android未经检查的单选按钮已经检查过

<RadioGroup xmlns:android="https://schemas.android.com/apk/res/android"
    android:id="@+id/rg"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.radiogroup.MainActivity" >

    <RadioButton
        android:id="@+id/rb_true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center_vertical" />

    <RadioButton
        android:id="@+id/rb_false"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center_vertical" />

</RadioGroup>
<RadioGroup xmlns:android="https://schemas.andr