how to make search function with edittext . i have four edit

package com.example.indradeo;
import android.app.Activity;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.content.Intent;

public class MainActivity extends  Activity implements OnClickListener
    {
        EditText editRollno, editName, editMarks;
        Button  btnView;
        SQLiteDatabase db;
        /** Called when the activity is first created. */
 @Override
 public void onCreate (Bundle savedInstanceState)
        {
            super.onCreate( savedInstanceState );
            setContentView( R.layout.activity_main );
            editRollno = (EditText) findViewById( R.id.editRollno );
            editName = (EditText) findViewById( R.id.editName );
            editMarks = (EditText) findViewById( R.id.editMarks );

            btnView = (Button) findViewById( R.id.btnView );


            btnView.setOnClickListener( this );

            db = openOrCreateDatabase( "StudentDB", Context.MODE_PRIVATE, null );
            db.execSQL( "CREATE TABLE IF NOT EXISTS student(rollno VARCHAR,name VARCHAR,marks VARCHAR);" );
        }
        public void onClick (View view)
        {



            if (view == btnView) {
                if (editRollno.getText().toString().trim().length() == 0) {
                    showMessage( "Error", "Please enter Emp.ID" );
                    return;
                }
                Cursor c = db.rawQuery( "SELECT * FROM student WHERE rollno='" + editRollno.getText() + "'", null );
                if (c.moveToFirst()) {
                    editName.setText( c.getString( 1 ) );
                    editMarks.setText( c.getString( 2 ) );
                } else {
                    showMessage( "Error", "Invalid Emp.ID" );
                    clearText();
                }
                String username = editRollno.getText().toString()+"\n";
                String location = editName.getText().toString();
                String designation = editMarks.getText().toString();

                //dbHandler.insertUserDetails(username,location,designation);
               // intent = new Intent(MainActivity.this,DetailsActivity.class);
                //startActivity(intent);
                //Toast.makeText(getApplicationContext(), "Details fatch Inserted Successfully",Toast.LENGTH_SHORT).show();
 }


        }
        public void showMessage (String title, String message)
        {
            Builder builder = new Builder( this );
            builder.setCancelable( true );
            builder.setCancelable( true );
            builder.setTitle( title );
            builder.setMessage( message );
            builder.show();
        }
        public void clearText ()
        {
            editRollno.setText( "" );
            editName.setText( "" );
            editMarks.setText( "" );
            editRollno.requestFocus();
        }
    }

xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout 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:id="@+id/myLayout"
 android:stretchColumns="0"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent">
    <TextView
 android:layout_width="147dp"
 android:layout_height="33dp"
 android:layout_x="130dp"
 android:layout_y="206dp"
 android:text="@string/title" />

    <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_x="7dp"
 android:layout_y="310dp"
 android:text="@string/roll_no" />

    <EditText
 android:id="@+id/editRollno"
 android:layout_width="150dp"
 android:layout_height="40dp"
 android:layout_x="257dp"
 android:layout_y="297dp"
 android:inputType="number" />

    <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_x="10dp"
 android:layout_y="370dp"
 android:text="@string/name" />

    <EditText
 android:id="@+id/editName"
 android:layout_width="150dp"
 android:layout_height="40dp"
 android:layout_x="254dp"
 android:layout_y="367dp"
 android:inputType="text" />

    <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_x="2dp"
 android:layout_y="443dp"
 android:text="@string/marks" />

    <EditText
 android:id="@+id/editMarks"
 android:layout_width="150dp"
 android:layout_height="40dp"
 android:layout_x="254dp"
 android:layout_y="442dp"
 android:inputType="number" />

    <Button
 android:id="@+id/btnView"
 android:layout_width="100dp"
 android:layout_height="40dp"
 android:layout_x="287dp"
 android:layout_y="508dp"
 android:text="@string/Search" />


AbsoluteLayout>