这是在离开深度嵌套堆栈时清理 Fragment 返回堆栈的正确方法吗? [英] Is this the right way to clean-up Fragment back stack when leaving a deeply nested stack?

问题描述

我正在使用 Android 兼容性库来实现片段并扩展了布局示例，以便片段包含一个触发另一个片段的按钮.

I'm using the Android Compatibility library to implement fragments and have extended the layout sample so that a fragment contains a button which fires off another fragment.

在左侧的选择窗格中，我有 5 个可选项目 - A B C D E.

In the selection pane on the left I have 5 selectable items - A B C D E.

每个都在详细信息窗格中加载一个片段(通过 FragmentTransaction:replace) - a b c d e

Each loads up a fragment (via FragmentTransaction:replace) in the details pane - a b c d e

现在我扩展了片段 e 以包含一个按钮，该按钮也在详细信息窗格中加载另一个片段 e1.我在片段 e 的 onClick 方法上做了这个，如下所示:

Now I've extended fragment e to contain a button which loads up another fragment e1 also in the details pane. I've done this on fragment e's onClick method as follows:

FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
ft.replace(R.id.details_frag, newFrag);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();

如果我做出以下选择:

E - e - e1 - D - E

然后片段 e 位于详细信息窗格中.这很好，也是我想要的.但是，如果我此时按下 back 按钮，它什么也不做.我必须单击它两次，因为 e1 仍在堆栈中.此外，单击周围后，我在 onCreateView 中得到了一个空指针异常:

Then fragment e is in the details pane. This is fine and what I want. However, if I hit the back button at this point it does nothing. I have to click it twice because e1 is still on the stack. Furthermore after clicking around I got a null pointer exception in onCreateView:

为了解决"这个问题，我在选择 A B C D E 时添加了以下内容:

To 'solve' this problem I added the following whenever A B C D E is selected:

FragmentManager fm = getActivity().getSupportFragmentManager();
for(int i = 0; i < fm.getBackStackEntryCount(); ++i) {
    fm.popBackStack();
}

只是想知道这是否是正确的解决方案，或者我是否应该做一些不同的事情?

Just wondering whether this is the correct solution or whether I should be doing something different?

推荐答案

好吧，根据预期的行为，有几种方法可以解决此问题，但此链接应该为您提供所有最佳解决方案，毫不奇怪来自 Dianne Hackborn

Well there are a few ways to go about this depending on the intended behavior, but this link should give you all the best solutions and not surprisingly is from Dianne Hackborn

http://groups.google.com/group/android-developers/browse_thread/thread/d2a5c203dad6ec42

基本上你有以下选择

• 为您的初始返回堆栈状态使用一个名称并使用FragmentManager.popBackStack(String name,FragmentManager.POP_BACK_STACK_INCLUSIVE).
• 使用FragmentManager.getBackStackEntryCount()/getBackStackEntryAt().getId()检索返回堆栈上第一个条目的 ID，以及FragmentManager.popBackStack(int id,FragmentManager.POP_BACK_STACK_INCLUSIVE).
• FragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE)应该弹出整个后退堆栈...我认为文档那是错误的.(实际上我想它只是不包括以下情况你传入 POP_BACK_STACK_INCLUSIVE),

• Use a name for your initial back stack state and use FragmentManager.popBackStack(String name, FragmentManager.POP_BACK_STACK_INCLUSIVE).
• Use FragmentManager.getBackStackEntryCount()/getBackStackEntryAt().getId() to retrieve the ID of the first entry on the back stack, and FragmentManager.popBackStack(int id, FragmentManager.POP_BACK_STACK_INCLUSIVE).
• FragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE) is supposed to pop the entire back stack... I think the documentation for that is just wrong. (Actually I guess it just doesn't cover the case where you pass in POP_BACK_STACK_INCLUSIVE),

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