FaceActivity.java

public class FaceActivity extends Activity implements Camera.FaceDetectionListener{

    String TAG = this.getClass().getName();
    private CameraPreview mPreview;
    private Camera mCamera;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_face);

        if (!checkCameraHardware(this))finish();

        mCamera = getCameraInstance();

        if (mCamera == null)finish();

        mPreview = new CameraPreview(this, mCamera);

        FrameLayout preview = (FrameLayout)findViewById(R.id.camera_preview);

        preview.addView(mPreview);

    }

    @Override
    protected void onDestroy(){
        super.onDestroy();
        try {
            mCamera.release();
        } catch (Exception e){

        }
    }

    /** Check if this device has a camera */
    private boolean checkCameraHardware(Context context) {
        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
            // this device has a camera
            return true;
        } else {
            // no camera on this device
            return false;
        }
    }

    /** A safe way to get an instance of the Camera object. */
    public static Camera getCameraInstance(){
        Camera c = null;
        try {
            c = Camera.open(); // attempt to get a Camera instance
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }

    @Override
    public void onFaceDetection(Camera.Face[] faces, Camera camera) {
        if (faces.length > 0){
            Camera.Face f = faces[0];
            Log.v(TAG, ("Detected" + faces.length + "faces，the ID of first face is：" + f.id ));

            Log.v(TAG, "leftEye : " + f.leftEye);
            Log.v(TAG, "mouth   : " + f.mouth);
            Log.v(TAG, "rect    : " + f.rect);
            Log.v(TAG, "rightEye: " + f.rightEye);

            mCamera.stopFaceDetection();
        }
    }

    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
    public void onClick(View v){
        switch (v.getId()){
            case R.id.button_capture:
                mCamera.setFaceDetectionListener(this);
                mCamera.startFaceDetection();
                break;
        }
    }
}