago

Or maybe this method is being called before onCreate

Blackbelt Over a year ago

@GuillermoMerino exactly but if you call it before, it still does not make part of the activity's view hierarchy, at that point.

Bipin Bedi · Accepted Answer · 2015-01-21 07:58:22Z

1

Button logIn = (Button) findViewById(R.id.login);

This error is mainly caused due to the declaration, initialization done outside on onCreate(). Either you declare and initialize inside onCreate(), or you declare it outside and initialize it using a method by calling the same inside onCreate().

answered Jan 21, 2015 at 7:58

Bipin Bedi

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Comments

olegr · Accepted Answer · 2014-03-17 14:44:00Z

0

You called findViewById() before Activity got window. You should call findViewById() after setContentView(R.layout.activity_main);. I can see that you call it after, but I don't see whole MainActivity.java. I believe you put another findViewById() somewhere before.

Check line 22 in com.example.lifeahead.MainActivity. Your code fails there.

answered Mar 17, 2014 at 14:44

olegr

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Comments

Petrovich Denis · Accepted Answer · 2014-10-19 20:41:46Z

0

Maybe you use Fragments and your problem is resolved in layouts... See:

<fragment ... android:name="your.package.activity" ... />

Rename the android:name to new package name!

answered Oct 19, 2014 at 20:41

Petrovich Denis

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