FragmentTransaction 隐藏/显示有时不起作用 [英] FragmentTransaction hide/show doesn't work sometimes

问题描述

我有一个带有底部导航选项卡的活动，这些选项卡正在更改其中的片段.当我在这些选项卡上来回单击时，它会在某些时候停止工作.代码执行得很好，因为我在其中放入了一些日志.但是片段没有被切换.

I have an activity with bottom navigation tabs that are changing the fragments in it. When I click back and forth on those tabs, at some point it stops working. Code executes just fine as I put some logs in it. But the fragments aren't being switched.

代码在 kotlin 中，但相当简单

Code is in kotlin but it's rather straight forward

fun showTabFragment(tag: String) {
        val currentFragment: Fragment? = supportFragmentManager.fragments?.lastOrNull()
        var fragment = supportFragmentManager.findFragmentByTag(tag)
        val fragmentExists = fragment != null
        if (fragment == null) {
            when (tag) {
                TAG_LOGBOOK -> fragment = LogbookFragment()
                TAG_RECIPES -> fragment = RecipesFragment()
                TAG_PROFILE -> fragment = ProfileFragment()
                else -> fragment = MeetingPlacesFragment()
            }
        }

        val transaction = supportFragmentManager.beginTransaction()

        if (currentFragment != null) {
            Log.i("jacek", "hiding " + currentFragment.javaClass.simpleName)
            transaction.hide(currentFragment)
        }

        if (fragmentExists) {
            Log.i("jacek", "showing " + fragment.javaClass.simpleName)
            transaction.show(fragment)
        } else {
            Log.i("jacek", "adding " + fragment.javaClass.simpleName)
            transaction.add(R.id.container, fragment, tag)
        }

        transaction.commit()
    }

碎片很重.我会尝试一些轻量级的，但在我看来这应该不是问题.还有什么我可以尝试的吗?

The fragments are quite heavy. I will try with some lightweight ones, but still that shouldn't be a problem in my opinion. Is there anything else I could try?

我使用的是最新的支持库 - 25.2.0此外，我对替换片段不感兴趣，因为重点是添加淡入淡出动画而不重新创建它们

I'm using the latest support library - 25.2.0 Also I'm not interested in replacing the fragments as the point is to add crossfade animation without recreating them

推荐答案

您需要重复使用要隐藏或显示的片段的同一个实例.

You need to reuse the same instance of a fragment that you wanted to hide or show.

private fun replaceFragment(fragment: Fragment) {
    supportFragmentManager.beginTransaction().apply {
        if (fragment.isAdded) {
            show(fragment)
        } else {
            add(R.id.fmFragmentContainer, fragment)
        }

        supportFragmentManager.fragments.forEach {
            if (it != fragment && it.isAdded) {
                hide(it)
            }
        }
    }.commit()
}

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