android - 无法在使用 Kotlin 的方法调用中为接口(interface)传递 lambda(就像 setOnClickListener 的做法一样)

Question

我创建了类:

class SomeClass {
    var listener: SomeListener? = null

    interface SomeListener {
        fun onClick(v: View?)
    }

    fun addSomeListener(l: SomeListener){
        listener = l
    }

}

我这样调用它，效果很好:

SomeClass().addSomeListener(object : SomeClass.SomeListener {
            override fun onClick(v: View?) {
                // Do something
            }
        })

但是，以下语法在 Android Studio 中失败::

  SomeClass().addSomeListener{ view ->
                // Do something
        }

Type mismatch. Required: SomeClass.SomeListener Found:() → Unit

---

这个我不明白，因为Android的setOnClickListener方法也是这样实现的:

/**
     * Register a callback to be invoked when this view is clicked. If this view is not
     * clickable, it becomes clickable.
     *
     * @param l The callback that will run
     *
     * @see #setClickable(boolean)
     */
    public void setOnClickListener(@Nullable OnClickListener l) {
        if (!isClickable()) {
            setClickable(true);
        }
        getListenerInfo().mOnClickListener = l;
    }

和...

/**
     * Interface definition for a callback to be invoked when a view is clicked.
     */
    public interface OnClickListener {
        /**
         * Called when a view has been clicked.
         *
         * @param v The view that was clicked.
         */
        void onClick(View v);
    }

这显然可以称为:

someView.setOnClickListener { view ->
// Do something
        }

我错过了什么？

Answer 1

它正在调用 SAM Conversions。如果你想让它工作，你需要为你的界面添加关键字fun，这样它看起来像这样:

fun interface SomeListener {
        fun onClick(v: View?)
    }

您可以通过阅读此 accepted answer 了解更多信息.