public class MainActivity extends AppCompatActivity {

    ImageButton btnSwitch;
    private Camera camera;
    private boolean isFlashOn, hasFlash;
    private MediaPlayer mp;
    private Camera.Parameters params;

    protected void onCreate(Bundle b) {
        super.onCreate(b);
        setContentView(R.layout.activity_main);
        // flash switch button
        btnSwitch = (ImageButton) findViewById(R.id.btnSwitch);
        // First check if device is supporting flashlight or not
        hasFlash = getApplicationContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
        if (!hasFlash) {
            AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
            builder.setTitle("Error")
                    .setMessage("Sorry, your device doesn't support flash light!")
                    .setCancelable(false)
                    .setNegativeButton
                            ("Close", new DialogInterface.OnClickListener() {
                                        public void onClick(DialogInterface dialog, int id) {
                                            finish();
                                        }
                                    }
                            );
            AlertDialog alert = builder.create();
            alert.show();
            return;
        }
        // get the camera
        getCamera();
        // displaying button image
        toggleButtonImage();
        // Switch button click event to toggle flash on/off
        btnSwitch.setOnClickListener
                (new View.OnClickListener() {
                     public void onClick(View v) {
                         if (isFlashOn) {
                             // turn off flash
                             turnOffFlash();
                         } else {
                             // turn on flash
                             turnOnFlash();
                         }
                     }
                 }
                );
    }

    protected void getCamera() {
        if (camera == null) {
            try {
                camera = Camera.open();
                params = camera.getParameters();
            } catch (RuntimeException e) {
                Log.e("Failed to Open. Error: ", e.getMessage());
            }
        }
    }

    protected void turnOnFlash() {
        if (!isFlashOn) {
            if (camera == null || params == null) {
                return;
            }
            // play sound
            playSound();
            params = camera.getParameters();
            params.setFlashMode(android.hardware.Camera.Parameters.FLASH_MODE_TORCH);
            camera.setParameters(params);
            camera.startPreview();
            isFlashOn = true;
            // changing button/switch image
            toggleButtonImage();
        }
    }

    protected void turnOffFlash() {
        if (isFlashOn) {
            if (camera == null || params == null) {
                return;
            }
            // play sound
            playSound();
            params = camera.getParameters();
            params.setFlashMode(android.hardware.Camera.Parameters.FLASH_MODE_OFF);
            camera.setParameters(params);
            camera.stopPreview();
            isFlashOn = false;
            // changing button/switch image
            toggleButtonImage();
        }
    }

    protected void playSound() {
        if (isFlashOn) {
            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_off);
        } else {
            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_on);
        }
        mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            public void onCompletion(MediaPlayer mp) {
                // TODO Auto-generated method stub
                mp.release();
            }
        });
        mp.start();
    }

    protected void toggleButtonImage() {
        if (isFlashOn) {
            btnSwitch.setImageResource(R.drawable.btn_switch_on);
        } else {
            btnSwitch.setImageResource(R.drawable.btn_switch_off);
        }
    }

    protected void onDestroy() {
        super.onDestroy();
    }

    protected void onPause() {
        super.onPause();
        // on pause turn off the flash
        turnOffFlash();
    }

    protected void onRestart() {
        super.onRestart();
    }

    protected void onResume() {
        super.onResume();
        // on resume turn on the flash
        if (hasFlash)
            turnOnFlash();
    }

    protected void onStart() {
        super.onStart();
        // on starting the app get the camera params
        getCamera();

    }

    protected void onStop() {
        super.onStop();
        // on stop release the camera
        if (camera != null) {
            camera.release();
            camera = null;
        }
    }

}