IntentFlagSample

package ドメイン.intentflagsample

import android.content.Intent

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import android.util.Log

import android.widget.Toast

import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        val data = intent.getStringExtra("sub2_data")

        if (data != null) {

            Toast.makeText(applicationContext, data, Toast.LENGTH_SHORT).show()

        }

        button.setOnClickListener {

            startActivity(Intent(this, Sub1Activity::class.java))

        }

    }

}

package ドメイン.intentflagsample

import android.content.Intent

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import kotlinx.android.synthetic.main.activity_sub1.*

class Sub1Activity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_sub1)

        button2.setOnClickListener {

            startActivity(Intent(this, Sub2Activity::class.java))

        }

    }

}

package ドメイン.intentflagsample

import android.content.Intent

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import kotlinx.android.synthetic.main.activity_sub2.*

class Sub2Activity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_sub2)

        button3.setOnClickListener {

            val intent = Intent(this, MainActivity::class.java).apply {

                flags = Intent.FLAG_ACTIVITY_CLEAR_TOP

                putExtra("sub2_data", editText.text.toString())

            }

            startActivity(intent)

        }

    }

}

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

    xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

    <TextView

        android:id="@+id/textView3"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="MainActivity"

        android:textAppearance="@style/TextAppearance.AppCompat.Medium"

        app:layout_constraintBottom_toTopOf="@+id/button"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

    <Button

        android:id="@+id/button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Button"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/textView3" />

</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

    xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".Sub1Activity">

    <TextView

        android:id="@+id/textView"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Sub1Activity"

        android:textAppearance="@style/TextAppearance.AppCompat.Medium"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

    <Button

        android:id="@+id/button2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Button"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/textView" />

</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

    xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".Sub2Activity">

    <TextView

        android:id="@+id/textView2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Sub2Activity"

        android:textAppearance="@style/TextAppearance.AppCompat.Medium"

        app:layout_constraintBottom_toTopOf="@+id/editText"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

    <Button

        android:id="@+id/button3"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Button"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <EditText

        android:id="@+id/editText"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:layout_marginStart="8dp"

        android:layout_marginEnd="8dp"

        android:ems="10"

        android:inputType="textPersonName"

        android:text="Name"

        app:layout_constraintBottom_toTopOf="@+id/button3"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintHorizontal_bias="0.5"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toBottomOf="@+id/textView2" />

</androidx.constraintlayout.widget.ConstraintLayout>