FragmentActivity和Fragments:popBackStack

Question

我的FragmentActivity在tabhost中管理4个listfragments(每个listfragment,我都会记录它的backstack).ListFragment共享一个FrameLayout,在其中附加其内容.触发onListItemClick时的每个ListFragment让FragmentActivity启动一个新的Fragment,以便用新的片段替换当前片段的内容.如果您调用A当前显示的Fragmetn(由ListFragment A管理)和B,则在内容A与B的内容重叠的片段之间切换时,会发生将替换A(由ListFragment B管理)的片段,至少是i清除片段的后台关闭(示例中为A).按照片段我之间的顺序

    if (activeTab != tv) {
        if (activeTab != null) {
            Log.i(TAG, "tag: " + activeTab.getTag() + " detaching...");
            FragmentInfo fragmentInfo = fragments.get(activeTab.getTag());
            //detach the current fragment

            //getSupportFragmentManager().popBackStack((String)activeTab.getTag(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
            ft.detach(fragmentInfo.fragment);
        }

        //get the new 
        FragmentInfo fragmentInfo = fragments.get(tv.getTag());
        Log.i(TAG, "tag: " + tv.getTag() + " fragment: " + fragmentInfo.mClass.getName());
        if (fragmentInfo != null) {
            if (fragmentInfo.fragment == null) {
                fragmentInfo.fragment = Fragment.instantiate(this, fragmentInfo.mClass.getName(), fragmentInfo._args);
                ft.add(R.id.mytabcontent, fragmentInfo.fragment, fragmentInfo._tag);
            } else {
                Log.i(TAG, "attacching fragment: " + fragmentInfo.mClass.getName());
                ft.attach(fragmentInfo.fragment);
            }
        }
    }

而当我需要在OnListemItemClick被触发时更改listfragment内容时,我使用

    private void replaceFragment(Fragment fragment, String tag, String backstack) {

    FragmentTransaction ft = manager.beginTransaction();
    ft.replace(R.id.mytabcontent, fragment, tag);
    ft.setTransition(FragmentTransaction.TRANSIT_NONE);
    ft.addToBackStack(backstack);
    ft.commit();
}

你能帮我理解为什么吗？提前谢谢,抱歉我的英语不好

编辑:我的问题是为什么每次我在ListFragment之间切换时都需要清除backstack,以避免Fragment的内容重叠.我犯了什么错

Answer 1

好的,所以这个答案假定你想要在每次交换标签时擦除每个标签的历史记录.我的意思是Tab 1从frag 1开始,然后你单击并将其更改为frag 2.如果你选择Tab 2,你将撤消Tab 1的历史记录,下次你点击Tab 1你会回到碎片1.

有了这个说这里是解决方案:用下面的替换你的onTabUnselected

public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            //this segment removes the back history of everything in the tab you are leaving so when you click on the tab again you go back to a fresh start
            FragmentManager man = mActivity.getFragmentManager();
            if(man.getBackStackEntryCount()>0) //this check is required to prevent null point exceptions when clicking off of a tab with no history
                man.popBackStack(man.getBackStackEntryAt(0).getName(), FragmentManager.POP_BACK_STACK_INCLUSIVE); //this pops the stack back to index 0 so you can then detach and then later attach your initial fragment
            //also it should be noted that if you do popbackstackimmediate here instead of just popbackstack you will see a flash as the gui changes back to the first fragment when the code executes
            //end
            ft.detach(mFragment);
        }
    }