Running State Changing Example

Different States of an Android Activity

Methords

 @Override

    protected void onStart() {

        super.onStart();

        Log.i(TAG, "onStart");

    }

    @Override

    protected void onResume() {

        super.onResume();

        Log.i(TAG, "onResume");

    }

    @Override

    protected void onPause() {

        super.onPause();

        Log.i(TAG, "onPause");

    }

    @Override

    protected void onStop() {

        super.onStop();

        Log.i(TAG, "onStop");

    }

    @Override

    protected void onRestart() {

        super.onRestart();

        Log.i(TAG, "onRestart");

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        Log.i(TAG, "onDestroy");

    }

    @Override

    protected void onSaveInstanceState(Bundle outState) {

        super.onSaveInstanceState(outState);

        Log.i(TAG, "onSaveInstanceState");

    }

    @Override

    protected void onRestoreInstanceState(Bundle savedInstanceState) {

        super.onRestoreInstanceState(savedInstanceState);

        Log.i(TAG, "onRestoreInstanceState");

    }

If you have abstract methods to implement, press Alt+Enter over class name to open a wizard. Otherwise, for overriding a function, just start typing the name of your method (without any access attribute or type), anywhere in your class scope. Then, Android Studio should suggest you overridable methods.

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Method Overriding in Java

If subclass (child class) has the same method as declared in the parent class, it is known as method overriding in java.

In other words, If subclass provides the specific implementation of the method that has been provided by one of its parent class, it is known as method overriding.

Usage of Java Method Overriding

• Method overriding is used to provide specific implementation of a method that is already provided by its super class.
• Method overriding is used for runtime polymorphism

Rules for Java Method Overriding

1. method must have same name as in the parent class
2. method must have same parameter as in the parent class.
3. must be IS-A relationship (inheritance).

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Example of adding different activity in my android application

package com.example.root.myfirstandroidapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.util.Log;


public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MyActivity";

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.i(TAG,"onCreate");
    }

    @Override    protected void onStart() {
        super.onStart();
        Log.i(TAG, "onStart");
    }


    @Override    protected void onResume() {
        super.onResume();
        Log.i(TAG, "onResume");
    }


    @Override    protected void onPause() {
        super.onPause();
        Log.i(TAG, "onPause");
    }


    @Override    protected void onStop() {
        super.onStop();
        Log.i(TAG, "onStop");
    }


    @Override    protected void onRestart() {
        super.onRestart();
        Log.i(TAG, "onRestart");
    }


    @Override    protected void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "onDestroy");
    }


    @Override    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        Log.i(TAG, "onSaveInstanceState");
    }


    @Override    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        Log.i(TAG, "onRestoreInstanceState");
    }


    public void onButtonClick(View V){

        EditText e1 = (EditText)findViewById(R.id.editText);
        EditText e2 = (EditText)findViewById(R.id.editText2);
        EditText e3 = (EditText)findViewById(R.id.editText3);

        int num1 = Integer.parseInt(e1.getText().toString());
        int num2 = Integer.parseInt(e2.getText().toString());

        int sum = num1+num2;

       
        e3.setText(Integer.toString(sum));

       
    }

}

Log details of above code run

06-29 11:12:48.872 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onCreate

06-29 11:12:48.872 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onStart

06-29 11:12:48.872 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onResume

06-29 11:28:18.959 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onPause

06-29 11:28:19.037 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onStop

06-29 11:28:19.037 2996-2996/com.example.root.myfirstandroidapplication I/MyActivity: onDestroy