NullPointerException with ViewPager and three Fragments in onCreate

Question

So uh... i have a ViewPager Activity (MasterActivity) with 3 Fragments (Master1Fragment, Master2Fragment, Master3Fragment) which store values in excel file. I have no problem saving the data collected from controls (EditText, Spinner, CheckBox etc) in all 3 fragments (i place the Save Button on third fragment, Master3Fragment) with OnClick Event in 3rd Fragment.

Problem arise when i try to load data from the OnCreate event in the MasterActivity (I suspect it's because the fragments haven't finished created) if that is so, in what event should i put my LoadData Function? I want to load the data automatically when the user open the Activity.

Error generated at here:

...
} else {
    //non empty cells handler
    switch (cn) {
        case 0:
            Master2Fragment.etKrg1.setText((int) c.getNumericCellValue());
            break;
        case 1:
...

Part of LogCat:

08-29 14:31:17.591  12886-12886/com.bakemono.fertilizerchecking.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.bakemono.fertilizerchecking.app, PID: 12886
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.bakemono.fertilizerchecking.app/com.bakemono.fertilizerchecking.app.MasterActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2250)
        at android.app.ActivityThread.access$800(ActivityThread.java:139)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1200)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5105)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at com.bakemono.fertilizerchecking.app.MasterActivity.loadMaster(MasterActivity.java:575)
        at com.bakemono.fertilizerchecking.app.MasterActivity.onCreate(MasterActivity.java:120)
        at android.app.Activity.performCreate(Activity.java:5275)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)

possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — jww, Aug 29 '14 at 08:49
What i seek here is an explanation related to ViewPager and Fragments lifecycle, i can't found any relevance with the possible duplicate stated above since i'm fully aware what a Null Pointer Exception is and i'm not asking for an explanation about Null Pointer Exception. — Milanor, Aug 29 '14 at 09:26
maybe i need to change the title though.. now that i read the title again.. it really seems off. — Milanor, Aug 29 '14 at 09:27

score 3 · Accepted Answer · answered Aug 29 '14 at 08:31

3

Yes, you're right: The fragment lifecycle hasn't yet started when you're running onCreate() of your activity.

First, get rid of the public static (or package-private static) members in your fragments and make them private and non-static. Other classes should have no business touching a fragment's internals, and making them static causes its set of problems, too.

Then, access and set up fragment views in onCreateView() or onViewCreated() callbacks in the fragment itself.

answered Aug 29 '14 at 08:31

laalto

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so it means i should load the data on creation of each fragments rather than load it all and assign the values to the fragments' controls from the activity? – Milanor Aug 29 '14 at 08:34
Fragments should be relatively independent pieces of UI functionality that manage their own data and so on. – laalto Aug 29 '14 at 08:35
I see.. yes, in my other application i load the data from the fragment itself. Just want to try out new ideas on this one. But it seems it doesn't work ~_~ or rather i've not followed the lifecycle. – Milanor Aug 29 '14 at 08:38
Anyway, thanks for the explanation. At least you make it clearer to me. – Milanor Aug 29 '14 at 08:42

NullPointerException with ViewPager and three Fragments in onCreate

1 Answers1