【Android】保存Fragment切换状态

< LinearLayout  xmlns:android ="http://schemas.android.com/apk/res/android"
    android:layout_width ="match_parent"
    android:layout_height ="match_parent"
    android:orientation ="vertical"   >

     < FrameLayout
         android:id ="@+id/container"
        android:layout_width ="match_parent"
        android:layout_height ="0dip"
        android:layout_weight ="1.0"   >
     </ FrameLayout >

     < RadioGroup
         android:id ="@+id/main_radio"
        android:layout_width ="fill_parent"
        android:layout_height ="wrap_content"
        android:layout_gravity ="bottom"
        android:gravity ="bottom"
        android:layout_marginBottom ="-6dp"
        android:orientation ="horizontal"   >

         < RadioButton
             android:id ="@+id/radio_button0"
            style ="@style/main_tab_bottom"
            android:drawableTop ="@drawable/bottom_1"   />

         < RadioButton
             android:id ="@+id/radio_button1"
            style ="@style/main_tab_bottom"
            android:drawableTop ="@drawable/bottom_2"   />

         < RadioButton
             android:id ="@+id/radio_button2"
            style ="@style/main_tab_bottom"
            android:drawableTop ="@drawable/bottom_3"   />

         < RadioButton
             android:id ="@+id/radio_button3"
            style ="@style/main_tab_bottom"
            android:drawableTop ="@drawable/bottom_4"   />

         < RadioButton
             android:id ="@+id/radio_button4"
            style ="@style/main_tab_bottom"
            android:drawableTop ="@drawable/bottom_5"   />
     </ RadioGroup >

</ LinearLayout >

    @Override
     public  void onCheckedChanged(CompoundButton buttonView,  boolean isChecked) {
         if (isChecked) {
            Fragment fragment = (Fragment) mFragmentPagerAdapter.instantiateItem(mContainer, buttonView.getId());
            mFragmentPagerAdapter.setPrimaryItem(mContainer, 0, fragment);
            mFragmentPagerAdapter.finishUpdate(mContainer);
        } 
    }

     private FragmentPagerAdapter mFragmentPagerAdapter =  new FragmentPagerAdapter(getSupportFragmentManager()) {

        @Override
         public Fragment getItem( int position) {
             switch (position) {
             case R.id.radio_button1:
                 return  new Fragment1();
             case R.id.radio_button2:
                 return  new Fragment2();
             case R.id.radio_button3:
                 return  new Fragment3();
             case R.id.radio_button4:
                 return  new Fragment4();
             case R.id.radio_button0:
             default:
                 return  new Fragment0();
            }
        }

        @Override
         public  int getCount() {
             return 5;
        }
    };

    @Override
     public Object instantiateItem(ViewGroup container,  int position) {
         if (mCurTransaction ==  null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }

         final  long itemId = getItemId(position);

         //  Do we already have this fragment?
        String name = makeFragmentName(container.getId(), itemId);
        Fragment fragment = mFragmentManager.findFragmentByTag(name);
         if (fragment !=  null) {
             if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
            mCurTransaction.attach(fragment);
        }  else {
            fragment = getItem(position);
             if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
            mCurTransaction.add(container.getId(), fragment,
                    makeFragmentName(container.getId(), itemId));
        }
         if (fragment != mCurrentPrimaryItem) {
            fragment.setMenuVisibility( false);
            fragment.setUserVisibleHint( false);
        }

         return fragment;
    }

    @Override
     public  void destroyItem(ViewGroup container,  int position, Object object) {
         if (mCurTransaction ==  null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
         if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
                + " v=" + ((Fragment)object).getView());
        mCurTransaction.detach((Fragment)object);
    }

    @Override
     public  void setPrimaryItem(ViewGroup container,  int position, Object object) {
        Fragment fragment = (Fragment)object;
         if (fragment != mCurrentPrimaryItem) {
             if (mCurrentPrimaryItem !=  null) {
                mCurrentPrimaryItem.setMenuVisibility( false);
                mCurrentPrimaryItem.setUserVisibleHint( false);
            }
             if (fragment !=  null) {
                fragment.setMenuVisibility( true);
                fragment.setUserVisibleHint( true);
            }
            mCurrentPrimaryItem = fragment;
        }
    }

    @Override
     public  void finishUpdate(ViewGroup container) {
         if (mCurTransaction !=  null) {
            mCurTransaction.commitAllowingStateLoss();
            mCurTransaction =  null;
            mFragmentManager.executePendingTransactions();
        }
    }