Parameter specified as non-null

问题

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter convertView
        at absolutely.kotlin.adapter.MyExpandAdapter.getGroupView(Unknown Source:2)
        at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:446)
        at android.widget.AbsListView.obtainView(AbsListView.java:2408)
        at android.widget.ListView.makeAndAddView(ListView.java:2126)
        at android.widget.ListView.fillDown(ListView.java:851)
        at android.widget.ListView.fillDown(ListView.java:833)
        at android.widget.ListView.fillFromTop(ListView.java:921)
        at android.widget.ListView.layoutChildren(ListView.java:1872)
        at android.widget.AbsListView.onLayout(AbsListView.java:2207)
        at absolutely.kotlin.clean.base.view.ExpandListView.onLayout(ExpandListView.kt:87)
        ...

原因

    Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull意为必不为空的参数为空了，一般发生将java代码转为Kotlin代码时，因为java中的参数可以传null，而装换过来的Kotlin代码使用是的非空类型，当该方法传入null值时，就会产生该错误，在这里是很明显是getGroupView的参数出了问题。

解决

    我的MyExpandAdapter是继承自BaseExpandableListAdapter的适配器，转换后的Kotlin代码中的getGroupView有四个参数，如下：

fun getGroupView(groupPosition: Int, isExpanded: Boolean ,
            convertView: View, parent: ViewGroup ):View {
    .....
    return convertView;
}

    其中参数convertView，parent都可能为null，所以需要将其变为可空类型，即在其类型后加上?，如下：

fun getGroupView(groupPosition: Int, isExpanded: Boolean ,
            convertView: View?, parent: ViewGroup? ):View {
    .....
    return convertView;
}

    同理，该类中的getChildView方法需要相同处理