How are keycodes decided?

Is there a key with a keyCode of 1? I’ve tried researching but could not find anything. What decides the keycodes of each key? Just wondering… var directions = { 37: “left”, 38: “up”, 39: “right”, 40: “down”, 87:”up”, 68:”right”, 83:”down”, 65:”left” }; Here it shows they keycodes of the left, right, up , down…

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Navigation Host Fragment is overwriting destination fragment on previous fragment

I am trying fragment transaction using navigation host fragment, but on navigating to the destination fragment the old fragment is still visible on screen like fragment added on one another. Here is my code: settings_nav.xml <?xml version=”1.0″ encoding=”utf-8″?> <navigation xmlns:android=”http://schemas.android.com/apk/res/android” xmlns:app=”http://schemas.android.com/apk/res-auto” android:id=”@+id/settings_nav” app:startDestination=”@+id/WelcomeFragment”> <fragment android:id=”@+id/WelcomeFragment” android:name=”com.example.ui.fragment.WelcomeFragment” android:label=”WelcomeFragment”> <action android:id=”@+id/action_WelcomeFragment_to_secondFragment” app:destination=”@+id/secondFragment” /> </fragment> <fragment android:id=”@+id/secondFragment” android:name=”com.example.ui.fragment.ConfigFragment”…

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