【问题汇总】ScrollView嵌套ListView的问题

因产品的需求，需要在ScrollView中嵌套ListView来达到效果。众所周知，ScrollVIew和ListView都是可滑动的容器，嵌套使用一定会出现一些问题。

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <ScrollView
        android:id="@+id/scrollview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <ListView
            android:id="@+id/listview"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" >
        </ListView>
    </ScrollView>

</FrameLayout>

ScrollView中唯一可存在的子View是一个ListView。但是这么写会出现问题。就是ListView会显示不全，只能显示ListView的部分内容，同时，ListView也是不可滑动的。

然后我发现了ScrollView有一个属性，叫 android:fillViewport="true"，如果设置这个属性为true，那么ListView会全屏显示，但是依旧不可滑动。先看看这个属性是什么意思。

XML Attributes
Attribute Name	Related Method	Description
android:fillViewport	setFillViewport(boolean)	Defines whether the scrollview should stretch its content to fill the viewport.

意思大概是，定义scrollview是否把它的内容拉伸去充满整个窗口。

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <ScrollView
        android:id="@+id/scrollview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        <span style="color:#ff0000;">android:fillViewport="true"</span> >

        <ListView
            android:id="@+id/listview"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" >
        </ListView>
    </ScrollView>

</FrameLayout>

有网友反应上述的属性在他们的测试机上面不起作用。然后搜索了一下stackoverflow.com，国外有一个牛人写了一个方法，用于对Listview重新布局。

public class Utility {
        public static void setListViewHeightBasedOnChildren(ListView listView) {
              ListAdapter listAdapter = listView.getAdapter();
            if (listAdapter == null) {
            // pre-condition
                  return;
            }

            int totalHeight = listView.getPaddingTop() + listView.getPaddingBottom();
            for (int i = 0; i < listAdapter.getCount(); i++) {
                 View listItem = listAdapter.getView(i, null, listView);
                 if (listItem instanceof ViewGroup) {
                    listItem.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
                 }
                 listItem.measure(0, 0);
                 totalHeight += listItem.getMeasuredHeight();
            }

            ViewGroup.LayoutParams params = listView.getLayoutParams();
            params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
                      listView.setLayoutParams(params);
        }
     }

注意：ListView的item必须是LinearLayout，才能起作用。

好了，解决了ListView显示不全的问题，下一步要解决的就是ListView滑动的问题了。

有大神说可以重写ScrollView，拦截相关的点击事件，已达到listview可以滑动的效果。

public class VerticalScrollview extends ScrollView {
    public VerticalScrollview(Context context) {
        super(context);
    }

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

    public VerticalScrollview(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        final int action = ev.getAction();
        switch (action) {
        case MotionEvent.ACTION_DOWN:
            Log.i("VerticalScrollview",
                    "onInterceptTouchEvent: DOWN super false");
            super.onTouchEvent(ev);
            break;

        case MotionEvent.ACTION_MOVE:
            return false; // redirect MotionEvents to ourself

        case MotionEvent.ACTION_CANCEL:
            Log.i("VerticalScrollview",
                    "onInterceptTouchEvent: CANCEL super false");
            super.onTouchEvent(ev);
            break;

        case MotionEvent.ACTION_UP:
            Log.i("VerticalScrollview", "onInterceptTouchEvent: UP super false");
            return false;

        default:
            Log.i("VerticalScrollview", "onInterceptTouchEvent: " + action);
            break;
        }

        return false;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        super.onTouchEvent(ev);
        Log.i("VerticalScrollview", "onTouchEvent. action: " + ev.getAction());
        return true;
    }
}

以上代码测试成功，在ScrollView中的ListView可以滑动。

另外，还可以对ListView设置onTouchListener，在onTouch中去控制外层ScrollView是否拦截触摸事件。

mListView.setOnTouchListener(new OnTouchListener() {

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        int action = event.getAction();
        switch (action) {
        case MotionEvent.ACTION_DOWN:
            // Disallow ScrollView to intercept touch events.
            v.getParent().requestDisallowInterceptTouchEvent(true);
            break;

        case MotionEvent.ACTION_UP:
            // Allow ScrollView to intercept touch events.
            v.getParent().requestDisallowInterceptTouchEvent(false);
            break;
        }

        // Handle ListView touch events.
        v.onTouchEvent(event);
        return true;
    }
});

以上的所有代码确实解决了ListView滑动的问题。但是，ScrollView的滑动问题没有解决。如果ScrollView中除了ListView还有其他View，那么其他View可能显示不出来。

可以重写ListView去解决这个问题，这个是我所知道的最好的解决方案。

public class NestedListView extends ListView implements OnTouchListener,
        OnScrollListener {

    private int listViewTouchAction;
    private static final int MAXIMUM_LIST_ITEMS_VIEWABLE = 99;

    public NestedListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        listViewTouchAction = -1;
        setOnScrollListener(this);
        setOnTouchListener(this);
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        if (getAdapter() != null
                && getAdapter().getCount() > MAXIMUM_LIST_ITEMS_VIEWABLE) {
            if (listViewTouchAction == MotionEvent.ACTION_MOVE) {
                scrollBy(0, -1);
            }
        }
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int newHeight = 0;
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY) {
            ListAdapter listAdapter = getAdapter();
            if (listAdapter != null && !listAdapter.isEmpty()) {
                int listPosition = 0;
                for (listPosition = 0; listPosition < listAdapter.getCount()
                        && listPosition < MAXIMUM_LIST_ITEMS_VIEWABLE; listPosition++) {
                    View listItem = listAdapter.getView(listPosition, null,
                            this);
                    // now it will not throw a NPE if listItem is a ViewGroup
                    // instance
                    if (listItem instanceof ViewGroup) {
                        listItem.setLayoutParams(new LayoutParams(
                                LayoutParams.WRAP_CONTENT,
                                LayoutParams.WRAP_CONTENT));
                    }
                    listItem.measure(widthMeasureSpec, heightMeasureSpec);
                    newHeight += listItem.getMeasuredHeight();
                }
                newHeight += getDividerHeight() * listPosition;
            }
            if ((heightMode == MeasureSpec.AT_MOST) && (newHeight > heightSize)) {
                if (newHeight > heightSize) {
                    newHeight = heightSize;
                }
            }
        } else {
            newHeight = getMeasuredHeight();
        }
        setMeasuredDimension(getMeasuredWidth(), newHeight);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (getAdapter() != null
                && getAdapter().getCount() > MAXIMUM_LIST_ITEMS_VIEWABLE) {
            if (listViewTouchAction == MotionEvent.ACTION_MOVE) {
                scrollBy(0, 1);
            }
        }
        return false;
    }
}

参考资料

http://stackoverflow.com/questions/6210895/listview-inside-scrollview-is-not-scrolling-on-android

http://stackoverflow.com/questions/3495890/how-can-i-put-a-listview-into-a-scrollview-without-it-collapsing

http://developer.android.com/reference/android/widget/ScrollView.html