Question

Here is an interesting one…

I have an application I am writing for devices running android 2.3.3 and above.

It has a main activity which calls the camera via an Intent.

If the user clicks a button to launch the camera; then takes a picture; then clicks “Done” to return to the main activity – the application works fine and displays the new picture in an imageview on the main activity.

however, if the user uses the main activity in portrait orientation; then clicks the button to open the camera intent and changes the orientation to landscape; then click done to return to the main activity – the application crashes

but then…however, if the user uses the main activity in portrait orientation; then clicks the button to open the camera intent and changes the orientation to landscape; then changes the orientation back to portrait (in the camera) before clicking done to return to the main activity – then the application continues to run normally.

Stuff I have tried:
I have changed the manifest file to force the application (main activity) to be oriented in portrait (I have also removed this)
I have added this line to the main activity in an attempt to handle the re-drawing of the activity on it return from the camera intent:

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

In the debug window I get errors describing nullpointer exceptions – I think this is because the views are no longer there after an orientation change for the image to be passed into unless the orientation is the same as when it was left.

I’m a bit stuck so would appreciate some advice.

Answer 1

When your screen orientation changes, your Activity is destroyed and recreated in the new orientation. So any variables that gained a reference during the life of the Activity will no longer refer to anything, and if you then try to access objects they refer to without re-assigning them values, you’ll get a NullPointerException.

The method onSaveInstanceState() is used to save temporary data between configuration changes. This creates a Bundle which is passed to onCreate() when the Activity starts up again.

Without any code, I don’t know if that’s your problem, but it’s worth a look.

See http://developer.android.com/reference/android/app/Activity.html#ConfigurationChanges for more information (and more accurate information than I’ve provided, no doubt).