<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
  <FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    />

  <Button
    android:id="@+id/button_capture"
    android:text="Capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    />
</LinearLayout>

public class MainActivity extends Activity {

    private Camera mCamera;
    private CameraPreview mPreview;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Create an instance of Camera
        mCamera = getCameraInstance();

        // Create our Preview view and set it as the content of our activity.
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
    }
}

    private PictureCallback mPicture = new PictureCallback() {

        @Override
        public void onPictureTaken(byte[] data, Camera camera) {

            File pictureFile = new File("/sdcard/" + System.currentTimeMillis()+".jpg");
            try {
                FileOutputStream fos = new FileOutputStream(pictureFile);
                fos.write(data);
                fos.close();
            } catch (IOException e) {
                Log.d("TAG", "Error accessing file: " + e.getMessage());
            }
        }
    };

        // Add a listener to the Capture button
        Button captureButton = (Button) findViewById(R.id.button_capture);
        captureButton.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // get an image from the camera
                    mCamera.takePicture(null, null, mPicture);
                }
            }
        );