Acitvity LifeCycle of Android Application

This tutorial explains how android activity lifecycle works. Activity is a window that contains the user interface of your application.

To create an activity your class need to extends Activty base class.An Application has more than on activity . Activity base class contains events that governs the life cycle of an activity.

• onCreate () : Called when the activity is first created.
• onStart(): Called when the activity become visible to the user.
• onResume(): Called when the activity start interacting with the user.
• onPause(): Called when the current activity is being paused and the previous activity is being resumed.
• onStop(): Called when the activity is no longer visible to the user.
• onDestroy(): Called before the activity is destroyed by the system.
• onRestart(): Called when the activity has been stoped and is restarting again.

Step 1:
Create a project with the following details:

ProjectName      :            LifeCycle

PackageName    :            sat.tuts4mobile.lifecycle

ActivityName        :                LifeCycleActivity  

Step 2:

In the LifeCycleActivity.java file , add the following code:

package sat.tuts4mobile.lifecycle;

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

import android.widget.Toast;

public class LifeCycleActivity extends Activity {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

       

        Toast.makeText(LifeCycleActivity.this,"ON CREATE", Toast.LENGTH_SHORT).show();

       

    }

   

    @Override

    protected void onStart() {

       // TODO Auto-generated method stub

       super.onStart();

      

        Toast.makeText(LifeCycleActivity.this,"ON START", Toast.LENGTH_SHORT).show();

    }

   

    @Override

    protected void onResume() {

       // TODO Auto-generated method stub

       super.onResume();

   

        Toast.makeText(LifeCycleActivity.this,"ON RESUME", Toast.LENGTH_SHORT).show();

    }

   

    @Override

    protected void onPause() {

       // TODO Auto-generated method stub

       super.onPause();

   

        Toast.makeText(LifeCycleActivity.this,"ON PAUSE", Toast.LENGTH_SHORT).show();

    }

   

    @Override

    protected void onRestart() {

       // TODO Auto-generated method stub

       super.onRestart();

      

        Toast.makeText(LifeCycleActivity.this,"ON RESTART", Toast.LENGTH_SHORT).show();

    }

   

    @Override

    protected void onStop() {

       // TODO Auto-generated method stub

       super.onStop();

      

        Toast.makeText(LifeCycleActivity.this,"ON STOP", Toast.LENGTH_SHORT).show();

    }

   

    @Override

    protected void onDestroy() {

       // TODO Auto-generated method stub

       super.onDestroy();

      

        Toast.makeText(LifeCycleActivity.this,"ON DESTROY", Toast.LENGTH_SHORT).show();

    }

   

}

Step 3:

When you run the following code , you see when the application starts there are three toast messages comes after one another.

First is ON CREATE , second is ON START and third is ON RESUME.

When you press the home button from the emulator , ON PAUSE and ON STOP methods call.

And when you opens the application again ON RESTART , ON START and ON RESUME methods call.

And in last when you press the back button from emulator , ON PAUSE , ON STOP and ON DESTROY method calls

Click here to download source code of application.