Android：详情界面左右滑动看更多，ViewPager动态添加Fragment，仿51job详情界面

在项目中遇到一个需求：在邮件列表中任意一个进入邮件详情，在详情界面中，可以左右滑动查看上一条或下一条邮件详情。

界面简单，主要是实现效果

这时我们第一时间想到的就是ViewPager+Fragment，但是我的数据可能会有上百条，这就要考虑Fragment的回收问题，开始自己折腾了很久，后来网上查到了用FragmentStatePagerAdapter 代替 FragmentPagerAdapter，Android：FragmentStatePagerAdapter分页。这样实现起来非常简单切更可靠。具体实现看如下代码：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <android.support.v4.view.ViewPager        android:id="@+id/vp_detail"        android:layout_width="match_parent"        android:layout_height="match_parent"></android.support.v4.view.ViewPager></LinearLayout>

MainActivity.java

package com.hmy;import android.content.Context;import android.os.Bundle;import android.support.design.widget.FloatingActionButton;import android.support.design.widget.Snackbar;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentStatePagerAdapter;import android.support.v4.view.ViewPager;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.view.View;import android.view.Menu;import android.view.MenuItem;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private Context mContext;    private ViewPager mViewPager;    private DetailPagerAdapter mAdapter;    private List<Integer> mList;    private int TOTAL_SIZE = 26;    private final int PAGE_SIZE = 10;    private int mCount = 0;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        initView();    }    private void initData() {        mContext = this;        mList = new ArrayList<>();        for (int i = 0; i < PAGE_SIZE; i++) {            mCount++;            mList.add(mCount);        }    }    private void initView() {        mViewPager = (ViewPager) findViewById(R.id.vp_detail);        mAdapter = new DetailPagerAdapter(getSupportFragmentManager());        mViewPager.setAdapter(mAdapter);        mViewPager.addOnPageChangeListener(new OnFragmentPageChangeListener());        mViewPager.setCurrentItem(mList.size() / 2);    }    private class DetailPagerAdapter extends FragmentStatePagerAdapter {        public DetailPagerAdapter(FragmentManager fm) {            super(fm);        }        @Override        public Fragment getItem(int position) {            return DetailFragment.newInstance(position);        }        @Override        public int getCount() {            return mList == null ? 0 : mList.size();        }    }    private class OnFragmentPageChangeListener implements ViewPager.OnPageChangeListener {        @Override        public void onPageScrolled(int position, float offsetPerc,                                   int offsetPixel) {        }        @Override        public void onPageScrollStateChanged(int state) {        }        @Override        public void onPageSelected(int position) {            int size = mList.size();            if (position == size - 1 && TOTAL_SIZE > size) {                //实际项目中是网络请求下一页的列表数据                getMoreDetailList();            }        }    }    private void getMoreDetailList() {        for (int i = mCount; i < TOTAL_SIZE; i++) {            mCount++;            mList.add(mCount);        }        mAdapter.notifyDataSetChanged();    }}

fragment_detail.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent">    <TextView        android:id="@+id/tv_id"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:gravity="center"        android:text="1"        android:textSize="40sp"        android:textStyle="bold" /></FrameLayout>

DetailFragment.java

package com.hmy;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;public class DetailFragment extends Fragment {    private TextView mIdTv;    private static final String ARG_PARAM1 = "param1";    private int mParam1;    public DetailFragment() {        // Required empty public constructor    }    public static DetailFragment newInstance(int param1) {        DetailFragment fragment = new DetailFragment();        Bundle args = new Bundle();        args.putInt(ARG_PARAM1, param1);        fragment.setArguments(args);        return fragment;    }    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if (getArguments() != null) {            mParam1 = getArguments().getInt(ARG_PARAM1);        }    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.fragment_detail, container, false);        mIdTv = (TextView) view.findViewById(R.id.tv_id);        mIdTv.setText("-----" + mParam1 + "-----");        return view;    }}

Demo代码下载：http://download.csdn.net/detail/hmyang314/9261467