如何从活动返回到先前的片段? [英] How to go back to previous fragment from activity?

问题描述

我有一个带有导航抽屉的应用程序，可以切换片段.从其中一个片段的内部，我正在调用一项新的活动.当我在该活动中(在工具栏中)单击时，我想返回到先前选择的片段，但是它使我回到了第一个片段.我正在将片段添加到堆栈中，所以这应该不是问题.

I've got an app with nav drawer, which is switching fragments. From inside one of those fragments, I am calling a new activity. When I click back in this activity (in toolbar), I want to go back to previous selected fragment but instead it puts me back to first fragment. I am adding my fragment to back stack so this should not be a problem.

这是我已经尝试过的:

我在第2个活动中重写了onBackPressed方法，如下所示:

I have overriden the onBackPressed method in my 2nd activity like this:

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() == 0) {
        this.finish();
    } else {
        getFragmentManager().popBackStack();
    }
}

它不起作用.我也将当前片段的索引保存在onsaveinstancestate方法内，并检索它但结果相同.我还尝试将当前片段始终放在变量中，然后尝试重新显示它，但仍然无法正常工作.我还能尝试什么吗?

It is not working. I also saved index of current fragment inside onsaveinstancestate method and retrieve it but same result. I also tried with always putting current fragment inside variable and try to reshow it but still, it does not work. Anything else I could try?

有趣的事实:如果我在底部面板内按回，它实际上会返回到先前的片段.

Fun fact: if I press back inside bottom panel, it does actually goes back to previous fragment.

这是我执行此操作的代码:

Here is my code for doing this:

 private void replaceFragment(Fragment fragment)
 {
     if (fragment != null)
     {
         FragmentManager manager = getSupportFragmentManager();
         manager.beginTransaction()
                    .replace(R.id.main_content, fragment)
                    .addToBackStack(null)
                    .commit();
        }
    }

如果saveInstanceState为null，则仅添加第一个片段，如下所示:

I add first fragment only, if savedInstanceState is null, like so:

if (savedInstanceState == null) {
    // first time
    mTitle = getResources().getString(R.string.home);
    replaceFragment(HomeFragment.newInstance()); 
}

是的，所有这些都是在onCreate()方法中完成的.

And yes, all this is done inside onCreate() method.

推荐答案

我知道，人们仍在努力帮助我.此答案帮助我解决了我的问题: Android-从活动导航向上片段

I see, that people are still trying to help me. This answer helped me fix my problem: Android - Navigation Up from Activity to Fragment

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