Activity中销毁fragment

应用场景：Activity中add多个fragment，fragmentA跳到fragmentB，再从B跳到A，此时要销毁fragmentB

1、在添加fragment中给每一个fragment添加一个tag,

 /**
     * 暂存Fragment
     */
    private var mFragment = Fragment()

    /**
     * 选择Fragment存放
     */
    private fun switchContent(to: Fragment?, tag: String) {

        if (to != null && mFragment !== to) {
            val transaction = supportFragmentManager.beginTransaction()
            // 先判断是否被add过
            if (!to.isAdded) {
                // 隐藏当前的fragment，add下一个到Activity中
                transaction.hide(mFragment).add(R.id.layout_fragment, to, tag)
                    .commitAllowingStateLoss()
            } else {
                // 隐藏当前的fragment，显示下一个
                transaction.hide(mFragment).show(to).commitAllowingStateLoss()
            }
            mFragment = to
        }
    }

2、fragment中根据设置的tag获取fragment的实例并且销毁它

override fun onHiddenChanged(hidden: Boolean) {
        super.onHiddenChanged(hidden)
        if (hidden) {
            //当前fragment不可见的时候，销毁它
            activity?.supportFragmentManager?.findFragmentByTag("b")?.let {
                activity?.supportFragmentManager?.beginTransaction()?.remove(
                    it
                )?.commit()
            }
            (activity as MainActivity).bFragment=null
            
        } else {
            
        }
    }

3、特别注意：

不要在销毁的fragment中直接获取activity的fragment总数，这时候的总数是还没有变化的，测试的时候可以写一个按钮直接获取

activity中fragment的总数

btnremove.setOnClickListener {
    var size = supportFragmentManager.fragments.size.toString()
   var s= supportFragmentManager.findFragmentByTag("b")==null
    Toast.makeText(this, size+s.toString(), 0).show()
}