Android：如何在主活动文件中单击按钮时重定向到片段类？

public void addListenerOnButton()
{
    final Context context = this;
    inquiry = (Button)findViewById(R.id.btnInquiry);
    link = (Button)findViewById(R.id.btnLink);
    inquiry.setOnClickListener(new OnClickListener() {
       @Override
       public void onClick(View v) {
           Intent i = new Intent(context,QuickInquiry.class);
           startActivity(i);
       }
    });
    link.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent i = new Intent(context,PortfolioFragment.class);
            startActivity(i);
        }
    });
}
public void addListenerOnButton()
{
    final C