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

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：