java - 将布局改回后按钮无法使用

Question

我创建了一个登录布局(从 MainActivity 开始)

public class MainActivity extends AppCompatActivity implements View.OnClickListener, BottomNavigationView.OnNavigationItemSelectedListener{
    private Button regiBtn;
    private Button loginBtn;
    private Button forgotBtn;
    private EditText loginEmail;
    private EditText loginPwd;
    public static FirebaseAuth mAuth;
    public static FirebaseUser currentUser;

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        Fragment fragment = null;
        switch (menuItem.getItemId()){
            case R.id.navigation_profile:
                fragment = new ProfileFragment();
                break;

            case R.id.navigation_task:
                fragment = new TaskFragment();
                break;

            case R.id.navigation_leadingboard:
                fragment = new LeadingBoardFragment();
                break;

            case R.id.navigation_home:
                fragment = new HomeFragment();
                break;
        }

        return loadFragment(fragment);
    }

    private boolean loadFragment(Fragment fragment){
        if(fragment!=null){

            getSupportFragmentManager()
                    .beginTransaction()
                    .replace(R.id.fragment_container, fragment)
                    .commit();

            return true;
        }
        return false;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAuth = FirebaseAuth.getInstance();

        // check if user is signed in (non-null)
        currentUser = mAuth.getCurrentUser();

        loginBtn = (Button) findViewById(R.id.loginBtn);
        forgotBtn = (Button) findViewById(R.id.forgotBtn);
        regiBtn = (Button) findViewById(R.id.regiBtn);
        loginEmail = (EditText) findViewById(R.id.loginEmail);
        loginPwd = (EditText) findViewById(R.id.loginPwd);
        regiBtn.setOnClickListener(this);
        loginBtn.setOnClickListener(this);
        forgotBtn.setOnClickListener(this);

        // check if user is logged in or not
        updateUI(currentUser);
    }

    @Override
    public void onClick(View view) {
        switch(view.getId()){
            case R.id.regiBtn:{
                Intent intent = new Intent(this, RegisterActivity.class);
                this.startActivity(intent);
                break;
            }
            case R.id.loginBtn:{
                // perform login authentication function
                mAuth.signInWithEmailAndPassword(loginEmail.getText().toString(), loginPwd.getText().toString())
                        .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                if(task.isSuccessful()){
                                    currentUser = mAuth.getCurrentUser();
                                    updateUI(currentUser);
                                } else{
                                    Toast.makeText(MainActivity.this, task.getException().getMessage(), Toast.LENGTH_LONG).show();
                                }
                            }
                        });
                break;
            }
            case R.id.forgotBtn:{
                // perform find lost password function
                Intent intent = new Intent(this, ForgotPwdActivity.class);
                startActivity(intent);
                break;
            }
        }
    }

    public void updateUI(FirebaseUser user){
        if(user!=null){
            setContentView(R.layout.activity_dashboard);
            BottomNavigationView navView = findViewById(R.id.nav_view);

            // set default to home fragment
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragment_container, new HomeFragment())
                    .commit();
            navView.setOnNavigationItemSelectedListener(this);
        }
    }
}

如您所见，当用户登录后，MainActivity 将其布局更改为底部导航布局，用户可以在其中选择要执行特定操作的部分。

在其中一个 fragment 中，我想执行注销功能

public class ProfileFragment extends Fragment {

    private Button logoutBtn;
    private Button storeBtn;
    private Button updateBtn;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_profile, null);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        logoutBtn = (Button) getView().findViewById(R.id.logoutBtn);
        storeBtn = (Button) getView().findViewById(R.id.storeBtn);
        updateBtn = (Button) getView().findViewById(R.id.updateProfileBtn);

        logoutBtn.setOnClickListener(new View.OnClickListener(){
           public void onClick(View v){
                MainActivity.mAuth.signOut();
                getActivity().setContentView(R.layout.activity_main);
           }
        });
    }
}

我想将当前 Activity (应该是 MainActivity 对吗？)布局更改为 activity_main(用户执行登录功能的地方)，布局确实发生了变化，但按钮无法正常工作。 布局更改为 activity_main(用户登录)-> activity_dashboard(带 fragment )-> main_activity(当用户从​​ fragment 注销时) 我想知道我哪里出错了。

Answer 1

the layout changed indeed, but the buttons failed to work.

MainActivity 扩展到 AppCompatActivity。您应该使用 Intent 打开 MainActivity，而不是创建一个新的 setContentView。

logoutBtn.setOnClickListener(new View.OnClickListener(){
           public void onClick(View v){
               MainActivity.mAuth.signOut();
               Intent i = new Intent(getActivity(),MainActivity.class);
               startActivity(i);
               getActivity().finish();
           }
        });