Firebase 身份验证后退按钮

Question

我的 android 应用程序中的 firebase 身份验证没有后退按钮。如果 onActivityResult 产生取消结果，我希望能够导航回主 activity。

如何启用此功能？我正在使用预先构建的身份验证。

    final int RC_SIGN_IN = 0;
    List<AuthUI.IdpConfig> providers = Arrays.asList(
            new AuthUI.IdpConfig.EmailBuilder().build(),
            new AuthUI.IdpConfig.PhoneBuilder().build(),
            new AuthUI.IdpConfig.GoogleBuilder().build()
    );

    Intent intent = AuthUI.getInstance()
            .createSignInIntentBuilder()
            .setAvailableProviders(providers)
            .setTheme(R.style.FirebaseUI)
            .build();

    startActivityForResult(intent, RC_SIGN_IN);

Answer 1

调用 super.onBackPressed() 将导航回上一个 activity

我假设您使用的是 firebase google 身份验证。如果发生任何故障，以下代码片段可能会帮助您导航回 MainActivity。

要启动身份验证，请调用signIn()方法

如果发生任何 API 异常，onActivityResult() 方法将导航回上一个 activity

    private static final int RC_SIGN_IN = 1;

    private void signIn () {
        Intent signInIntent = mGoogleSignInClient.getSignInIntent ();
        startActivityForResult ( signInIntent, RC_SIGN_IN );
        //Show user that authentication has started
    }

    @Override
    public void onActivityResult ( int requestCode, int resultCode, Intent data ) {
        super.onActivityResult ( requestCode, resultCode, data );
        if (requestCode == RC_SIGN_IN) {
            Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent ( data );
            try {
                GoogleSignInAccount account = task.getResult ( ApiException.class );
                assert account != null;
                firebaseAuthWithGoogle ( account.getIdToken () );
            } catch (ApiException e) {
                Toast.makeText ( this, "Google Sign In failed", Toast.LENGTH_SHORT ).show ();
                mGoogleSignInClient.signOut ();
                mAuth.signOut ();
                //Show user that authentication failed
                //In your case navigate to MainActivity()
                super.onBackPressed (); //Navigates to previous activity
            }
        }
    }

以下代码检查返回的用户是否有效。如果没有导航回上一个 activity

    private void firebaseAuthWithGoogle ( String idToken ) {
        AuthCredential credential = GoogleAuthProvider.getCredential ( idToken, null );
        mAuth.signInWithCredential ( credential )
                .addOnCompleteListener ( this, task -> {
                    if (task.isSuccessful ()) {
                        FirebaseUser user = mAuth.getCurrentUser ();
                        if (user != null) {
                            //Authenticated successfully
                        } else {
                            //Try to authenticate again
                            //This might not happen in most scenarios
                            signIn ();
                        }
                    } else {
                        Toast.makeText ( this, "Google Sign In failed", Toast.LENGTH_SHORT ).show ();
                        mGoogleSignInClient.signOut ();
                        mAuth.signOut ();
                        //Show user that authentication failed
                        //In your case navigate to MainActivity()
                        super.onBackPressed (); //Navigates to previous activity
                    }
                } );
    }

希望这个回答对您有所帮助

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