如何在viewPager中使用相同的片段？

Question

I develope currently a small sample app with fragments and a viewPager. The viewPager shows 3 pages. In each page i instantiate a fragment of the same type. The fragment contains a textView and a button. On button click I want to replace the current fragment with another one. Now my problem is, no matter which button I press only the fragment of page 1 gets replaced. I dont know what I have to do in my pageAdapter class but I guess it has to do with using the same fragment and layout. I think I have to make sure, that my pageAdapter updates the correct page, but how do I achieve that?

For a better understanding why I want to achieve that, that I receive a json string within 3 node of type menu and I want to use each of them as a page in my viewPager.

Can someone show me a short and easy example for such a behavior? I think its a basic approach, so it cant be so difficult.

--------Edit---------

Here is the code:

public class FragmentPagerSupport extends FragmentActivity {
static final int NUM_ITEMS = 4;
MyAdapter mAdapter;
ViewPager mPager;

@Override
public void onBackPressed() {
    FragmentManager fm = getFragmentManager();
    if (fm.getBackStackEntryCount() > 0) {
        fm.popBackStack();
    } else {
        super.onBackPressed();
    }
}

public MyAdapter getmAdapter() {
    return mAdapter;
}

public ViewPager getmPager() {
    return mPager;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fragment_pager);
    mAdapter = new MyAdapter(getFragmentManager(), this);
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setOffscreenPageLimit(NUM_ITEMS + 2);
    mPager.setAdapter(mAdapter);

    Button button = (Button) findViewById(R.id.goto_first);
    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            mPager.setCurrentItem(0);
        }
    });

    button = (Button) findViewById(R.id.goto_last);
    button.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            mPager.setCurrentItem(NUM_ITEMS - 1);
        }
    });
}
}

MyAdapter:

public MyAdapter(FragmentManager fm, FragmentPagerSupport fragmentPagerSupport) {
super(fm);
this.fragmentPagerSupport = fragmentPagerSupport;
}

@Override
public int getCount() {
return NUM_ITEMS;
}

@Override
public Fragment getItem(int position) {
        Fragment newInstance = null;
        switch (position) {
        case 0:
            newInstance = frag1.newInstance(position);
            break;
        case 1:
            newInstance = frag1.newInstance(position);
            break;
        case 2:
            newInstance = frag2.newInstance(position);
            break;
        case 3:
            newInstance = frag2.newInstance(position);
            break;
        }
        return newInstance;
    }

Frag1 & Frag2 & ListItemFrag:

    public static class frag1 extends ListFragment {
    int mNum;
    static frag1 newInstance(int num) {
        frag1 f = new frag1();
        Supply num input as an argument.
        Bundle args = new Bundle();
        args.putInt("num", num);
        f.setArguments(args);
        return f;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mNum = getArguments() != null ? getArguments().getInt("num") : 1;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
        v.setId(mNum);
        View tv = v.findViewById(R.id.text);
        ((TextView) tv).setText("Fragment #" + mNum);
        return v;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        String[] cheeses = { "Edamer", "Gauda", "Cheddar", "Mozarella", "Maasdamer" };
        setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, cheeses));
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        Log.i("FragmentList", "Item clicked: " + id);
        String itemName = (String) l.getItemAtPosition(position);
        Fragment listItemFragment = ListItemFragment.newInstance(itemName);
        FragmentTransaction trans = getActivity().getFragmentManager().beginTransaction();
        trans.replace(R.id.root, listItemFragment, listItemFragment.getClass().getName() + "_" + mNum);
        trans.addToBackStack(itemName);
        trans.commit();
    }
}

public static class frag2 extends ListFragment {
    int mNum;
    static frag2 newInstance(int num) {
        frag2 f = new frag2();
        Bundle args = new Bundle();
        args.putInt("num", num);
        f.setArguments(args);
        return f;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mNum = getArguments() != null ? getArguments().getInt("num") : 1;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
        v.setId(mNum);
        View tv = v.findViewById(R.id.text);
        ((TextView) tv).setText("Fragment #" + mNum);
        return v;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        String[] cheeses = { "Edamer", "Gauda", "Cheddar", "Mozarella", "Maasdamer" };
        setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, cheeses));
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        Log.i("FragmentList", "Item clicked: " + id);
        String itemName = (String) l.getItemAtPosition(position);
        Fragment listItemFragment = ListItemFragment.newInstance(itemName);
        FragmentTransaction trans = getActivity().getFragmentManager().beginTransaction();
        trans.replace(R.id.root, listItemFragment, listItemFragment.getClass().getName() + "_" + mNum);
        trans.addToBackStack(itemName);
        trans.commit();
    }
}

public static class ListItemFragment extends Fragment {
    String itemName;
    static ListItemFragment newInstance(String itemName) {
        ListItemFragment i = new ListItemFragment();
        Bundle args = new Bundle();
        args.putString("text", itemName);
        i.setArguments(args);
        return i;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        itemName = getArguments() != null ? getArguments().getString("text") : "NULL";
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_item, container, false);
        View tv = v.findViewById(R.id.textView1);
        ((TextView) tv).setText("Cheese: " + itemName + " selected!");
        return v;
    }
}

Pager Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:padding="4dip"
    android:gravity="center_horizontal"
    android:layout_width="match_parent" android:layout_height="match_parent">
<android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="1">
</android.support.v4.view.ViewPager>
<LinearLayout android:orientation="horizontal"
        android:gravity="center" android:measureWithLargestChild="true"
        android:layout_width="match_parent" android:layout_height="wrap_content"
        android:layout_weight="0">
    <Button
        android:id="@+id/goto_first"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="first" />
    <Button android:id="@+id/goto_last"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="last">
    </Button>
</LinearLayout>

Frag1 Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#99EE11"
android:id="@+id/test">
<TextView android:id="@+id/text"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:gravity="center_vertical|center_horizontal"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="@string/hello_world"/>
<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="0dip"
    android:layout_weight="1"
    android:id="@+id/root" >
    <ListView android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:drawSelectorOnTop="false"/>
</FrameLayout>

Frag2 Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#99EE11"
android:id="@+id/test2">
<TextView android:id="@+id/text"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:gravity="center_vertical|center_horizontal"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="@string/hello_world"/>
<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="0dip"
    android:layout_weight="1"
    android:id="@+id/root2" >
    <ListView android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:drawSelectorOnTop="false"/>
</FrameLayout>

ListItemFrag Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ll"
android:layout_width="fill_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginTop="230dp"
android:background="#AA33EE"
android:orientation="vertical" >
<TextView
    android:id="@+id/textView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>

Answer 1

Hi I was facing same kind of issue. I fixed the issue by using

getChildFragmentManager().beginTransaction()

instead of

getActivity().getSupportFragmentManager().beginTransaction()

As in this case we are trying to make transaction from within a fragment (one out of the list of fragments which are attached to the ViewPager, thus the Activity holding the ViewPager) so we have to use getChildFragmentManager() here for desired results.

NOTE: I am using android support v4 library and thus corresponding FragmentManager.