ViewPager inside ScrollView - vertical scroll doesn't work

Question

So, I have this ScrollView with one child - a LinearLayout that has two children: a TextView and a ViewPager. ViewPager contains layout with many elements, that's why i need the ability to scroll vertically. Only pages in ViewPager may be scrolled horizontally (that is: I'd like to swipe horizontally only within the ViewPager). That one TextView must not scroll horizontally but should scroll together with my ViewPager.

Simple? No.

I've seen extremely similar issues at StackOverflow popping up (here, here and here and here). None of the suggested solutions work for me :(

What I see is this <- my sweet UI :), However I cannot scroll vertically :(

Embedding ScrollViews inside ViewPager is not an option - desing of the UI forbids this.

Maybe it's something with my programmatically filling each page in view pager? Hmmm...

Any suggestions would be appreciated.

My code:

activity_main.xml:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"

                android:id="@+id/scrollView"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:background="@android:color/white"
                android:fillViewport="true" >

                <LinearLayout
                    android:id="@+id/linearLayoutGeneral"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical">

                    <TextView
                    android:id="@+id/tvText"
                    android:layout_width="fill_parent"
                    android:layout_height="200dp"
                    android:text="Test text" />

                <android.support.v4.view.ViewPager
                            android:id="@+android:id/viewpager"
                            android:layout_width="fill_parent"
                            android:layout_height="fill_parent" >
                </android.support.v4.view.ViewPager>


                </LinearLayout>
</ScrollView>

each page in ViewPager has this layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <LinearLayout
        android:id="@+id/layoutData"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >
    </LinearLayout>

</LinearLayout>

single element's layout in such a page:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="40dp"
    android:gravity="center"
    android:orientation="vertical"
    android:background="@android:color/white" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Large Text"
        android:background="@android:color/black"
        android:textColor="@android:color/white"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</LinearLayout>

A single page Fragment is also very simple:

public class DayFragment extends Fragment {

    private static final String TAG = DayFragment.class.getSimpleName();

    public String tag;

    LinearLayout data;

    View mView;

    final int ROWS_NUM = 60;

    public DayFragment() {

    }

    /**
     * (non-Javadoc)
     * 
     * @see android.support.v4.app.Fragment#onCreateView(android.view.LayoutInflater,
     *      android.view.ViewGroup, android.os.Bundle)
     */
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        if (container == null) {
            // We have different layouts, and in one of them this
            // fragment's containing frame doesn't exist. The fragment
            // may still be created from its saved state, but there is
            // no reason to try to create its view hierarchy because it
            // won't be displayed. Note this is not needed -- we could
            // just run the code below, where we would create and return
            // the view hierarchy; it would just never be used.
            return null;
        }

        mView = (LinearLayout) inflater.inflate(R.layout.day, container, false);

        setUpControls();

        generateData();

        String text = getArguments().getString("text");
        Log.d(TAG, "creating view with text: " + text);

        return mView;
    }

    private void setUpControls() {
        data = (LinearLayout) mView.findViewById(R.id.layoutData);
    }

    private void generateData() {
        for (int i = 0; i < ROWS_NUM; i++) {
            View v = createRow(i);
            data.addView(v);
        }
    }

    private View createRow(int num) {
        LayoutInflater inflater = (LayoutInflater) getActivity()
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflater.inflate(R.layout.row, null);

        TextView tv = (TextView) v.findViewById(R.id.textView);
        tv.setText("Data nr: " + num);

        return v;
    }

    public static DayFragment newInstance(String text) {
        Log.d(TAG, "newInstance with text: " + text);
        DayFragment f = new DayFragment();

        f.tag = text;

        // Supply text input as an argument.
        Bundle args = new Bundle();
        args.putString("text", text);
        f.setArguments(args);

        return f;
    }

}

Answer 1

I had the problem that ViewPager behaved weird and I found out the reason for that it is because sometimes the ScrollView regains focus and the ViewPager then loses focus. If you have a ViewPager in a ScrollView and you want it always to stay in focus when you touch it and the ScrollView never getting a focus, setting the requestDisallowInterceptTouchEvent does that. Did that help?

    mViewPager= (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(adapter);
    mViewPager.setOnTouchListener(new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            mViewPager.getParent().requestDisallowInterceptTouchEvent(true);
            return false;
        }
    });

Answer 2

Extending on to Marius's answer to allow vertical scrolling on the parent:

I noticed that when you call the 'requestDisallowInterceptTouchEvent' method on the initial scroll, it will block scrolling vertically on the parent view when scrolling vertically on top of the view pager.

My solution was to only trigger that method after the user started scrolling horizontally for a specified distance (the 'margin' variable).

mViewPager.setOnTouchListener(new View.OnTouchListener() {
    public boolean onTouch(View v, MotionEvent e) {
        // How far the user has to scroll before it locks the parent vertical scrolling.
        final int margin = 10;
        final int fragmentOffset = v.getScrollX() % v.getWidth();

        if (fragmentOffset > margin && fragmentOffset < v.getWidth() - margin) {
            mViewPager.getParent().requestDisallowInterceptTouchEvent(true);
        }
        return false;
    }
});