Android 获取'；滚动视图'；从ListView

如何从ListView获取“滚动视图”

我想实现这个功能

public void onScrollChanged(ScrollView who, int l, int t, int oldl, int oldt) {
  final int headerHeight = getActivity().findViewById(R.id.fragment_mensagem_list_header)
          .getHeight() - getActivity().getActionBar().getHeight();
  final float ratio = (float) Math.min(Math.max(t, 0), headerHeight) / headerHeight;
  final int newAlpha = (int) (ratio * 255);
  mActionBarBackgroundDrawable.setAlpha(newAlpha);
}

((NotifyingScrollView) LISTVIEWHERE    ).setOnScrollChangedListener(mOnScrollChangedListener);

---

请更清楚地回答您想要实现的目标

• 为什么要将

  滚动视图

  添加到

  列表视图

• 在android中，向列表视图中添加

  ScrollView

  是一种糟糕的做法 因为

  listView

  已经提供了滚动功能
• 如果在

  列表视图中添加
  滚动视图
  ，android会感到困惑
  在哪个触摸屏上检测，
  列表视图
  或
  滚动视图

• 如果要将

  ScrollView

  添加到

  ListView

  中，请重新考虑 因为这不是一个好的实践

---

从文件中引用 您不应该将

滚动视图

与

列表视图

一起使用，因为

列表视图

负责自己的垂直滚动。最重要的是，这样做会破坏

ListView

中处理大型列表的所有重要优化，因为它有效地迫使

ListView

显示其整个项目列表，以填充

ScrollView

提供的无限容器

您可以将视图作为页眉和页脚添加到listview中。页眉和页脚将滚动

---

您也可以尝试解决此问题，从中检查此解决方案，但我不建议这样做，因为这是一种不好的做法，可能会导致性能问题

---

ExpandableHeightGridView.java:

    package com.example;
    public class ExpandableHeightGridView extends GridView
    {

        boolean expanded = false;

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

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

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

        public boolean isExpanded()
        {
            return expanded;
        }

        @Override
        public void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
        {
            // HACK! TAKE THAT ANDROID!
            if (isExpanded())
            {
                // Calculate entire height by providing a very large height hint.
                // View.MEASURED_SIZE_MASK represents the largest height possible.
                int expandSpec = MeasureSpec.makeMeasureSpec(MEASURED_SIZE_MASK,
                        MeasureSpec.AT_MOST);
                super.onMeasure(widthMeasureSpec, expandSpec);

                ViewGroup.LayoutParams params = getLayoutParams();
                params.height = getMeasuredHeight();
            }
            else
            {
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            }
        }

        public void setExpanded(boolean expanded)
        {
            this.expanded = expanded;
        }
    }

    <com.example.ExpandableHeightGridView
        android:id="@+id/myId"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:horizontalSpacing="2dp"
        android:isScrollContainer="false"
        android:numColumns="4"
        android:stretchMode="columnWidth"
        android:verticalSpacing="20dp" />

    mAppsGrid = (ExpandableHeightGridView) findViewById(R.id.myId);
    mAppsGrid.setExpanded(true);

像这样将其包含在布局中：

    package com.example;
    public class ExpandableHeightGridView extends GridView
    {

        boolean expanded = false;

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

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

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

        public boolean isExpanded()
        {
            return expanded;
        }

        @Override
        public void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
        {
            // HACK! TAKE THAT ANDROID!
            if (isExpanded())
            {
                // Calculate entire height by providing a very large height hint.
                // View.MEASURED_SIZE_MASK represents the largest height possible.
                int expandSpec = MeasureSpec.makeMeasureSpec(MEASURED_SIZE_MASK,
                        MeasureSpec.AT_MOST);
                super.onMeasure(widthMeasureSpec, expandSpec);

                ViewGroup.LayoutParams params = getLayoutParams();
                params.height = getMeasuredHeight();
            }
            else
            {
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            }
        }

        public void setExpanded(boolean expanded)
        {
            this.expanded = expanded;
        }
    }

    <com.example.ExpandableHeightGridView
        android:id="@+id/myId"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:horizontalSpacing="2dp"
        android:isScrollContainer="false"
        android:numColumns="4"
        android:stretchMode="columnWidth"
        android:verticalSpacing="20dp" />

    mAppsGrid = (ExpandableHeightGridView) findViewById(R.id.myId);
    mAppsGrid.setExpanded(true);

---

---

如果需要帮助，请告诉我

您可以为listview添加OnScrollListener，并获得如下滚动状态的回调

yourListViewReference.setOnScrollListener(new OnScrollListener(){
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
  // TODO Auto-generated method stub
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
  // TODO Auto-generated method stub

    final int headerHeight = getActivity().findViewById(R.id.fragment_mensagem_list_header)
      .getHeight() - getActivity().getActionBar().getHeight();
    final float ratio = (float) Math.min(Math.max(t, 0), headerHeight) / headerHeight;
    final int newAlpha = (int) (ratio * 255);
    mActionBarBackgroundDrawable.setAlpha(newAlpha);
}
 });
 }

---

将OnScrollListener用于ListView和GridView，可以通过以下公式获得“t”

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            View c = view.getChildAt(0);
            if (c != null) {
                int t = -c.getTop() + view.getFirstVisiblePosition() * c.getHeight();
                final int headerHeight = mHeaderImage.getHeight() - getActionBar().getHeight();
                final float ratio = (float) Math.min(Math.max(t, 0), headerHeight) / headerHeight;
                final int newAlpha = (int) (ratio * 255);
                ((MainActivity) mActivity).getDrawableBGActionBar().setAlpha(newAlpha);

            }

        }

---

尝试在ListView的getView（）中执行此操作，而不是使用ListView滚动。它足够强大，可以处理列表上发生的所有更改。我需要一些参数，如参数l Current horizontal scroll origin。t当前垂直滚动原点。oldl上一个水平滚动原点。oldt上一个垂直滚动原点。