如何使用NavigationDrawer切换时，只保留一个片段的实例？

问题描述

我的应用开始于一个AddressFragment。从NavigationDrawer我开始（其中包括）一个新 AddressFragment有：

My App starts with a AddressFragment. From the NavigationDrawer I start (amongst others) a new AddressFragment with:

getSupportFragmentManager().beginTransaction()
                .replace(R.id.container, new AddressFragment())
                .addToBackStack(null)
                .commit();

但我宁愿只是回到第一个实例。我怎么能这样做呢？

But I would rather just go back the first instance. How could I do that?

或者更一般情况下，我怎么能找出来，无论是片段的实例已经存在，然后启动，如果有的话，否则创建一个？

Or more general, how can I find out, whether an instance of a fragment already exists and then start that, if yes, otherwise create one?

推荐答案

在创建片段为它设置一个标记，再后来就可以通过碎片经理找到它，并替换/创建相应。

When creating the fragment set a tag for it, then later you can find it through the fragment manager and replace/create accordingly.

FragmentManager fManager = getFragmentManager();
FragmentTransaction fTransaction = fManager.beginTransaction();
Fragment fragment = fManager.findFragmentByTag("uniqueTag");

// If fragment doesn't exist yet, create one
if (fragment == null) {
    fTransaction.add(R.id.fragment_list, new ListFrag(), "uniqueTag");
}
else { // re-use the old fragment
    fTransaction.replace(R.id.fragment_list, fragment, "uniqueTag");
}

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