如何将输入流从外部存储传递到我的xmlparser？

Question

我创建了用于解析xml文件的类，并在listview中显示了它，我的类构造函数在参数中获得了Inputstream，我想将它和inputstream传递给它。

当我想从外部存储中获取文件并将其传递给我的类构造函数时，我不知道该怎么做。我用很多韦，但我做得不正确。

public class MainActivity extends AppCompatActivity {

    Button xml;
    Button json;
    ListView dataShow;

    List<book> bookList;
    ArrayAdapter<book> adapter;


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

        xml = findViewById(R.id.btnXmlShow);
        json = findViewById(R.id.btnJsonShow);
        dataShow = findViewById(R.id.parsedDataListView);


        File file = new File(Environment.getExternalStorageDirectory()
                .getAbsolutePath() + "/mine", "products_xml");

        final FileInputStream fis = null;

        try {
            fis = new FileInputStream(file);

            /*Toast.makeText(this,Environment.getExternalStorageDirectory()
                    .getAbsolutePath().toString(),Toast.LENGTH_SHORT).show();*/

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        xml.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //getResources().openRawResource(R.raw.products_xml)
                bookList = new xmlpullparser(fis).parsedXml();
                adapter = new ArrayAdapter<book> 
              (MainActivity.this,android.R.layout.simple_list_item_1,bookList);
                dataShow.setAdapter(adapter);
            }
        });
    }
}

/////////////////////////////

public class xmlpullparser {

    private InputStream input;
    private List<book> bookList;
    private book currentBook;
    private String currentTag;

    public xmlpullparser(InputStream input){ this.input = input; }

    public List<book> parsedXml(){
        bookList = new ArrayList<>();

        try {

            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            factory.setNamespaceAware(true);
            XmlPullParser parser = factory.newPullParser();
            parser.setInput(input,null);

            int eventType = parser.getEventType();

            while (eventType != XmlPullParser.END_DOCUMENT){

                if (eventType ==  XmlPullParser.START_TAG){
                    handleStartTag(parser.getName());
                }else if (eventType == XmlPullParser.TEXT){
                    handleText(parser.getText());
                }else if (eventType == XmlPullParser.END_TAG){
                    currentTag = null;
                }

                eventType = parser.next();
            }

            input.close();

        } catch (XmlPullParserException | IOException e) {
            e.printStackTrace();
        }


        return bookList;
    }

    private void handleText(String text) {

        if(currentBook == null || currentTag == null) return;
        switch (currentTag){
            case "id":
                currentBook.setId(Integer.valueOf(text));
                break;
            case "author":
                currentBook.setAuthor(text);
                break;
            case "title":
                currentBook.setTitle(text);
                break;
            case "genre":
                currentBook.setGenre(text);
                break;
            case "price":
                currentBook.setPrice(Double.valueOf(text));
                break;
            case "publishDate":
                currentBook.setPublishDate(text);
                break;
            case "description":
                currentBook.setDescription(text);
                break;
            default: break;
        }
    }

    private void handleStartTag(String tagName) {

        if (tagName.equals("book")){
            currentBook = new book();
            bookList.add(currentBook);
        }else{
            currentTag = tagName;
        }
    }
}

//////////////////////////////////////

package com.example.sobhan.parserproject;

public class book {


    private int id;
    private String author;
    private String title;
    private String genre;
    private double price;
    private String publishDate;
    private String description;


    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getGenre() {
        return genre;
    }
    public void setGenre(String genre) {
        this.genre = genre;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public String getPublishDate() {
        return publishDate;
    }
    public void setPublishDate(String publishDate) {
        this.publishDate = publishDate;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }



    @Override
    public String toString() {
        return "Title: " + title + "\nAuthor: " + author + "\n" + "Price: " + price ;
    }
}

//////////////////////////////////////

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <LinearLayout
        android:id="@+id/buttonLayer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:padding="10dp"
        android:orientation="horizontal">


        <Button
            android:id="@+id/btnXmlShow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Xml" />

        <Button
            android:id="@+id/btnJsonShow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Json" />

    </LinearLayout>

    <ListView
        android:id="@+id/parsedDataListView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/buttonLayer"
        android:padding="5dp"
        android:layout_weight="1" />


</RelativeLayout>

我如何将fis对象传递给类。 谢谢。