android - 无限项的无限滚动

Question

我有一个 GridView，其中包含 5x50 内的项目。

我需要向各个方向滚动它们，而不是在到达末尾时停止，而是从顶部/左侧开始。

例如从左到右滚动

滚动前

1 2 3 4 5
6 7 8 9 10

向右滚动后

5 1 2 3 4
10 6 7 8 9

对于自上而下(或自下而上)

滚动到底部之前

1 2 3 4 5
6 7 8 9 10
11 12 13 14 15

滚动后

6 7 8 9 10
11 12 13 14 15
1 2 3 4 5

我尝试让它像 GridView 原生滚动一样平滑滚动。

Answer 1

在 activity_main.xml 中指定了以下 View 层次结构:

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

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

还有一个基本的列表项 - TextView，在 item.xml 内:

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="center"/>

然后在 Activity 中:

public class MainActivity extends AppCompatActivity {

    private static final int spanCount = 5;
    private static final int totalItemCount = 15;

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

        RecyclerView recyclerView = findViewById(R.id.recycler);
        // Shamelessly stolen from devunwired bit.ly/2yCqVIp
        recyclerView.addItemDecoration(new GridDividerDecoration(this));
        recyclerView.setLayoutManager(new GridLayoutManager(this, spanCount, LinearLayoutManager.VERTICAL, false));
        recyclerView.setAdapter(new MyAdapter(totalItemCount));
    }

    static class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {

        private final int totalSizeOfItems;
        private boolean hasBeenSetup = false;

        MyAdapter(int totalSizeOfItems) {
            this.totalSizeOfItems = totalSizeOfItems;
        }

        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
            final int cellSize = parent.getMeasuredWidth() / spanCount;
            view.setMinimumWidth(cellSize);
            view.setMinimumHeight(cellSize);
            setupRecyclerHeightIfNeeded(parent, cellSize);
            return new MyViewHolder(view);
        }

        // We need to perform this operation once, not each time `onCreateViewHolder` is called
        private void setupRecyclerHeightIfNeeded(View parent, int cellSize) {
            if (hasBeenSetup) return;
            hasBeenSetup = true;
            ViewGroup.MarginLayoutParams params = (ViewGroup.MarginLayoutParams) parent.getLayoutParams();
            int numOfRows = (int) (totalItemCount / (double) spanCount);
            params.height = numOfRows * cellSize;
            new Handler().post(parent::requestLayout);
        }

        @Override
        public void onBindViewHolder(MyViewHolder holder, int pos) {
            int position = holder.getAdapterPosition() % totalSizeOfItems;
            holder.textView.setText(Integer.toString(position + 1));
        }

        @Override
        public int getItemCount() {
            // this will result the list to be "infinite"
            return Integer.MAX_VALUE;
        }
    }

    static class MyViewHolder extends RecyclerView.ViewHolder {

        TextView textView;

        MyViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView;
        }
    }
}

在输出时你会得到:

处理水平滚动需要进行少量更改:

• GridLayoutManager 的方向应更改为 HORIZONTAL
• 应替换适配器内部适当的宽度/高度 setter

除此之外 - 一切都应该相似。