Navigation in Android

There are two primary forms of intents you will use, They are:

• Explicit Intent
• Implicit Intent

Explicit Intent:

 After writing a single Activity, There comes a need  to navigate to another activity to perform another task . For this we use Explicit Inents.

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"

    tools:context=".MainActivity" >

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentTop="true"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="111dp"

        android:text="Call Act2"

        android:textSize="20dp" />

</RelativeLayout>

act2.xml:

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

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

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="This is Activity2"

        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button

        android:id="@+id/button1back"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Back" />

</LinearLayout>

MainActivity.java:

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button b = (Button)findViewById(R.id.button1);

b.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

Intent in = new Intent(getApplicationContext(), Act2.class);

startActivity(in);

}

});

}

}

Act2.java:

public class Act2 extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

// TODO Auto-generated method stub

super.onCreate(savedInstanceState);

setContentView(R.layout.act2);

Button b = (Button)findViewById(R.id.button1back);

b.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View arg0) {

// TODO Auto-generated method stub

//startActivity(new Intent(getApplicationContext(), MainActivity.class));

finish();

}

});

}

}

AndroidManifest.xml:

  <activity android:name="Act2"></activity>

Implicit Intent:

 Implicit Intents do not specify the java class which should be called .
They specify the action which should be performed and optionally an URI which should be used for this action.
For example following tell the android system to view a webpage.
Intent intent = new Intent(Intent.ACTION_VIEW,URI.Parse("http://www.google.com"));

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"

    tools:context=".MainActivity" >

    <Button

        android:id="@+id/googleButton"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentTop="true"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="152dp"

        android:text="Google" />

</RelativeLayout>

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button gbtn= (Button)findViewById(R.id.googleButton);

gbtn.setOnClickListener(new OnClickListener() {

public void onClick(View v) {

//Intent intent = new Intent(Intent.ACTION_VIEW,URI.Parse("http://www.google.com"));

Intent webIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.com"));

startActivity(webIntent);

}

});

}

 

}