activity_main3.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000">

    <TextView
        android:id="@+id/tv_indicator"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:textSize="30sp"
        android:textColor="#ffffff"
        />
    <fr.castorflex.android.verticalviewpager.VerticalViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/tv_indicator"
        />

</RelativeLayout>

fragment_picture_slide.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
        android:id="@+id/iv_main_pic"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerVertical="true"
        />

</LinearLayout>

Main3Activity.java

package com.example.administrator.tunpage;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
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.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

import java.util.ArrayList;

import fr.castorflex.android.verticalviewpager.VerticalViewPager;

public class Main3Activity extends AppCompatActivity {

    private VerticalViewPager viewPager;
    private TextView tv_indicator;
    private int currentIndex;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        viewPager =  findViewById(R.id.viewpager);
        tv_indicator = findViewById(R.id.tv_indicator);

        viewPager.setAdapter(new PictureSlidePagerAdapter(getSupportFragmentManager()));

        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                tv_indicator.setText(String.valueOf(position+1)+"/"+ImagePool.getImagesList().size());
            }

            @Override
            public void onPageSelected(int position) {
            }

            @Override
            public void onPageScrollStateChanged(int state) {
            }
        });
        viewPager.setCurrentItem(ImagePool.getIndex());
        registerForContextMenu(tv_indicator);
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
                                    ContextMenu.ContextMenuInfo menuInfo) {
        getMenuInflater().inflate(R.menu.pic_menu, menu);
        super.onCreateContextMenu(menu, v, menuInfo);
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.re_save) {
            if (ImagePool.savePic(currentIndex) < 0 ){
                new AlertDialog.Builder(this)
                        .setTitle("提示")
                        .setMessage("保存失败")
                        .setPositiveButton("确定", null)
                        .show();
            }
        }
        return super.onContextItemSelected(item);
    }


     private  class PictureSlidePagerAdapter extends FragmentStatePagerAdapter {

        public PictureSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            currentIndex = position;
            return PictureSlideFragment.newInstance(ImagePool.getImagesList().get(position));
        }

        @Override
        public int getCount() {
            return ImagePool.getImagesList().size();
        }
    }

}

PictureSlideFragment.java

package com.example.administrator.tunpage;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.AlertDialog;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.resource.drawable.GlideDrawable;
import com.bumptech.glide.request.animation.GlideAnimation;
import com.bumptech.glide.request.target.GlideDrawableImageViewTarget;

import uk.co.senab.photoview.PhotoViewAttacher;

public class PictureSlideFragment extends Fragment {
    private String url;
    private PhotoViewAttacher mAttacher;
    private ImageView imageView;

    public static PictureSlideFragment newInstance(String url) {
        PictureSlideFragment f = new PictureSlideFragment();

        Bundle args = new Bundle();
        args.putString("url", url);
        f.setArguments(args);

        return f;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        url = getArguments() != null ? getArguments().getString("url") : "xxxx.jpg";

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_picture_slide,container,false);

        imageView= v.findViewById(R.id.iv_main_pic);
        mAttacher = new PhotoViewAttacher(imageView);

        Glide.with(getActivity()).load(url).crossFade().into(new GlideDrawableImageViewTarget(imageView) {
            @Override
            public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> animation) {
                super.onResourceReady(resource, animation);
                mAttacher.update();
            }
        });
        return v;
    }

}

ImagePool.java

package com.example.administrator.tunpage;

import android.os.Environment;
import android.text.TextUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

public class ImagePool {

    public static List<String> imageList;

    private static int index = 1;

    public static void setIndex(int idx){
        index = idx;
    }

    public static int getIndex(){
        return index;
    }


    public static List<String>  getImagesList(){
        if( imageList!=null && imageList.size()>0 ) {
            return imageList;
        }
        imageList = new ArrayList<>();
        File file = null;

        // Check for SD Card
        if (!Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED))
        {
            // error
        }
        else
        {
            file = new File(Environment.getExternalStorageDirectory()
                    .getPath() + "/images" );
        }

        addFolderToURLList( file , imageList);
        return imageList;
    }


    private static void addFolderToURLList(File file, List<String> imageList) {
        if (file.isDirectory())
        {
            File[] listFile = file.listFiles();
            String filePath = null;
            String newPath = null;
            for (int i = 0; i < listFile.length; i++)
            {
                File filei = listFile[i];
                if ( filei.isDirectory() ) {
                    addFolderToURLList(filei,imageList);
                } else {
                    filePath = listFile[i].getAbsolutePath();
                    
                    if(filePath.endsWith(".jpg") ) {
                        imageList.add("file://" + filePath);
                    }
                }
            }
        }
    }

}