Android StaggeredGridLayoutManager布局RecyclerView在滚动状态可见范围刷新数据

爱被打了一巴掌 2023-10-17 19:10 48阅读 0赞

**Android StaggeredGridLayoutManager布局RecyclerView在滚动状态可见范围刷新数据**

之所以把StaggeredGridLayoutManager布局的RecyclerView单列出来处理滚动状态下可见（可视）范围内的数据更新问题，是因为在StaggeredGridLayoutManager布局下的RecyclerView，对于第一个可视item和最后一个可视item，即第一个可视item位置和最后一个可视item位置，不像在LinearLayoutManager布局下直接获取，需要进行一个简单计算。关键的计算过程我写在了getOutRange()方法内。

package zhangphil.recyclerview;
    
    import android.graphics.Color;
    import android.os.Bundle;
    import android.support.annotation.NonNull;
    import android.support.annotation.Nullable;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.RecyclerView;
    import android.support.v7.widget.StaggeredGridLayoutManager;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.TextView;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    
    public class RecyclerViewActivity extends AppCompatActivity {
        private RecyclerView mRecyclerView;
        private RecyclerViewAdapter mAdapter;
        private StaggeredGridLayoutManager layoutManager;
        private ArrayList<String> mItems;
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.recycler_view_activity);
    
            mItems = new ArrayList<>();
            for (int i = 0; i < 110; i++) {
                mItems.add(i + "");
            }
    
            initRecyclerView();
    
            mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                @Override
                public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                    super.onScrollStateChanged(recyclerView, newState);
    
                    if (recyclerView.getScrollState() == RecyclerView.SCROLL_STATE_IDLE) {
                        int[] outRange = getOutRange();
                        int len = outRange[1] - outRange[0] + 1;
    
                        int num = (int) (Math.random() * 10);
                        for (int i = 0; i < len; i++) {
                            mItems.set(outRange[0] + i, num + "");
                        }
    
                        mAdapter.notifyDataSetChanged();
                    }
                }
            });
        }
    
        private int[] getOutRange() {
            int[] range = new int[2];
    
            int[] first = new int[layoutManager.getSpanCount()];
            layoutManager.findFirstVisibleItemPositions(first);
    
            int[] last = new int[layoutManager.getSpanCount()];
            layoutManager.findLastVisibleItemPositions(last);
    
            range[0] = first[0];
    
            Arrays.sort(last);
            range[1] = last[last.length - 1];
    
            return range;
        }
    
        private void initRecyclerView() {
            mRecyclerView = findViewById(R.id.recycler_view);
            layoutManager = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
            mRecyclerView.setLayoutManager(layoutManager);
    
            mAdapter = new RecyclerViewAdapter();
            mRecyclerView.setAdapter(mAdapter);
        }
    
        private class RecyclerViewAdapter extends RecyclerView.Adapter<MyVH> {
    
            @NonNull
            @Override
            public MyVH onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(getApplicationContext()).inflate(android.R.layout.simple_list_item_2, parent, false);
                return new MyVH(view);
            }
    
            @Override
            public void onBindViewHolder(@NonNull MyVH holder, int position) {
                holder.text1.setText("" + position);
                holder.text2.setText(mItems.get(position));
            }
    
            @Override
            public int getItemCount() {
                return mItems.size();
            }
        }
    
        private class MyVH extends RecyclerView.ViewHolder {
            public TextView text1;
            public TextView text2;
    
            public MyVH(View itemView) {
                super(itemView);
                text1 = itemView.findViewById(android.R.id.text1);
                text1.setTextColor(Color.WHITE);
                text1.setBackgroundColor(Color.RED);
                text2 = itemView.findViewById(android.R.id.text2);
                text2.setTextColor(Color.DKGRAY);
            }
        }
    }

代码实现一个简单意图，用StaggeredGridLayoutManager控制RecyclerView，当RecyclerView滚动停止后，更新可可范围内的数据到最新。

如图：

![20180416182613923][]

[20180416182613923]: https://img-blog.csdn.net/20180416182613923