无需娱乐即可在片段之间移动 - Kotlin

Question

我正在尝试在两个 fragments 之间移动而不重新创建它们，这样前一个片段中的数据就不会消失。

我试图在互联网上寻找答案并尝试了几个小时但没有成功。我查看了这些链接：

在 show() 和 hide() 之后我也尝试了 AddToBackStack() 但没有成功

class MainActivity : AppCompatActivity(){

    private val onNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
        @Override
        when (item.itemId) {
            R.id.navigation_home -> {
                //replaceFragment(SignInFragment())
                supportFragmentManager.beginTransaction().hide(AllEventsFragment()).commit()
                supportFragmentManager.beginTransaction().show(SignInFragment()).commit()
                return@OnNavigationItemSelectedListener true
            }
            R.id.navigation_events -> {
                //replaceFragment(AllEventsFragment())
                supportFragmentManager.beginTransaction().hide(SignInFragment()).commit()
                supportFragmentManager.beginTransaction().show(AllEventsFragment()).commit()
                if (currentUser.isNotEmpty()) {
                    updateRecyclerView()
                    sign_in_error?.visibility = View.INVISIBLE
                }
                return@OnNavigationItemSelectedListener true
            }
        }
        return@OnNavigationItemSelectedListener false
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        supportFragmentManager.beginTransaction().add(R.id.activity_main, AllEventsFragment(), "2").commit()
        supportFragmentManager.beginTransaction().add(R.id.activity_main, SignInFragment(), "1").commit()
        val navView: BottomNavigationView = findViewById(R.id.nav_view)
        navView.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)
        personInEvent = false
    }

结果是片段重叠，没有真正在它们之间导航的选项。我真的尝试了所有我知道的方法，互联网上有一些答案，但 none 帮助我解决了我的问题。对于这个令人沮丧的问题，我非常感谢您的帮助。

导航前：

导航后：

Answer 1

看看架构组件，你也可以用老方法实现它Android - save/restore fragment state 当片段不可见时，它会暂停甚至可能被销毁，使用 bundle 来保存数据。你想要达到的目标可以使用两个容器来完成，但你真的不应该

Answer 2

supportFragmentManager.beginTransaction().hide(AllEventsFragment()).commit()

你每次都在重新创建你的片段！调用 AllEventsFragment() 等同于 new AllEventsFragment()

你需要先实例化它们例如，你的代码需要像这样，

    val fragment1: Fragment = SignInFragment()
    val fragment2: Fragment = AllEventsFragment()
    var active = fragment1

      override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            supportFragmentManager.beginTransaction().add(R.id.activity_main,fragment2 , "2").commit()
            supportFragmentManager.beginTransaction().add(R.id.activity_main, fragment1, "1").commit()
            val navView: BottomNavigationView = findViewById(R.id.nav_view)
            navView.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)
            personInEvent = false
        }

在你的听众里面

    R.id.navigation_home -> {
                 supportFragmentManager.beginTransaction().beginTransaction().hide(active).show(fragment1).commit();
                    active = fragment1;
                return@OnNavigationItemSelectedListener true
            }
 R.id.navigation_events -> {
                //replaceFragment(AllEventsFragment())
                supportFragmentManager.beginTransaction().beginTransaction().hide(active).show(fragment2).commit();
active = fragment2
)

    //handle rest of the cases

无需娱乐即可在片段之间移动 - Kotlin

Move between fragments without recreation- Kotlin

android

android-fragments

kotlin

android-navigation-bar