Android : how to detect drawing/swipe direction on a canvas in android?

in my app i am displaying a video. When i touch and drag on the screen it has to draw a straight line and i have to get the direction of the line. My app supports only landscape mode. I could draw a straight line on touch and drag.But i dont know how to get the direction of that line. How can i do this? Given below is my code.

 public class MainActivity extends Activity implements OnTouchListener {

ImageView view;
Bitmap bitmap;
Canvas canvas;
Paint paint;
float startX = 0, startY = 0, endX = 0, endY = 0, upx = 0, upy = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    view = (ImageView) findViewById(R.id.imageView1);
    view.setOnTouchListener(this);
    Display currentDisplay = getWindowManager().getDefaultDisplay();
    float dw = currentDisplay.getWidth();
    float dh = currentDisplay.getHeight();

    bitmap = Bitmap.createBitmap((int) dw, (int) dh,
            Bitmap.Config.ARGB_8888);
    canvas = new Canvas(bitmap);
    paint = new Paint();
    paint.setColor(Color.WHITE);
    view.setImageBitmap(bitmap);
}

@Override
public boolean onTouch(View v, MotionEvent event) {
    // TODO Auto-generated method stub
    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        startX = event.getX();
        startY = event.getY();
        break;
    case MotionEvent.ACTION_MOVE:
        upx = event.getX();
        upy = event.getY();
        //canvas.drawLine(startX, startY, upx, upy, paint);
        if(Math.abs(upx-startX)<Math.abs(upy-startY))
         canvas.drawLine(startX, startY,startX, upy, paint);
        else
         canvas.drawLine(startX, startY,upx, startY, paint);
        view.invalidate();
        break;
    case MotionEvent.ACTION_UP:
        endX = event.getX();
        endY = event.getY();
        view.invalidate();
        calculateDistanceAndDirection();
        hideDrawing();
        break;
    }
    return true;
}

private void hideDrawing() {
    view.postDelayed(new Runnable() {
        @Override
        public void run() {
            canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
            view.invalidate();
        }
    }, 500);
}

private void calculateDistanceAndDirection() {
    double dist = Math.sqrt(Math.pow((startX - endX), 2)
            + Math.pow((startY - endY), 2));
    Toast.makeText(this, "distance is: " + dist, Toast.LENGTH_SHORT).show();

}

}