Application crashes when activity starts in landscape mode

Question

I have an application. The main activity has a page that has a button. This button only opens another activity. Here's the problem though. When I do this in the portrait mode, it works perfectly. Even after the activity has started, I can change it to landscape mode and it works fine. The application only crashes when the first activity is in landscape mode and I click the button to start the new activity. Any ideas how I should fix this? Why is it not working only during startup? and why is it working fine in landscape mode after I start it in portrait mode?

Another interesting thing I noticed, I deleted the layout xml files in the landscape folder and it doesn't crash anymore.

04-26 15:09:50.558: E/AndroidRuntime(7034): FATAL EXCEPTION: main
04-26 15:09:50.558: E/AndroidRuntime(7034): Process: com.example.msapp2, PID: 7034
04-26 15:09:50.558: E/AndroidRuntime(7034): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.msapp2/com.example.msapp2.exercises.WorkoutBuddy}: java.lang.NullPointerException
04-26 15:09:50.558: E/AndroidRuntime(7034):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-26 15:09:50.558: E/AndroidRuntime(7034):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-26 15:09:50.558: E/AndroidRuntime(7034):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-26 15:09:50.558: E/AndroidRuntime(7034):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)

Answer 1

Chances are what's going on is that you are probably getting a reference to a layout element that exists in your portrait (/layouts/activity*.xml) layout but doesn't exist in your landscape layout (/layouts-land/activity*.xml).

For example,

Button button = (Button) findviewbyid(R.id.myButton);

Might work if you're in portrait because you have a <Button /> element in it. But your landscape layout does not have the same element.

This leads to a NullPointerException which is the exception you got. It occurs when you try to access an object that has not been initialized. So look out for where you are doing that.