将片段状态/数据从片段保存到片段

Question

我试图弄清楚如果用户离开并返回，如何将用户输入的数据保存在片段上。我有一个活动，几个片段可以解决。我发现的所有示例都是在离开 Fragment 和 Activity 时保存状态。我永远不会离开活动；因此片段中的 onSaveInstanceState 永远不会被调用。 onPause 被调用，但我无法弄清楚如何在那里保存状态。

此应用程序显示门票列表。当用户点击工单时，它会从本地数据库中获取只读字段的初步信息，并允许用户在提交前输入工单信息。我试图让用户在不丢失输入信息的情况下点击工单、输入数据、离开并返回该工单。

在我研究过的所有示例中，在我看来，我可以使用 Fragmenttransaction 来保存 Fragment 的 ID。以下是所有 Fragment 都附加到的主 Activity：

public class Activity_Main extends Activity 
implements  Fragment_OpenTickets.INT_OnOpenTicketSelectedListener,
            Fragment_SubTickets.INT_OnSubTicketSelectedListener,
            Fragment_Ticket.INT_SubmitNewTicket {
DBController dbc;
Fragment fr;
boolean gps_enabled = false;
boolean network_enabled = false;
HashMap<String, String> addInfo;
RadioButton btn_radio_open;
RadioButton btn_radio_submitted;
RadioButton btn_radio_settings;
String ticketDate, ticketTime;
int m, d, y, hr, min;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn_radio_open = (RadioButton)findViewById(R.id.radio_open);
    btn_radio_submitted = (RadioButton)findViewById(R.id.radio_submitted);
    btn_radio_settings = (RadioButton)findViewById(R.id.radio_settings);
    dbc = new DBController(this);
    if (dbc.checkCredentials() != null) {
        fr = new Fragment_OpenTickets();
    } else {
        fr = new Fragment_Settings();
        btn_radio_open.setChecked(false);
        btn_radio_submitted.setChecked(false);
        btn_radio_settings.setChecked(true);
    }
    FragmentManager fm = getFragmentManager();
    final FragmentTransaction ft = fm.beginTransaction();
    ft.add(R.id.fragment_place, fr);
    ft.addToBackStack(null); // For back button action.
    ft.commit();

    // Start scheduler service.
    this.startService(new Intent(this, Service_Send.class));
    // Start GPS service.
    startGPS();
}

/**
 * Top menu buttons.
 */
public void selectFrag(View view) {
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    switch (view.getId()) {
        case R.id.radio_open:
            //fr = new Fragment_OpenTickets();
            ft.replace(R.id.fragment_place, new Fragment_OpenTickets());
            ft.addToBackStack(null);
            btn_radio_submitted.setChecked(false);
            btn_radio_settings.setChecked(false);
            ft.commit();
            break;
        case R.id.radio_submitted:
            //fr = new Fragment_SubTickets();
            ft.replace(R.id.fragment_place, new Fragment_SubTickets());
            ft.addToBackStack(null);
            btn_radio_open.setChecked(false);
            btn_radio_settings.setChecked(false);
            ft.commit();
            break;
        case R.id.radio_settings:
            //fr = new Fragment_Settings();
            ft.replace(R.id.fragment_place, new Fragment_Settings());
            ft.addToBackStack(null);
            btn_radio_open.setChecked(false);
            btn_radio_submitted.setChecked(false);
            ft.commit();
            break;
    }
}

/**
 * Open ticket selection action.
 */
public void onOpenTicketSelected(HashMap position) {
    // Create fragment and give it an argument for the selected ticket.
    fr = new Fragment_Ticket();
    Bundle args = new Bundle();
    args.putSerializable("HashMap", position);
    fr.setArguments(args);

    FragmentManager fm = getFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    ft.add(R.id.fragment_place, fr);
    ft.addToBackStack(null); // For back button action.
    ft.commit();
}

/**
 * Submitted ticket selection action.
 */
public void onSubTicketSelected(HashMap position) {
    // Create fragment and give it an argument for the selected ticket.
    fr = new Fragment_SubTicket();
    Bundle args = new Bundle();
    args.putSerializable("HashMap", position);
    fr.setArguments(args);

    FragmentManager fm = getFragmentManager();
    FragmentTransaction fragmentTransaction = fm.beginTransaction();
    fragmentTransaction.replace(R.id.fragment_place, fr);
    fragmentTransaction.addToBackStack(null); // For back button action.
    fragmentTransaction.commit();
}

任何帮助将不胜感激。如果我需要发布更多代码，请告诉我。谢谢！

Answer 1

我认为您应该在用户离开片段时将票证信息存储在您的 Activity 中，并在您回来时获取信息并显示它。

在 Activity_Main 类中，您创建了 2 个方法：

public void saveTicketInfo(TicketInfo info) {
    // save info here
}

还有：

public TicketInfo getTicketInfo() {
    // get info here
}

在您的片段中：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
    ...
    // get ticket info and display it
    Activity_Main mainActivity = (Activity_Main)getActivity();
    TicketInfo info = mainActivity.getTicketInfo();
    if (info != null) {
        // handle display info here
    }
    ...
}

@Override
public void onDestroyView() {
    TicketInfo info = new TicketInfo();
    // get info from view and store in the object
    Activity_Main mainActivity = (Activity_Main)getActivity();
    mainActivity.saveTicketInfo(info)
    super.onDestroyView();
}

Answer 2

我在 SO@Passing data between fragments contained in an activity 上发布了一个冗长的详细答案。搜索我的答案。这是一种将数据从 Fragment 传递到 Activity 的安全方法。然后您可以轻松地将这些数据从 Activity 传递到 Fragment 的构造函数或公共方法。