今天研究了下RecyclerView的滑动事件，特别是下拉刷新和加载更多事件，在现在几乎所有的APP显示数据列表时都用到了。自定义RecyclerView下拉刷新和加载更多听上去很复杂，实际上并不难，只要是对滑动事件的监听和处理。
一、自定义RecyclerView实现下拉刷新和加载更多
1、如何判断RecyclerView是在上滑还是下滑
在RecyclerView的OnScrollListener滑动事件监听中有个好用的方法，就是onScrolled(RecyclerView recyclerView, int dx, int dy)，其中根据dx的值的正负就可以判断是在左滑还是右滑，而根据dy的值就可以判断是在上滑还是下滑。
//上滑 if(dy>0){ //相应操作代码 } //下滑 else if(dy<0){ //相应操作代码 }
2、如何判断是否滑到了顶部或者底部
同样在RecyclerView的OnScrollListener滑动事件监听中onScrolled(RecyclerView recyclerView, int dx, int dy)方法中处理，根据canScrollVertically(int direction)来进行判断。
//是否滑到底部 if(!recyclerView.canScrollVertically(1)){ //相应处理操作 } //是否滑到顶部 if(!recyclerView.canScrollVertically(-1)){ //相应处理操作 }
3、自定义RecyclerView
知道了滑动事件的判断和处理，就可以很轻松得实现下拉刷新和加载更多了。
import android.content.Context; import android.support.annotation.Nullable; import android.support.v7.widget.RecyclerView; import android.util.AttributeSet; import android.util.Log; /** * Package:com.liuting.library * author:liuting * Date:2017/2/14 * Desc:自定义RecycleView，下拉刷新以及上拉加载更多 */ public class RefreshLoadMoreRecycleView extends RecyclerView { private Boolean isLoadMore;//是否可以加载更多标志 private Boolean isLoadEnd;//加载到最后的标志 private Boolean isLoadStart;//顶部的标志 private Boolean isRefresh;//是否可以下拉刷新标志 private int lastVisibleItem;//最后一项 private IOnScrollListener listener;//事件监听 public RefreshLoadMoreRecycleView(Context context) { super(context); init(context); } public RefreshLoadMoreRecycleView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); init(context); } public RefreshLoadMoreRecycleView(Context context, @Nullable AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context); } public void init(Context context) { isLoadEnd=false; isLoadStart =true; this.addOnScrollListener(new RecyclerView.OnScrollListener() { @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); //SCROLL_STATE_DRAGGING 和 SCROLL_STATE_IDLE 两种效果自己看着来 if (newState == RecyclerView.SCROLL_STATE_IDLE) { if (isLoadEnd) { // 判断是否已加载所有数据 if (isLoadMore) {//未加载完所有数据，加载数据，并且还原isLoadEnd值为false，重新定位列表底部 if (getListener() != null) { getListener().onLoadMore(); } } else {//加载完了所有的数据 if(getListener()!=null){ getListener().onLoaded(); } } isLoadEnd = false; } else if (isLoadStart) { if(isRefresh){ if (getListener() != null) { getListener().onRefresh(); } isLoadStart=false; } } } } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); //上滑 if(dy>0){ //是否滑到底部 if(!recyclerView.canScrollVertically(1)){ isLoadEnd = true; }else{ isLoadEnd = false; } } //下滑 else if(dy<0){ //是否滑到顶部 if(!recyclerView.canScrollVertically(-1)){ isLoadStart=true; }else{ isLoadStart=false; } } } }); } //监听事件 public interface IOnScrollListener { void onRefresh(); void onLoadMore(); void onLoaded(); } public IOnScrollListener getListener() { return listener; } public void setListener(IOnScrollListener listener) { this.listener = listener; } public Boolean getLoadMore() { return isLoadMore; } //设置是否支持加载更多 public void setLoadMoreEnable(Boolean loadMore) { isLoadMore = loadMore; } public Boolean getRefresh() { return isRefresh; } //设置是否支持下拉刷新 public void setRefreshEnable(Boolean refresh) { isRefresh = refresh; } }
二、实际用例
已经定义好了RecyclerView，下面在Demo中实际使用和处理。
1、定义布局
布局文件很简单，就是一个RecyclerView
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context="com.liuting.refreshloadmorelistview.MainActivity"> <com.liuting.library.RefreshLoadMoreRecycleView android:id="@+id/main_recycle_view_data" android:layout_width="match_parent" android:layout_height="match_parent" android:scrollbars="none" /> </LinearLayout>
2、定义RecyclerView.Adapter
RecyclerView.Adapter在这里就简单处理了，列表布局直接使用Android自带的。
import android.content.Context; import android.support.v7.widget.RecyclerView; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import java.util.List; /** * Package:com.liuting.refreshloadmorelistview.adapter * author:liuting * Date:2017/2/16 * Desc:列表Adapter */ public class RefreshLoadMoreRecycleAdapter extends RecyclerView.Adapter<RefreshLoadMoreRecycleAdapter.ViewHolder> { private List<String> list; private Context context; public RefreshLoadMoreRecycleAdapter(Context context,List<String> list) { this.context =context; this.list = list; } @Override public RefreshLoadMoreRecycleAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_expandable_list_item_1, parent, false); RefreshLoadMoreRecycleAdapter.ViewHolder viewHolder = new RefreshLoadMoreRecycleAdapter.ViewHolder(view); return viewHolder; } @Override public void onBindViewHolder(ViewHolder holder, int position) { holder.text.setText(list.get(position)); holder.itemView.setTag(position); } @Override public int getItemCount() { return list.size(); } class ViewHolder extends RecyclerView.ViewHolder{ private TextView text; public ViewHolder(View itemView) { super(itemView); text=(TextView)itemView.findViewById(android.R.id.text1); } } }
3、在Activity中定义好控件以及数据加载操作
实现自定义RecyclerView中的数据加载事件监听，刷新、加载更多以及加载完成。
import android.app.ProgressDialog; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.LinearLayoutManager; import android.widget.Toast; import com.liuting.library.RefreshLoadMoreRecycleView; import com.liuting.refreshloadmorelistview.adapter.RefreshLoadMoreRecycleAdapter; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity implements RefreshLoadMoreRecycleView.IOnScrollListener{ private RefreshLoadMoreRecycleView recycleView;//下拉刷新RecycleView private List<String> list;//列表 private RefreshLoadMoreRecycleAdapter adapter;//Adapter private ProgressDialog dialog;//提示框 private static final int REFRESH_Load=0;//下拉刷新 private static final int MORE_Load=1;//加载更多 private Handler handler =new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what){ case REFRESH_Load: recycleView.setLoadMoreEnable(true); dismissDialog(); if(list!=null){ list.clear(); } loadData(); adapter.notifyDataSetChanged(); break; case MORE_Load: recycleView.setLoadMoreEnable(false); dismissDialog(); loadData(); adapter.notifyDataSetChanged(); break; } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); } public void initView(){ dialog = new ProgressDialog(MainActivity.this); list=new ArrayList<>(); loadData(); recycleView = (RefreshLoadMoreRecycleView)findViewById(R.id.main_recycle_view_data); final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(MainActivity.this); recycleView.setLayoutManager(linearLayoutManager); adapter = new RefreshLoadMoreRecycleAdapter(MainActivity.this,list); recycleView.setAdapter(adapter); recycleView.setListener(this); recycleView.setRefreshEnable(true); recycleView.setLoadMoreEnable(true); } /** * 加载数据 */ public void loadData(){ for(int i=0;i<10;i++ ){ list.add("It is "+i); } } @Override public void onRefresh() { showDialog(); new Thread(){ @Override public void run() { super.run(); try { sleep(5000); handler.sendEmptyMessage(REFRESH_Load); } catch (InterruptedException e) { e.printStackTrace(); } } }.start(); } @Override public void onLoadMore() { showDialog(); new Thread(){ @Override public void run() { super.run(); try { sleep(5000); handler.sendEmptyMessage(MORE_Load); } catch (InterruptedException e) { e.printStackTrace(); } } }.start(); } @Override public void onLoaded() { Toast.makeText(MainActivity.this,"Loaded all",Toast.LENGTH_SHORT).show(); } /** * dismiss dialog */ private void dismissDialog(){ if (dialog!=null&&dialog.isShowing()){ dialog.dismiss(); } } /** * show dialog */ private void showDialog(){ if (dialog!=null&&!dialog.isShowing()){ dialog.show(); } } }
三、最终效果图
到这里就轻松实现了RecyclerView的下拉刷新和加载更多了。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。