安卓RadioGroup在双向DataBinding中检查RadioButton索引(位置)

<RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <RadioButton
        android:id="@+id/radioButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 1" />

    <RadioButton
        android:id="@+id/radioButton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 2" />

    <RadioButton
        android:id="@+id/radioButton3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 3" />

</RadioGroup>

private int radioButtonIndex;

public int getRadioButtonIndex() {
    return radioButtonIndex;
}

public void setRadioButtonIndex(int index) {
    radioButtonIndex = index;
}

ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.setVariable(BR.radioButtonIndex, 0); // 初始索引为0
binding.setRadioGroupOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        int index = group.indexOfChild(group.findViewById(checkedId));
        binding.setRadioButtonIndex(index);
    }
});

<RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:checkedButton="@={radioButtonIndex}">

    <!-- 省略RadioButton的定义 -->

</RadioGroup>