Question

我将我的适配器移植到RecyclerView.Adapter

我想要实现的目标： 当用户向下滚动到最后我想开始获取数据时，我还想在最后添加i ProgressBar视图，让用户知道更多数据即将到来。

我在我的BaseAdapter中实现这个的方式：在getView附近请求的视图中，我将开始获取更多数据，调用notifyDataSetChanged（以获取ProgressBar视图show）然后才返回getView所需的视图。

我在RecyclerView.Adapter尝试做的事情：我试图基本上做同样的事情，这次是在方法onBindViewHolder，

但如果我尝试在此方法中调用notifyItemInserted，则会出现以下异常：

IllegalStateException: Cannot call this method while RecyclerView is computing a layout or scrolling

我尝试了什么：我注意到onBindViewHolder来自onLayoutChildren来自LayoutManager，我尝试覆盖它并在其notifyItemInserted之后调用super但我得到了同样的例外

我如何实现目标？

Answer 1

        Handler handler = new Handler();

        final Runnable r = new Runnable() {
            public void run() {
                adapter.notifyDataSetChanged();
            }
        };

        handler.post(r);

我的示例代码，我调用adapter.notifyDataSetChanged（）;来自活动

Answer 2

同样值得注意的是RecyclerView.isComputingLayout()方法上的JavaDoc会触发此异常：

/**
 * Returns whether RecyclerView is currently computing a layout.
 * <p>
 * If this method returns true, it means that RecyclerView is in a lockdown state and any
 * attempt to update adapter contents will result in an exception because adapter contents
 * cannot be changed while RecyclerView is trying to compute the layout.
 * <p>
 * It is very unlikely that your code will be running during this state as it is
 * called by the framework when a layout traversal happens or RecyclerView starts to scroll
 * in response to system events (touch, accessibility etc).
 * <p>
 * This case may happen if you have some custom logic to change adapter contents in
 * response to a View callback (e.g. focus change callback) which might be triggered during a
 * layout calculation. In these cases, you should just postpone the change using a Handler or a
 * similar mechanism.
 *
 * @return <code>true</code> if RecyclerView is currently computing a layout, <code>false</code>
 *         otherwise
 */
public boolean isComputingLayout() {
    return mLayoutOrScrollCounter > 0;
}

显着的短语是：

在这些情况下，您应该使用Handler或a来推迟更改类似的机制。

在我的情况下，我正在修改另一个线程的适配器内容，这偶尔会导致冲突。将更新转移到UI线程上的处理程序自然可以解决这个问题。

Answer 3

使用Handler添加项目并从notify...()调用Handler为我解决了问题。

Answer 4

整洁和轻松方式：

  recyclerView.post(new Runnable() {
                    @Override
                    public void run() {
                        adapter.notifyDataSetChanged();
                    }
                });

说明：您使用RecyclerView实例并在post方法中添加了一个新的Runnable消息队列。 runnable将在用户界面线程上运行。这是Android从后台访问UI线程的限制（例如，将在后台线程中运行的方法）。

Answer 5

试试这个

if (!recyclerView.isComputingLayout()) {
        recyclerView.notifyDataSetChanged();
    }

Answer 6

我用这个：

Handler handler = new Handler();
private void notifyItemInsertedEx(final int position) {
    try {
        notifyItemInserted(position);
    } catch (Exception ex) {
        handler.post(new Runnable(){
            public void run(){
                notifyItemInserted(position);
            }
        });
    }
}

RecyclerView notifyItemInserted IllegalStateException

6 个答案: