Question

我发现了许多类似问题的实例，但不幸的是，没有答案符合我的要求。

我在一个活动中有很多片段，并且我从一个片段传输到另一个片段。该对象将由每个片段修改，我希望在回栈时可以恢复以前的片段实例和使用onSaveInstanceState尝试过的对象的先前版本，但是显然在片段中备份时onSaveInstanceState不被称为< / p>

  override fun onSaveInstanceState(outState: Bundle) {
    outState?.run {
        putParcelable("PRODUCT",Product)
    }

    super.onSaveInstanceState(outState)
}

Answer 1

修改片段时，需要创建一个新片段，并.replace创建一个旧片段。

    public BlankFragment modifyFragment() {
        int newVar = myVar; // your modified variable. Not the best example

        // you need to create a new instance of the fragment
        // everytime you modify your fragment so that you can replace the
        // one you want to go back to later
        BlankFragment blankFragment = BlankFragment.newInstance(++newVar);

        getActivity().getSupportFragmentManager().beginTransaction()
                .replace(R.id.a_main_fl_root, blankFragment) // When you click back press. It will restore the replaced fragment.
                .addToBackStack(null) 
                .commit();

        return blankFragment; // the new fragment is returned so you can replace it again and again.
        // what I didn't include is how to get the instance of the replaced fragment when you click back press.
    }

不需要saveInstanceState，因为它仅在活动被销毁并重新创建时才使用。

如何正确保存和还原片段的实例状态回栈？

1 个答案: