设置一次性加载页面个数 Android viewpager2

转载

mob64ca13f9a97c 2024-12-24 20:12:56

文章标签 recycler 脚布局上拉加载 android ide 文章分类 Android 移动开发

先看一下效果

设置一次性加载页面个数 Android viewpager2_android

刷新的时候是这样的:

设置一次性加载页面个数 Android viewpager2_ide_02

没有更多的时候是这样的:

设置一次性加载页面个数 Android viewpager2_android_03

既然有刷新的时候有两种状态就要定义两个状态

//普通布局的type
    static final int TYPE_ITEM = 0;
    //脚布局
    static final int TYPE_FOOTER = 1;

在特定的时候去显示:

@Override
    public int getItemViewType(int position) {
        //如果position加1正好等于所有item的总和,说明是最后一个item,将它设置为脚布局
        if (position + 1 == getItemCount()) {
            return TYPE_FOOTER;
        } else {
            return TYPE_ITEM;
        }
    }

然后根据这个type来inflate不同的布局:

@Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_ITEM) {
            View view = View.inflate(mContext, R.layout.item_recycler, null);
            MyViewHolder holder = new MyViewHolder(view);
            return holder;
        } else if (viewType == TYPE_FOOTER) {
           //脚布局
            View view = View.inflate(mContext, R.layout.recycler_load_more_layout, null);
            FootViewHolder footViewHolder = new FootViewHolder(view);
            return footViewHolder;
        }
        return null;
    }

以上只是控制了Loading布局的出现可隐藏,还要2中状态需要控制就是上面的2个图,一个是正在加载,一个是加载完成状态,这两个状态在adapter里显然是控制不了的,必须要在请求数据的时候才能知道这两种状态,而加载数据又是在activity中执行的,所以我们需要一个用来传递状态的方法:

/**
     * 改变脚布局的状态的方法,在activity根据请求数据的状态来改变这个状态
     *
     * @param state
     */
    public void changeState(int state) {
        this.footer_state = state;
        notifyDataSetChanged();
    }

用来接收状态的变量:

//    //上拉加载更多
//    static final int PULL_LOAD_MORE = 0;
    //正在加载更多
    static final int LOADING_MORE = 1;
    //没有更多
    static final int NO_MORE = 2;
    //脚布局当前的状态,默认为没有更多
    int footer_state = 1;

然后就可以根据这几种状态来控制布局控件的改变了:

@Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof MyViewHolder) {
            ((MyViewHolder) holder).mTextView.setText(mList.get(position));
        } else if (holder instanceof FootViewHolder) {
            FootViewHolder footViewHolder = (FootViewHolder) holder;
            if (position == 0) {//如果第一个就是脚布局,,那就让他隐藏
                footViewHolder.mProgressBar.setVisibility(View.GONE);
                footViewHolder.tv_line1.setVisibility(View.GONE);
                footViewHolder.tv_line2.setVisibility(View.GONE);
                footViewHolder.tv_state.setText("");
            }
            switch (footer_state) {//根据状态来让脚布局发生改变
//                case PULL_LOAD_MORE://上拉加载
//                    footViewHolder.mProgressBar.setVisibility(View.GONE);
//                    footViewHolder.tv_state.setText("上拉加载更多");
//                    break;
                case LOADING_MORE:
                    footViewHolder.mProgressBar.setVisibility(View.VISIBLE);
                    footViewHolder.tv_line1.setVisibility(View.GONE);
                    footViewHolder.tv_line2.setVisibility(View.GONE);
                    footViewHolder.tv_state.setText("正在加载...");
                    break;
                case NO_MORE:
                    footViewHolder.mProgressBar.setVisibility(View.GONE);
                    footViewHolder.tv_line1.setVisibility(View.VISIBLE);
                    footViewHolder.tv_line2.setVisibility(View.VISIBLE);
                    footViewHolder.tv_state.setText("我是有底线的");
                    footViewHolder.tv_state.setTextColor(Color.parseColor("#ff00ff"));
                    break;
            }
        }
    }

不要忘了返回的count也要加1,因为添加了一个脚布局:

@Override
    public int getItemCount() {
        return mList != null ? mList.size() + 1 : 0;
    }

那么什么时候去传递状态到adapter呢?这里就需要给RecyclerView添加滑动监听了,当他滑动到底部的时候显示加载中的状态:

//给recyclerView添加滑动监听
        mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                /*
                到达底部了,如果不加!isLoading的话到达底部如果还一滑动的话就会一直进入这个方法
                就一直去做请求网络的操作,这样的用户体验肯定不好.添加一个判断,每次滑倒底只进行一次网络请求去请求数据
                当请求完成后,在把isLoading赋值为false,下次滑倒底又能进入这个方法了
                 */
                if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
                    //到达底部之后如果footView的状态不是正在加载的状态,就将 他切换成正在加载的状态
                    if (page < totlePage) {
                        Log.e("duanlian", "onScrollStateChanged: " + "进来了");
                        isLoading = true;
                        mAdapter.changeState(1);
                        new Handler().postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                getData();
                                page++;
                            }
                        }, 2000);
                    } else {
                        mAdapter.changeState(2);

                    }
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                //拿到最后一个出现的item的位置
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
            }
        });

重点就这几个,下面给出脚布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:id="@+id/ll_below"
                android:layout_width="match_parent"
                android:layout_height="45dp"
    >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="45dp"
        android:gravity="center"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_line1"
            android:layout_width="60dp"
            android:layout_height="1dp"
            android:layout_marginRight="10dp"
            android:background="#ff00ff"
            android:visibility="gone"/>

        <ProgressBar
            android:id="@+id/progressbar"
            android:layout_width="25dp"
            android:layout_height="25dp"
            android:visibility="visible"/>

        <TextView
            android:id="@+id/foot_view_item_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="4dp"
            android:text="上拉加载更多"/>

        <TextView
            android:id="@+id/tv_line2"
            android:layout_width="60dp"
            android:layout_height="1dp"
            android:layout_marginLeft="10dp"
            android:background="#ff00ff"
            android:visibility="gone"/>
    </LinearLayout>
</RelativeLayout>

Adapter的代码:

package com.duanlian.recyclerviewloadmoredemo;

import android.content.Context;
import android.graphics.Color;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.util.List;


public class MyRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private Context mContext;
    private List<String> mList;
    //普通布局的type
    static final int TYPE_ITEM = 0;
    //脚布局
    static final int TYPE_FOOTER = 1;
    //    //上拉加载更多
//    static final int PULL_LOAD_MORE = 0;
    //正在加载更多
    static final int LOADING_MORE = 1;
    //没有更多
    static final int NO_MORE = 2;
    //脚布局当前的状态,默认为没有更多
    int footer_state = 1;

    public MyRecyclerAdapter(Context context, List<String> list) {
        mContext = context;
        mList = list;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_ITEM) {
            View view = View.inflate(mContext, R.layout.item_recycler, null);
            MyViewHolder holder = new MyViewHolder(view);
            return holder;
        } else if (viewType == TYPE_FOOTER) {
           //脚布局
            View view = View.inflate(mContext, R.layout.recycler_load_more_layout, null);
            FootViewHolder footViewHolder = new FootViewHolder(view);
            return footViewHolder;
        }
        return null;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof MyViewHolder) {
            ((MyViewHolder) holder).mTextView.setText(mList.get(position));
        } else if (holder instanceof FootViewHolder) {
            FootViewHolder footViewHolder = (FootViewHolder) holder;
            if (position == 0) {//如果第一个就是脚布局,,那就让他隐藏
                footViewHolder.mProgressBar.setVisibility(View.GONE);
                footViewHolder.tv_line1.setVisibility(View.GONE);
                footViewHolder.tv_line2.setVisibility(View.GONE);
                footViewHolder.tv_state.setText("");
            }
            switch (footer_state) {//根据状态来让脚布局发生改变
//                case PULL_LOAD_MORE://上拉加载
//                    footViewHolder.mProgressBar.setVisibility(View.GONE);
//                    footViewHolder.tv_state.setText("上拉加载更多");
//                    break;
                case LOADING_MORE:
                    footViewHolder.mProgressBar.setVisibility(View.VISIBLE);
                    footViewHolder.tv_line1.setVisibility(View.GONE);
                    footViewHolder.tv_line2.setVisibility(View.GONE);
                    footViewHolder.tv_state.setText("正在加载...");
                    break;
                case NO_MORE:
                    footViewHolder.mProgressBar.setVisibility(View.GONE);
                    footViewHolder.tv_line1.setVisibility(View.VISIBLE);
                    footViewHolder.tv_line2.setVisibility(View.VISIBLE);
                    footViewHolder.tv_state.setText("我是有底线的");
                    footViewHolder.tv_state.setTextColor(Color.parseColor("#ff00ff"));
                    break;
            }
        }
    }


    @Override
    public int getItemViewType(int position) {
        //如果position加1正好等于所有item的总和,说明是最后一个item,将它设置为脚布局
        if (position + 1 == getItemCount()) {
            return TYPE_FOOTER;
        } else {
            return TYPE_ITEM;
        }
    }

    @Override
    public int getItemCount() {
        return mList != null ? mList.size() + 1 : 0;
    }

    /**
     * 正常布局的ViewHolder
     */
    class MyViewHolder extends RecyclerView.ViewHolder {
        TextView mTextView;

        public MyViewHolder(View itemView) {
            super(itemView);
            mTextView = (TextView) itemView.findViewById(R.id.item_textView);
        }
    }

    /**
     * 脚布局的ViewHolder
     */
    public static class FootViewHolder extends RecyclerView.ViewHolder {
        private ProgressBar mProgressBar;
        private TextView tv_state;
        private TextView tv_line1;
        private TextView tv_line2;


        public FootViewHolder(View itemView) {
            super(itemView);
            mProgressBar = (ProgressBar) itemView.findViewById(R.id.progressbar);
            tv_state = (TextView) itemView.findViewById(R.id.foot_view_item_tv);
            tv_line1 = (TextView) itemView.findViewById(R.id.tv_line1);
            tv_line2 = (TextView) itemView.findViewById(R.id.tv_line2);

        }
    }

    /**
     * 改变脚布局的状态的方法,在activity根据请求数据的状态来改变这个状态
     *
     * @param state
     */
    public void changeState(int state) {
        this.footer_state = state;
        notifyDataSetChanged();
    }

}

activity中的代码:

package com.duanlian.recyclerviewloadmoredemo;

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecycler;
    private List<String> mList;
    private List<String> list;
    private MyRecyclerAdapter mAdapter;
    LinearLayoutManager linearLayoutManager;
    int lastVisibleItem;
    int page = 0;
    boolean isLoading = false;//用来控制进入getdata()的次数
    int totlePage = 5;//模拟请求的一共的页数

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        getData();
    }

    private void initView() {
        mRecycler = (RecyclerView) findViewById(R.id.recycler);
        linearLayoutManager = new LinearLayoutManager(this);
        mRecycler.setLayoutManager(linearLayoutManager);
        mList = new ArrayList<>();
        mAdapter = new MyRecyclerAdapter(this, mList);
        mRecycler.setAdapter(mAdapter);
        //给recyclerView添加滑动监听
        mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                /*
                到达底部了,如果不加!isLoading的话到达底部如果还一滑动的话就会一直进入这个方法
                就一直去做请求网络的操作,这样的用户体验肯定不好.添加一个判断,每次滑倒底只进行一次网络请求去请求数据
                当请求完成后,在把isLoading赋值为false,下次滑倒底又能进入这个方法了
                 */
                if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
                    //到达底部之后如果footView的状态不是正在加载的状态,就将 他切换成正在加载的状态
                    if (page < totlePage) {
                        Log.e("duanlian", "onScrollStateChanged: " + "进来了");
                        isLoading = true;
                        mAdapter.changeState(1);
                        new Handler().postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                getData();
                                page++;
                            }
                        }, 2000);
                    } else {
                        mAdapter.changeState(2);

                    }
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                //拿到最后一个出现的item的位置
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
            }
        });

    }

    /**
     * 模拟请求数据
     */
    private void getData() {
        list = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            list.add("第" + i + "条");
        }
        mList.addAll(list);
        isLoading = false;
        mAdapter = new MyRecyclerAdapter(this, mList);
        mRecycler.setAdapter(mAdapter);
    }
}

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