android - fragment 不会在方向改变时持续存在

Question

我使用下拉导航，由于一些主题问题，我使用了 Spinner。我使用以下方法设置 Actionbar:

public void setupActionBar() {
    Spinner navSpinner = new Spinner(new ContextThemeWrapper(this, R.style.Theme_Apptheme_Widget_ActionBarSpinner));
    navSpinner.setSelection(getSharedPreferences(APP_NAME, MODE_PRIVATE).getInt(SELECTED_POSITION, 0));
    Log.d(getClass().getName(), navSpinner.getSelectedItemPosition() + "");
    navSpinner.setAdapter(new ActionBarSpinnerAdapter(getActionBar().getThemedContext(), dataSource.getAllShoppingLists()));
    navSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            if (position < dataSource.getAllShoppingLists().size()) {
                if(fragmentManager.findFragmentByTag("shoppinglist" + position) == null) {
                    ShoppingListFragment shoppingListFragment = ShoppingListFragment.
                            newInstance(dataSource.getShoppingListForPosition(position).getId());
                    fragmentTransaction.replace(R.id.container, shoppingListFragment, "shoppinglist" + position);
                    }
            } else if (position == dataSource.getAllShoppingLists().size()) {
                if(fragmentManager.findFragmentByTag("shoppinglistmanager") == null) {
                    ShoppingListManagerFragment shoppingListFragment = ShoppingListManagerFragment.newInstance();
                    fragmentTransaction.replace(R.id.container, shoppingListFragment, "shoppinglistmanager");
                }
            }
            fragmentTransaction.commit();
            SharedPreferences preferences = getSharedPreferences(APP_NAME, MODE_PRIVATE);
            preferences.edit().putInt(SELECTED_POSITION, position).commit();
        }
    });

    getActionBar().setCustomView(navSpinner);
}

我在 Fragment 的 onCreate() 上调用了 setRetainInstance(true);，但 Fragment 仍然没有被持久化。我通过拥有和 EditText 并向其输入文本来检查这一点。为什么会这样？

Answer 1

您需要为EditText设置一个标识符，以便Android系统保存和恢复 View 状态。

来自 docs :

Note: In order for the Android system to restore the state of the views in your activity, each view must have a unique ID, supplied by the android:id attribute.

如果您正在使用布局文件，请通过属性 android:id 指定它，或者如果您正在使用 API 创建 EditText，则使用 View.setId .