java类继续告诉强制关闭

Question

我有这个代码，这是一个列表类，我将在这里保存我的笔记，但每当我打开这个课程时它会一直告诉我强制关闭它。

知道为什么吗？

public class Class1 extends ListActivity {

    private static final int ACTIVITY_CREATE1=0;
    private static final int ACTIVITY_EDIT1=1;

    private static final int DELETE_ID1 = Menu.FIRST;
    private int mNoteNumber1 = 1;

    private Class1Db mDbHelper1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.class1);
        mDbHelper1 = new Class1Db (this);
        mDbHelper1.open();
        fillData();             
        registerForContextMenu(getListView());
        Button addnote = (Button)findViewById(R.id.addnotebutton);
        addnote.setOnClickListener(new View.OnClickListener() {     
            @Override
            public void onClick(View v) {
                createNote();
                }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.class1, menu);
        return true;        
    }



    private void createNote() {
        Intent i = new Intent(this, DeleteEdit1.class);
        startActivityForResult(i, ACTIVITY_CREATE1);        
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Intent i = new Intent(this, DeleteEdit1.class);
        i.putExtra(Class1Db.KEY_ROWID1, id);
        startActivityForResult(i, ACTIVITY_EDIT1);
    }

    private void fillData() {
        // Get all of the notes from the database and create the item list
        Cursor notesCursor = mDbHelper1.fetchAllNotes();
        startManagingCursor(notesCursor);


        String[] from = new String[] { Class1Db.KEY_TITLE1 ,Class1Db.KEY_DATE1};
        int[] to = new int[] { R.id.text1 ,R.id.date_row};

        // Now create an array adapter and set it to display using our row
        SimpleCursorAdapter notes =
            new SimpleCursorAdapter(this, R.layout.class1row, notesCursor, from, to);
        setListAdapter(notes);
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
            ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        menu.add(0, DELETE_ID1, 0, R.string.menu_delete);
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        switch(item.getItemId()) {
            case DELETE_ID1:
                AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
                mDbHelper1.deleteNote(info.id);
                fillData();
                return true;
        }
        return super.onContextItemSelected(item);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
        super.onActivityResult(requestCode, resultCode, intent);
        fillData();        
    }   

}