在 Android 中很好地设置 ListView 滚动位置
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Setting ListView scroll position nicely in Android
提问by Carl Manaster
I am aware of setSelection(), setSelectionFromTop(), and setSelectionAfterHeaderView(), but none of them seems to do what I want.
我知道setSelection(), setSelectionFromTop(), 和setSelectionAfterHeaderView()，但他们似乎都没有做我想做的事。
Given an item in the list, I want to scroll so that it is in view. If the item is above the visible window of the list, I want to scroll until the item is the first visible item in the list; if the item is below the visible window, I want it to scroll up until it is the last visible item in the list. If the item is already visible, I don't want any scrolling to occur.
给定列表中的一个项目，我想滚动以使其可见。如果该项目在列表的可见窗口上方，我想滚动直到该项目成为列表中的第一个可见项目；如果该项目位于可见窗口下方，我希望它向上滚动，直到它成为列表中的最后一个可见项目。如果该项目已经可见，我不希望发生任何滚动。
How do I go about this?
我该怎么做？
回答by Sergey
It occurs because listView isn't created yet. Try to post runnable such as:
发生这种情况是因为尚未创建 listView。尝试发布可运行的，例如：
getListView().postDelayed(new Runnable() {
@Override
public void run() {
lst.setSelection(15);
}
},100L);
回答by strange-corner
I think, I was looking for the same, then I found the following solution:
我想，我一直在寻找相同的东西，然后我找到了以下解决方案：
if (listview.getFirstVisiblePosition() > pos
|| listview.getLastVisiblePosition() <= pos) {
listview.smoothScrollToPosition(pos);
}
API 8is required to use smoothScrollToPosition(which is a reasonable minimum anyways) so you are aware.
需要使用API 8smoothScrollToPosition（无论如何这是一个合理的最低限度），所以你知道。
回答by Alessandro Roaro
Sergey's answer works, but I believe that the right way of doing this is setting up an observer to be notified when the ListViewhas been created.
Sergey 的回答有效，但我相信这样做的正确方法是设置一个观察者，以便ListView在创建时收到通知。
listView.getViewTreeObserver().addOnGlobalLayoutListener(
new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
scrollTo(scrollToPosition);
listView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
}
});
回答by foshoshin
A better solution to Sergey's answeris to call setSelection()later in the Activity/Fragment life cycle, perhaps in onStart(). That way, you have a guarantee that the View is ready rather than using some arbitrary delay.
Sergey 的答案的一个更好的解决方案是setSelection()在 Activity/Fragment 生命周期的后期调用，也许在onStart(). 这样，您就可以保证 View 已准备就绪，而不是使用一些任意延迟。
