Registering OnCheckedChangeListeners for 2 separate RadioGroups

Question

I have an issue registering a second listener for a 2nd radio group.
XML:

 <RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="124dp"
    android:layout_height="123dp"
    android:layout_marginTop="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.014">

    <RadioButton
        android:id="@+id/WhiteLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/whiteLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/BlueLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/blueLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/RedLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/redLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/InfraredLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/irLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/OffLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:checked="true"
        android:text="@string/offLed"
        android:textColor="@color/colorWhite" />
</RadioGroup>

<SeekBar
    android:id="@+id/seekBar5"
    style="@style/Widget.AppCompat.SeekBar.Discrete"
    android:layout_width="258dp"
    android:layout_height="67dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="56dp"
    android:layout_marginEnd="8dp"
    android:max="20"
    android:progress="0"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toEndOf="@+id/radioGroup"
    app:layout_constraintTop_toTopOf="parent" />

<RadioGroup
    android:layout_width="210dp"
    android:layout_height="120dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.043"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/seekBar5"
    app:layout_constraintVertical_bias="0.112">

    <RadioButton
        android:id="@+id/HDMI1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:checked="true"
        android:text="@string/Camera1"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera2"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera3"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera4"
        android:textColor="@color/colorWhite" />
</RadioGroup>

Java (copied from onCreate()):

    final RadioGroup LEDGroup = findViewById(R.id.radioGroup);
    final SeekBar LEDIntensity = findViewById((R.id.seekBar5));
    final RadioGroup CameraGroup = findViewById((R.id.cameraGroup)) ;

    LEDGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected
            //LEDIntensity.setProgress (2);
            Toast.makeText(MainActivity.this, "This is LED select",
                    Toast.LENGTH_LONG).show();
            //send selected LED to USB port where checkedId is teh selected LED
        }
    });

    CameraGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener(){
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected
            Toast.makeText(MainActivity.this, "This is Camera select",
                    Toast.LENGTH_LONG).show();
            //send selected camera to USB port where checkId is the selected camera
        }
    });

When I start debugging the code, I get a NullPointerException on the CamerGroup.setOnCheckedChangeListener line. When I comment out that section of code, my app starts up properly. Is it actually possible to have 2 separate onCheckedChanged registered, or do I have to make one listener and figure out which RadioGroup is calling the listener in the listener itself.
All my searches have shown examples using only one RadioGroup, and I can't seem to recall any apps that I have every used that have had more than one RadioGroup at a time.

Answer 1

Give your 2nd radiogroup this id:

android:id="@+id/cameraGroup"

you forgot it.

So this line:

final RadioGroup CameraGroup = findViewById((R.id.cameraGroup)) ;

since cameraGroup can't be found makes CameraGroup null
and CameraGroup.setOnCheckedChangeListener() throws NPE.

And yes you can have as many listeners as the radio groups.