Enable Night mode using RadioButton in Android

I have an app which has Dialogbox with 3 Radios and RadioGroup,

So if the Light Radio is checked, after clicking Okay, the theme of the app will be changed to light theme.
If Dark is checked, after clicking Okay, the theme will be changed to night theme
and if system it will be changed to system.

Toolbar:

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#FFF"
    style="@style/TextAppearance.AppCompat.Widget.Button.Borderless.Colored"
    android:elevation="0dp"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light">

</androidx.appcompat.widget.Toolbar>

Menu:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:tools="http://schemas.android.com/tools"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/chooseTheme"
        android:onClick="chooseTheme"
        android:title="Choose Theme"
        app:showAsAction="never"
        tools:ignore="HardcodedText" />
</menu>

DialogBox:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical">

    <RadioGroup
        android:id="@+id/themeGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:elevation="5dp"
        android:gravity="center"
        android:paddingStart="20dp"
        android:paddingTop="20dp"
        android:paddingEnd="20dp"
        android:paddingBottom="5dp"
        tools:ignore="UselessParent">

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="start"
            android:layout_marginBottom="20dp"
            android:text="Choose Theme"
            android:textColor="@color/black"
            android:textColorHint="#FFFFFF"
            android:textSize="20sp"
            tools:ignore="HardcodedText" />

        <RadioButton
            android:id="@+id/radioLight"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="5dp"
            android:layout_marginBottom="10dp"
            android:buttonTint="@color/colorPrimary"
            android:checked="true"
            android:text="Light"
            android:textSize="18sp"
            tools:ignore="HardcodedText" />

        <RadioButton
            android:id="@+id/radioDark"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="5dp"
            android:layout_marginBottom="10dp"
            android:buttonTint="@color/colorPrimary"
            android:text="Dark"
            android:textSize="18sp"
            tools:ignore="HardcodedText" />

        <RadioButton
            android:id="@+id/radioSystem"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="5dp"
            android:layout_marginBottom="10dp"
            android:buttonTint="@color/colorPrimary"
            android:text="System"
            android:textSize="18sp"
            tools:ignore="HardcodedText" />

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|right"
            android:layout_marginStart="80dp"
            android:orientation="horizontal"
            tools:ignore="RtlHardcoded">

            <Button
                android:id="@+id/btn_cancel"
                style="?android:attr/borderlessButtonStyle"
                android:layout_width="100dp"
                android:layout_height="60dp"
                android:gravity="center|center_vertical|fill_vertical"
                android:scaleY="0.9"
                android:text="Cancel"
                android:textAlignment="center"
                android:textAllCaps="false"
                android:textColor="@color/colorPrimary"
                android:textSize="14sp"
                tools:ignore="ButtonStyle,HardcodedText" />

            <Button
                android:id="@+id/btn_okay"
                style="?android:attr/borderlessButtonStyle"
                android:layout_width="100dp"
                android:layout_height="60dp"
                android:layout_marginStart="10dp"
                android:gravity="center|center_vertical|fill_vertical"
                android:scaleY="0.9"
                android:text="Okay"
                android:textAlignment="center"
                android:textAllCaps="false"
                android:textColor="@color/colorPrimary"
                android:textSize="14sp"
                tools:ignore="ButtonStyle,HardcodedText" />
        </LinearLayout>

    </RadioGroup>

</LinearLayout>

MainActivity:

public void chooseTheme(MenuItem item) {
        final AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);
        View mView = getLayoutInflater().inflate(R.layout.dialog_theme,null);
        Button btn_cancel = mView.findViewById(R.id.btn_cancel);
        Button btn_okay = mView.findViewById(R.id.btn_okay);
        alert.setView(mView);
        final AlertDialog alertDialog = alert.create();
        alertDialog.setCanceledOnTouchOutside(false);

        RadioButton radioLight = findViewById(R.id.radioLight);
        final RadioButton radioDark =findViewById(R.id.radioDark);
        RadioButton radioSystem =findViewById(R.id.radioSystem);
        btn_cancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                alertDialog.dismiss();
            }
        });
        btn_okay.setOnClickListener(new View.OnClickListener() {
            @SuppressLint("SetTextI18n")
            @Override
            public void onClick(View v) {
                alertDialog.dismiss();
            }
        });
        alertDialog.show();
    }

I tried everything I knew, not I have no idea how to do it. Thank you for attention!

The following will check which radio button is checked inside RadioGroup:

RadioGroup radioGroup = mView.findViewById(R.id.themeGroup);

radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(RadioGroup radioGroup, int i) {
            switch(i) {
                case R.id.radioLight:
                     setLightTheme();
                    Toast.makeText(getApplicationContext(),"Light mode",Toast.LENGTH_LONG).show();
                    break;
                case R.id.radioDark:
                     setDarkTheme();
                    Toast.makeText(getApplicationContext(),"Dark mode",Toast.LENGTH_LONG).show();
                    break;
            }
        }
    });