Android的onBackStackChanged（）不叫 [英] Android onBackStackChanged() not called

问题描述

我有一个活动像code如下：

I have an Activity like the code below:

public class AuthenticatedMainActivity extends Activity implements FragmentManager.OnBackStackChangedListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        .............
        FragmentManager fragmentManager = getFragmentManager();           
        fragmentManager.beginTransaction().add(R.id.frame_container,fragment, "First").addToBackStack(null).commit();
    }

    private void switchFragment(Fragment fragment){            
      FragmentManager fragmentManager = getFragmentManager();
      fragmentManager.beginTransaction()
        .replace(R.id.frame_container, fragment).addToBackStack("Tag").commit();
    }

    @Override
public void onBackStackChanged() {
    System.out.println("====================================================changeeeeeeeeeeeeeeeeeeeeeeeeee");
}       
}

但 onBackStackChanged（）方法不会被调用甚至与 switchFragment 方法后成功取代片段。

But the onBackStackChanged() method is never called even After successfully replaced fragments with the switchFragment method.

推荐答案

您需要添加活动为 OnBackStackChangedListener 使用 addOnBackStackChangedListener 。

例如：

@Override
protected void onCreate(Bundle savedInstanceState) {
    .............
    FragmentManager fragmentManager = getFragmentManager();     
    fragmentManager.addOnBackStackChangedListener(this);      
    fragmentManager.beginTransaction().add(R.id.frame_container,fragment, "First").addToBackStack(null).commit();
}

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