Android Activity Lifecycle

Android Activity Lifecycle with examples of Activity and Intent, Fragments, Menu, Service, alarm manager, storage, sqlite, xml, json, multimedia, speech, web service, telephony, animation and graphics

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Android Activity Lifecycle

Android Activity Lifecycle is controlled by 7 methods of android.app.Activity class. The android Activity is the subclass of ContextThemeWrapper class.

An activity is the single screen in android. It is like window or frame of Java.

By the help of activity, you can place all your UI components or widgets in a single screen.

The 7 lifecycle method of Activity describes how activity will behave at different states.

Android Activity Lifecycle methods

Let's see the 7 lifecycle methods of android activity.

Method	Description
onCreate	called when activity is first created.
onStart	called when activity is becoming visible to the user.
onResume	called when activity will start interacting with the user.
onPause	called when activity is not visible to the user.
onStop	called when activity is no longer visible to the user.
onRestart	called after your activity is stopped, prior to start.
onDestroy	called before the activity is destroyed.

File: activity_main.xml

Android Activity Lifecycle Example

It provides the details about the invocation of life cycle methods of activity. In this example, we are displaying the content on the logcat.

File: MainActivity.java

package example.TheDeveloperBlog.com.activitylifecycle;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("lifecycle","onCreate invoked");
    }
    @Override
    protected void onStart() {
        super.onStart();
        Log.d("lifecycle","onStart invoked");
    }
    @Override
    protected void onResume() {
        super.onResume();
        Log.d("lifecycle","onResume invoked");
    }
    @Override
    protected void onPause() {
        super.onPause();
        Log.d("lifecycle","onPause invoked");
    }
    @Override
    protected void onStop() {
        super.onStop();
        Log.d("lifecycle","onStop invoked");
    }
    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d("lifecycle","onRestart invoked");
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d("lifecycle","onDestroy invoked");
    }
}

Output:

You will not see any output on the emulator or device. You need to open logcat.

Now see on the logcat: onCreate, onStart and onResume methods are invoked.

android activity life cycle example output 2

Now click on the HOME Button. You will see onPause method is invoked.

android activity life cycle example output 3

After a while, you will see onStop method is invoked.

android activity life cycle example output 4

Now see on the emulator. It is on the home. Now click on the center button to launch the app again.

android activity life cycle example output 5

Now click on the lifecycleactivity icon.

android activity life cycle example output 6

Now see on the logcat: onRestart, onStart and onResume methods are invoked.

android activity life cycle example output 7

If you see the emulator, application is started again.

android activity life cycle example output 8

Now click on the back button. Now you will see onPause methods is invoked.

android activity life cycle example output 9

After a while, you will see onStop and onDestroy methods are invoked.

android activity life cycle example output 10

The onCreate() and onDestroy() methods are called only once throughout the activity lifecycle.

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TheDeveloperBlog.com

Android Activity Lifecycle

Android Activity Lifecycle

Android Activity Lifecycle methods

Android Activity Lifecycle Example

Output:

The onCreate() and onDestroy() methods are called only once throughout the activity lifecycle.

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