android listView Sqlite适配器Sig 9突然终止

我正在使用android studio进行android编程。关于ListView SQLite 适配器

我的项目在android stduo中没有错误。当我在emulator中启动我的应用程序时。 它不会启动，“不幸的是，应用程序已停止” 和信号9

我的主要活动来源在这里

public class MainActivity extends Activity {
    final static int BOOK_ADD = 0;  
    final static int BOOK_INFO = 1;

    ArrayList<Book> bookItem; 
    MyListAdapter Myadapter;
    ListView BookList; 


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

        DbOpenHelper db =new DbOpenHelper(this);

        List<Book> mbook = db.getAllBooks();
        for(Book bk : mbook){
            bookItem.add(bk);
        }

        Myadapter = new MyListAdapter(this, R.layout.icontext , bookItem);
        BookList = (ListView) findViewById(R.id.list);
        BookList.setAdapter(Myadapter);
        BookList.setOnItemClickListener(bItemClickListener);

    }


OnItemClickListener bItemClickListener = new OnItemClickListener() {
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                    Book item = (Book) parent.getItemAtPosition(position);
                    Intent intent = new Intent(getApplicationContext(), BookinfoActivity.class);
                    intent.putExtra("bookObject", item);

                    startActivityForResult(intent, BOOK_INFO);
                }
            };

    public boolean onCreateOptionsMenu(Menu menu) {

        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.actionbarmenu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    public void mOnClick(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.addbook: 

                Book bookObject = new Book();
                Intent intent = new Intent(MainActivity.this, AddBookActivity.class);
                intent.putExtra("bookObject", bookObject);
                startActivityForResult(intent, BOOK_ADD);
                break;
            case android.R.id.home: 
               break;
        }
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (requestCode) {
            case BOOK_ADD:
                if (resultCode == RESULT_OK) { 

                    Book newBook = (Book) data.getSerializableExtra("newBook");
                    DbOpenHelper db =new DbOpenHelper(this);
                    db.addBook(newBook);
                    bookItem.add(newBook);

                    Myadapter.notifyDataSetChanged();

                    break;
                }
            case BOOK_INFO:
                if (resultCode == RESULT_OK) {
                    Book newBook = (Book) data.getSerializableExtra("newBook");
                }
                break;
        }
    }

    protected void onDestroy() {
        super.onDestroy();
    }
}


class MyListAdapter extends ArrayAdapter<Book> {
    private Context context;
    private ArrayList<Book> arSrc = new ArrayList<Book>();
    private int layoutResourceId;

    public MyListAdapter(Context context, int layoutResourceId, ArrayList<Book> data) {
        super(context,layoutResourceId,data);
        this.context= context;
        this.arSrc=data;
        this.layoutResourceId = layoutResourceId;
    }

    public int getCount() {
        return arSrc.size();
    }

    public Book getItem(int position) {
        return arSrc.get(position);
    }

    public long getItemId(int position) {
        return position;
    }


    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        BookHolder holder;
        if (row == null) {
            LayoutInflater inflater =((Activity)context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId,parent,false);
            holder = new BookHolder();
            holder.bname = (TextView)row.findViewById(R.id.bname);
            holder.imgIcon =(ImageView)row.findViewById(img);

            row.setTag(holder);
        } else {
            holder = (BookHolder)row.getTag();
        }


        Book bbb = arSrc.get(position);
        holder.bname.setText(bbb.getBname());
        holder.author.setText(bbb.getAuthor());
        holder.publisher.setText(bbb.getPublisher());
        holder.page = bbb.getPage();
        holder.read = bbb.getRead();

        byte[] outImage = bbb.getIcon(); 
        ByteArrayInputStream imageStream = new ByteArrayInputStream(outImage);
        Bitmap theImage = BitmapFactory.decodeStream(imageStream);
        holder.imgIcon.setImageBitmap(theImage);

        //img.setImageBitmap(arSrc.get(position).getIcon().getDrawingCache());
        //img.setImageBitmap(ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(bbb.getPath()),96,96));
        //img.setImageResource(R.drawable.ic_add_circle_outline_black_24dp);

        ProgressBar mProgBar = (ProgressBar)convertView.findViewById(R.id.prog);
        mProgBar.setMax(arSrc.get(position).getPage());
        mProgBar.setProgress(arSrc.get(position).getRead());

        return row;
    }
    static class BookHolder{
        ImageView imgIcon;
        TextView bname,publisher,author;
        int page,read;
    }
}

public class DbOpenHelper extends SQLiteOpenHelper {
        private static final String DATABASE_NAME = "Book.db";
        private static final int DATABASE_VERSION = 1;

        public DbOpenHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        public void onCreate(SQLiteDatabase db) {
            db.execSQL(DataBase.CreateDB._CREATE);
        }

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            //table 변경 시시
            db.execSQL("DROP TABLE IF EXISTS " + DataBase.CreateDB._TABLENAME);
            onCreate(db);
        }

        public void addBook(Book book){
            SQLiteDatabase db = this.getWritableDatabase();
            ContentValues values = new ContentValues();

            values.put(DataBase.CreateDB.NAME, book.getBname());
            values.put(DataBase.CreateDB.PUBLISHER, book.getPublisher());
            values.put(DataBase.CreateDB.AUTHOR, book.getAuthor());
            values.put(DataBase.CreateDB.PAGE, book.getPage());
            values.put(DataBase.CreateDB.READ, book.getRead());
            values.put(DataBase.CreateDB.ICON, book.getIcon());

            db.insert(DataBase.CreateDB._TABLENAME,null,values);
            db.close();
        }
        Book getBook(int id){
            SQLiteDatabase db = this.getReadableDatabase();
            Cursor cursor = db.query(DataBase.CreateDB._TABLENAME,new String[] {
                    DataBase.CreateDB._ID,
                    DataBase.CreateDB.NAME,
                    DataBase.CreateDB.PUBLISHER,
                    DataBase.CreateDB.AUTHOR,
                    DataBase.CreateDB.PAGE,
                    DataBase.CreateDB.READ,
                    DataBase.CreateDB.ICON},
                    DataBase.CreateDB._ID+"=?",new String[]{ String.valueOf(id)},
                    null,null,null,null);
            if (cursor != null)
                cursor.moveToFirst();
            Book book = new Book(Integer.parseInt(cursor.getString(0)),
                    cursor.getString(1),cursor.getString(2),cursor.getString(3),
                    Integer.parseInt(cursor.getString(4)),
                    Integer.parseInt(cursor.getString(5)),
                    cursor.getBlob(6));
            cursor.close();
            return book;
        }

        public List<Book> getAllBooks(){
            List<Book> bookList = new ArrayList<Book>();
            String selectQuery = "SELECT * FROM Book";
            SQLiteDatabase db = this.getWritableDatabase();
            Cursor cursor = db.rawQuery(selectQuery,null);

            if(cursor.moveToFirst()){
                do{
                    Book book = new Book();
                    book.set_id(Integer.parseInt(cursor.getString(0)));
                    book.setBname(cursor.getString(1));
                    book.setPublisher(cursor.getString(2));
                    book.setAuthor(cursor.getString(3));
                    book.setPage(Integer.parseInt(cursor.getString(4)));
                    book.setRead(Integer.parseInt(cursor.getString(5)));
                    book.setIcon(cursor.getBlob(6));
                    bookList.add(book);
                }while (cursor.moveToNext());
            }
            cursor.close();
            db.close();
            return bookList;
        }

        public void deleteBook(Book book) {
            SQLiteDatabase db = this.getWritableDatabase();
            db.delete(DataBase.CreateDB._TABLENAME, DataBase.CreateDB._ID + " = ?",
                    new String[] { String.valueOf(book.get_id()) });
            db.close();
        }
    }

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.kang.book, PID: 25110
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.kang.book/com.example.kang.book.MainActivity}:

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                      at android.app.ActivityThread.-wrap11(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
                      at com.example.kang.book.MyListAdapter.getCount(MainActivity.java:136)
                      at android.widget.ListView.setAdapter(ListView.java:491)
                      at com.example.kang.book.MainActivity.onCreate(MainActivity.java:50)
                      at android.app.Activity.performCreate(Activity.java:6237)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:148) 
                      at android.app.ActivityThread.main(ActivityThread.java:5417) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Application terminated.