RecyclerView 设置最大高度

https://blog.51cto.com/u_14496797/5364085

方法1：使用约束布局

implementation 'androidx.constraintlayout:constraintlayout:2.0.4'

<androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/view_constraintLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/rc_filter"
            android:layout_width="match_parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            android:layout_height="0dp"
            app:layout_constraintHeight_default="wrap"
            app:layout_constraintHeight_max="350dp" />

</androidx.constraintlayout.widget.ConstraintLayout>

　　关键代码就是

android:layout_height="0dp"
app:layout_constraintHeight_default="wrap"
app:layout_constraintHeight_max="350dp"

　　

当然也可以使用 ConstraintSet 在代码中设置来实现以上代码相同的结果：

ConstraintSet constraintSet = new ConstraintSet();
constraintSet.clone(view_constraintLayout);
constraintSet.constrainMaxHeight(R.id.rc_filter,Utils.dpToPx(mContext,350));
TransitionManager.beginDelayedTransition(view_constraintLayout);
constraintSet.applyTo(view_constraintLayout);

　　方法2：重写 onMessure()方法

https://blog.csdn.net/baidu_40389775/article/details/107566050

class MaxRecyclerView : RecyclerView {
    private var mMaxHeight = 0

    constructor(context: Context) : super(context) {}
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
        init(context, attrs)
    }
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr) {
        init(context, attrs)
    }

    private fun init(context: Context, attrs: AttributeSet?) {
        val arr = context.obtainStyledAttributes(attrs, R.styleable.MaxRecyclerView)
        mMaxHeight = arr.getLayoutDimension(R.styleable.MaxRecyclerView_maxHeight, mMaxHeight)
        arr.recycle()
    }

    override fun onMeasure(widthSpec: Int, heightSpec: Int) {
        super.onMeasure(widthSpec, heightSpec)
        val height = measuredHeight
        if (height > mMaxHeight) {
            setMeasuredDimension(widthSpec, mMaxHeight)
        }
    }
}

　　如果测量的高度 大于 最大高度，则使用最大高度，否则默认使用测量的高度

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