基于Android官方Paging Library的RecyclerView分页加载框架
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我之前写了一篇RecyclerView分页加载机制的文章,是基于Android官方的AsyncListUtil实现的,详情见附录文章1。现在再介绍一种RecyclerView分页加载框架:Android Paging Library。
Android Paging Library是Android官方support-v7支持包中专门做的分页框架,详细文档见谷歌官方文档附录2页面。我写这篇文章时候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’
implementation 'android.arch.paging:runtime:1.0.0-alpha3'
下面我写示例代码做一个简单的演示:
- 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);//触发Android Paging的加载事务逻辑。
- }
- });
- }
- private void makePageList() {
- PagedList.Config mPagedListConfig = new PagedList.Config.Builder()
- .setPageSize(3) //分页数据的数量。在后面的DataSource之loadRange中,count即为每次加载的这个设定值。
- .setPrefetchDistance(5) //初始化时候,预取数据数量。
- .setEnablePlaceholders(false)
- .build();
- mPagedList = new PagedList.Builder()
- .setConfig(mPagedListConfig)
- .setDataSource(mDataSource)
- .setMainThreadExecutor(new BackgroundThreadTask()) //初始化阶段启用
- .setBackgroundThreadExecutor(new MainThreadTask()) //初始化阶段启动
- .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,这里需要后台线程化。
- @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;
- }
- }
- /
- 假设这里需要做一些后台线程的数据加载任务。
- @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 = ”zhangphil@” + 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;
- }
- }
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;@Overrideprotected 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);//触发Android Paging的加载事务逻辑。 } });}private void makePageList() { PagedList.Config mPagedListConfig = new PagedList.Config.Builder() .setPageSize(3) //分页数据的数量。在后面的DataSource之loadRange中,count即为每次加载的这个设定值。 .setPrefetchDistance(5) //初始化时候,预取数据数量。 .setEnablePlaceholders(false) .build(); mPagedList = new PagedList.Builder() .setConfig(mPagedListConfig) .setDataSource(mDataSource) .setMainThreadExecutor(new BackgroundThreadTask()) //初始化阶段启用 .setBackgroundThreadExecutor(new MainThreadTask()) //初始化阶段启动 .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,这里需要后台线程化。 * * @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; }}/** * 假设这里需要做一些后台线程的数据加载任务。 * * @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 = "zhangphil@" + 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;}
}
附录:
1,《基于Android官方AsyncListUtil优化改进RecyclerView分页加载机制(一)》链接:http://blog.csdn.net/zhangphil/article/details/78603499
2,谷歌Android官方Android Paging Library技术文档主页:https://developer.android.google.cn/topic/libraries/architecture/paging.html#classes
转自:http://blog.csdn.net/zhangphil/article/details/78627332
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