entityMap|blocks|key|atqhq|text|我现在设法找到了一种方法，它是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|eem7d|NavHostFragment+navHostFragment+=+supportFragmentManager.findFragmentById(R.id.nav_host);
navHostFragment.getChildFragmentManager().getFragments().get(0);|code-block|syntax|javascript|e9pq6|当然，如果你知道它是第一个片段。我仍然在研究一种没有这个的方法。我同意这不是最好的方式，但这应该是目前的一些东西。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

I managed to discover a way for now and it is as follows:

<pre><code>NavHostFragment navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host);
navHostFragment.getChildFragmentManager().getFragments().get(0);
</code></pre>

In case of course you know it is the first fragment. I am still investigating a way without this. I agree it is not the best way but that should be something for now.

entityMap|blocks|key|4scti|text|我无法找到检索当前片段实例的方法。但是，您可以使用以下代码获取最后添加的片段的ID。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|6fms5|navController.currentDestination?.getId()|code-block|syntax|javascript|335lu|它返回导航文件中的ID。希望这能有所帮助。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

There is no way I can find to retrieve the current fragment instance. However, you can get the ID of lastly added fragment using the code below.
<pre><code>navController.currentDestination?.getId()
</code></pre>
It returns the ID in navigation file. Hope this helps.

entityMap|blocks|key|c8l20|text|您应该查看nav片段的childFragmentManager+primaryNavigationFragment属性，这是引用当前显示的片段的位置。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4ia9r|val+navHost+=+supportFragmentManager.findFragmentById(R.id.main_nav_fragment)
++++navHost?.let+{+navFragment+->
++++++++navFragment.childFragmentManager.primaryNavigationFragment?.let+{fragment->
++++++++++++++++//DO+YOUR+STUFF
++++++++}
++++}
}|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

You should look the childFragmentManager primaryNavigationFragment property of your nav fragment, this is where the current displayed fragment is referenced.

<pre><code>val navHost = supportFragmentManager.findFragmentById(R.id.main_nav_fragment)
 navHost?.let { navFragment -&gt;
 navFragment.childFragmentManager.primaryNavigationFragment?.let {fragment-&gt;
 //DO YOUR STUFF
 }
 }
}
</code></pre>

entityMap|blocks|key|5slm3|text|这似乎是最干净的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|9mdq2|更新：|athb5|已将扩展函数更改为属性。谢谢|bnpnm|伊戈尔·沃伊达|4mb9k|..。|8lkct|1.创建如下扩展|4p5da|import+androidx.fragment.app.Fragment
import+androidx.fragment.app.FragmentManager

val+FragmentManager.currentNavigationFragment:+Fragment?
++++get()+=+primaryNavigationFragment?.childFragmentManager?.fragments?.first()|code-block|syntax|javascript|8lvrr|2.在|6ss01|bqf6p|ejb83|使用|5vau0|4942f|emit1|像这样使用它：|24d0q|val+currentFragment+=+supportFragmentManager.currentNavigationFragment^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|13|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|14|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|15|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|16|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|17|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|18|9|@]|A|@]|B|$]]|$2|M|4|N|6|O|8|19|9|@]|A|@]|B|$P|Q]]|$2|R|4|S|6|7|8|1A|9|@]|A|@]|B|$]]|$2|T|4|-4|6|7|8|1B|9|@]|A|@]|B|$]]|$2|U|4|-4|6|7|8|1C|9|@]|A|@]|B|$]]|$2|V|4|W|6|7|8|1D|9|@]|A|@]|B|$]]|$2|X|4|-4|6|7|8|1E|9|@]|A|@]|B|$]]|$2|Y|4|-4|6|7|8|1F|9|@]|A|@]|B|$]]|$2|Z|4|10|6|7|8|1G|9|@]|A|@]|B|$]]|$2|11|4|12|6|O|8|1H|9|@]|A|@]|B|$P|Q]]]]

This seems like the cleanest solution. Update: Changed extension function to property. Thanks <a href="https://stackoverflow.com/users/1211920/igor-wojda">Igor Wojda</a>.

1. Create the following extension

<pre><code>import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager

val FragmentManager.currentNavigationFragment: Fragment?
 get() = primaryNavigationFragment?.childFragmentManager?.fragments?.first()
</code></pre>

2. In <code>Activity</code> with <code>NavHostFragment</code> use it like this:

<pre><code>val currentFragment = supportFragmentManager.currentNavigationFragment
</code></pre>

entityMap|blocks|key|a50te|text|使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|soqq|在活动中有|9sdsj|对于Java|ff7hk|NavController+navController=+Navigation.findNavController(MainActivity.this,R.id.your_nav_host);

++++++++navController.addOnDestinationChangedListener(new+NavController.OnDestinationChangedListener()+{
++++++++++++@Override
++++++++++++public+void+onDestinationChanged(@NonNull+NavController+controller,+@NonNull+NavDestination+destination,+@Nullable+Bundle+arguments)+{
++++++++++++++++Log.e(TAG,+"onDestinationChanged:+"%2Bdestination.getLabel());
++++++++++++}
++++++++});|code-block|syntax|javascript|g5tq|对于Kotlin|vilc|var+navController+:NavController=Navigation.findNavController(this,+R.id.nav_host_fragment)
++++navController.addOnDestinationChangedListener+{+controller,+destination,+arguments+->
++++++++Log.e(TAG,+"onDestinationChanged:+"%2Bdestination.label);

++++}^0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|P|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|Q|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|R|9|@]|A|@]|B|$]]|$2|G|4|H|6|I|8|S|9|@]|A|@]|B|$J|K]]|$2|L|4|M|6|7|8|T|9|@]|A|@]|B|$]]|$2|N|4|O|6|I|8|U|9|@]|A|@]|B|$J|K]]]]

Use <code>addOnDestinationChangedListener</code> in activity having <code>NavHostFragment</code>

For Java

<pre><code> NavController navController= Navigation.findNavController(MainActivity.this,R.id.your_nav_host);

 navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
 @Override
 public void onDestinationChanged(@NonNull NavController controller, @NonNull NavDestination destination, @Nullable Bundle arguments) {
 Log.e(TAG, "onDestinationChanged: "+destination.getLabel());
 }
 });
</code></pre>

For Kotlin

<pre><code>var navController :NavController=Navigation.findNavController(this, R.id.nav_host_fragment)
 navController.addOnDestinationChangedListener { controller, destination, arguments -&gt;
 Log.e(TAG, "onDestinationChanged: "+destination.label);

 }
</code></pre>

entityMap|blocks|key|2nqbs|text|这可能有点晚了，但对于任何还在寻找的人来说|type|unstyled|depth|inlineStyleRanges|entityRanges|data|cdn2g|val+currentFragment+=+NavHostFragment.findNavController(nav_host_fragment).currentDestination?.id|code-block|syntax|javascript|a9e4q|然后你可以做一些类似这样的事情|487fm|if(currentFragment+==+R.id.myFragment){
+++++//do+something
}|iccg|注意，这是针对kotlin的，java代码应该几乎相同。^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|N|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|O|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|P|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|Q|9|@]|A|@]|B|$F|G]]|$2|L|4|M|6|7|8|R|9|@]|A|@]|B|$]]]]

this might be late but for anyone who's still looking
<pre><code>val currentFragment = NavHostFragment.findNavController(nav_host_fragment).currentDestination?.id
</code></pre>
then you can do something like
<pre><code>if(currentFragment == R.id.myFragment){
 //do something
}
</code></pre>
note that this is for kotlin, java code should be almost the same

entityMap|blocks|key|4tbvs|text|navController().currentDestination?.id|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|cfev4|会给你你目前的|unstyled|cra62|的id所在位置|7lhag|private+fun+navController()+=+Navigation.findNavController(this,+R.id.navHostFragment)|a5up2|此id是您在|9bsc1|下的文件|fq3fs|标签。你也可以比较|fua4c|如果你想的话。^0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|T|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|U|9|@]|A|@]|B|$]]|$2|H|4|I|6|G|8|V|9|@]|A|@]|B|$]]|$2|J|4|K|6|7|8|W|9|@]|A|@]|B|$C|D]]|$2|L|4|M|6|G|8|X|9|@]|A|@]|B|$]]|$2|N|4|O|6|G|8|Y|9|@]|A|@]|B|$]]|$2|P|4|Q|6|G|8|Z|9|@]|A|@]|B|$]]|$2|R|4|S|6|G|8|10|9|@]|A|@]|B|$]]]]

<pre><code>navController().currentDestination?.id
</code></pre>

will give you your current <code>Fragment</code>'s id where 

<pre><code>private fun navController() = Navigation.findNavController(this, R.id.navHostFragment)

</code></pre>

this id is the id which you have given in your <code>Navigation Graph XML</code> file under <code>fragment</code> tag. You could also compare <code>currentDestination.label</code> if you want.

entityMap|blocks|key|c9fou|text|我的需求是从父活动中获取当前可见的片段，我的解决方案是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|82udd|private+LoginFragment+getCurrentVisibleFragment()+{
++++++++NavHostFragment+navHostFragment+=+(NavHostFragment)getSupportFragmentManager().getPrimaryNavigationFragment();
++++++++FragmentManager+fragmentManager+=+navHostFragment.getChildFragmentManager();
++++++++Fragment+loginFragment+=+fragmentManager.getPrimaryNavigationFragment();
++++++++if(loginFragment+instanceof+LoginFragment){
++++++++++++return+(LoginFragment)loginFragment;
++++++++}
++++++++return+null;
++++}|code-block|syntax|javascript|mirb|这可能会帮助一些有同样问题的人。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

My requirement is to get the current visible fragment from Parent activity,my solution is

<pre><code> private LoginFragment getCurrentVisibleFragment() {
 NavHostFragment navHostFragment = (NavHostFragment)getSupportFragmentManager().getPrimaryNavigationFragment();
 FragmentManager fragmentManager = navHostFragment.getChildFragmentManager();
 Fragment loginFragment = fragmentManager.getPrimaryNavigationFragment();
 if(loginFragment instanceof LoginFragment){
 return (LoginFragment)loginFragment;
 }
 return null;
 }
</code></pre>

This may help some one with same problem.

entityMap|blocks|key|1sd2f|text|首先，您通过id获取当前片段，然后您可以根据该id找到该片段。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|700m9|int+id+=+navController.getCurrentDestination().getId();
Fragment+fragment+=+getSupportFragmentManager().findFragmentById(id);|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

First, you get the current fragment by id, then you can find the fragment, depending on that id.
<pre><code>int id = navController.getCurrentDestination().getId();
Fragment fragment = getSupportFragmentManager().findFragmentById(id);
</code></pre>

entityMap|blocks|key|54o03|text|找到了有效的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5irb6|private+fun+getCurrentFragment():+Fragment?+{
++++val+currentNavHost+=+supportFragmentManager.findFragmentById(R.id.nav_host_id)
++++val+currentFragmentClassName+=+((this+as+NavHost).navController.currentDestination+as+FragmentNavigator.Destination).className
++++return+currentNavHost?.childFragmentManager?.fragments?.filterNotNull()?.find+{
++++++++it.javaClass.name+==+currentFragmentClassName
++++}
}|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

Found working solution.

<pre><code>private fun getCurrentFragment(): Fragment? {
 val currentNavHost = supportFragmentManager.findFragmentById(R.id.nav_host_id)
 val currentFragmentClassName = ((this as NavHost).navController.currentDestination as FragmentNavigator.Destination).className
 return currentNavHost?.childFragmentManager?.fragments?.filterNotNull()?.find {
 it.javaClass.name == currentFragmentClassName
 }
}
</code></pre>

entityMap|blocks|key|7dgfu|text|从使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|e7egq|，您可以使用下面的代码来检索|codo8|..。|avjn6|val+fragmentInstance+=+myNavHostFragment?.childFragmentManager?.primaryNavigationFragment|code-block|syntax|javascript^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|M|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|N|9|@]|A|@]|B|$]]|$2|G|4|H|6|I|8|O|9|@]|A|@]|B|$J|K]]]]

From an Activity that uses <code>NavHostFragment</code>, you can use the code below to retrieve the instance of the <code>Active Fragment</code>.

<pre><code>val fragmentInstance = myNavHostFragment?.childFragmentManager?.primaryNavigationFragment
</code></pre>

entityMap|blocks|key|alltv|text|根据@slhddn的回答和评论，这就是我如何使用它和检索片段的方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|45fk8|来自nav的id|6tmnf|_|dau8r|graph.xml|bgl2k|文件：|6cvi3|class+MainActivity+:+AppCompatActivity()+{
override+fun+onCreate(savedInstanceState:+Bundle?)+{
++++super.onCreate(savedInstanceState)
++++setContentView(R.layout.activity_main)

++++setSupportActionBar(findViewById(R.id.toolbar))

++++val+navController+=+findNavController(this,+R.id.nav_host_fragment)

++++ivSettingsCog.setOnClickListener+{

++++++++if+(navController.currentDestination?.id+==+R.id.updatesFragment)+//+Id+as+per+set+up+on+nav_graph.xml+file
++++++++{
++++++++++++navController.navigate(R.id.action_updatesFragment_to_settingsFragment)
++++++++}

++++}

}

}|code-block|syntax|javascript^0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|P|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|Q|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|R|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|S|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|T|9|@]|A|@]|B|$]]|$2|K|4|L|6|M|8|U|9|@]|A|@]|B|$N|O]]]]

As per @slhddn answer and comment this is how I'm using it and retrieving the fragment id from the nav_graph.xml file:
<pre><code>class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 setContentView(R.layout.activity_main)

 setSupportActionBar(findViewById(R.id.toolbar))

 val navController = findNavController(this, R.id.nav_host_fragment)

 ivSettingsCog.setOnClickListener {

 if (navController.currentDestination?.id == R.id.updatesFragment) // Id as per set up on nav_graph.xml file
 {
 navController.navigate(R.id.action_updatesFragment_to_settingsFragment)
 }

 }

}

}
</code></pre>

entityMap|blocks|key|58esi|text|制作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|efpq|·在片段中的某个按钮中：|d6meg|val+navController+=+findNavController(this)
++navController.popBackStack()|code-block|syntax|javascript|e9dsm|·在您的活动onBackPressed()中|d4mgf|override+fun+onBackPressed()+{
++++++++val+navController+=+findNavController(R.id.nav_host_fragment)
++++++++val+id+=+navController.currentDestination?.getId()
++++++++if+(id+==+R.id.detailMovieFragment){
++++++++++++navController.popBackStack()
++++++++++++return
++++++++}

++++++++super.onBackPressed()
++++}^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|N|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|O|9|@]|A|@]|B|$]]|$2|E|4|F|6|G|8|P|9|@]|A|@]|B|$H|I]]|$2|J|4|K|6|7|8|Q|9|@]|A|@]|B|$]]|$2|L|4|M|6|G|8|R|9|@]|A|@]|B|$H|I]]]]

Make : 

• in some button in your fragment:

<pre><code>val navController = findNavController(this)
 navController.popBackStack()
</code></pre>

• In your Activity onBackPressed()

<pre><code>override fun onBackPressed() {
 val navController = findNavController(R.id.nav_host_fragment)
 val id = navController.currentDestination?.getId()
 if (id == R.id.detailMovieFragment){
 navController.popBackStack()
 return
 }

 super.onBackPressed()
 } 
</code></pre>

entityMap|blocks|key|cm9bp|text|navhost片段中的第一个片段是当前片段|type|unstyled|depth|inlineStyleRanges|entityRanges|data|eti6m|Fragment+navHostFragment+=+getSupportFragmentManager().getPrimaryNavigationFragment();
if+(navHostFragment+!=+null)+
{Fragment+fragment+=+navHostFragment.getChildFragmentManager().getFragments().get(0);}|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

The first fragment in navhost fragment is the current fragment

<pre><code>Fragment navHostFragment = getSupportFragmentManager().getPrimaryNavigationFragment();
if (navHostFragment != null) 
{Fragment fragment = navHostFragment.getChildFragmentManager().getFragments().get(0);}
</code></pre>

entityMap|blocks|key|c9e5c|text|使用导航组件，我使用下面这行代码获得了当前显示的片段：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|8cn3v|val+fragment+=+parentFragmentManager.primaryNavigationFragment|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

Using navigation components, I got the current displayed fragment using this line of code:
<pre><code>val fragment = parentFragmentManager.primaryNavigationFragment
</code></pre>

entityMap|blocks|key|b7at4|text|你能帮我查一下吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4n457|呼叫|5k67j|NavHostFragment+fragment+=+supportFragmentManager.findFragmentById(R.id.nav_host);
MyFragment+frag+=+(MyFragment)+fragment.getChildFragmentManager().findFragmentByTag(tag);|code-block|syntax|javascript^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|K|9|@]|A|@]|B|$]]|$2|E|4|F|6|G|8|L|9|@]|A|@]|B|$H|I]]]]

can you please check with <code>getChildFragmentManager()</code> call with 

<pre><code>NavHostFragment fragment = supportFragmentManager.findFragmentById(R.id.nav_host);
MyFragment frag = (MyFragment) fragment.getChildFragmentManager().findFragmentByTag(tag);
</code></pre>

entityMap|blocks|key|cvmmc|text|如果你需要你的片段的实例，你可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|68mc0|(练习)+=>|c5c0c|这是|cmch6|非常|bcbm0|虽然很难看，但您可以从那里检查它是否是您想要处理的片段的实例^0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|K|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|L|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|M|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|N|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|O|9|@]|A|@]|B|$]]]]

If you need the instance of your fragment, you can go with:

(Activity) => <code>supportFragmentManager.fragments.first().childFragmentManager.fragments.first()</code>

It's very ugly but from there you can check if it's an instance of the fragment you want to play around with

entityMap|blocks|key|eamlc|text|在Androidx上，我尝试了许多方法来查找所需的片段|type|unstyled|depth|inlineStyleRanges|entityRanges|data|atc9g|..。最后，我可以用下面的方法来破解它。|81t0t|public+Fragment+getFunctionalFragment+(String+tag_name)
{
++++NavHostFragment+navHostFragment+=+(NavHostFragment)+getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
++++FragmentManager+navHostManager+=+Objects.requireNonNull(navHostFragment).getChildFragmentManager();

++++Fragment+fragment=null;
++++List+fragment_list+=+navHostManager.getFragments();

++++for+(int+i=0;+i+<+fragment_list.size()+;+i+%2B%2B+)
++++{
++++++++if+(+fragment_list.get(i)+instanceof+HomeFragment+&&+tag_name.equals("frg_home"))+{
++++++++++++fragment+=+(HomeFragment)+fragment_list.get(i);
++++++++++++break;
++++++++}
++++}

++++return+fragment;
}|code-block|syntax|javascript^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|K|9|@]|A|@]|B|$]]|$2|E|4|F|6|G|8|L|9|@]|A|@]|B|$H|I]]]]

On Androidx, I have tried many methods for finding out required fragment from <code>NavHostFragment</code>. Finally I could crack it with below method 

<pre><code>public Fragment getFunctionalFragment (String tag_name)
{
 NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
 FragmentManager navHostManager = Objects.requireNonNull(navHostFragment).getChildFragmentManager();

 Fragment fragment=null;
 List fragment_list = navHostManager.getFragments();

 for (int i=0; i &lt; fragment_list.size() ; i ++ )
 {
 if ( fragment_list.get(i) instanceof HomeFragment &amp;&amp; tag_name.equals("frg_home")) {
 fragment = (HomeFragment) fragment_list.get(i);
 break;
 }
 }

 return fragment;
}
</code></pre>

entityMap|blocks|key|80sd0|text|这段代码是我写的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|nl6j|NavDestination+current+=+NavHostFragment.findNavController(getSupportFragmentManager().getPrimaryNavigationFragment().getFragmentManager().getFragments().get(0)).getCurrentDestination();

switch+(current.getId())+{
++++case+R.id.navigation_saved:
++++++++//+WRITE+CODE
++++++++break;
}|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

This code works from me

<pre><code>NavDestination current = NavHostFragment.findNavController(getSupportFragmentManager().getPrimaryNavigationFragment().getFragmentManager().getFragments().get(0)).getCurrentDestination();

switch (current.getId()) {
 case R.id.navigation_saved:
 // WRITE CODE
 break;
}
</code></pre>

entityMap|blocks|key|6cggv|text|这可能会很晚，但可能会对以后的人有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|d8mjr|如果您使用的是嵌套导航，则可以在Kotlin中获得如下所示的id|8vujv|val+nav+=+Navigation.findNavController(requireActivity(),+R.id.fragment_nav_host).currentDestination|code-block|syntax|javascript|8u055|这是片段中的一个片段|ftihg|_|b96v3|导航|2fgbu|66ajm|host.xml|9o8v4|你可以像这样检查所有你需要的东西|3d0ud|if+(nav.id+==+R.id.sampleFragment+%7C%7C+nav.label+==+"SampleFragment"){}^0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|W|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|X|9|@]|A|@]|B|$]]|$2|E|4|F|6|G|8|Y|9|@]|A|@]|B|$H|I]]|$2|J|4|K|6|7|8|Z|9|@]|A|@]|B|$]]|$2|L|4|M|6|7|8|10|9|@]|A|@]|B|$]]|$2|N|4|O|6|7|8|11|9|@]|A|@]|B|$]]|$2|P|4|M|6|7|8|12|9|@]|A|@]|B|$]]|$2|Q|4|R|6|7|8|13|9|@]|A|@]|B|$]]|$2|S|4|T|6|7|8|14|9|@]|A|@]|B|$]]|$2|U|4|V|6|G|8|15|9|@]|A|@]|B|$H|I]]]]

this might be late but may help someone later.

if you are using nested navigations you can get id like this in Kotlin

<pre><code>val nav = Navigation.findNavController(requireActivity(), R.id.fragment_nav_host).currentDestination
</code></pre>

and this is one of fragments in fragment_nav_host.xml

<pre><code>&lt;fragment
 android:id="@+id/sampleFragment"
 android:name="com.app.sample.SampleFragment"
 android:label="SampleFragment"
 tools:layout="@layout/fragment_sample" /&gt;
</code></pre>

and you can check all you need like this

<pre><code>if (nav.id == R.id.sampleFragment || nav.label == "SampleFragment"){}
</code></pre>

entityMap|blocks|key|7r32m|text|最后，对于那些仍在搜索的人来说，有效的解决方案实际上非常简单，您可以使用回调来实现这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|dq83|请执行以下步骤：|2i8ba|在要从活动onCreate()获取实例的片段中创建侦听器|11k4n|公共类HomeFragment扩展片段{私有OnCreateFragment+createLIstener；公共视图onCreateView(@NonNull+LayoutInflater膨胀器，ViewGroup容器，捆绑包savedInstanceState)+{+createLIstener.onFragmentCreated(this)；查看根=+inflater.inflate(R.layout.fragment|ir9n|_|cbthm|home，container，false)；//findViews(根)；返回根目录；}+@Override+public+void+onCreateOptionsMenu(@Non空菜单菜单，@NonNull+MenuInflater充气容器){super.onCreateOptionsMenu(菜单，充气容器)；inflater.inflate(R.menu.menu|598qo|1b2th|main，menu)；}+@Override+public+boolean+onOptionsItemSelected(@NonNull+MenuItem+item)+{+if+(item.getItemId()==R.id.action|4hon9|ei3pb|显示|f1bfh|5702t|filter){+//做点什么}+return+super.onOptionsItemSelected(item)；}+@Override+public+void+onAttach(Context+context)+{+super.onAttach(context)；try+{+createLIstener+=+(OnCreateFragment)+context；}+catch+(ClassCastException+e)+{抛出新的ClassCastException(context.toString()+%2B“必须实现OnArticleSelectedListener")；}}公共接口OnCreateFragment{+void+onFragmentCreated(片段f)；}}|b6j3p|在主机片段/活动中实现侦听器|aunbo|公共类MainActivity扩展了AppCompatActivity实现了HomeFragment.OnCreateFragment+{+@Override+protected+void+onCreate(捆绑包savedInstanceState)+{+super.onCreate(savedInstanceState)；setContentView(R.layout.activity|84gas|cl9li|main)；BottomNavigationView+navView+=+findViewById(R.id.nav|dgfir|2tj1k|视图)；//将每个菜单ID作为一组ID传递，因为每个//菜单都应该被视为顶级目的地。AppBarConfiguration+appBarConfiguration+=新AppBarConfiguration.Builder(+R.id.navigation|8o5r1|136cl|home，R.+-)+.build()；NavController+navController+=+Navigation.findNavController(this，R.id.nav|8li0v|dsdtp|主机|77n2k|b0oor|fragment)；NavigationUI.setupActionBarWithNavController(this，navController，appBarConfiguration)；NavigationUI.setupWithNavController(navView，navController)；}+@Override+public+void+onFragmentCreated(Fragment+f)+{+if+(f!=null){+H.debug("fragment+created+listener："%2Bf.getId())；f.setHasOptionsMenu(true)；}else+{+H.debug("fragment+created+listener:+NULL")；}}}|434de|这就是你完成这项工作所需要的一切。帮助某人^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|1G|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|1H|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|1I|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|1J|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|1K|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|1L|9|@]|A|@]|B|$]]|$2|M|4|J|6|7|8|1M|9|@]|A|@]|B|$]]|$2|N|4|O|6|7|8|1N|9|@]|A|@]|B|$]]|$2|P|4|J|6|7|8|1O|9|@]|A|@]|B|$]]|$2|Q|4|R|6|7|8|1P|9|@]|A|@]|B|$]]|$2|S|4|J|6|7|8|1Q|9|@]|A|@]|B|$]]|$2|T|4|U|6|7|8|1R|9|@]|A|@]|B|$]]|$2|V|4|W|6|7|8|1S|9|@]|A|@]|B|$]]|$2|X|4|Y|6|7|8|1T|9|@]|A|@]|B|$]]|$2|Z|4|J|6|7|8|1U|9|@]|A|@]|B|$]]|$2|10|4|11|6|7|8|1V|9|@]|A|@]|B|$]]|$2|12|4|J|6|7|8|1W|9|@]|A|@]|B|$]]|$2|13|4|14|6|7|8|1X|9|@]|A|@]|B|$]]|$2|15|4|J|6|7|8|1Y|9|@]|A|@]|B|$]]|$2|16|4|17|6|7|8|1Z|9|@]|A|@]|B|$]]|$2|18|4|J|6|7|8|20|9|@]|A|@]|B|$]]|$2|19|4|1A|6|7|8|21|9|@]|A|@]|B|$]]|$2|1B|4|J|6|7|8|22|9|@]|A|@]|B|$]]|$2|1C|4|1D|6|7|8|23|9|@]|A|@]|B|$]]|$2|1E|4|1F|6|7|8|24|9|@]|A|@]|B|$]]]]

Finally the working solution for those of you who are still searching
Actually it is very simple and you can achieve this using callback.
follow these steps:
<ol>
<li>Create a listener inside the fragment you want to get the instance from activity onCreate()
<pre><code>public class HomeFragment extends Fragment {

private OnCreateFragment createLIstener;

public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
 createLIstener.onFragmentCreated(this);
 View root = inflater.inflate(R.layout.fragment_home, container, false);
 //findViews(root);
 return root;
}

@Override
public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
 super.onCreateOptionsMenu(menu, inflater);
 inflater.inflate(R.menu.menu_main, menu);

}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
 if (item.getItemId()==R.id.action_show_filter){
 //do something
 }
 return super.onOptionsItemSelected(item);
}

@Override
public void onAttach(Context context) {
 super.onAttach(context);
 try {
 createLIstener = (OnCreateFragment) context;
 } catch (ClassCastException e) {
 throw new ClassCastException(context.toString() + &quot; must implement OnArticleSelectedListener&quot;);
 }
 }

 public interface OnCreateFragment{
 void onFragmentCreated(Fragment f);
 }
}
</code></pre>
</li>
<li>Implement your listener in the host Fragment/Activity
<pre><code>public class MainActivity extends AppCompatActivity implements HomeFragment.OnCreateFragment {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 BottomNavigationView navView = findViewById(R.id.nav_view);
 // Passing each menu ID as a set of Ids because each
 // menu should be considered as top level destinations.
 AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
 R.id.navigation_home,
 R. ----)
 .build();
 NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
 NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
 NavigationUI.setupWithNavController(navView, navController);
 }

 @Override
 public void onFragmentCreated(Fragment f) {
 if (f!=null){
 H.debug(&quot;fragment created listener: &quot;+f.getId());
 f.setHasOptionsMenu(true);
 }else {
 H.debug(&quot;fragment created listener: NULL&quot;);
 }
 }
}
</code></pre>
</li>
</ol>
And that is everything you need to do the job.
Hop this help someone

entityMap|blocks|key|da32c|text|我能用1个片段，Kotlin，导航用法弄清楚的最好的方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|f6tb2|在布局文件中添加标记："android:tag="main|br40g|_|88ag7|片段|dejfd|94tb6|标签“”|4jovn|关于你的活动：|101h0|val+navHostFragment+=+supportFragmentManager.findFragmentByTag("main_fragment_tag")+as+NavHostFragment
val+mainFragment+=+navHostFragment.childFragmentManager.fragments[0]+as+MainFragment
mainFragment.mainFragmentMethod()|code-block|syntax|javascript^0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|S|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|T|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|U|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|V|9|@]|A|@]|B|$]]|$2|I|4|F|6|7|8|W|9|@]|A|@]|B|$]]|$2|J|4|K|6|7|8|X|9|@]|A|@]|B|$]]|$2|L|4|M|6|7|8|Y|9|@]|A|@]|B|$]]|$2|N|4|O|6|P|8|Z|9|@]|A|@]|B|$Q|R]]]]

The best way I could figure out with 1 fragment, Kotlin, Navigation usage:
On your layout file add the tag: &quot;android:tag=&quot;main_fragment_tag&quot;&quot;
<pre><code>&lt;fragment
 android:layout_width=&quot;match_parent&quot;
 android:layout_height=&quot;match_parent&quot;
 android:id=&quot;@+id/nav_host&quot;
 app:navGraph= &quot;@navigation/nav_item&quot;
 android:tag=&quot;main_fragment_tag&quot;
 android:name=&quot;androidx.navigation.fragment.NavHostFragment&quot;
 app:defaultNavHost= &quot;true&quot;
 /&gt;
</code></pre>
On your Activity:
<pre><code>val navHostFragment = supportFragmentManager.findFragmentByTag(&quot;main_fragment_tag&quot;) as NavHostFragment
val mainFragment = navHostFragment.childFragmentManager.fragments[0] as MainFragment
mainFragment.mainFragmentMethod()
</code></pre>

entityMap|blocks|key|trs3|text|val+fragment:+YourFragment?+=+yourNavHost.findFragment()|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|e8dg9|注意：|unstyled|72bnl|扩展函数位于|elhfe|包，它的泛型函数^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|M|9|@]|A|@]|B|$]]|$2|H|4|I|6|G|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|G|8|O|9|@]|A|@]|B|$]]]]

<pre><code>val fragment: YourFragment? = yourNavHost.findFragment()
</code></pre>
Note: <code>findFragment</code> extension function is located in <code>androidx.fragment.app</code> package, and it's generic function

entityMap|blocks|key|av12f|text|下面是我对java的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|9sung|NavHostFragment++navHostFragment=+(NavHostFragment)+getSupportFragmentManager().getFragments().get(0);
++++MyFragment++fragment+=+(MyFragment)+navHostFragment.getChildFragmentManager().getFragments().get(0);
++++fragment.doSomething();|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

Here is my solution for java
<pre><code> NavHostFragment navHostFragment= (NavHostFragment) getSupportFragmentManager().getFragments().get(0);
 MyFragment fragment = (MyFragment) navHostFragment.getChildFragmentManager().getFragments().get(0);
 fragment.doSomething();
</code></pre>

entityMap|blocks|key|1v15l|text|我结合了|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3k1m1|Andrei+Toaders回答|bo91j|和|gs96|Mukul+Bhardwajs回答|caude|使用一个|anl9o|..。|3ltso|作为属性：|bl22s|private+FooFragment+fragment;|code-block|syntax|javascript|fbv4k|在我的|ellv4|NavHostFragment+navHostFragment+=+(NavHostFragment)+getSupportFragmentManager().findFragmentById(R.id.nav_host);
FragmentManager+navHostManager+=+Objects.requireNonNull(navHostFragment).getChildFragmentManager();
FragmentManager.OnBackStackChangedListener+listener+=+()+->+{
++++++++List+frags+=+navHostManager.getFragments();
++++++++if(!frags.isEmpty())+{
++++++++++++fragment+=+(FooFragment)+frags.get(0);
++++++++}
};
navController.addOnDestinationChangedListener((controller,+destination,+arguments)+->+{
++++++++if(destination.getId()==R.id.FooFragment){
++++++++++++navHostManager.addOnBackStackChangedListener(listener);
++++++++}+else+{
++++++++++++navHostManager.removeOnBackStackChangedListener(listener);
+++++++++++fragment+=+null;
++++++++}
});|11a59|这样我就可以得到一个片段，稍后会显示出来。其中一个甚至可以循环|81bqm|并使用以下命令检查多个片段|5mpag^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|12|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|13|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|14|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|15|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|16|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|17|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|18|9|@]|A|@]|B|$]]|$2|O|4|P|6|Q|8|19|9|@]|A|@]|B|$R|S]]|$2|T|4|U|6|7|8|1A|9|@]|A|@]|B|$]]|$2|V|4|W|6|Q|8|1B|9|@]|A|@]|B|$R|S]]|$2|X|4|Y|6|7|8|1C|9|@]|A|@]|B|$]]|$2|Z|4|10|6|7|8|1D|9|@]|A|@]|B|$]]|$2|11|4|L|6|7|8|1E|9|@]|A|@]|B|$]]]]

I combined <a href="https://stackoverflow.com/a/51732378/1849612">Andrei Toaders answer</a> and <a href="https://stackoverflow.com/a/56218631/1849612">Mukul Bhardwajs answer</a> with an <code>OnBackStackChangedListener</code>.

As an attribute:

<pre><code>private FooFragment fragment;
</code></pre>

In my <code>onCreate</code>

<pre><code>NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.nav_host);
FragmentManager navHostManager = Objects.requireNonNull(navHostFragment).getChildFragmentManager();
FragmentManager.OnBackStackChangedListener listener = () -&gt; {
 List&lt;Fragment&gt; frags = navHostManager.getFragments();
 if(!frags.isEmpty()) {
 fragment = (FooFragment) frags.get(0);
 }
};
navController.addOnDestinationChangedListener((controller, destination, arguments) -&gt; {
 if(destination.getId()==R.id.FooFragment){
 navHostManager.addOnBackStackChangedListener(listener);
 } else {
 navHostManager.removeOnBackStackChangedListener(listener);
 fragment = null;
 }
});
</code></pre>

This way i can get a fragment, which will be displayed later on.
One even may be able to loop though <code>frags</code> and check multiple fragments with <code>instanceof</code>.

entityMap|blocks|key|7unb5|text|我需要这样做来设置一个底部导航视图，我是这样做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|ard2h|val+navController+=+Navigation.findNavController(requireActivity(),+R.id.nav_tabs_home)
++++++++val+bottomNavBar:+BottomNavigationView+=+nav_content_view
++++++++NavigationUI.setupWithNavController(bottomNavBar,+navController)|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

I need to do this to setup a bottom navigation view and I did it this way:

<pre><code>val navController = Navigation.findNavController(requireActivity(), R.id.nav_tabs_home)
 val bottomNavBar: BottomNavigationView = nav_content_view
 NavigationUI.setupWithNavController(bottomNavBar, navController)
</code></pre>

entityMap|blocks|key|3gokm|text|实现这一点的最好方法是注册一个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|8sh07|片段生命周期回调|bhhj2|..。|fb3kg|根据原问题，如果你的|b5jdq|定义为...|actfh|然后在你的主要活动中|otha|d4iac|nav_host.childFragmentManager.registerFragmentLifecycleCallbacks(
++++object:FragmentManager.FragmentLifecycleCallbacks()+{
++++++++override+fun+onFragmentViewCreated(
++++++++++++fm:+FragmentManager,+f:+Fragment,+v:+View,
++++++++++++savedInstanceState:+Bundle?
++++++++)+{
++++++++++++//+callback+method+always+called+whenever+a
++++++++++++//+fragment+is+added,+or,+a+back-press+returns
++++++++++++//+to+the+start-destination
++++++++}
++++}
)|code-block|syntax|javascript|fu2ab|其他回调方法可能会被覆盖以满足您的要求。^0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|U|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|V|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|W|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|X|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|Y|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|Z|9|@]|A|@]|B|$]]|$2|M|4|F|6|7|8|10|9|@]|A|@]|B|$]]|$2|N|4|O|6|P|8|11|9|@]|A|@]|B|$Q|R]]|$2|S|4|T|6|7|8|12|9|@]|A|@]|B|$]]]]

The best way to achieve this is to register a fragment lifecycle callback.

As per the original question, if your <code>NavHostFragment</code> is defined as...

<pre><code>&lt;fragment
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:id="@+id/nav_host"
 app:navGraph= "@navigation/nav_item"
 android:name="androidx.navigation.fragment.NavHostFragment"
 app:defaultNavHost= "true"
 /&gt;
</code></pre>

Then in your main activity <code>onCreate(..)</code>...

<pre><code>nav_host.childFragmentManager.registerFragmentLifecycleCallbacks(
 object:FragmentManager.FragmentLifecycleCallbacks() {
 override fun onFragmentViewCreated(
 fm: FragmentManager, f: Fragment, v: View,
 savedInstanceState: Bundle?
 ) {
 // callback method always called whenever a
 // fragment is added, or, a back-press returns
 // to the start-destination
 }
 }
)
</code></pre>

Other callback methods may be overridden to fit your requirements.

entityMap|blocks|key|eh291|text|这个解决方案在大多数情况下都有效，试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1t610|val+mainFragment+=+fragmentManager?.primaryNavigationFragment?.parentFragment?.parentFragment+as+MainFragment|code-block|syntax|javascript|cug2u|或者这样：|8ss93|val+mainFragment+=+fragmentManager?.primaryNavigationFragment?.parentFragment+as+MainFragment^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|M|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|O|9|@]|A|@]|B|$F|G]]]]

This solution will work in most situations
Try this:

<pre><code>val mainFragment = fragmentManager?.primaryNavigationFragment?.parentFragment?.parentFragment as MainFragment
</code></pre>

or this:

<pre><code>val mainFragment = fragmentManager?.primaryNavigationFragment?.parentFragment as MainFragment
</code></pre>

entityMap|blocks|key|bpoip|text|这对我很有效|type|unstyled|depth|inlineStyleRanges|entityRanges|data|6amfc|(navController.currentDestination+as+FragmentNavigator.Destination).className|code-block|syntax|javascript|c55uc|它会回来的|f9leg|你的片段^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|M|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|7|8|O|9|@]|A|@]|B|$]]]]

This works for me 

<pre><code>(navController.currentDestination as FragmentNavigator.Destination).className 
</code></pre>

It will return <code>canonicalName</code> of your fragment

entityMap|blocks|key|18tse|text|在您活动中定义一个片段对象。并且从每个片段通过传递fragment对象来调用此方法，这样静态片段对象每次都会被当前显示的片段覆盖。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|kf7e|//method+in+MainActivity
private+static+Fragment+fragment;

public+void+setFragment(Fragment+fragment){
this.fragment+=+fragment;
}

//And+from+your+fragment+class,+you+can+call
(()getActivity()).setFragment();

//if+you+want+to+set+it+directly;
+(()getActivity()).fragment=;|code-block|syntax|javascript|cj3bq|您还可以设置从片段到活动的回调，以获得更好的方法并传递当前的片段对象。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

In your activity define a fragment object. And from each fragment call this method by passing fragment object, like
So the static fragment object will be overridden by current showing fragment every time.

<pre><code>//method in MainActivity
private static Fragment fragment;

public void setFragment(Fragment fragment){
this.fragment = fragment;
}

//And from your fragment class, you can call
((&lt;yourActivity in which fragment present&gt;)getActivity()).setFragment(&lt;your fragment object&gt;);

//if you want to set it directly;
 ((&lt;yourActivity in which fragment present&gt;)getActivity()).fragment=&lt;your fragment object&gt;;
</code></pre>

You can also set callback from fragment to activity, for a better approach and pass your current fragment object.

Before trying the Navigation component I used to manually do fragment transactions and used the fragment tag in order to fetch the current fragment.

<code>val fragment:MyFragment = supportFragmentManager.findFragmentByTag(tag):MyFragment</code>

Now in my main activity layout I have something like:

<pre><code>&lt;fragment
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:id="@+id/nav_host"
 app:navGraph= "@navigation/nav_item"
 android:name="androidx.navigation.fragment.NavHostFragment"
 app:defaultNavHost= "true"
 /&gt;
</code></pre>

How can I retrieve the current displayed fragment by the Navigation component? 
Doing 

<code>supportFragmentManager.findFragmentById(R.id.nav_host)</code>

returns a <code>NavHostFragment</code> and I want to retrieve my shown 'MyFragment`.

Thank you.

Android Navigation Architecture Component - Get current visible fragment

容器

Kotlin

Java

 在尝试使用导航组件之前，我习惯于手动执行片段事务，并使用片段标记来获取当前片段。 现在，在我的主活动布局中，我有如下内容： 如何通过导航组件检索当前显示的片段？做什么 返回一个 我想找回我展示的'MyFragment`。 谢谢你。

问Android导航架构组件-获取当前可见片段
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