Ciclo de vida de actividad en Android con aplicación de demostración

En Android , una actividad se conoce como una pantalla en una aplicación. Es muy similar a una ventana única de cualquier aplicación de escritorio. Una aplicación de Android consta de una o más pantallas o actividades. 
Cada actividad pasa por varias etapas o un ciclo de vida y es administrada por pilas de actividades. Así, cuando comienza una nueva actividad, la anterior siempre permanece debajo de ella. Hay cuatro etapas de una actividad. 

1. Si una actividad está en primer plano de la pantalla, es decir, en la parte superior de la pila, se dice que está activa o en ejecución. Esta suele ser la actividad con la que el usuario está interactuando actualmente.
2. Si una actividad ha perdido el foco y una actividad transparente o de tamaño no completo se ha centrado en la parte superior de su actividad. En tal caso, otra actividad tiene una posición más alta en el modo de ventanas múltiples o la actividad en sí no se puede enfocar en el modo de ventana actual. Tal actividad está completamente viva.
3. Si una actividad está completamente oculta por otra actividad, se detiene u oculta. Todavía retiene toda la información, y como su ventana está oculta, a menudo el sistema la eliminará cuando se necesite memoria en otro lugar.
4. El sistema puede destruir la actividad de la memoria pidiéndole que finalice o simplemente eliminando su proceso. Cuando se vuelve a mostrar al usuario, debe reiniciarse por completo y restaurarse a su estado anterior.

Para cada etapa, Android nos proporciona un conjunto de 7 métodos que tienen su propio significado para cada etapa del ciclo de vida. La imagen muestra una ruta de migración cada vez que una aplicación cambia de un estado a otro.

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
       
        // Bundle containing previous frozen state
        setContentView(R.layout.activity_main);
       
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
     
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
         
        // Bundle containing previous frozen state
        setContentView(R.layout.activity_main)
 
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
       
        // Bundle containing previous frozen state
        setContentView(R.layout.activity_main);
       
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onStart()
    {
        // It will show a message on the screen
        // then onStart is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onStart Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onStart() {
        super.onStart()
        // It will show a message on the screen
        // then onStart is invoked
        val toast  = Toast.makeText(applicationContext, "onStart Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
         
        // Bundle containing previous frozen state
        setContentView(R.layout.activity_main);
         
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onRestart() {
        // It will show a message on the screen
        // then onRestart is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onRestart Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onRestart() {
        super.onRestart()
        // It will show a message on the screen
        // then onRestart is invoked
        val toast = Toast.makeText(applicationContext, "onRestart Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
import com.example.share.R;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
         
        // Bundle containing previous frozen state
        super.onCreate(savedInstanceState);
 
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        setContentView(R.layout.activity_main);
 
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onResume() {
        // It will show a message on the screen
        // then onResume is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onResume Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onResume() {
        super.onResume()
        // It will show a message on the screen
        // then onResume is invoked
        val toast = Toast.makeText(applicationContext, "onResume Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
 
        // Bundle containing previous frozen state
        super.onCreate(savedInstanceState);
 
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        setContentView(R.layout.activity_main);
 
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onPause() {
        // It will show a message on the screen
        // then onPause is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onPause Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onPause() {
        super.onPause()
        // It will show a message on the screen
        // then onPause is invoked
        val toast = Toast.makeText(applicationContext, "onPause Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
 
        // Bundle containing previous frozen state
        super.onCreate(savedInstanceState);
 
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        setContentView(R.layout.activity_main);
 
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onStop() {
        // It will show a message on the screen
        // then onStop is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onStop Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onStop() {
        super.onStop()
        // It will show a message on the screen
        // then onStop is invoked
        val toast = Toast.makeText(applicationContext, "onStop Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
         
        // Bundle containing previous frozen state
        super.onCreate(savedInstanceState);
 
        // The content view pointing to the id of layout
        // in the file activity_main.xml
        setContentView(R.layout.activity_main);
 
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onDestroy() {
        // It will show a message on the screen
        // then onDestroy is invoked
        Toast toast = Toast.makeText(getApplicationContext(), "onDestroy Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onDestroy() {
        super.onDestroy()
        // It will show a message on the screen
        // then onDestroy is invoked
        val toast = Toast.makeText(applicationContext, "onDestroy Called", Toast.LENGTH_LONG).show()
    }
}

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toast toast = Toast.makeText(getApplicationContext(), "onCreate Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onStart() {
        super.onStart();
        Toast toast = Toast.makeText(getApplicationContext(), "onStart Called", Toast.LENGTH_LONG).show();
    }
 
    @Override
    protected void onRestart() {
        super.onRestart();
        Toast toast = Toast.makeText(getApplicationContext(), "onRestart Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onPause() {
        super.onPause();
        Toast toast = Toast.makeText(getApplicationContext(), "onPause Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onResume() {
        super.onResume();
        Toast toast = Toast.makeText(getApplicationContext(), "onResume Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onStop() {
        super.onStop();
        Toast toast = Toast.makeText(getApplicationContext(), "onStop Called", Toast.LENGTH_LONG).show();
    }
 
    protected void onDestroy() {
        super.onDestroy();
        Toast toast = Toast.makeText(getApplicationContext(), "onDestroy Called", Toast.LENGTH_LONG).show();
    }
}

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        val toast = Toast.makeText(applicationContext, "onCreate Called", Toast.LENGTH_LONG).show()
        }
 
    override fun onStart() {
        super.onStart()
        val toast = Toast.makeText(applicationContext, "onStart Called", Toast.LENGTH_LONG).show()
    }
 
    override fun onRestart() {
        super.onRestart()
        val toast = Toast.makeText(applicationContext, "onRestart Called", Toast.LENGTH_LONG).show()
    }
 
    override fun onPause() {
        super.onPause()
        val toast = Toast.makeText(applicationContext, "onPause Called", Toast.LENGTH_LONG).show()
    }
 
    override fun onResume() {
        super.onResume()
        val toast = Toast.makeText(applicationContext, "onResume Called", Toast.LENGTH_LONG).show()
    }
 
    override fun onStop() {
        super.onStop()
        val toast = Toast.makeText(applicationContext, "onStop Called", Toast.LENGTH_LONG).show()
    }
 
    override fun onDestroy() {
        super.onDestroy()
        val toast = Toast.makeText(applicationContext, "onDestroy Called", Toast.LENGTH_LONG).show()
    }
}