导航到fragment2时，需要从back-stack中删除fragment1

片段1

<fragment
android:id="@+id/fragment1"
android:name="packagenameforFragment1"
android:label="fragment1"
tools:layout="@layout/fragment_1" >
<action
    android:id="@+id/action_Fragment1_to_Fragment2"
    app:destination="@id/Fragment2_id"
    app:launchSingleTop="true"
    app:popUpTo="@+id/your_MainGraph_id"
    app:popUpToInclusive="true" />

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然后当你从fragment1导航到fragment2时，调用这个

findNavController(fragment).navigate(R.id.action_Fragment1_to_Fragment2)

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要从Fragment2中删除后退按钮，您可以使用此

在Activity onCreate（）中

val appBarConfiguration = AppBarConfiguration
        .Builder(R.id.your_fragment2_id,R.id.any_other_ids_you_want)
        .build()

型
然后像这样设置工具栏

setupActionBarWithNavController(this, yourNavController, appBarConfiguration)

型

这是我的代码，你必须像我一样手动设置appBarConfiguration。

appBarConfiguration = AppBarConfiguration(setOf(
    R.id.nav_home,
    R.id.nav_safety,
    R.id.nav_myskin,
    R.id.nav_setting
  ))
setupActionBarWithNavController(navController, appBarConfiguration)

字符串
完整代码：

package limitless.android.uvindex.ui.activity

import android.content.Intent
import android.os.Bundle
import com.google.android.material.snackbar.Snackbar
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.navigateUp
import androidx.navigation.ui.setupActionBarWithNavController
import android.view.Menu
import android.view.MenuItem
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.setupWithNavController
import limitless.android.uvindex.R
import limitless.android.uvindex.databinding.ActivityMainBinding
import limitless.android.uvindex.utils.Utils

class MainActivity : AppCompatActivity() {

    private lateinit var appBarConfiguration: AppBarConfiguration
    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
        setSupportActionBar(binding.toolbar)

        // Get the NavController
        val navController = findNavController(R.id.nav_host_fragment_content_main)
        binding.bnv.setupWithNavController(navController)
        navController.graph = navController.navInflater.inflate(R.navigation.nav_graph)
        appBarConfiguration = AppBarConfiguration(setOf(
            R.id.nav_home,
            R.id.nav_safety,
            R.id.nav_myskin,
            R.id.nav_setting
        ))
        setupActionBarWithNavController(navController, appBarConfiguration)
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        return when (item.itemId) {
            R.id.action_premium -> {
                Utils.startActivity(this, Intent(this, PremiumActivity::class.java))
                true
            }
            else -> super.onOptionsItemSelected(item)
        }
    }

}

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结果：Screenshot