android - 在选定的底部导航 View 项上重新创建 fragment

以下是我选择的底部导航 View 项目的代码

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    Fragment fragment = null;
    switch (item.getItemId()) {
        case R.id.action_one:
            // Switch to page one
            fragment = FragmentA.newInstance();
            break;
        case R.id.action_two:
            // Switch to page two
            fragment = FragmentB.newInstance();
            break;
        case R.id.action_three:
            // Switch to page three
            fragment = FragmentC.newInstance();
            break;
    }
    getSupportFragmentManager().beginTransaction().replace(R.id.container,fragment,"TAG").commit();
    return true;
}
});

现在我的问题是每次重新创建片段时都不希望每次我也尝试添加addToBackStack(null)时都希望重新创建片段，但是这种情况在按下后退按钮时会不断从堆栈中弹出不需要的片段。

有什么方法可以在不重新创建片段的情况下在底部导航栏上显示片段

最佳答案

使用支持库v26，您可以执行此操作

FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

Fragment curFrag = mFragmentManager.getPrimaryNavigationFragment();
if (curFrag != null) {
    fragmentTransaction.detach(curFrag);
}

Fragment fragment = mFragmentManager.findFragmentByTag(tag);
if (fragment == null) {
    fragment = new YourFragment();
    fragmentTransaction.add(container.getId(), fragment, tag);
} else {
    fragmentTransaction.attach(fragment);
}

fragmentTransaction.setPrimaryNavigationFragment(fragment);
fragmentTransaction.setReorderingAllowed(true);
fragmentTransaction.commitNowAllowingStateLoss();