Unfortunately system ui has stopped

Bonjour,

quand je lance mon émulateur je reçois l'erreur suivant:

"unfortunately <nom du projet > has stopped"
c'est quoi le problème s'il vous plait ??
voici mon code :
package com.formation.camera;

import java.io.File;
import java.io.FileOutputStream;

import android.app.Activity;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;
import android.view.SurfaceHolder.Callback;
import android.widget.Toast;

public class Main extends Activity implements Callback {
/** Called when the activity is first created. */
Camera camera = null;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
SurfaceView view = new SurfaceView(this);
view.getHolder().addCallback(this);
view.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
setContentView(view);
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(width, height);
parameters.setPictureFormat(PixelFormat.JPEG);
camera.setParameters(parameters);
camera.startPreview();

}

@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
camera = Camera.open();
camera.setPreviewDisplay(holder);
} catch (Exception e) {
e.printStackTrace();
}
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
camera.stopPreview();
camera.release();
camera = null;
}

@Override
public boolean onTouchEvent(MotionEvent event) {
switch(event.getAction()){
case MotionEvent.ACTION_DOWN:

PictureCallback jpegCallback = new PictureCallback() {
public void onPictureTaken(byte[] _data, Camera _camera) {
try {
File fs = new File(Main.this.getFilesDir()+"/image.jpg");
FileOutputStream fos = new FileOutputStream(fs);
fos.write(_data);
fos.flush();
fos.close();
Toast.makeText(Main.this,fs.getAbsolutePath(),0).show();
} catch (Exception e) {
e.printStackTrace();
}
camera.startPreview();
}
};
camera.takePicture(null, null, jpegCallback);
break;
}
return super.onTouchEvent(event);
}

}

mercii d'avance :)