当我单击导航抽屉时，它不会打开，包括其他菜单图标

Question

在尝试添加导航抽屉之前，NewNote图标可以正常工作。它工作得很好。当我在代码中添加导航抽屉部分时。工具栏上的图标似乎不再起作用，即使我单击了汉堡包图标，它也不想打开导航抽屉。但是我仍然可以通过滑动来打开导航抽屉。

下面是主要活动（活动3）的代码

private ListView mListViewNotes;
private DrawerLayout drawer;




@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_3);


    android.support.v7.widget.Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    drawer = findViewById(R.id.drawer_layout);

    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    mListViewNotes = (ListView) findViewById(R.id.main_listview_notes);


}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId())  {
        case R.id.action_main_create_new_note:
            //start NoteActivity in NewNote mode
            Intent newNoteActivity = new Intent(this, NoteActivity.class);
            startActivity(newNoteActivity);
            break;

    }

    return true;
}

@Override
protected void onResume() {
    super.onResume();
    mListViewNotes.setAdapter(null);

    ArrayList<Note> notes = Utilities.getAllSavedNotes(this);

    if(notes == null || notes.size() == 0) {
        Toast.makeText(this, "You have no saved notes!", Toast.LENGTH_SHORT).show();
        return;
    } else {
        NoteAdapter na = new NoteAdapter(this, R.layout.items_note, notes);
        mListViewNotes.setAdapter(na);

        mListViewNotes.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                String fileName = ((Note)mListViewNotes.getItemAtPosition(position)).getmDateTime()
                        + Utilities.FILE_EXTENSION;

                Intent viewNoteIntent = new Intent(getApplicationContext(), NoteActivity.class);
                viewNoteIntent.putExtra("NOTE_FILE", fileName);
                startActivity(viewNoteIntent);
            }
        });

    }
}

}

我该怎么做才能使图标可点击？我会很感激您的帮助，因为我对：）编码非常陌生。请询问您是否需要澄清。