android - 如何在 Recyclerview 中向上滚动时显示 Snackbar 并在向下滚动时关闭

Question

我正在尝试实现一个 Snackbar，当用户在 RecyclerView 上滚动时它将显示和关闭。这是 View 的 .xml 文件。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/activityFriendsList">

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/friendsRecyclerView"/>

    </android.support.design.widget.CoordinatorLayout>
</RelativeLayout>

这也是应该完成这项工作的函数

Snackbar snackbar;


 recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            snackbar = Snackbar.make(activity, "Add new friend", Snackbar.LENGTH_INDEFINITE);
            snackbar.show();
            if (dy > 0) {
                Log.i("Info", "Scrolling up");
                if(snackBarIsShowing) {
                    snackBarIsShowing = false;
                }
            }
            if (dy < 0){
                Log.i("Info", "Scrolling down");
                if(!snackBarIsShowing) {
                    snackBarIsShowing = true;
                }
            }

            if (snackBarIsShowing) {
                Log.i("Info", "Create new");
                snackbar.dismiss();
            } else {
                Log.i("Info", "Dismiss the old one");

            }
        }

    });

我认为问题可能在于，现在我并不想放弃正确的 snackbar 。 知道我如何克服这个问题。

Answer 1

试试这个，我已经测试过了，它工作正常。

  RecyclerAdapter adapter;
RecyclerView recyclerView;
private Snackbar snackbar;

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

    snackbar = Snackbar.make(findViewById(android.R.id.content), "should disappear when scrolling!", Snackbar.LENGTH_LONG);
    recyclerView = findViewById(R.id.recyclerView);
    RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
    adapter = new RecyclerAdapter(myList);
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(adapter);

    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            if (!recyclerView.canScrollVertically(-1)) {

                if (!snackbar.isShown())
                    snackbar.show();

            } else if (!recyclerView.canScrollVertically(1)) {
                if (snackbar.isShown())
                    snackbar.dismiss();
            }
            if (dy < 0) {
                if (!snackbar.isShown())
                    snackbar.show();
            } else if (dy > 0) {
                if (snackbar.isShown())
                    snackbar.dismiss();
            }
        }
    });
}

注意: canScrollVertically(int Direction) direction int:负数表示检查向上滚动，正数表示检查向下滚动。请参阅文档 here