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: