SwipeRefreshLayout interferes with ScrollView in a ViewPager

Question

I have a SwipeRefreshLayout around a ViewPager. The fragments loaded by the ViewPager contain ScrollViews. When I scroll down it works fine, but when I scroll up, the SwipeRefreshLayout activates without letting the ScrollView scroll up first. How can I make sure the ScrollView has priority?

It worked fine when the SwipeRefreshLayout was in the individual fragments just outside the ScrollView, but I need it to be on the activity itself around the ViewPager.

Here are the relevant layouts:

Activity:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#EEEEEE"
    android:fitsSystemWindows="true">

    <include layout="@layout/toolbar" />

    <io.karim.MaterialTabs
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:background="@color/primary"
        app:mtIndicatorColor="@color/icons"
        app:mtIndicatorHeight="2dp"
        app:mtSameWeightTabs="true"
        app:mtPaddingMiddle="false"
        app:mtTextColorSelected="@color/icons"
        android:textColor="@color/icons"
        android:elevation="4dp"
        tools:ignore="UnusedAttribute" />

    <android.support.v4.widget.SwipeRefreshLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/swipeRefresh"
        android:layout_height="wrap_content"
        android:layout_width="match_parent">

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="0dp" />

    </android.support.v4.widget.SwipeRefreshLayout>

</LinearLayout>

Fragment loaded by the ViewPager (there are 5 tabs, each with one of these):

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="me.sargunvohra.android.purduediningcourts.presenter.MenuFragment">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:paddingStart="@dimen/activity_horizontal_margin"
            android:paddingEnd="@dimen/activity_horizontal_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            android:paddingBottom="@dimen/activity_vertical_margin"
            >

            <!-- Content snipped for brevity -->

            <!-- blah blah... lots of content here -->

        </LinearLayout>

</ScrollView>

And HERE is the repo on GitHub in case you need more information:

Answer 1

Google resolve this issue with an example posted on the google-sample github projet.

Create a view that extends the original SwipeRefreshLayout :

/*
 * Copyright 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.swiperefreshmultipleviews;

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AbsListView;

/**
 * A descendant of {@link android.support.v4.widget.SwipeRefreshLayout} which supports multiple
 * child views triggering a refresh gesture. You set the views which can trigger the gesture via
 * {@link #setSwipeableChildren(int...)}, providing it the child ids.
 */
public class MultiSwipeRefreshLayout extends SwipeRefreshLayout {

    private View[] mSwipeableChildren;

    public MultiSwipeRefreshLayout(Context context) {
        super(context);
    }

    public MultiSwipeRefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    /**
     * Set the children which can trigger a refresh by swiping down when they are visible. These
     * views need to be a descendant of this view.
     */
    public void setSwipeableChildren(final int... ids) {
        assert ids != null;

        // Iterate through the ids and find the Views
        mSwipeableChildren = new View[ids.length];
        for (int i = 0; i < ids.length; i++) {
            mSwipeableChildren[i] = findViewById(ids[i]);
        }
    }

    // BEGIN_INCLUDE(can_child_scroll_up)
    /**
     * This method controls when the swipe-to-refresh gesture is triggered. By returning false here
     * we are signifying that the view is in a state where a refresh gesture can start.
     *
     * <p>As {@link android.support.v4.widget.SwipeRefreshLayout} only supports one direct child by
     * default, we need to manually iterate through our swipeable children to see if any are in a
     * state to trigger the gesture. If so we return false to start the gesture.
     */
    @Override
    public boolean canChildScrollUp() {
        if (mSwipeableChildren != null && mSwipeableChildren.length > 0) {
            // Iterate through the scrollable children and check if any of them can not scroll up
            for (View view : mSwipeableChildren) {
                if (view != null && view.isShown() && !canViewScrollUp(view)) {
                    // If the view is shown, and can not scroll upwards, return false and start the
                    // gesture.
                    return false;
                }
            }
        }
        return true;
    }
    // END_INCLUDE(can_child_scroll_up)

    // BEGIN_INCLUDE(can_view_scroll_up)
    /**
     * Utility method to check whether a {@link View} can scroll up from it's current position.
     * Handles platform version differences, providing backwards compatible functionality where
     * needed.
     */
    private static boolean canViewScrollUp(View view) {
        if (android.os.Build.VERSION.SDK_INT >= 14) {
            // For ICS and above we can call canScrollVertically() to determine this
            return ViewCompat.canScrollVertically(view, -1);
        } else {
            if (view instanceof AbsListView) {
                // Pre-ICS we need to manually check the first visible item and the child view's top
                // value
                final AbsListView listView = (AbsListView) view;
                return listView.getChildCount() > 0 &&
                        (listView.getFirstVisiblePosition() > 0
                                || listView.getChildAt(0).getTop() < listView.getPaddingTop());
            } else {
                // For all other view types we just check the getScrollY() value
                return view.getScrollY() > 0;
            }
        }
    }
    // END_INCLUDE(can_view_scroll_up)
}

Use this view in your xml layout :

<com.example.android.swiperefreshmultipleviews.MultiSwipeRefreshLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/swiperefresh"
      android:layout_width="match_parent"
      android:layout_height="match_parent">

    <!-- your code -->

</com.example.android.swiperefreshmultipleviews.MultiSwipeRefreshLayout>

And in your activity or fragment, you can use this component with :

mSwipeRefreshLayout = (MultiSwipeRefreshLayout) view.findViewById(R.id.swiperefresh);
mSwipeRefreshLayout.setSwipeableChildren(android.R.id.list, android.R.id.empty);

android.R.id.list and android.R.id.empty is the ids for your list or recycler view. The view work perfectly with two list with same ids.

You can see real example at the google-sample github project.

Answer 2

Replace your ScrollView with a NestedScrollView the scrolling behavior will work as you expect it to.

Answer 3

I solved the problem. I created SwipeRefreshLayout like this:

public class MenuSwipeRefreshLayout: SwipeRefreshLayout {

    public var target: View? = null

    constructor(ctx: Context): super(ctx)
    constructor(ctx: Context, attr: AttributeSet): super(ctx, attr)

    override fun canChildScrollUp(): Boolean {
        return target?.canScrollVertically(-1) ?: super.canChildScrollUp()
    }
}

and I set the target to the visible ScrollView every time the ViewPager changes views.

BTW that's Kotlin, not Java.