java - 在 Fragment 中使用 Kotlin ViewBinding 时出现 NullPointerException

Question

我正在尝试使用 kotlin 视图绑定将点击侦听器添加到我的片段内的按钮。我在 onCreateView 方法中设置点击监听器。当我这样做时，我得到一个空指针异常，因为尚未创建按钮。我认为 kotlin 视图绑定负责视图初始化，所以按钮不应该为空？

这是我的代码：

class FragmentStart : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view = inflater.inflate(R.layout.fragment_start, container, false)
        start_button.setOnClickListener(
            Navigation.createNavigateOnClickListener(R.id.action_fragmentStart_to_fragmentQuestion,null)
        )
        return view
    }
}

这是一个例外：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

标签： javaandroidkotlinandroid-viewbinding

Answer 1

Because the view has not been created yet. You should call the view in the onViewCreated () function. read more

 override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

start_button.setOnClickListener(
                Navigation.createNavigateOnClickListener(R.id.action_fragmentStart_to_fragmentQuestion,null)
            )
    }