Android数据绑定空结合运算符

我正在尝试在数据绑定中使用Null合并运算符.我有一个复合drawable,我需要显示三个drawable图标之一,具体取决于变量是null,true还是false.

XML

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://scheR_356_11845@as.android.com/apk/res/android">

<data>

    <import type="android.view.View" />

    <variable
        name="dataModel"
        type="com.my.app.MyDataModel" />
</data>

<TextView
    android:id="@id/mCompoundDrawable"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:drawableRight="@{(dataModel.isSELEcted ? @drawable/SELEcted : @drawable/not_SELEcted) ?? @drawable/not_specified }"
    android:focusable="true"
    android:gravity="center_vertical"
    android:scrollHorizontally="false"
    android:text="@{dataModel.text}" />
</layout>

数据模型

public class MyDataModel
{
    public String text;
    public Boolean isSELEcted;

    public MyDataModel(String text,Boolean isSELEcted)
    {
        this.text = text;
        this.isSELEcted = isSELEcted;
    }
}

我通过调用来调用它：

@H_508_9@myDataModel dataModel = new MyDataModel(text,null); binding.setDataModel(dataModel);

我以为

android:drawableRight="@{(dataModel.isSELEcted ? @drawable/SELEcted : @drawable/not_SELEcted) ?? @drawable/not_specified }

实际上与以下内容相同：

android:drawableRight="@{dataModel.isSELEcted != null? (dataModel.isSELEcted ? @drawable/SELEcted : @drawable/not_SELEcted) : @drawable/not_specified }

但是,我在运行时遇到以下异常：
                                                                 Java.lang.NullPointerException：尝试在空对象引用上调用虚方法’Boolean java.lang.Boolean.BooleanValue()’

我想知道如何克服这个错误.谢谢！