• 对于自定义的控件如果要支持wrap_content属性就必须重写onMeasure()方法
• 重写onMeasure()方法其实就是为了给自定义的控件一个在AT_MOST模式下的默认大小。

kotlin模板代码如下：

//重写onMeasure方法,使得控件支持AT_MOST
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
    setMeasuredDimension(
        measureWidth(widthMeasureSpec),
        measureHeight(heightMeasureSpec)
    )
}
private fun measureWidth(measureSpec: Int): Int {
    var result = 0
    val specMode = MeasureSpec.getMode(measureSpec)
    val specSize = MeasureSpec.getSize(measureSpec)
    if (specMode == MeasureSpec.EXACTLY) {
        result = specSize
    } else {
        result = 375//宽度默认大小
        if (specMode == MeasureSpec.AT_MOST) {
            result = Math.min(result, specSize)
        }
    }
    return result
}
private fun measureHeight(measureSpec: Int): Int {
    var result: Int
    val specMode = MeasureSpec.getMode(measureSpec)
    val specSize = MeasureSpec.getSize(measureSpec)
    if (specMode == MeasureSpec.EXACTLY) {
        result = specSize
    } else {
        result = 350//高度默认大小
        if (specMode == MeasureSpec.AT_MOST) {
            result = Math.min(result, specSize)
        }
    }
    return result
}