Intent with its different use

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class Example extends Activity {
    /** Called when the activity is first created. */
   
Button b1,b2,b3,b4;
int requestcode=1;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        b1=(Button)findViewById(R.id.button1);
     
        b1.setOnClickListener(new OnClickListener()
        {

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Intent i=new Intent(android.content.Intent.ACTION_VIEW,Uri.parse("http://www.google.com"));
startActivity(i);

}
       
        });
        b2=(Button)findViewById(R.id.button2);
        b2.setOnClickListener(new OnClickListener()
        {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i1=new Intent(android.content.Intent.ACTION_DIAL,Uri.parse("tel:+8095880668"));
startActivity(i1);

}
       
        });
        b3=(Button)findViewById(R.id.button3);
        b3.setOnClickListener(new OnClickListener()
        {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub

Intent i2 = new Intent(android.content.Intent.ACTION_VIEW,Uri.parse("geo:37.827500,-122.481670"));
startActivity(i2);
}
       
        });
        b4=(Button)findViewById(R.id.button4);
        b4.setOnClickListener(new OnClickListener()
        {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i3=new Intent(android.content.Intent.ACTION_PICK);
i3.setType(ContactsContract.Contacts.CONTENT_TYPE);
startActivityForResult(i3,requestcode);
}
       
        });
    }
    public void onActivityResult(int requestCode, int resultCode, Intent data)
    {
    if (requestCode == requestcode)
    {
    if (resultCode == RESULT_OK)
    {
    Toast.makeText(this,data.getData().toString(),
    Toast.LENGTH_SHORT).show();
    Intent i = new Intent(
    android.content.Intent.ACTION_VIEW,
    Uri.parse(data.getData().toString()));
    startActivity(i);
    }
    }
    }
}