Explicit Intent

ewillwin·2023년 4월 5일

kotlin

Mobile App Programming Lab

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6/7

Intent

An Intent is a messaging object you can use to request an action from another app component.
Three fundamental use cases:
- Starting an activity
- Starting a service
- Delivering a broadcast
Two types of intents:
- Explicit intents: Specify package name or component class name
- Implicit intents: Do not specify above name

Explicit Intent

Specify package name or component class name
Start an activity in Intent object
Data can be passed via Extras

Activity Lifecycle

startActivity
- onCreate
- onStart
- onResume
Pressing home button
- onPause
- onStop
Get back to application
- onRestart
- onStart
- onResume
Back button(close)
- onPause
- onStop
- onDestroy

Practice

finish() to kill activity
Text clear on on[Some function on activity lifecycle]() function
- edittext.text.clear() when activity re-loaded
- Do NOT forget super call

MainActivity.kt

package com.example.week6

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast

class MainActivity : AppCompatActivity() {
    companion object{
        const val EXT_NAME = "extra_key_name"
        const val EXT_AGE = "extra_key_age"
    }

    override fun onResume() {
        super.onResume()
        val editTextName = findViewById<EditText>(R.id.editTextName)
        val editTextAge = findViewById<EditText>(R.id.editTextAge)

        editTextName.text.clear()
        editTextAge.text.clear()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState) //override 할 때 super call 해줘야 함
        setContentView(R.layout.activity_main)

        val btnNewActivity = findViewById<Button>(R.id.buttonNewActivity)
        btnNewActivity.setOnClickListener {
            val editTextName = findViewById<EditText>(R.id.editTextName)
            val editTextAge = findViewById<EditText>(R.id.editTextAge)

            val name = editTextName.text.toString()
            val age = editTextAge.text.toString().toInt()

            val intent = Intent(this, NothingActivity::class.java).apply {
                putExtra(EXT_NAME, name)
                putExtra(EXT_AGE, age)
            }
            startActivity(intent)
        }
    }
}

NothingActivity.kt

package com.example.week6

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import android.widget.Toast

class NothingActivity : AppCompatActivity() {
    companion object{
        const val EXT_NAME = "extra_key_name"
        const val EXT_AGE = "extra_key_age"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_nothing)

        val name = intent.getStringExtra(MainActivity.EXT_NAME)
        val age = intent.getIntExtra(MainActivity.EXT_AGE, -1)

        val textView = findViewById<TextView>(R.id.textView3)
        textView.text = "You typed name ${name} and age ${age}, is that right?"

        val yesButton = findViewById<Button>(R.id.button)
        yesButton.setOnClickListener{
            val intent = Intent(this, LastActivity::class.java).apply {
                putExtra(MainActivity.EXT_NAME, name)
                putExtra(MainActivity.EXT_AGE, age)
            }
            startActivity(intent)
        }

        val noButton = findViewById<Button>(R.id.button2)
        noButton.setOnClickListener {
            finish()
        }
    }
}

LastActivity.kt

package com.example.week6

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast

class LastActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_last)

        val name = intent.getStringExtra(NothingActivity.EXT_NAME)
        val sid = intent.getIntExtra(NothingActivity.EXT_AGE, -1)

        Toast.makeText(
            applicationContext,
            "Welcome, ${name}(${sid})!",
            Toast.LENGTH_SHORT
        ).show()
    }
}

activity_main.xml

<?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">

    <Button
        android:id="@+id/buttonNewActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <EditText
        android:id="@+id/editTextName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:ems="10"
        android:hint="Enter your name"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="@+id/guideline2"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editTextAge"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="40dp"
        android:layout_marginEnd="8dp"
        android:ems="10"
        android:hint="Enter your age"
        android:inputType="number"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline2"
        app:layout_constraintTop_toBottomOf="@+id/editTextName" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.2" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="Name"
        app:layout_constraintBottom_toBottomOf="@+id/editTextName"
        app:layout_constraintEnd_toStartOf="@+id/guideline2"
        app:layout_constraintTop_toTopOf="@+id/editTextName" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="Age"
        app:layout_constraintBottom_toBottomOf="@+id/editTextAge"
        app:layout_constraintEnd_toStartOf="@+id/guideline2"
        app:layout_constraintTop_toTopOf="@+id/editTextAge" />
</androidx.constraintlayout.widget.ConstraintLayout>

activity_nothing.xml

<?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=".NothingActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="YES"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/guideline3"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline4"
        app:layout_constraintVertical_bias="0.54" />

    <Button
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="NO"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline3"
        app:layout_constraintTop_toTopOf="@+id/guideline4" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.5" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.8" />
</androidx.constraintlayout.widget.ConstraintLayout>

activity_last.xml

<?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=".LastActivity">

</androidx.constraintlayout.widget.ConstraintLayout>