在 Android 中显示一次片段？科特林

Question

我想在我的应用程序中实现一个功能，当应用程序首次启动时，片段将只显示一次。遇到了问题。启动应用程序时显示错误。我正在寻求社区的帮助来解决这个问题。下面我附上了代码片段中的代码以及启动应用程序时出现的错误

登录片段


import android.content.Context
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.skreep.subeeapp.R
import android.content.Intent
import android.content.SharedPreferences
import androidx.navigation.fragment.findNavController
import com.skreep.subeeapp.MainActivity
import com.skreep.subeeapp.fragments.list.ListFragment
import kotlinx.android.synthetic.main.fragment_login.*
import java.nio.file.Files.move


private const val SHARED_PREFS_NAME = "shared_prefs_name"

class LoginFragment : Fragment() {


    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        val view = inflater.inflate(R.layout.fragment_login, container, false)
        return view
//        button_continue?.setOnClickListener {
//            findNavController().navigate(R.id.action_loginFragment2_to_listFragment)


    }


    override fun onResume() {
        super.onResume()
        val sharedPref = activity?.getPreferences(
            Context.MODE_PRIVATE
        ) ?: return
        val first = sharedPref.getString(SHARED_PREFS_NAME, "")

        if (first.equals("yes")) {
            val intent = Intent(this@LoginFragment.context, ListFragment::class.java)
            startActivity(intent)

        } else {
            val editor = sharedPref.edit();
            editor.putString(SHARED_PREFS_NAME, "yes");
            editor.apply();
        }
    }
}

错误

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.skreep.subeeapp, PID: 16473
    java.lang.RuntimeException: Unable to resume activity {com.skreep.subeeapp/com.skreep.subeeapp.MainActivity}: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.skreep.subeeapp/com.skreep.subeeapp.fragments.list.ListFragment}; have you declared this activity in your AndroidManifest.xml?
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4270)
        at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4302)
        at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2044)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:224)
        at android.app.ActivityThread.main(ActivityThread.java:7560)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
     Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.skreep.subeeapp/com.skreep.subeeapp.fragments.list.ListFragment}; have you declared this activity in your AndroidManifest.xml?
        at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:2064)
        at android.app.Instrumentation.execStartActivity(Instrumentation.java:1720)
        at android.app.Activity.startActivityForResult(Activity.java:5260)
        at androidx.activity.ComponentActivity.startActivityForResult(ComponentActivity.java:597)
        at android.app.Activity.startActivityForResult(Activity.java:5218)
        at androidx.activity.ComponentActivity.startActivityForResult(ComponentActivity.java:583)
        at android.app.Activity.startActivity(Activity.java:5589)
        at androidx.core.content.ContextCompat$Api16Impl.startActivity(ContextCompat.java:828)
        at androidx.core.content.ContextCompat.startActivity(ContextCompat.java:276)
        at androidx.fragment.app.FragmentHostCallback.onStartActivityFromFragment(FragmentHostCallback.java:166)
        at androidx.fragment.app.Fragment.startActivity(Fragment.java:1377)
        at androidx.fragment.app.Fragment.startActivity(Fragment.java:1365)
        at com.skreep.subeeapp.fragments.login.LoginFragment.onResume(LoginFragment.kt:47)
        at androidx.fragment.app.Fragment.performResume(Fragment.java:3039)
        at androidx.fragment.app.FragmentStateManager.resume(FragmentStateManager.java:607)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:306)
        at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:112)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1647)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3128)
        at androidx.fragment.app.FragmentManager.dispatchResume(FragmentManager.java:3086)
        at androidx.fragment.app.Fragment.performResume(Fragment.java:3048)
        at androidx.fragment.app.FragmentStateManager.resume(FragmentStateManager.java:607)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:306)
        at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:112)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1647)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3128)
        at androidx.fragment.app.FragmentManager.dispatchResume(FragmentManager.java:3086)
        at androidx.fragment.app.FragmentController.dispatchResume(FragmentController.java:273)
        at androidx.fragment.app.FragmentActivity.onResumeFragments(FragmentActivity.java:458)
        at androidx.fragment.app.FragmentActivity.onPostResume(FragmentActivity.java:447)
E/AndroidRuntime:     at androidx.appcompat.app.AppCompatActivity.onPostResume(AppCompatActivity.java:240)
        at android.app.Activity.performResume(Activity.java:8081)
        at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4260)
            ... 11 more
I/skreep.subeeap: ProcessProfilingInfo new_methods=1175 is saved saved_to_disk=1 resolve_classes_delay=8000

Answer 1

ListFragment 是片段而不是 activity，不能使用 startActivity() 启动片段。

您可以像这样从片段事务开始您的列表片段

Fragment someFragment = new ListFragment(); 
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_container, someFragment ); // give your fragment container id in first parameter
transaction.addToBackStack(null);  // if written, this transaction will be added to backstack
transaction.commit();

如果您使用的是导航图，则可以使用导航控制器和片段方向

https://developer.android.com/guide/navigation/navigation-navigate

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