求大神解答，利用接口实现Fragment切换，为什么Log打印说Activity被销毁了

Question

MainActivity： @Override public void onClick(View view) {     switch (view.getId()) {         case R.id.bt_user:             cf.setinitif(new Interface_ChangeFragment() {                 @Override                 public Fragment initif() {                     return tab_user;                 }                   @Override                 public int initTAG() {                     return 3;                 }             });             break;         case R.id.bt_find:             cf.setinitif(new Interface_ChangeFragment() {                 @Override                 public Fragment initif() {                     return tab_found;                 }                   @Override                 public int initTAG() {                     return 2;                 }             });             break;         case R.id.bt_watchmoive:             cf.setinitif(new Interface_ChangeFragment() {                 @Override                 public Fragment initif() {                     return tab_watchMoive;                 }                   @Override                 public int initTAG() {                     return 1;                 }             });             break;         case R.id.bt_selectsong:             cf.setinitif(new Interface_ChangeFragment() {                 @Override                 public Fragment initif() {                     return tab_selectSong;                 }                   @Override                 public int initTAG() {                     return 0;                 }             });             break;         case R.id.bt_frist:             break;     }                             接口的实现类：     public class ChangeFragment extends FragmentActivity {     int TAG;     Tab_selectSong tab_selectSong;     Tab_watchMoive tab_watchmoive;     Tab_Found tab_found;     Tab_User tab_user;     public void setinitif(Interface_ChangeFragment interface_changeFragment) {         FragmentManager manager = getSupportFragmentManager();         FragmentTransaction fts = manager.beginTransaction();         if (interface_changeFragment.initif() == null) {             TAG = interface_changeFragment.initTAG();             switch (TAG) {                 case 0:                    tab_selectSong = new Tab_selectSong();                     fts.add(R.id.activity_fragment,tab_selectSong);                     hideall();                     fts.show(tab_selectSong);                     fts.commit();                     break;                 case 1:                     tab_watchmoive = new Tab_watchMoive();                     fts.add(R.id.activity_fragment,tab_watchmoive);                     hideall();                     fts.show(tab_watchmoive);                     fts.commit();                     break;                 case 2:                     tab_found = new Tab_Found();                     fts.add(R.id.activity_fragment,tab_found);                     hideall();                     fts.show(tab_found);                     fts.commit();                     break;                 case 3:                    tab_user = new Tab_User();                     fts.add(R.id.activity_fragment,tab_user);                     hideall();                     fts.show(tab_user);                     fts.commit();                     break;             }         } else {             TAG = interface_changeFragment.initTAG();             switch (TAG) {                 case 0:                     hideall();                     fts.show(tab_selectSong);                     fts.commit();                     break;                 case 1:                     hideall();                     fts.show(tab_watchmoive);                     fts.commit();                     break;                 case 2:                     hideall();                     fts.show(tab_found);                     fts.commit();                     break;                 case 3:                    hideall();                     fts.show(tab_user);                     fts.commit();                     break;             }           }     }       private void hideall() {         FragmentManager manager = getSupportFragmentManager();         FragmentTransaction fts = manager.beginTransaction();         if(tab_selectSong!=null)         {             fts.hide(tab_selectSong);         }         if(tab_watchmoive!=null)         {             fts.hide(tab_watchmoive);         }         if(tab_found!=null)         {             fts.hide(tab_found);         }         if(tab_user!=null)         {             fts.hide(tab_user);         }     } }   用的是按钮的点击事件new出一个匿名内部类，之所以这么做，是不想让主MainAcitity变得臃肿，可是 结果出错了，Log打印出来是java.lang.IllegalStateException: Activity has been destroyed   求大神解答为什么啊？难道不可以这么写吗？ 我也是一个新手，才开始写我的第一个APP。求大神解答

Answer 1

能说下什么时候报的错吗？

--->个人推测可能是ChangeFragment extends FragmentActivity与MainActivity冲突的问题。（我多嘴一下，Fragment类和FragmentActivity类并不是继承关系）

【另外】你说你是新手，那我推荐一个开发中比较不错的用法吧（也是谷歌官方推荐的）：使用ViewPager+Fragment的形式，实现fragment页面之间的切换，具体使用可以参考这里：http://www.imooc.com/learn/198 或者 http://www.imooc.com/learn/273

------可能我说的你之前都懂，个人能力低微，已经尽力啦，能有帮助就最好-----