Functionality:

How to interact with activity,when a button is clicked,navigate from current screen(current activity) to another screen(another activity).

Activity:

In android,an activity is representing a single screen.Most applications have multiple activities to represent different screens.for example,one activity to display a list of the application settings,another to display application status.

To Create any application in android we have to deal with three files:

• AndroidManifest.xml
• activity_main.xml
• MainActivity.java

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.nav.navigation"
    >
   <application
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
    android:label="@string/title_activity_main" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<activity android:name="Second_screen"></activity>
    </application>
</manifest>

Strings.xml:

<resources>
    <string name="app_name">Navigation</string>
    <string name="hello_world">Hello world!</string>
    <string name="menu_settings">Settings</string>
    <string name="title_activity_main">MainActivity</string>
    <string name="button_name">Go to second screen</string>
    <string name="title1">Welcome to Navigation (First screen)</string>
    <string name="title2">Welcome to Navigation (second screen)</string>
</resources>

In this example,we have to navigate from one to another screen so we need to create two layout files and two java files.

activity_main.xml:

This is layout file which represents first screen.First screen contains one textview and button.Textview is texted as “Welcome to Navigation” and button texted as “Go To second screen”.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/head"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="26dp"
    android:text="@string/title1"  />

    <Button
        android:id="@+id/first_screen_button"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/head"
    android:layout_marginTop="16dp"
    android:text="@string/button_name"
        />
</RelativeLayout>

MainActivity.java:

This java file contains code to navigate to second screen.file has OnClickListener which make Button click to go to second screen.

package com.nav.navigation;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {
    private Button nextScreen;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        nextScreen = (Button) findViewById(R.id.first_screen_button);
        nextScreen.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent agn = new Intent(MainActivity.this, Second_screen.class);
                startActivity(agn);
            }
        });
    }
    public void onClick(View v) {
    }
}

second_screen.xml:

This is layout file which represents second screen.second screen contains one textview.Textview is texted as “Welcome to Second Screen”.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/head"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="@string/title2"/>
</RelativeLayout>

Second_screen.java

This java file contains code of action to be performed after clicking on button in first screen.

package com.nav.navigation;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
public class Second_screen extends Activity implements OnClickListener {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.second_screen);
        TextView tv = new TextView(this);
        tv.setText("Welcome to Second screen");
        setContentView(tv);
    }
    public void onClick(View v) {
    }
}

Output: