標籤:bin xtend etc extends end size tla tor for
基於Android官方Paging Library的RecyclerView分頁載入架構
我之前寫了一篇RecyclerView分頁載入機制的文章,是基於Android官方的AsyncListUtil實現的,詳情見附錄文章1。現在再介紹一種RecyclerView分頁載入架構:Android Paging Library。
Android Paging Library是Android官方support-v7支援包中專門做的分頁架構,詳細文檔見Google官方文檔附錄2頁面。我寫這篇文章時候Paging Library的版本是1.0.0-alpha3。
使用Android Paging Library首先需要在gradle添加引用:
implementation ‘android.arch.paging:runtime:1.0.0-alpha3‘
下面我寫範例程式碼做一個簡單的示範:
package zhangphil.demo;import android.arch.paging.PagedList;import android.arch.paging.PagedListAdapter;import android.arch.paging.TiledDataSource;import android.graphics.Color;import android.support.annotation.NonNull;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.recyclerview.extensions.DiffCallback;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.text.TextUtils;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.LinearLayout;import android.widget.TextView;import java.util.ArrayList;import java.util.List;import java.util.concurrent.Executor;public class MainActivity extends AppCompatActivity { private PagedList<DataBean> mPagedList; private MyDataSource mDataSource; private RecyclerView mRecyclerView; private PagedListAdapter mAdapter; private LinearLayoutManager mLayoutManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mDataSource = new MyDataSource(); makePageList(); mRecyclerView = findViewById(R.id.recycler_view); mLayoutManager = new LinearLayoutManager(this); mLayoutManager.setOrientation(LinearLayout.VERTICAL); mRecyclerView.setLayoutManager(mLayoutManager); mAdapter = new MyAdapter(); mRecyclerView.setAdapter(mAdapter); mAdapter.setList(mPagedList); mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { private int lastPos; @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); lastPos = mLayoutManager.findLastVisibleItemPosition(); mPagedList.loadAround(lastPos);//觸發Android Paging的載入事務邏輯。 } }); } private void makePageList() { PagedList.Config mPagedListConfig = new PagedList.Config.Builder() .setPageSize(3) //分頁資料的數量。在後面的DataSource之loadRange中,count即為每次載入的這個設定值。 .setPrefetchDistance(5) //初始化時候,預取資料數量。 .setEnablePlaceholders(false) .build(); mPagedList = new PagedList.Builder() .setConfig(mPagedListConfig) .setDataSource(mDataSource) .setMainThreadExecutor(new BackgroundThreadTask()) //初始化階段啟用 .setBackgroundThreadExecutor(new MainThreadTask()) //初始化階段啟動 .build(); } private class BackgroundThreadTask implements Executor { public BackgroundThreadTask() { this.execute(new Runnable() { @Override public void run() { Log.d("BackgroundThreadTask", "run"); } }); } @Override public void execute(@NonNull Runnable runnable) { runnable.run(); } } private class MainThreadTask implements Executor { public MainThreadTask() { this.execute(new Runnable() { @Override public void run() { Log.d("MainThreadTask", "run"); } }); } @Override public void execute(@NonNull Runnable runnable) { runnable.run(); } } private class MyDataSource extends TiledDataSource<DataBean> { @Override public int countItems() { return TiledDataSource.COUNT_UNDEFINED; } /** * 注意,這裡需要後台線程化。 * * @param startPosition * @param count * @return */ @Override public List<DataBean> loadRange(int startPosition, int count) { Log.d("MyDataSource", "loadRange:" + startPosition + "," + count); List<DataBean> list = loadData(startPosition, count); return list; } } /** * 假設這裡需要做一些後台線程的資料載入任務。 * * @param startPosition * @param count * @return */ private List<DataBean> loadData(int startPosition, int count) { List<DataBean> list = new ArrayList(); for (int i = 0; i < count; i++) { DataBean data = new DataBean(); data.id = startPosition + i; data.content = "[email protected]" + data.id; list.add(data); } return list; } private class MyViewHolder extends RecyclerView.ViewHolder { public TextView text1; public TextView text2; public MyViewHolder(View itemView) { super(itemView); text1 = itemView.findViewById(android.R.id.text1); text1.setTextColor(Color.RED); text2 = itemView.findViewById(android.R.id.text2); text2.setTextColor(Color.BLUE); } } private class MyAdapter extends PagedListAdapter<DataBean, MyViewHolder> { public MyAdapter() { super(mDiffCallback); } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(getApplicationContext()).inflate(android.R.layout.simple_list_item_2, null); MyViewHolder holder = new MyViewHolder(view); return holder; } @Override public void onBindViewHolder(MyViewHolder holder, int position) { DataBean data = mPagedList.get(position); holder.text1.setText(String.valueOf(position)); holder.text2.setText(String.valueOf(data.content)); } } private DiffCallback<DataBean> mDiffCallback = new DiffCallback<DataBean>() { @Override public boolean areItemsTheSame(@NonNull DataBean oldItem, @NonNull DataBean newItem) { Log.d("DiffCallback", "areItemsTheSame"); return oldItem.id == newItem.id; } @Override public boolean areContentsTheSame(@NonNull DataBean oldItem, @NonNull DataBean newItem) { Log.d("DiffCallback", "areContentsTheSame"); return TextUtils.equals(oldItem.content, newItem.content); } }; private class DataBean { public int id; public String content; }}
代碼實現的功能很簡單,當RecyclerView不斷下滑時,就觸發分頁載入,把RecyclerView後續使用的資料分頁載入顯示出來。暫時我將現階段對Android Paging Library技術的心得記錄下來,作為我學習Android Paging Library技術的階段性備忘錄。這部分代碼還有待進一步完善,Android Paging Library技術細節後續會繼續跟進研究。
附錄:
1,《基於Android官方AsyncListUtil最佳化改進RecyclerView分頁載入機制(一)》連結:http://blog.csdn.net/zhangphil/article/details/78603499
2,GoogleAndroid官方Android Paging Library技術文檔首頁:https://developer.android.google.cn/topic/libraries/architecture/paging.html#classes
基於Android官方Paging Library的RecyclerView分頁載入架構