Built-in ScrollView that scrolls with a head movement

Question

Saying "ok glass" calls up a list of commands that automatically scrolls based on the user's head movement.

Is there a built-in user interface element in the GDK that implements this? Or will I have to write my own code that uses sensors?

Answer 1

I tried to redefine parts of this. It's not as brilliant as Google, but they can serve as a starting point:

https://github.com/pscholl/glass_snippets/blob/master/lib/src/main/java/de/tud/ess/HeadListView.java https://github.com/pscholl/glass_snippets/blob/master/lib /src/main/java/de/tud/ess/HeadScrollView.java

Answer 2

I went through the GDK Developer Guides at https://developers.google.com/glass/develop/gdk/dev-guides and the link https://developers.google.com/glass/develop/gdk/reference/index and there is no GDK built-in user interface elements such as the XE 12 released in December 2013.

So, the answer at the moment is yes, you should use sensors to implement it.

Answer 3

There is currently no GDK user interface element for scrolling through a list using sensors (in fact, according to this problem , using ListView generally seems discouraged).

However, I was able to get the following to work well enough in my application . My list is fixed on 4 elements (which helps to determine how much scrolling happens), so you can configure it accordingly (see Comments).

 import com.google.android.glass.media.Sounds; import com.google.android.glass.touchpad.Gesture; import com.google.android.glass.touchpad.GestureDetector; import android.content.Context; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.media.AudioManager; import android.view.MotionEvent; import android.widget.ListView; /** * Implements sensor-based scrolling of a ListView */ public class SensorListController implements SensorEventListener, GestureDetector.BaseListener { static final String TAG = "SensorListController"; Context mContext; ListView mList; SensorManager mSensorManager; private float[] mRotationMatrix = new float[16]; private float[] mOrientation = new float[9]; private float[] history = new float[2]; private float mHeading; private float mPitch; boolean mActive = true; GestureDetector mGestureDetector; public SensorListController(Context context, ListView list) { this.mContext = context; this.mList = list; history[0] = 10; history[1] = 10; mGestureDetector = new GestureDetector(mContext); mGestureDetector.setBaseListener(this); } /** * Receive pass-through of event from View */ public boolean onMotionEvent(MotionEvent event) { return mGestureDetector.onMotionEvent(event); } @Override public boolean onGesture(Gesture gesture) { switch (gesture) { case TWO_LONG_PRESS: // Toggle on and off accelerometer control of the list by long press playSuccessSound(); toggleActive(); return true; case TWO_TAP: // Go to top of the list playSuccessSound(); scrollToTop(); return true; } return false; } /** * Should be called from the onResume() of Activity */ public void onResume() { mSensorManager = (SensorManager) mContext.getSystemService(Context.SENSOR_SERVICE); mSensorManager.registerListener(this, mSensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR), SensorManager.SENSOR_DELAY_UI); } /** * Should be called from the onPause() of Activity */ public void onPause() { mSensorManager.unregisterListener(this); } /** * Toggles whether the controller modifies the view */ public void toggleActive() { mActive = !mActive; } @Override public void onSensorChanged(SensorEvent event) { if (mList == null || !mActive) { return; } if (event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR) { SensorManager.getRotationMatrixFromVector(mRotationMatrix, event.values); SensorManager.remapCoordinateSystem(mRotationMatrix, SensorManager.AXIS_X, SensorManager.AXIS_Z, mRotationMatrix); SensorManager.getOrientation(mRotationMatrix, mOrientation); mHeading = (float) Math.toDegrees(mOrientation[0]); mPitch = (float) Math.toDegrees(mOrientation[1]); float xDelta = history[0] - mHeading; // Currently unused float yDelta = history[1] - mPitch; history[0] = mHeading; history[1] = mPitch; float Y_DELTA_THRESHOLD = 0.13f; // Log.d(TAG, "Y Delta = " + yDelta); int scrollHeight = mList.getHeight() / 19; // 4 items per page, scroll almost 1/5 an item // Log.d(TAG, "ScrollHeight = " + scrollHeight); if (yDelta > Y_DELTA_THRESHOLD) { // Log.d(TAG, "Detected change in pitch up..."); mList.smoothScrollBy(-scrollHeight, 0); } else if (yDelta < -Y_DELTA_THRESHOLD) { // Log.d(TAG, "Detected change in pitch down..."); mList.smoothScrollBy(scrollHeight, 0); } } } @Override public void onAccuracyChanged(Sensor sensor, int accuracy) { } private void scrollToTop() { mList.smoothScrollToPosition(0); } private void playSuccessSound() { // Play sound to acknowledge action AudioManager audio = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE); audio.playSoundEffect(Sounds.SUCCESS); } } 

I used above in ListActivity . I initialize it in onCreate() , and here this method initializes it:

 private void initListController() { mListView = getListView(); mListView.setChoiceMode(ListView.CHOICE_MODE_NONE); mListView.setSelector(android.R.color.transparent); mListView.setClickable(true); mListController = new SensorListController(this, mListView); } 

It also removes the selection indicator from the view, making it transparent.

The above controller also uses two fingers to pause / resume scrolling and two fingers to scroll to the top of the list (and confirms both of these actions with sound). Please note that for these gestures you need to override onGenericMotionEvent() in your activity and go through the event, for example:

 @Override public boolean onGenericMotionEvent(MotionEvent event) { // We need to pass events through to the list controller if (mListController != null) { return mListController.onMotionEvent(event); } return false; } 

The full source code for this solution can be seen on Github and the APK can be downloaded.