How to prevent showing MainActivity when navigating back, but keep app state when reopening?

I'm developing an Android app with three activities: MainActivity, LoginActivity, and WebViewActivity. The MainActivity is the launcher activity and determines if the user is logged in or not. Based on this, it starts either the LoginActivity or WebViewActivity.

I define the the MainActivity as a launcher in the AndroidManifest.xml file.

<activity
    android:name=".MainActivity"
    android:exported="true"
    android:label="@string/app_name"
    android:theme="@style/Theme.MyApp">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

In the MainActivity's onCreate method, I determine which Activity to launch.

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MyAppTheme {
            
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = colorResource(id = R.color.white)
                ) {
                    val intent: Intent = getIntentForInitialLaunch()
                    startActivity(intent)

                    // finish() ←　tried finishing the activity but did not solve the issue.
                   }
            }
        }
    }

    private fun getIntentForInitialLaunch(): Intent {
        val activityToLaunch = if (hasLoggedIn()) {
            WebViewActivity::class.java
        } else {
            LoginActivity::class.java
        }
        return Intent(this, activityToLaunch)
    }
}

The problem I'm facing is with the back button behavior. When the user navigates back from either the LoginActivity or WebViewActivity, they see the MainActivity, which is just a blank screen in my case. For a better user experience, I don't want the MainActivity to be visible at all when the user navigates back. Instead, I want the app to be sent to the background and resume the WebViewActivity when the app is reopened.

I tried calling the finish() method in MainActivity to prevent it from being shown, but this causes another issue: when the user reopens the app from the background, it restarts from the splash screen, losing the state of the WebViewActivity. This means the user loses their place in the WebView and has to start over from the root URL.

Here's a summary of the flow:

MainActivity checks login status in onCreate(). If logged in, starts WebViewActivity; if not, start LoginActivity. Pressing back in either LoginActivity or WebViewActivity currently shows MainActivity (undesired). Calling finish() in MainActivity solves the back button issue but causes the app to restart from the splash screen when reopened, losing WebView state.

How can I achieve the following:

Prevent MainActivity from being visible when navigating back from LoginActivity or WebViewActivity. Keep the state of the WebViewActivity when the app is reopened from the background. Any suggestions or best practices for handling this scenario would be greatly appreciated.

Solution

@Tenfour04's answer works. I finished the MainActivity and then added a logic to move the task to the back of the activity stack.

override fun onKeyDown(keyCode: Int, event: KeyEvent?): Boolean {
    
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        moveTaskToBack(true)
        return true
    }

    return super.onKeyDown(keyCode, event)
}

As @Leviathan mentioned, using navigation would also work, but the current project I'm working on uses activities, so that's the reason why I need to deal with three activities for now. But thank you so much for the assistance.