java - 根据 RecyclerView 中的 Scroll 事件更改方向

Question

我正在尝试根据用户向上/向下滚动或向左/向右滚动操作来更改 recyclerview 的方向。这是我的 onCreate() 方法:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler);
    recyclerView.setAdapter(new MyAdapter(totalItemCount));

    // default orientation is VERTICAL
    gridLayoutManager = new GridLayoutManager(this, spanCount, LinearLayoutManager.VERTICAL, false);
    recyclerView.setLayoutManager(gridLayoutManager);

    RecyclerView.OnScrollListener listener = new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            Log.i("TAG", "current orientation: " + gridLayoutManager.getOrientation());

            if (dx > 0) {
                Log.i("TAG", "dx = " + dx);
                recyclerView.post(new Runnable() {
                    @Override
                    public void run() {
                        gridLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
                    }
                });

            } else if (dy > 0) {
                Log.i("TAG", "dy = " + dy);
                recyclerView.post(new Runnable() {
                    @Override
                    public void run() {
                        gridLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
                    }
                });
            }
            recyclerView.setLayoutManager(gridLayoutManager);
        }
    };

    recyclerView.addOnScrollListener(listener);
}

问题是它不会改变 recyclerview 中的方向。改变方向是正确的方法吗？

编辑

建议的代码修改后没有异常(@RobCo)。但我仍然不能改变方向。

Answer 1

错误信息很清楚:

Cannot call this method in a scroll callback. Scroll callbacks might be run during a measure & layout pass where you cannot change theRecyclerView data. Any method call that might change the structure of the RecyclerView or the adapter contents should be postponed to the next frame.

因此，setOrientation 不能从布局或测量过程中调用，也不能在滚动回调期间调用。您必须将 Runnable 发布到下一帧:

    recyclerView.post(new Runnable() {
        @Override
        public void run() {
            gridLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        }
    });