无法修改 NavigationView 中的 TextView答案

【问题标题】：Cannot Modify the TextView in a NavigationView无法修改 NavigationView 中的 TextView
【发布时间】：2022-01-14 02:51:39
【问题描述】：

我正在尝试根据当前在 Firebase 中登录应用程序的用户更新 NavigationView 中的名称和电子邮件。这是我的代码（我使用 Android Studio 中的模板作为 NavigationView）：

public class MainApp2 extends AppCompatActivity{

    private AppBarConfiguration mAppBarConfiguration;
    private ActivityMainApp2Binding binding;
    FirebaseAuth fAuth;
    FirebaseUser user;
    String email, name;
    TextView mail, nam;

    //View header= naviView.getHeaderView(0);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        View naviView = LayoutInflater.from(this).inflate(R.layout.nav_header_main_app2, null);
        /*NavigationView navigView = (NavigationView) findViewById(R.id.nav_view);
        navigView.setNavigationItemSelectedListener(this);
        navigView.addHeaderView(naviView);*/

        fAuth=FirebaseAuth.getInstance();
        user= fAuth.getCurrentUser();

        binding = ActivityMainApp2Binding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        setSupportActionBar(binding.appBarMainApp2.toolbar);
       /* binding.appBarMainApp2.fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });*/
        DrawerLayout drawer = binding.drawerLayout;
        NavigationView navigationView = binding.navView;
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main_app2);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);


        mail=(TextView)naviView.findViewById(R.id.email_nav);
        nam=drawer.findViewById(R.id.name_nav);
        System.out.println("1."+user.getEmail());
        System.out.println("2."+user.getDisplayName());

        if(user!=null)
        {
            System.out.println(email=user.getEmail());
            email=user.getEmail();
            //name=user.getDisplayName().toString().trim();
            mail.setText(email);
            //nam.setText(name);
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_app2, menu);
        return true;
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main_app2);
        return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

我曾经得到空指针错误，但添加行后

View naviView = LayoutInflater.from(this).inflate(R.layout.nav_header_main_app2, null);

我没有收到错误，但文本也没有改变。我也试过

/*NavigationView navigView = (NavigationView) findViewById(R.id.nav_view);
        navigView.setNavigationItemSelectedListener(this);
        navigView.addHeaderView(naviView);*/

但我在 (this) 上遇到了错误。我是 Android Studio 的新手，我不知道如何在没有错误和文本实际更改的情况下解决这个问题。

【问题讨论】：

标签： java android navigationview

【解决方案1】：

我设法解决了这个错误。我必须在绑定之后初始化 NavigationView，所以在这两行之后

DrawerLayout drawer = binding.drawerLayout;
NavigationView navigationView = binding.navView;

我输入了我的代码，它可以正常工作。

【讨论】：