我有3个活动，第一个是LandingActivity。这是当您打开应用程序但未登录时的启动器活动，第二个是SignInActivity，第三个是HomeActivity，此活动在您已登录并打开应用程序时启动。
以下是代码：
LandingActivity
public class LandingActivity extends AppCompatActivity {
private FirebaseAuth auth;
private Button btnSignIn, btnSignUp;
TextView textSlogan;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_landing);
//Init Firebase Auth
auth = FirebaseAuth.getInstance();
//Check if Already Session
if (auth.getCurrentUser() != null){
startActivity(new Intent(LandingActivity.this, HomeActivity.class));
}
textSlogan = (TextView)findViewById(R.id.textSlogan);
Typeface face = Typeface.createFromAsset(getAssets(),"fonts/NABILA.TTF");
textSlogan.setTypeface(face);
btnSignIn = (Button)findViewById(R.id.main_sign_in_button);
btnSignUp = (Button)findViewById(R.id.main_sign_up_button);
btnSignIn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(LandingActivity.this, SignInActivity.class));
}
});
btnSignUp.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(LandingActivity.this, SignUpActivity.class));
}
});
}
}
SignInActivity
public class SignInActivity extends AppCompatActivity {
private EditText inputEmail, inputPassword;
private FirebaseAuth auth;
private ProgressBar progressBar;
private Button btnSignIn, btnResetPassword;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Get Firebase Auth Instance
auth = FirebaseAuth.getInstance();
setContentView(R.layout.activity_sign_in);
inputEmail = (EditText) findViewById(R.id.email);
inputPassword = (EditText) findViewById(R.id.password);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
btnSignIn = (Button) findViewById(R.id.action_sign_in_button);
btnResetPassword = (Button) findViewById(R.id.intent_reset_password_button);
//Get Firebase auth instance
auth = FirebaseAuth.getInstance();
btnSignIn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String email = inputEmail.getText().toString();
final String password = inputPassword.getText().toString();
if (TextUtils.isEmpty(email)) {
Toast.makeText(getApplicationContext(), "Enter Email Address", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(password)) {
Toast.makeText(getApplicationContext(), "Enter Password", Toast.LENGTH_SHORT).show();
return;
}
progressBar.setVisibility(View.VISIBLE);
//Authenticate User
auth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(SignInActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
// If sign in fails, display a message to the user. If sign in succeeds
// the auth state listener will be notified and logic to handle the
// signed in user can be handled in the listener.
progressBar.setVisibility(View.GONE);
if (!task.isSuccessful()) {
//There was an Error
if (password.length() < 6) {
inputPassword.setError(getString(R.string.minimum_password));
} else {
Toast.makeText(SignInActivity.this, getString(R.string.auth_failed), Toast.LENGTH_SHORT).show();
}
} else {
Intent intent = new Intent(SignInActivity.this, HomeActivity.class);
startActivity(intent);
finish();
}
}
});
}
});
btnResetPassword.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(SignInActivity.this, ResetPasswordActivity.class));
}
});
}
}
HomeActivity
public class HomeActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
private FirebaseAuth auth;
private FirebaseAuth.AuthStateListener authStateListener;
private ProgressBar progressBar;
private long backPressedTime;
private Toast backToast;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) 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();
NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_view);
navigationView.setNavigationItemSelectedListener(this);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
//Get Firebase Auth Instance
auth = FirebaseAuth.getInstance();
//Get Current User
final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
authStateListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
if (user == null) {
//User Auth State is Changed - User is Null
//Launch Login Activity
startActivity(new Intent(HomeActivity.this, LandingActivity.class));
finish();
}
}
};
}
@Override
public void onBackPressed() {
if (backPressedTime + 2000 > System.currentTimeMillis()){
backToast.cancel();
super.onBackPressed();
} else {
backToast = Toast.makeText(getBaseContext(), "Press Back again to Exit", Toast.LENGTH_SHORT);
backToast.show();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.actbar_menu, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem menuItem) {
int id = menuItem.getItemId();
progressBar.setVisibility(View.VISIBLE);
switch (id) {
case R.id.action_edit_password:
startActivity(new Intent(HomeActivity.this, ChangePasswordActivity.class));
progressBar.setVisibility(View.GONE);
break;
case R.id.action_sign_out:
auth.signOut();
progressBar.setVisibility(View.GONE);
Toast.makeText(this, "Signed Out", Toast.LENGTH_SHORT).show();
finish();
startActivity(new Intent(HomeActivity.this, LandingActivity.class));
}
return super.onOptionsItemSelected(menuItem);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_home) {
auth.getCurrentUser();
startActivity(new Intent(HomeActivity.this, HomeActivity.class));
} else if (id == R.id.nav_app_received) {
} else if (id == R.id.nav_app_submitted) {
} else if (id == R.id.nav_tutorial) {
startActivity(new Intent(HomeActivity.this, TutorialActivity.class));
} else if (id == R.id.nav_about_us) {
startActivity(new Intent(HomeActivity.this, AboutUsActivity.class));
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
如果按下后退按钮，我已经尝试onBackPressed()方法退出应用，但它仍会返回LandingActivity而不是退出应用。那么，当按下后退按钮但用户没有注销时如何退出应用程序。