Show toast widget underneath a view

android.widget.Toast defines a bunch of useful methods that allow customizing look and feel of a toast notification. Method you should look into is setGravity(int, int, int). With 0 offsets code below will anchor toast top to the bottom of the provided view and toast center to the center of the view.

public static void positionToast(Toast toast, View view, Window window, int offsetX, int offsetY) {
    // toasts are positioned relatively to decor view, views relatively to their parents, we have to gather additional data to have a common coordinate system
    Rect rect = new Rect();
    window.getDecorView().getWindowVisibleDisplayFrame(rect);
    // covert anchor view absolute position to a position which is relative to decor view
    int[] viewLocation = new int[2];
    view.getLocationInWindow(viewLocation);
    int viewLeft = viewLocation[0] - rect.left;
    int viewTop = viewLocation[1] - rect.top;

    // measure toast to center it relatively to the anchor view
    DisplayMetrics metrics = new DisplayMetrics();
    window.getWindowManager().getDefaultDisplay().getMetrics(metrics);
    int widthMeasureSpec = MeasureSpec.makeMeasureSpec(metrics.widthPixels, MeasureSpec.UNSPECIFIED);
    int heightMeasureSpec = MeasureSpec.makeMeasureSpec(metrics.heightPixels, MeasureSpec.UNSPECIFIED);
    toast.getView().measure(widthMeasureSpec, heightMeasureSpec);
    int toastWidth = toast.getView().getMeasuredWidth();

    // compute toast offsets
    int toastX = viewLeft + (view.getWidth() - toastWidth) / 2 + offsetX;
    int toastY = viewTop + view.getHeight() + offsetY;

    toast.setGravity(Gravity.LEFT | Gravity.TOP, toastX, toastY);
}

Using it will require modifying toast related lines in your onClick method:

int offsetY = getResources().getDimensionPixelSize(R.dimen.toast_offset_y);

Toast toast = Toast.makeText(MainActivity.this, "That number is greater than 100. Not Valid!", Toast.LENGTH_SHORT);
positionToast(toast, v, getWindow(), 0, offsetY);
toast.show();