小编vo1*_*men的帖子

当我想从操作栏隐藏动作按钮时,我得到一个NullPointerException.我有一个简单的Actionbar和一个Navigationdrawer.我只想在使用登录对话框成功登录时隐藏操作栏右上角的操作登录按钮.

NavigationDrawerFragment:

@Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        FragmentManager fragmentManager = getFragmentManager();

        Log.d("test12","onOptionsItemSelected");
        if (mDrawerToggle.onOptionsItemSelected(item))
        {
            Log.d("test12_1","onOptionsItemSelected");

            return true;
        }


        if (item.getItemId() == R.id.action_login)
        {
            Log.d("test13", "onOptionItemSelected");
            //Toast.makeText(getActivity(), "Example action.", Toast.LENGTH_SHORT).show();

            final Dialog dialog = new Dialog(getActivity());
            dialog.setContentView(R.layout.login);
            dialog.setTitle(R.string.title_login);

            login_button = (Button) dialog.findViewById(R.id.button_login);
            username = (EditText) dialog.findViewById(R.id.et_username);
            password = (EditText) dialog.findViewById(R.id.et_password);

            login_button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v)
                {
                    Log.d("test14", "Login Button geklickt");
                    if (username.getText().toString().equals("root") && password.getText().toString().equals("root")) {
                        Toast.makeText(getActivity(), "Hello " + username.getText(), Toast.LENGTH_LONG).show();
                        login_status = true;
                        updateAfterLogin(); // …