Question

有没有办法在Android 2.2或2.1上获得listview过度滚动？

我在Android 2.3中使用过度滚动，但它没有在2.2中运行。我怎样才能做到这一点？

Answer 1

创建“过度滚动”视图：

<?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"
>
  <View
    android:layout_width="fill_parent"
    android:layout_height="320px"
    android:background="@android:color/transparent"
  />
</LinearLayout>

您需要在主要活动中使用一些全局变量：

private int currentScrollState = OnScrollListener.SCROLL_STATE_IDLE;
// itemAtTop and itemOffset are needed for when the listview doesn't have enough items to fill the screen
private int itemAtTop = 0, itemOffset = 0; // reset both to 0 each time you populate the listview
private Handler mHandler = new Handler();

在主要活动的onCreate中，在设置listview的适配器之前，添加页眉和页脚：

View v        = LayoutInflater.from(this).inflate(R.layout.listview_overscrollview, null);
listview.addHeaderView(v, null, false);
listview.addFooterView(v, null, false);
listview.setOnScrollListener(this);

由于setOnScrollListener：

，您的主要活动必须覆盖2个方法

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
    checkTopAndBottom();
}


@Override
public void onScrollStateChanged(AbsListView view, int scrollState)
{
    currentScrollState = scrollState;
    checkTopAndBottom();
}

checkTopAndBottom（）函数，也应该在（重新）填充列表视图后调用：

public void checkTopAndBottom()
{
    if ( listview.getCount() <= 2 ) return;  // do nothing, only header and footer in listview
    if ( scrollState != OnScrollListener.SCROLL_STATE_IDLE ) return; // do nothing, listview still scrolling
    if ( listview.getFirstVisiblePosition() < 1 ) {
        listview.setSelectionFromTop(1, -1);
    }
    if ( listview.getLastVisiblePosition() == listview.getCount()-1 ) {
        listview.setSelectionFromTop(listview.getCount()-1, listview.getHeight());
    }
    mHandler.post(checkListviewBottom);
}

最后runnable（对于listview.getFirstVisiblePosition（）等是最新的）：

private final Runnable checkListviewBottom = new Runnable()
{
    @Override
    public void run() {
        if ( listview.getLastVisiblePosition() == listview.getCount()-1 ) {
            if ( itemAtTop == 0 ) {
                if ( listview.getFirstVisiblePosition() <= 1 ) {
                    itemAtTop  = 1;
                    itemOffset = -1;
                } else {
                    itemAtTop  = listview.getCount()-1;
                    itemOffset = listview.getHeight()+1;
                }
            }
            if ( itemAtTop == listview.getCount()-1 || (itemAtTop == 1 && listview.getFirstVisiblePosition() > 0) ) {
                listview.setSelectionFromTop(itemAtTop, itemOffset);
            }
        }
    }
};

有没有办法在Android 2.2或2.1上获得listview过度滚动？

1 个答案: