OnTouchListener

gistfile1.java

public class MainActivity extends Activity implements OnTouchListener {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        GridView gv = (GridView) findViewById(R.id.grid);
        gv.setOnTouchListener(this); // Uses onTouch override
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        boolean defaultResult = v.onTouchEvent(event);
        switch(event.getAction()){
            case MotionEvent.ACTION_DOWN: {
                downX = event.getX();
                downY = event.getY();
                return true;
            }
            case MotionEvent.ACTION_UP: {
                upX = event.getX();
                upY = event.getY();

                float deltaX = downX - upX;
                float deltaY = downY - upY;

                if((Math.abs(deltaX) > MIN_DISTANCE) || (Math.abs(deltaY) > MIN_DISTANCE)){
                    if (Math.abs(deltaX) > Math.abs(deltaY)) {
                        if(deltaX < 0) { Log.i(logTag, "LeftToRight"); return true; }
                        if(deltaX > 0) { Log.i(logTag, "RightToLeft"); return true; }
                    }

                    if (Math.abs(deltaX) < Math.abs(deltaY)) {
                        if(deltaY < 0) { Log.i(logTag, "TopToBottom"); return true; }
                        if(deltaY > 0) { Log.i(logTag, "BottomToTop"); return true; }
                    }
                } else {
                        Log.i(logTag, "Swipe was only " + Math.abs(deltaX) + " long, need at least " + MIN_DISTANCE);
                        return false;
                }
                return false;
            }
            default:
            return defaultResult;
        }
    }

}