void BackButton_Clicked (object sender, EventArgs e)
{
SyllableBackCard backcard=new SyllableBackCard(mCharacter.Split('/')[0],mRoot, this);
Navigation.PushAsync(backcard);
Navigation.RemovePage (this);
}
void TapGestureRecognizer_Tapped (object sender, EventArgs e)
{
SyllableBackCard backcard=new SyllableBackCard(mKana,mRoot, this);
Navigation.PushAsync(backcard);
Navigation.RemovePage (this);
}