Null pointer exception when adding TextView

Question

I have a ScrollView, and I'm trying to add TextViews to the LinearLayout in it but i keep getting an error.

TextView l = new TextView(StopWatch.this);
l.setText("Didn't work");
l.setTextSize(20);
llLocations.addView(l);

I was trying to use this code to see if the ArrayList i was using was empty, but it wasnt that. It says the error is caused by a NullPointerException at...

llLocations.addView(l);

I have other code that does the same thing, and i tried comparing them but there wasn't a difference so i'm confused. How do i fix this?

07-10 21:14:42.687: E/AndroidRuntime(5241): FATAL EXCEPTION: main
07-10 21:14:42.687: E/AndroidRuntime(5241): java.lang.IllegalStateException: Could not execute method of the activity
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.view.View$1.onClick(View.java:3599)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.view.View.performClick(View.java:4204)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.view.View$PerformClick.run(View.java:17355)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.os.Handler.handleCallback(Handler.java:725)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.os.Handler.dispatchMessage(Handler.java:92)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.os.Looper.loop(Looper.java:137)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.app.ActivityThread.main(ActivityThread.java:5041)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at java.lang.reflect.Method.invokeNative(Native Method)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at java.lang.reflect.Method.invoke(Method.java:511)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at dalvik.system.NativeStart.main(Native Method)
07-10 21:14:42.687: E/AndroidRuntime(5241): Caused by: java.lang.reflect.InvocationTargetException
07-10 21:14:42.687: E/AndroidRuntime(5241):     at java.lang.reflect.Method.invokeNative(Native Method)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at java.lang.reflect.Method.invoke(Method.java:511)
07-10 21:14:42.687: E/AndroidRuntime(5241):     at android.view.View$1.onClick(View.java:3594)
07-10 21:14:42.687: E/AndroidRuntime(5241):     ... 11 more
07-10 21:14:42.687: E/AndroidRuntime(5241): Caused by: java.lang.NullPointerException
07-10 21:14:42.687: E/AndroidRuntime(5241):     at com.TBJsoft.runprogress.StopWatch.done(StopWatch.java:506)
07-10 21:14:42.687: E/AndroidRuntime(5241):     ... 14 more

StopWath.java:506 is the

llLocations.addView(l);

line.

I'm trying to do this in an alert dialog that has a custom view with the scroll view in it. Do you think that could be causing the problem?

Answer 1

llLocations is null. Read up on findViewById . The end.

Answer 2

llLocations is null , so I guess you did something like that:

LinearLayout llLocations = (LinearLayout)findViewById(R.id.<here_the_id_of_the_linearleayout_in_your_xml_layout>);

If you did this, and the id is the correct one, and you setContentView of your activity with this layout which contains the linearlayout, then it should work.

Answer 3

normally you have to bind the TextView to an id! Like that:

example = findViewById(R.id.yourid);

For your own knowledge, R is dynamically generated by android out of your values-file(IDs are mostly assigned in the layout-files)

Answer 4

If you have a variable which is an instance of a class, you need to initialize it. If you do not initialize it, it will have a null pointer.

llocations was not initialized properly before you try to access its method. But you cannot access the method of a null pointer, right? It would be like shaking hands with nobody. So, this is an exceptional behavior and that is why the NullPointerException is thrown.