Hello World in Android

How to create your first application in Android:

Create a Project :

• Go to File click on new and choose Android application Project.
• Give a Application name.
• Click on Next -> Next -> Next -> Next -> finish.

Create an Activity :

Project is created. Go to src folder.

Open MainActivity.java.

public class MainActivity extends Activity {

       Button register;

       @Override

       protected void onCreate(Bundle savedInstanceState) {

              super.onCreate(savedInstanceState);

          setContentView(R.layout.activity_main);

}

       @Override

       public boolean onCreateOptionsMenu(Menu menu) {

              // Inflate the menu; this adds items to the action bar if it is present.

              getMenuInflater().inflate(R.menu.main, menu);

              return true;

       }

}

Class is extending an Activity class.

Every class which will be an activity must extends Activity class.

Override the onCreate method.

About Layout:

Activity in android doesn't contain anything of its own.

It loads xml layout view on the activity page.

                setContentView(R.layout.activity_main);

      

      Here, activity_main is an xml file

Edit Layout(activity_main.xml):

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

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world" />

</RelativeLayout>

Change XML File:

• Previous figure shows the graphical view of an activity.
• Go to XML view.
• Change the android:text project of textview.
• To change go to strings.xml file in values folder.

                <string name="hello_world">Hello welcome to world of android!</string>

Save and Run the project

• Save the changes and right click on the project.
• Choose run as - > Android application project.
• Wait some time. Project will run on emulator.

Reach us At: - 0120-4029000 / 24 / 25 / 27 / 29 Mbl: 9953584548

Write us at: - smruti@apextgi.com and pratap@apextgi.com