Activity cannot be cast to android.support.v4.app.Fragment-CodePudding

I am trying to change my App which has a bunch of single Activities into a swipe tab app. i want 3 activities in the swipe tabs. I used the google example wich eclipse created for me. I don't seem to get the correct way of doing that.

I have the following (relevant) code (the other stuff is in eclipse, it's too much to post here):

Main.class which is called at launch (the last inner class of it):

public static class DummySectionFragment extends Fragment {


public static final String ARG_SECTION_NUMBER = "section_number";

        // public DummySectionFragment() {
        // }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

            View rootView = inflater.inflate(R.layout.activity_fragment,
                    container, false);

            return rootView;
        }
    }

activity_fragment.xml:

<fragment
    android:id="@ id/main"
    android:name="com.mikebdev.refuel.MainActivity"
    
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="1" />

<fragment
    android:id="@ id/stats"
    android:name="com.mikebdev.refuel.Statistics"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="2" />

<fragment
    android:id="@ id/refuel"
    android:name="com.mikebdev.refuel.ReFuel"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="3" />

The Activities all extend FragmentActivity from android.support.v4.app.FragmentActivity

now when starting my app, i get the following error:

04-27 12:08:11.244: E/AndroidRuntime(28728): FATAL EXCEPTION: main
04-27 12:08:11.244: E/AndroidRuntime(28728): android.view.InflateException: Binary XML file line #8: Error inflating class fragment
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.LayoutInflater.rInflate(LayoutInflater.java:746)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at com.mikebdev.refuel.Main$DummySectionFragment.onCreateView(Main.java:184)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:461)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.view.ViewPager.populate(ViewPager.java:1011)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.view.ViewPager.populate(ViewPager.java:880)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1374)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.View.measure(View.java:15518)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.View.measure(View.java:15518)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.View.measure(View.java:15518)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2176)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.View.measure(View.java:15518)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.Choreographer.doFrame(Choreographer.java:532)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.os.Handler.handleCallback(Handler.java:725)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.os.Handler.dispatchMessage(Handler.java:92)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.os.Looper.loop(Looper.java:137)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.app.ActivityThread.main(ActivityThread.java:5041)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at java.lang.reflect.Method.invokeNative(Native Method)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at java.lang.reflect.Method.invoke(Method.java:511)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at dalvik.system.NativeStart.main(Native Method)
04-27 12:08:11.244: E/AndroidRuntime(28728): Caused by: java.lang.ClassCastException: com.mikebdev.refuel.MainActivity cannot be cast to android.support.v4.app.Fragment
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.Fragment.instantiate(Fragment.java:394)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.Fragment.instantiate(Fragment.java:369)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:272)
04-27 12:08:11.244: E/AndroidRuntime(28728):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:676)

CodePudding user response：

You can't have nested fragments embedded in a xml layout file. You'll have to add them at runtime.

Edit: There are countless tutorials on implementing swipeable tabs with fragments please look at them, many are self explanatory. The main points are:

create a layout file which will contain the tabs and the ViewPager
create the fragments that will be used as the tabs/pages in the ViewPager
create a FragmentPagerAdapter and assign it to the ViewPager
bind the tabs selection to the ViewPager pages.

You could use the ViewPager directly in the Activity or you could use a wrapper Fragment, the difference is that you'll need to pass getChildFragmentManager() to the FragmentPagerAdapter instead of getSupportFragmentManager().

CodePudding user response：

After a while i was able to solve everything by adding a switch case statement here:

@Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a DummySectionFragment (defined as a static inner class
            // below) with the page number as its lone argument.

            Fragment fragment;
            switch (position) {
                case 0:
                    fragment = new StatisticsFragment();
                    break;
                case 1:
                    fragment = new MainActivityFragment();
                    break;
                case 2:
                    fragment = new DbListViewFragment();
                    break;
                default:
                    fragment  = new DummySectionFragment();
                    break;
            }
            return fragment;
        }

and I made a copy of my activities and converted those to fragments like explained on this video:

Converting An Activity To A Fragment

now everything seems to work.