Calling autoFocus() from parent Activity returns NPE

Question

I have instantiated a fragment type that extends CameraFragment (and implements TabListener), and I am trying to call the autoFocus() from the the parent Activity. Calling autoFocus() from the fragment that extends CameraFragment works fine, but calling it from the parent Activity results in an NPE. I am listening for a onKeyDown() event in the main Activity, which works as expected as per the logcat. Here is my NPE trace:

09-10 10:00:16.410: D/app(5283): onKeyDown: 80

09-10 10:00:16.415: D/AndroidRuntime(5283): Shutting down VM

09-10 10:00:16.415: W/dalvikvm(5283): threadid=1: thread exiting with uncaught exception (group=0x40f7b2a0)

09-10 10:00:16.425: E/AndroidRuntime(5283): FATAL EXCEPTION: main

09-10 10:00:16.425: E/AndroidRuntime(5283): java.lang.NullPointerException

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.commonsware.cwac.camera.CameraFragment.autoFocus(CameraFragment.java:96)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.me.app.appCameraFragment.callAutoFocus(cameraFragment.java:232)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.me.app.MainTabActivity.onKeyDown(MainTabActivity.java:264)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.view.KeyEvent.dispatch(KeyEvent.java:2705)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.app.Activity.dispatchKeyEvent(Activity.java:2423)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:2019)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3851)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3799)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2934)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.os.Handler.dispatchMessage(Handler.java:99)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.os.Looper.loop(Looper.java:137)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at android.app.ActivityThread.main(ActivityThread.java:4921)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at java.lang.reflect.Method.invokeNative(Native Method)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at java.lang.reflect.Method.invoke(Method.java:511)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1036)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:803)

09-10 10:00:16.425: E/AndroidRuntime(5283):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

I'm not sure what version of the code you are working on, but line 96 is a closing brace in the current CameraFragment.

The only way autoFocus() can crash with a NullPointerException is if cameraView is null, and the only way cameraView should be null is if onCreateView() has not yet been called. You need the fragment to be visible and fully created before you request auto-focus.