Question

我正在尝试在两个fragments之间移动而不会重新创建它们，因此前一个片段中的数据不会消失。

我试图在互联网上寻找答案，尝试了几个小时，但没有成功。我看了那些链接：

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

link 4

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，而没有在它们之间真正导航的选项。我真的尝试了所有我知道的事情，但是在Internet上都有一些答案，但是没有一个答案可以帮助我解决问题。对于这个令人沮丧的问题，我将不胜感激。

导航之前：

导航后：

Answer 1

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

您每次都会重新创建片段！调用AllEventsFragment()等同于new AllEventsFragment()

您需要首先实例化它们例如，您的代码必须是这样的，

    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
        }

在听众内部

    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

Answer 2

看看架构组件，您还可以用旧的方法Android - save/restore fragment state实现这一点当片段不可见时，其暂停或什至可能被破坏，请使用捆绑软件保存数据。您想要达到的目标可以使用两个容器来完成，但您实际上不应该

在片段之间移动而无需娱乐-Kotlin

2 个答案: