How to create a flash light on Android

I always wonder the use of a flash light on a phone. This simple app is more useful than anything. So here is the code to build a flashlight app,

MainActivity.java

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageButton;
public class MainActivity extends Activity {
 
    ImageButton btnSwitch;
    private Camera camera;
    private boolean isFlashOn;
    private boolean hasFlash;
    Parameters params;
    MediaPlayer mp;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        // flash switch button
        btnSwitch = (ImageButton) findViewById(R.id.imageflash);
 
     
        // First check if device is supporting flashlight or not        
        hasFlash = getApplicationContext().getPackageManager()
                .hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
 
        if (!hasFlash) {
            // device doesn't support flash
            // Show alert message and close the application
            AlertDialog alert = new AlertDialog.Builder(MainActivity.this)
                    .create();
            alert.setTitle("Error");
            alert.setMessage("Sorry, your device doesn't support flash light!");
            alert.setButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    // closing the application
                    finish();
                }
            });
            alert.show();
            return;
        }
        getCamera();
    // Switch button click event to toggle flash on/off
    btnSwitch.setOnClickListener(new View.OnClickListener() {
 
         @Override
         public void onClick(View v) {
            if (isFlashOn) {
            // turn off flash
                turnOffFlash();
                } else {
            // turn on flash
                turnOnFlash();
                }
            }
        });
    }
 
    // Get the camera
    private void getCamera() {
        if (camera == null) {
            try {
                camera = Camera.open();
                params = camera.getParameters();
            } catch (RuntimeException e) {
                Log.e("Camera Error. Failed to Open. Error: ", e.getMessage());
            }
        }
    }
 
    // Turning On flash
    private void turnOnFlash() {
        if (!isFlashOn) {
            if (camera == null || params == null) {
                return;
            }      
            params = camera.getParameters();
            params.setFlashMode(Parameters.FLASH_MODE_TORCH);
            camera.setParameters(params);
            camera.startPreview();
            isFlashOn = true;         
        }
 
    }
    // Turning Off flash
    private void turnOffFlash() {
        if (isFlashOn) {
            if (camera == null || params == null) {
                return;
            }    
            params = camera.getParameters();
            params.setFlashMode(Parameters.FLASH_MODE_OFF);
            camera.setParameters(params);
            camera.stopPreview();
            isFlashOn = false;         
         
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
    }
 
    @Override
    protected void onPause() {
        super.onPause();
         
        // on pause turn off the flash
        turnOffFlash();
    }
 
    @Override
    protected void onRestart() {
        super.onRestart();
    }
    @Override
    protected void onStop() {
        super.onStop();
         
        // on stop release the camera
        if (camera != null) {
            camera.release();
            camera = null;
        }
    }
 
}

Activity_main_layout.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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.flashlight.MainActivity$PlaceholderFragment" >
   <ImageButton
       android:id="@+id/imageflash"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:src="@drawable/ic_launcher"
       android:layout_centerInParent="true"/>
</RelativeLayout>