导航绘制有问题，一次又一次地重复第一个选定的项目

Question

我使用了android studio的导航绘制活动，我的问题是当我的应用程序开始显示默认情况下第一项选择的活动，并且在按“＆lt; - ”时一次又一次地重复相同的活动箭头图标也 我已经选择列表的第1项开始差异活动但是这个活动再次重复n 代码如下：

@Override
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
  // Selectitem(position);
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
            .commit();


}








public void onSectionAttached(int number) {
    switch (number) {
        case 1:
            mTitle = getString(R.string.title_section1);

            startActivity(new Intent(this, extView.class));

            break;
        case 2:
            mTitle = getString(R.string.title_section2);
            break;
        case 3:
            mTitle = getString(R.string.title_section3);
            break;
    }
}

public void restoreActionBar() {
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    if (!mNavigationDrawerFragment.isDrawerOpen()) {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.main, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        ((MainActivity) activity).onSectionAttached(
                getArguments().getInt(ARG_SECTION_NUMBER));
    }
}

我的第二个活动代码是：

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_text_view);
        lv = (ListView) findViewById(R.id.listView1);
       /* modelItems = new Model[5];
        modelItems[0] = new Mdel("pizza", 0);
        modelItems[1] = new Model("burger", 1);
        modelItems[2] = new Model("olives", 1);
        modelItems  [3] = new Model("orange", 0);
        modelItems[4] = new Model("tomato", 1);*/
        initView();
    }
    private void initView() {
        // show progress dialog
        dialog = ProgressDialog.show(this, "", "Loading...");

        String url = "http://100.76.231.151/test/apps.php";
        FetchDataTask task = new FetchDataTask(this);
        task.execute(url);
    }

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


        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onFetchComplete(List<Model> data) {
        // dismiss the progress dialog
        if(dialog != null)  dialog.dismiss();
        // create new adapter
        Log.i("extView", "values = <<" + data + ">>");
        CustomAdaptor adapter = new CustomAdaptor(this, data);
        lv.setAdapter(adapter);

    }

    @Override
    public void onFetchFailure(String msg) {
        if(dialog != null)  dialog.dismiss();
        // show failure message
        Toast.makeText(this, msg, Toast.LENGTH_LONG).show();

    }
}