Listview平滑滚动，直到项目位于顶部

Question

I am working on an android application, I have a list view with 10 items. I need to do the following. When the user clicks a button, I want the list to smooth scroll to item at position 5, so this item is displayed on the top of the list.

I have found 2 methods that can be used for this, but both methods are not working exactly how I need:

listView.setSelection(5) this will scroll to the row and put it on top of the list But without animation

list.smoothScrollToPosition(5) this will scroll the listview untill the row is visible but it will not put it on top (it is at the bottom of the page) and if the row is allready visible it will not scroll as it considers it is visible.

So is there a way to have the same behavior as the setSelection method but with smoothscrolling?

Thank you

Answer 1

I believe smoothScrollToPositionFromTop() does what you want.

There's also one that will take the desired animation duration in milliseconds as an argument.

Answer 2

So is there a way to have the same behavior as the setSelection method but with smoothscrolling?

You could post a delayed Runnable and create your own smooth scroll effect using ListView.setSelection . Here's an example:

private ListView mListView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
    mListView.post(new PositionScroller(this));
}

private static final class PositionScroller implements Runnable {

    private static final int SMOOTH_SCROLL_DURATION = 25;
    private int mSelectedPosition;

    private final WeakReference<YourParentActivity> mParent;

    private PositionScroller(YourParentActivity parent) {
        mParent = new WeakReference<YourParentActivity>(parent);
    }

    @Override
    public void run() {
        final ListView list = mParent.get().mListView;
        if (mSelectedPosition <= 5) {
            if (list.postDelayed(this, SMOOTH_SCROLL_DURATION)) {
                list.setSelection(mSelectedPosition++);
            }
        }
    }

}