防止同一个片段堆叠多次（addToBackStack） [英] Prevent The Same Fragment From Stacking More Than Once ( addToBackStack)

问题描述

我有一个 Activity ，其中有三个Fragments，可以称它们为 A ， B 和 C < STRONG>。在Activity onCreate（）中调用 Fragment A 。

I have an Activity with three Fragments lets call them A, B and C. Fragment A is called in the Activity onCreate().

FragmentA fragA = new FragmentA();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.activity2_layout, fragA, "A");
transaction.commit();

然后被碎片 B 或 C 当某些按钮被按下，FragmentTransaction调用 addToBackStack（）。

And gets replaced with Fragment B or C when certain buttons are pressed, and the FragmentTransaction calls addToBackStack().

FragmentB fragB = new FragmentB(); //or C
FragmentTransaction transaction = manager.beginTransaction();
transaction.replace(R.id.activity2_layout, fragB, "B");  //or C
transaction.addToBackStack("B"); //or C
transaction.commit();

但是可以说我称之为 Fragment B 连续三次，我怎样才能防止它叠加到它自己？同时我希望这可以： B 调用> C 调用> B 调用 - 但是当我尝试返回时要将 B 仅打开一次（ C < B ）而不是（ B C B ）。所以基本上删除了第一个backStack。

But lets say I call Fragment B three times in a row, how can I prevent it from stacking on to it self? And at the same time I want this to be possible: B called > C called > B called - BUT when i try to go back I want B to be opened only once ( C < B) instead of (B < C < B). So basically removing the first backStack with the new one.

推荐答案

From 如何从BackStack恢复Fragment（如果存在），这可能与您的查询非常相似。

From How to resume Fragment from BackStack if exists, which maybe very similar to your query.

有一种方法可以将背面基于提交的事务名或ID提供的堆栈（例如，使用Fragment的类名作为
Thijs已经提到的）：

There is a way to pop the back stack based on either the transaction name or the id provided by commit (for eg. using the Fragment's class name as Thijs already mentioned):

String backStateName = fragment.getClass().getName();

添加到后台：

Adding to backstack:

FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content_frame, fragment);
ft.addToBackStack(backStateName);
ft.commit();

出现时：

When popping:

getSupportFragmentManager().popBackStackImmediate (backStateName, 0); 

因此，在替换fragment之前，我们可以检查backstack中的存在如：

So before replacing fragment, we can check existance in backstack like:

boolean fragmentPopped = manager.popBackStackImmediate (backStateName, 0);

if (!fragmentPopped){ //fragment not in back stack, create it.
    ...
    ...
    ft.addToBackStack(backStateName);
    ft.commit();
}

请查看以上问题和接受的答案以获得更多解释。

Please check the above question and the accepted answer for more explanation.

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