Java 我的OnNavigationItemSelectedListener kotlin android有什么问题？

我正在尝试在我的应用程序中使用bottomNavigation。现在我想将其中一个类从java移动到kotlin，在这个类中，我有一个导航菜单。在Java，我有这样的监听器：

bottomNavigationView.setOnNavigationItemSelectedListener(menuItem -> {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            Bundle bundle = new Bundle();
            switch (menuItem.getItemId()) {

                case R.id.full_jobAgent:

                    Objects.requireNonNull(getSupportActionBar()).show();
                    JobList jobList = new JobList();
                    bundle.putInt("offset", 1);
                    jobList.setArguments(bundle);
                    textViewTitle.setText("Jobagent");
                    tvSubTitle.setText(R.string.all_jobs);
                    textViewTitle.setTypeface(custom_font);
                    tvSubTitle.setTypeface(custom_font);
                    disableShowHideAnimation(getSupportActionBar());
                    transaction.replace(R.id.contentContainer, jobList).addToBackStack(null).commit();
                    return true;
                case R.id.received_mess:
                    disableShowHideAnimation(getSupportActionBar());
                    Objects.requireNonNull(getSupportActionBar()).show();


                    MessageList messageList = new MessageList();
                    bundle.putInt("type1", 0);
                    messageList.setArguments(bundle);
                    transaction.replace(R.id.contentContainer, messageList).addToBackStack(null).commit();
                    textViewTitle.setTypeface(custom_font);
                    tvSubTitle.setTypeface(custom_font);
                    textViewTitle.setText(R.string.title_activity_message_center);
                    tvSubTitle.setText(R.string.received);
                    return true;
                case R.id.home_screen:
                    disableShowHideAnimation(getSupportActionBar());
                    Objects.requireNonNull(getSupportActionBar()).hide();
                    transaction.replace(R.id.contentContainer, new PersonalData()).addToBackStack(null).commit();
                    return true;
                case R.id.more:
                    disableShowHideAnimation(getSupportActionBar());
                    textViewTitle.setText(R.string.more_bottom_nav);
                    textViewTitle.setTypeface(custom_font);
                    tvSubTitle.setVisibility(View.GONE);
                    Objects.requireNonNull(getSupportActionBar()).show();
                    transaction.replace(R.id.contentContainer, new MoreScreen()).addToBackStack(null).commit();
                    return true;
                case R.id.notespec:
                    disableShowHideAnimation(getSupportActionBar());
                    textViewTitle.setText(R.string.notepad_bottom_nav);
                    textViewTitle.setTypeface(custom_font);
                    tvSubTitle.setVisibility(View.GONE);
                    Objects.requireNonNull(getSupportActionBar()).show();
                    transaction.replace(R.id.contentContainer, new TestNotepadFragment()).addToBackStack(null).commit();
                    return true;
            }
            return false;
        });

我已将此方法重写为kotlin：

 private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
        val transaction = supportFragmentManager.beginTransaction()
        val bundle = Bundle()
        when (item.itemId) {
            R.id.full_jobAgent -> {
                ms.filter_data = HashMap<String, String>()
                disableShowHideAnimation(supportActionBar!!)

                val jobList = JobList()
                bundle.putInt("offset", 1)

                if (intent.getSerializableExtra("filter_data") != null) {
                    bundle.putSerializable("filter_data", intent.getSerializableExtra("filter_data"))
                }
                bottomNavigationView.selectedItemId = R.id.full_jobAgent
                transaction.replace(R.id.contentContainerT, jobList).addToBackStack(null).commit()
                textSetter("Jobagent", resources.getString(R.string.all_jobs))
                //return@OnNavigationItemSelectedListener true
            }

            R.id.received_mess -> {
                disableShowHideAnimation(supportActionBar!!)
                supportActionBar!!.show()
                val messageList = MessageList()
                bundle.putInt("type1", 0)
                messageList.arguments = bundle
                textSetter(resources.getString(R.string.title_activity_message_center), resources.getString(R.string.received))
                transaction.replace(R.id.contentContainerT, messageList).addToBackStack(null).commit()
                //return@OnNavigationItemSelectedListener true
            }

            R.id.home_screen -> {
                disableShowHideAnimation(supportActionBar!!)
                supportActionBar!!.hide()
                transaction.replace(R.id.contentContainerT, PersonalData()).addToBackStack(null).commit()
                //return@OnNavigationItemSelectedListener true
            }

            R.id.notespec -> {
                disableShowHideAnimation(supportActionBar!!)
                supportActionBar!!.show()
                textSetter(resources.getString(R.string.more_bottom_nav), "")
                transaction.replace(R.id.contentContainerT, NotepadScr()).addToBackStack(null).commit()
                //return@OnNavigationItemSelectedListener true
            }

            R.id.more ->{
                disableShowHideAnimation(supportActionBar!!)
                supportActionBar!!.show()
                textSetter(resources.getString(R.string.more_bottom_nav),"")
                transaction.replace(R.id.contentContainerT,MoreScreen()).addToBackStack(null).commit()
                //return@OnNavigationItemSelectedListener true
            }
        }
        false
    }

---

你们中的一些人会问我我的应用程序的日志，但我无法从logcat获取它们，因为它重新加载得非常快。所以在java中，我们不必选择所选的项目，但在kotlin中，当我删除错误的选择行时，我看不出现在选择了哪个项目。也许我做错了？

尝试在结尾处使用

返回true

。。。我看到smb使用此返回，有些使用

return true

这些语句之间的区别在哪里？您需要在使用

时添加
else
return@OnNavigationItemSelectedListener正确

。关于这个true和return true，我不知道它到底是如何工作的。

else

at

when

语句？所以我必须为它添加一些条件？看起来是这样的。尝试在elsetry中使用结尾处的

return true

放置一个简单的日志语句。。。我看到smb使用此返回，有些使用

return true

这些语句之间的区别在哪里？您需要在使用

时添加
else
return@OnNavigationItemSelectedListener正确

。关于这个true和return true，我不知道它到底是如何工作的。

else

at

when

语句？所以我必须为它添加一些条件？看起来是这样的。尝试将一个简单的日志语句放在其他语句中

navigation.setOnNavigationItemSelectedListener(this)

override fun onNavigationItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.navigation_catalog -> {
            swapFragments(item.itemId, "Catalog")
            return true
        }
        R.id.navigation_shopping_cart -> {
            swapFragments(item.itemId, "ShoppingCart")
            return true
        }
        R.id.navigation_account -> {
            swapFragments(item.itemId, "Account")
            return true
        }
    }
    return false
}


private fun swapFragments(@IdRes actionId: Int, key: String) {
    if (supportFragmentManager.findFragmentByTag(key) == null) {
        savedFragmentState(actionId)
        createFragment(key, actionId)
    }
}

private fun savedFragmentState(actionId: Int) {
    val currentFragment = supportFragmentManager.findFragmentById(R.id.fragment_home)
    if (currentFragment != null) {
        savedStateSparseArray.put(currentSelectItemId,
                supportFragmentManager.saveFragmentInstanceState(currentFragment)
        )
    }
    currentSelectItemId = actionId
}

private fun createFragment(key: String, actionId: Int) {
    when (actionId) {
        R.id.navigation_catalog -> {
            val fragment = CatalogFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
        R.id.navigation_shopping_cart -> {
            val fragment = ShoppingcartFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
        R.id.navigation_account -> {
            val fragment = AccountFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
    }

}

navigation.setOnNavigationItemSelectedListener(this)

override fun onNavigationItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.navigation_catalog -> {
            swapFragments(item.itemId, "Catalog")
            return true
        }
        R.id.navigation_shopping_cart -> {
            swapFragments(item.itemId, "ShoppingCart")
            return true
        }
        R.id.navigation_account -> {
            swapFragments(item.itemId, "Account")
            return true
        }
    }
    return false
}


private fun swapFragments(@IdRes actionId: Int, key: String) {
    if (supportFragmentManager.findFragmentByTag(key) == null) {
        savedFragmentState(actionId)
        createFragment(key, actionId)
    }
}

private fun savedFragmentState(actionId: Int) {
    val currentFragment = supportFragmentManager.findFragmentById(R.id.fragment_home)
    if (currentFragment != null) {
        savedStateSparseArray.put(currentSelectItemId,
                supportFragmentManager.saveFragmentInstanceState(currentFragment)
        )
    }
    currentSelectItemId = actionId
}

private fun createFragment(key: String, actionId: Int) {
    when (actionId) {
        R.id.navigation_catalog -> {
            val fragment = CatalogFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
        R.id.navigation_shopping_cart -> {
            val fragment = ShoppingcartFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
        R.id.navigation_account -> {
            val fragment = AccountFragment.newInstance(key)
            fragment.setInitialSavedState(savedStateSparseArray[actionId])
            supportFragmentManager.beginTransaction()
                    .replace(R.id.fragment_home, fragment, key)
                    .commit()
        }
    }

}