Android Lifecycle Method

Here we are going to learn  lifecycle methods in android.

In Android Activity is controlled by 7 lifecycle methods.

If you have worked with C or C++ or Java programming  then you must have seen that your program starts with main() function.

Main is the starting point of your program.

So, in android when activity opens your onCreate method will invoke first.

We have 7 lifecycle methods in android

• onCreate
• onStart  
• onResume
• onPause
• onStop
• onRestart
• onDestroy

onCreate  methods called when activity is first opened or created.

onStart  method called when activity is visible to the user.

onResume  method called when user start interacting with the activity.

onPause method called when activity is not visible to the user.

onStop method called when activity is not  visible to the user.

(Both onPause and onStop method call at the same time)

onRestart method called when user restart activity.

onDestroy method called when activity destroyed.

Let's see example ::

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:background="#589"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="150dp"
        android:text="         Android \nLifeCycle Methods"
        android:textSize="32sp"
        />

</LinearLayout>

MainActivity.java

package com.example.malik.blog;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

public class MainActivity extends AppCompatActivity {

    public static final String USER_TAG = "USER_TAG";

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Log.e(USER_TAG, "onCreate Method Call");

    }

    @Override

    protected void onStart() {

        super.onStart();

        Log.e(USER_TAG, "onStart Method Call");

    }

    @Override

    protected void onResume() {

        super.onResume();

        Log.e(USER_TAG, "onResume Method Call");

    }

    @Override

    protected void onPause() {

        super.onPause();

        Log.e(USER_TAG, "onPause Method Call");

    }

    @Override

    protected void onStop() {

        super.onStop();

        Log.e(USER_TAG, "onStop Method Call");

    }

    @Override

    protected void onRestart() {

        super.onRestart();

        Log.e(USER_TAG, "onRestart Method Call");

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        Log.e(USER_TAG, "onDestroy Method Call");

    }

}

AndroidManifest.xml

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

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

    package="com.example.malik.blog">

    <application

        android:allowBackup="true"

        android:icon="@mipmap/ic_launcher"

        android:label="@string/app_name"

        android:roundIcon="@mipmap/ic_launcher_round"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity

            android:name=".MainActivity"

            android:screenOrientation="portrait">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

</manifest>

build.gradle

apply plugin: 'com.android.application'

android {

    compileSdkVersion 25

    buildToolsVersion "25.0.2"

    defaultConfig {

        applicationId "com.example.malik.blog"

        minSdkVersion 18

        targetSdkVersion 25

        versionCode 1

        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        }

    }

}

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])

    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {

        exclude group: 'com.android.support', module: 'support-annotations'

    })

    compile 'com.android.support:appcompat-v7:25.3.1'

    compile 'com.android.support.constraint:constraint-layout:1.0.2'

    testCompile 'junit:junit:4.12'

}