更改您的回收站视图高度和宽度从wrap_content更改为match_parent，或者您也可以为回收站给予固定高度视图为android:layout_height="150dp"

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#888888" />

</RelativeLayout>

或者你可以试试

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:background="#888888" />

</RelativeLayout>

使用下面的代码更改您的item.xml布局内容。它将解决您的问题。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="160dp"
    android:layout_height="match_parent"
    android:background="#888888">
    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hi"
        android:textSize="30sp" />

</LinearLayout>

您可以使用FlexboxLayoutManager Google库解决此问题，方法是将FlexDirection定义为FlexDirection.ROW，将FlexWrap定义为FlexWrap.NOWRAP，并在BaseViewHolder构造函数中将每个项目的FlexShrink设置为0.0f以便能够水平滚动。有关如何实现此目的的更多详细信息，请参见此处：带有动态项目高度的水平循环视图

主要活动：

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;

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

        mAdapter = createAdapter();

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
        mRecyclerView.setAdapter(mAdapter);
    }

    private RecyclerView.Adapter<ViewHolder> createAdapter() {
        RecyclerView.Adapter adapter = new RecyclerView.Adapter<ViewHolder>() {
            @Override
            public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
                return new ViewHolder(v);
            }

            @Override
            public void onBindViewHolder(ViewHolder holder, int position) {
                if (position < 33) {
                    holder.mText.setText("1 line");
                } else if (position > 66) {
                    holder.mText.setText("2 lines\n2 lines");
                } else {
                    holder.mText.setText("3 lines\n3 lines\n3 lines");
                }
            }

            @Override
            public int getItemCount() {
                return 100;
            }
        };
        return adapter;
    }

    private static class ViewHolder extends RecyclerView.ViewHolder {
        TextView mText;
        public ViewHolder(View itemView) {
            super(itemView);
            mText = (TextView) itemView.findViewById(R.id.text);
        }
    }
}

活动_主要.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">

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

item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#888888">
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hi"
        android:textSize="30sp" />

</LinearLayout>

要使RecyclerView水平，您需要使用android:layout_centerHorizontal="true"。此外，其他一切都与垂直相同。

<androidx.recyclerview.widget.RecyclerView
        android:id="@+id/RecyclerView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_below="@id/toolbar"/>

尝试添加您的文本View android:singleLine="false"当有多行时它会更改

只需调用itemAdapter.notifyDataSetChanged（）;