Android World: Starting new Activity in Android

An Android application, at most, contains more than one screen. But, how we can open a new screen after clicking a button, choosing a menu, or other? It is not too difficult to do in Android.

There are a few step to do, to open a new screen in android. You have to create an activity class, an xml layout, update AndroidManifest to know your second/third .. activity class, and put a code to call the new activity / screen.

An Activity class can be created with extending from Activity, ListActivity or other Activity class. Each Activity Class should have an xml layout as a view screen as a representation of the Activity Class.

Android Manifest should be updated to know the new activity / screen. so, when requested to show the new screen, it knows which class to execute.

At last you should put a piece of code to first screen, to show the new screen. Below is an example to open a new screen:

//screen1.java

package test.android;
import android.app.Activity;
import android.os.Bundle;
import android.content.Intent;
import android.widget.Button;

public class Screen1 extends Activity
{
   public void onCreate(Bundle icicle)
   {
      super.onCreate(icicle);
      setContentView(R.layout.screen1);
      Button b = (Button) findViewById(R.id.btnClick);
      b.setOnClickListener(new View.OnClickListener() {
         public void onClick(View arg0) {
         Intent i = new Intent(screen1.this, screen2.class);
         startActivity(i);
         }
      });
   }
}

//screen1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
>
<TextView
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="You are in the first Screen"
/>
<Button
   id ="@+id/btnClick"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Open New Screen"
/>

</LinearLayout>

//screen2.java

package test.android;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;

public class Screen2 extends Activity
{
   public void onCreate(Bundle icicle)
   {
      super.onCreate(icicle);
      setContentView(R.layout.screen2);
      Button b = (Button) findViewById(R.id.btnClick2);
      b.setOnClickListener(new View.OnClickListener() {
         public void onClick(View arg0) {
         setResult(RESULT_OK);
         finish();
         }
      });
   }
}

//screen2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
>
<TextView
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="You are in the New Screen"
/>
<Button
   id ="@+id/btnClick2"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Close"
/>

</LinearLayout>

//AndroidManifest.xml

</manifest>

Sunday, September 26, 2010

Starting new Activity in Android