SwipeRefreshLayout 内的 ScrollView 内的 ViewPager

Question

我有一个包含 SwipeRefreshLayout、ScrollView 和 ViewPager 的布局。

SwipeRefreshLayout 用于刷新 ViewPager，而 ScrollView 是因为 ViewPager 可以包含不适合显示的内容。

当我尝试向下滚动时，没有任何反应，但我可以看到有更多内容要显示。当我向上滚动 SwipeRefresh 被调用。

我的 XML：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="${relativePackage}.${activityClass}" >

<android.support.design.widget.TabLayout
    android:id="@+id/tab_layout"
    style="@style/TabLayout"
    android:paddingEnd="16dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingStart="16dp" />

<com.gmail.bathingrad.school.widget.SwipeRefreshView
    android:id="@+id/refresh"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <android.support.v4.view.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</com.gmail.bathingrad.school.widget.SwipeRefreshView>

</LinearLayout>

它的外观截图（最后一个紫色框不在显示范围内）： http://i.stack.imgur.com/hlrdz.png

编辑： 经过一番研究，我发现问题是因为 ScrollView 不知道 ViewPager 中最大项目的高度。我正在寻找一种动态更改 ViewPager 高度的方法。

Answer 1

经过一番思考、编写和测试，我找到了一个可行的解决方案。 我在 ViewPager 的每个页面中都放置了一个扩展的 ScrollView，然后在 ScrollView 中我添加了一个带有 Context 和 SwipeRefreshLayout 的构造函数。

我重写了 onScrollChanged 方法并检查了 ScrollView 是否滚动到顶部。如果不是，我禁用了 SwipeRefreshLayout。

<com.gmail.bathingrad.school.widget.SwipeRefreshView
    android:id="@+id/refresh"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <android.support.v4.view.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </android.support.v4.view.ViewPager>
</com.gmail.bathingrad.school.widget.SwipeRefreshView>

ScrollView.class：

public class ScrollView extends android.widget.ScrollView {

    SwipeRefreshLayout swipeRefresh;

    public ScrollView(Context context, SwipeRefreshLayout swipeRefresh) {
        super(context);

        this.swipeRefresh = swipeRefresh;
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);

        Log.i("School", "T: " + t);

        if (t != 0) {
            swipeRefresh.setEnabled(false);
        } else if (t == 0) {
            swipeRefresh.setEnabled(true);
        }
    }
}

ViewPagerAdapter 实例化项方法：

@Override
public Object instantiateItem(ViewGroup container, int position) {
        LinearLayout[] schemeLayout = readScheme.generateScheme();
        ScrollView[] scrollView = new ScrollView[5];

        // SwipeRefreshLayout
        SwipeRefreshLayout swipeRefresh = (SwipeRefreshLayout) container.getParent();

        swipeRefresh.setEnabled(true);

        scrollView[position] = new ScrollView(context, swipeRefresh);

        scrollView[position].addView(schemeLayout[position]);

        container.addView(scrollView[position]);

        return scrollView[position];
}

这行得通！

我之所以调用swipeRefresh.setEnabled(true); 是因为当用户向下滚动然后滑动到另一个页面时，swipeRefresh 被禁用。

希望有人会觉得这很有用

Answer 2

Google 通过 google-sample github 项目上发布的示例解决了此问题。

创建一个扩展原始 SwipeRefreshLayout 的视图：

/*
 * 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)
}

在你的 xml 布局中使用这个视图：

<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>

在您的活动或片段中，您可以将此组件与：

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

android.R.id.list 和 android.R.id.empty 是您的列表或回收站视图的 ID。该视图与两个具有相同 ID 的列表完美配合。

你可以在google-sample github project看到真实的例子。