1：实例代码

private void showFragment(int index){        //开启事物        FragmentTransaction transaction = manager.beginTransaction();        hideFragment(transaction);        switch (index) {        case 0:            if(fragment1 != null){
   //如过已经实例化，那么可直接显示出来                transaction.show(fragment1);            }else{
   //如果没有实例化，先实例化，在添加                fragment1 = new TabFragment1();                transaction.add(R.id.content, fragment1);            }            break;        case 1:            if(fragment2 != null){                transaction.show(fragment2);            }else{                fragment2 = new TabFragment2();                transaction.add(R.id.content, fragment2);            }                        break;        case 2:            if(fragment3 != null){                transaction.show(fragment3);            }else{                fragment3 = new TabFragment3();                transaction.add(R.id.content, fragment3);            }            break;        default:            break;        }        transaction.commit();//切记要提交事物    }                /**     * 隐藏所有的Fragment     * @param ft     */    private void hideFragment(FragmentTransaction ft){        if(fragment1 != null){            ft.hide(fragment1);        }        if(fragment2 != null){            ft.hide(fragment2);        }        if(fragment3 != null){            ft.hide(fragment3);        }            }