findFragmentByTag()始终返回null-Android

问题描述

在我的应用程序中，我有一个主要活动和几个片段.当用户单击后退按钮时，片段将一一弹出.我想确定当前在后堆栈中的哪个片段.因此，用于通过片段标签名称识别片段.我使用以下代码段获取片段标签名称，但始终返回空值.

In my application i have one main activity and several fragments. when user click the back button fragments pops one by one. I want to identify which fragment currently in the back stack. So use to identify fragments by fragment tag name. i used following code segment to get fragment tag name but it always returns null value.

FragmentManager fm = MainActivity.this.getSupportFragmentManager();
String fragmentTag = fm.getBackStackEntryAt(fm.getBackStackEntryCount() - 1).getName();

请帮助.

编辑

用标签替换片段

FragmentManager fm = MainActivity.this.getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.activity_main_content_fragment, fragment, text);

推荐答案

我发现了我的错误，是我忘记了将TAG添加到堆栈中.

i found my mistake, it is i forgot to add TAG to back stack.

FragmentManager fm = mainActivity.getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.activity_main_content_fragment, fragment, text);
ft.addToBackStack(text);

然后我可以按如下方式获取当前的片段TAG名称，

And then i can get the current fragment TAG name as follows,

FragmentManager fm = MainActivity.this.getSupportFragmentManager();
String currentFragmentTag = fm.getBackStackEntryAt(fm.getBackStackEntryCount() - 1).getName();

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