This video tutorial describes how to capture an image using device camera.
To captured an Image using device camera use to following code:-

private static int REQ_CAMERA = 1001;

Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
     startActivityForResult(takePictureIntent, REQ_CAMERA);
 }

To get the thumbnail of captured image override the onActivityResult() method of an activity class like this:-

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQ_CAMERA && resultCode == RESULT_OK) {
     Bundle extras = data.getExtras();
     Bitmap imageBitmap = (Bitmap) extras.get("data");
     // Now add this bitmap in the image view
    }
}