Fragment切换问题

片断一： add  hind

@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
    switch (checkedId){
        case R.id.rb_common_frame://常用框架
            position = 0;
            break;
        case R.id.rb_thirdparty://第三方
            position = 1;
            break;
        case R.id.rb_custom://自定义
            position = 2;
            break;
        case R.id.rb_other://其他
            position = 3;
            break;
        default:
            position = 0;
            break;
    }

    //根据位置得到对应的Fragment
    BaseFragment to = getFragment();
    //替换
    switchFrament(mContent,to);

/**
     *
     * @param from 刚显示的Fragment,马上就要被隐藏了
     * @param to 马上要切换到的Fragment，一会要显示
     */
    private void switchFrament(Fragment from,Fragment to) {
        if(from != to){
            mContent = to;
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            //才切换
            //判断有没有被添加
            if(!to.isAdded()){
                //to没有被添加
                //from隐藏
                if(from != null){
                    ft.hide(from);
                }
                //添加to
                if(to != null){
                    ft.add(R.id.fl_content,to).commit();
                }
            }else{
                //to已经被添加
                // from隐藏
                if(from != null){
                    ft.hide(from);
                }
                //显示to
                if(to != null){
                    ft.show(to).commit();
                }
            }
        }

    }

    /**
     * 根据位置得到对应的Fragment
     * @return
     */
    private BaseFragment getFragment() {
        BaseFragment fragment = mBaseFragment.get(position);
        return fragment;
    }

片断二：

 private void switchFrament(BaseFragment fragment) {
     //1.得到FragmentManger
     FragmentManager fm = getSupportFragmentManager();
     //2.开启事务
     FragmentTransaction transaction = fm.beginTransaction();
     //3.替换
     transaction.replace(R.id.fl_content, fragment);
     //4.提交事务
     transaction.commit();
 }

片断三：

//初始化Fragmet
private void initFragment() {
    fragmentList.clear();
    ItemFragmentOrder itemFragmentOrder = new ItemFragmentOrder();
    ItemFragmentIntent itemFragmentIntent = new ItemFragmentIntent();
    fragmentList.add(itemFragmentOrder);
    fragmentList.add(itemFragmentIntent);
}

//初始化ViewPager
private void initViewPager() {
    mPageAdapter = new MainFragmentPageAdapter(activity.getSupportFragmentManager());
    viewPager.setAdapter(mPageAdapter);
    viewPager.setOffscreenPageLimit(fragmentList.size());
}

//fragmentViewPaager适配器
class MainFragmentPageAdapter extends FragmentPagerAdapter {

    public MainFragmentPageAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        return fragmentList.get(position);
    }

    @Override
    public int getCount() {
        return fragmentList.size();
    }
}

//切换页面
public void showFragment(int position) {
    viewPager.setCurrentItem(position, false);
}

片断四：

@Override
public Fragment getItem(int position) {
    BaseFragment fragment = null;
    switch (fragmentFlag) {
        case FragmentMainVp:
            switch (position) {
                case MainActivity.fristPage:
                    fragment = new FragmentFirst();
                    break;
                case MainActivity.order:
                    fragment = new FragmentOrder();
                    break;
                case MainActivity.mine:
                    fragment = new FragmentMine();
                    break;
            }//end of switch
            break;
    }//end of switch
    Bundle bundle = new Bundle();
    bundle.putInt(BaseFragment.ParamIndex, position);
    if (null != paramBundle) bundle.putBundle(BaseFragment.ParamBundle, paramBundle);
    if (null != fragment) fragment.setArguments(bundle);
    if (null != fragmentAry) fragmentAry[position] = fragment;
    return fragment;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    Fragment fragment = (Fragment) super.instantiateItem(container, position);//得到缓存的fragment
    if (needReload && null != fragment && null != fm) {
        String fragmentTag = fragment.getTag();//得到tag,这点很重要
        FragmentTransaction ft = fm.beginTransaction();
        if (null != ft) {
            ft.remove(fragment);//移除旧的fragment
            fragment = getItem(position);//换成新的fragment
            ft.add(container.getId(), fragment, fragmentTag);//添加新fragment时必须用前面获得的tag,这点很重要
            ft.attach(fragment);
            fragment.setUserVisibleHint(true);
            ft.commit();
        }//end of if
        if ((getCount() - 1) == position)
            needReload = false;//清除更新标记(只有重新启动的时候需要去创建新的fragment对象),防止正常情况下频繁创建对象
    }//end of if
    return fragment;
}

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