有一个需求：

列表高度随内容条数增多而增高，当达到一定高度值时，则不再增高

如何实现呢？

我们知道RecyclerView有android:minHeight属性用来设置最小高度，然而设置最大高度却没有android:maxHeight？？？

那我们自己造一个！

class MaxHeightRecycler(context: Context, attrs: AttributeSet?) : RecyclerView(context, attrs) {

    private var maxHeight: Float

    init {
        val typedArray = context.obtainStyledAttributes(attrs, R.styleable.MaxHeightRecycler)
        maxHeight = typedArray.getDimension(R.styleable.MaxHeightRecycler_maxHeight, 200.dp)
        typedArray.recycle()
    }

    override fun onMeasure(widthSpec: Int, heightSpec: Int) {
        val maxHeightSpec = MeasureSpec.makeMeasureSpec(maxHeight.toInt(), MeasureSpec.AT_MOST)
        super.onMeasure(widthSpec, maxHeightSpec)
    }
}

attrs.xml

<declare-styleable name="MaxHeightRecycler">
     <attr name="maxHeight" format="dimension" />
</declare-styleable>

Kotlin扩展函数 200.dp

val Float.dp
    get() = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, this, Resources.getSystem().displayMetrics)
val Int.dp
    get() = this.toFloat().dp

Finish~