如何检查我的 ListView 是否具有可滚动的项目数? [英] How to check if a my ListView has scrollable number of items?

问题描述

您如何知道您的 ListView 是否有足够数量的项目以便它可以滚动?

How do you know if your ListView has enough number of items so that it can scroll?

例如，如果我的 ListView 上有 5 个项目，所有项目都将显示在一个屏幕上.但是如果我有 7 个或更多，我的 ListView 就会开始滚动.我如何知道我的列表是否可以以编程方式滚动?

For instance, If I have 5 items on my ListView all of it will be displayed on a single screen. But if I have 7 or more, my ListView begins to scroll. How do I know if my List can scroll programmatically?

推荐答案

Diegosan 的回答无法区分屏幕上部分可见的最后一项.这是该问题的解决方案.

Diegosan's answer cannot differentiate when the last item is partially visible on the screen. Here is a solution to that problem.

首先，ListView 必须在屏幕上呈现，然后我们才能检查其内容是否可滚动.这可以通过 ViewTreeObserver 来完成:

First, the ListView must be rendered on the screen before we can check if its content is scrollable. This can be done with a ViewTreeObserver:

ViewTreeObserver observer = listView.getViewTreeObserver();
    observer.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

        @Override
        public void onGlobalLayout() {
            if (willMyListScroll()) {
                 // Do something
            } 
        }
    });

这里是willMyListScroll():

boolean willMyListScroll() {   
    int pos = listView.getLastVisiblePosition();
    if (listView.getChildAt(pos).getBottom() > listView.getHeight()) {
        return true;
    } else {
        return false;
    }
}

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