聊天的时候会遇到下拉加载更多消息,并且定位到加载的数据最后一条,这里用recyclerview来写一个简单的demo,完成下拉加载更多数据,并且定位到加载的数据的最后一条

github代码链接 (https://github.com/yukunkun/TextDemo/tree/master/app/src/main/java/com/yukun/textapplication/chat)

布局文件很简单

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/sr_refresh"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <android.support.v7.widget.RecyclerView
            android:id="@+id/rv_chat"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    </android.support.v4.widget.SwipeRefreshLayout>

下面是activity里的代码

public class ChatListActivity extends AppCompatActivity {

    @BindView(R.id.rv_chat)
    RecyclerView mRvChat;
    @BindView(R.id.sr_refresh)
    SwipeRefreshLayout mSrRefresh;
    private List<String> mList=new ArrayList<>();
    private RecyclerItemAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat_list);
        ButterKnife.bind(this);
        init();
        getaddInfo();
        setListener();
    }
    private void init() {
        mSrRefresh.setRefreshing(true);
        LinearLayoutManager mLayoutManager=new LinearLayoutManager(this);
        mRvChat.setLayoutManager(mLayoutManager);
        mAdapter = new RecyclerItemAdapter(mList,getApplicationContext());
        mRvChat.setAdapter(mAdapter);
    }

    private void setListener() {

        mSrRefresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                getaddInfo();
            }
        });
    }

    private void getaddInfo() {
        //新的数据
        List<String> mListNew=new ArrayList<>();
        for (int j = 1; j <=20;j++) {
            mListNew.add("第"+j+"个!!");
        }
        mListNew.add("加载更多的底部");
        //从头插入数据,原来的保留
        mList.addAll(0,mListNew);

        mSrRefresh.setRefreshing(false);
        mAdapter.addMesasge(mList);
        mAdapter.notifyDataSetChanged();
        mRvChat.smoothScrollToPosition(mListNew.size()-1);
    }
}

东西其实很少,就是几个常用的方法

主要是下面的这几句完成加载更多的数据,并且定位

 //新的数据
            List<String> mListNew=new ArrayList<>();
            for (int j = 1; j <=20;j++) {
                mListNew.add("第"+j+"个!!");
            }
            mListNew.add("加载更多的底部");
            //从头插入数据,原来的保留
            mList.addAll(0,mListNew);
    
            mSrRefresh.setRefreshing(false);
            mAdapter.addMesasge(mList);
            mAdapter.notifyDataSetChanged();
            //定位到加载的最后一条数据
            mRvChat.smoothScrollToPosition(mListNew.size()-1);

adapter和常用的没啥区别,代码贴出来,为了完整性

public class RecyclerItemAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
    List<String> mList;
    Context context;

    public RecyclerItemAdapter(List<String> list, Context context) {
        mList = list;
        this.context = context;
    }
    public void addMesasge(List<String> mList){
        this.mList=mList;
    }
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new MyHolder(LayoutInflater.from(context).inflate(R.layout.recycler_item,null));
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        ((MyHolder)holder).mTextView.setText(mList.get(position));
    }

    @Override
    public int getItemCount() {
        return mList.size();
    }
    class MyHolder extends RecyclerView.ViewHolder {
        TextView mTextView;
        public MyHolder(View itemView) {
            super(itemView);
            mTextView = (TextView) itemView.findViewById(R.id.tv_content);
        }
    }
}

adapter的布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">
    <TextView
        android:text=""
        android:textSize="20dp"
        android:textColor="#70f57b"
        android:gravity="center"
        android:id="@+id/tv_content"
        android:layout_width="match_parent"
        android:layout_height="30dp"/>
    <View
        android:background="#ff8888"
        android:layout_width="match_parent"
        android:layout_height="0.5dp"/>

</LinearLayout>

这里就OK了,虽然简单,下次遇到了才能更好的完成.留个笔记.