Eu estou enfrentando um problema de sobreposição de fragmentos quando eu alternar entre guias e anexar fragmentos a uma vista de guia abaixo é o meu código por favor me ajude

public class FragmentManage extends Fragment implements ActionBar.TabListener {

    private Fragment mFragment;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
            Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fragment_manage, container, false);

        OnClickListener clickListener = new OnClickListener() { 
            public void onClick(View v) {
                FragmentTransaction ft = getFragmentManager().beginTransaction();
                switch(v.getId()) {
                    case R.id.imageBtnCategory:
                        if (mFragment == null){
                            mFragment = new FragmentCategory();
                        }
                        ft.replace(android.R.id.content, mFragment);
                        break;
                    case R.id.imageBtnManageKey:
                        if (mFragment == null){
                            mFragment = new FragmentKeys();
                        }
                        ft.replace(android.R.id.content, mFragment);
                        break;
                    case R.id.imageBtnChangePswd:
                        if (mFragment == null){
                            mFragment = new FragmentChangePwd();
                        }
                        ft.replace(android.R.id.content, mFragment);
                        break;
                }
                ft.commit();
             }
        };

        ImageButton imageBtnCategory = (ImageButton) v.findViewById(R.id.imageBtnCategory);
        ImageButton imageBtnManageKey = (ImageButton) v.findViewById(R.id.imageBtnManageKey);
        ImageButton imageBtnChangePswd = (ImageButton) v.findViewById(R.id.imageBtnChangePswd);

        imageBtnCategory.setOnClickListener(clickListener);
        imageBtnManageKey.setOnClickListener(clickListener);
        imageBtnChangePswd.setOnClickListener(clickListener);

        return v;
    }

    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        mFragment = new FragmentManage();
        ft.add(android.R.id.content, mFragment);
        ft.attach(mFragment);
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        ft.remove(mFragment);
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {

    }
}