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FragmentPagerAdapter在屏幕旋转后无法恢复片段

androidandroid-fragmentsandroid-fragmentactivityandroid-pageradapter
8
编辑：我发现Activity保存了实例，但是Fragment保存的数据并没有传递到Activity的savedInstanceState中。我在outState中保存了当前时间，但是这个时间并没有传递到Activity的SavedInstanceState中。如果我将其打印到日志中，Activity中的时间返回“null”...
我正在构建一个应用程序，其中包含计时器。计时器的基本托管活动是FragmentActivity，它托管一个FragementPagerAdapter，在代码中填充了两个片段（我没有为XML中的片段定义ID，因为它们在.xml中没有定义为片段）。一切都很正常，直到方向改变，然后活动似乎失去与旧片段的联系，只选择创建新的片段。这意味着任何当前倒计时都会丢失，并且任何选择的时间也会在配置更改时丢失。我需要保持计数（如果已经开始），并保留任何当前显示的数字...
我知道适配器应该自己处理这些事情，并在OnCreate和OnCreateView中设置SetRetainInstance（true）。
我在Fragment代码中添加了钩子，以便在saveInstanceState不为null时让我知道情况，但似乎实例始终为NULL，并且从头开始创建...一直。
其他一些解决方案让我重写instantiateItem，但似乎它仅用于重置回调，其他则更改Manifest中的设置（这被反对）...其他解决方案看起来对我来说设置正确...但显然，我在途中搞砸了什么。我只提供FragmentActivity、FragementPagerAdapter和一些Fragment代码的代码，因为我不想在帖子中发布可能不是问题的代码。
FragmentActivity
public class Timer_Main extends FragmentActivity {
    ViewPager pager;
    Timer_Pager mAdapter;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.timer_pager);

        mAdapter = new Timer_Pager(this, getSupportFragmentManager());

        pager = (ViewPager) findViewById(R.id.timer_pager_display);
        pager.setAdapter(mAdapter);

    }

    public static String getTitle(Context ctxt, int position) {
                // TODO Auto-generated method stub
        return null;
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt("pageItem", pager.getCurrentItem());

    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

    }
}

The FragementPagerAdapter

public class Timer_Pager extends FragmentPagerAdapter{
    Context ctxt = null;
    public Timer_Pager(Context ctxt, FragmentManager fm) {
        super(fm);
        this.ctxt = ctxt;
        }


    @Override
    public Fragment getItem(int position) {

        switch (position) {
        case 0: {
            return(Countdown_Fragment.newInstance());
        }
        case 1:
            return(Countup_Fragment.newInstance());
        }
        return null;
    }

    @Override
    public String getPageTitle(int position) {

        switch (position) {
        case 0: 
            return(String.format(ctxt.getString(R.string.Countdown_label)));
        case 1: 
            return(String.format(ctxt.getString(R.string.Countup_label)));
        }
        return null;
    }

    @Override
    public int getCount() {
        // doing only three pages, right now...one for countdown, one for countup,         and one for Tabata.
        return 2;
    }

    private static String makeFragmentName(int viewId, int position)
    {
         return "android:switcher:" + viewId + ":" + position;
    }
}

这个Fragment代码有点多，所以我只会推送核心问题的部分... 如果需要更多内容，我会将它们拼接在一起。

public class Countdown_Fragment extends Fragment implements OnClickListener {
    Calendar CountdownTime = Calendar.getInstance();
    static AutoResizeTextView tv;
    static ImageButton HoursUp;
    static ImageButton HoursDown;
    static ImageButton MinutesUp;
    static ImageButton MinutesDown;
    static ImageButton SecondsUp;
    static ImageButton SecondsDown;
    static ImageButton Reset;
    static ImageButton StartPausecount;
    static ImageButton Stopcount;
    static Boolean Arewecounting = false;
    static Boolean Arewecountingdown = false;
    static AutoResizeTextView ThreetwooneGO;
    static MyCountdownTimer Countdown_Timer_Activity;
    ThreetwooneCount Start_countdown;
    static Long MillstoPass;

    static Countdown_Fragment newInstance() {

        Countdown_Fragment frag = new Countdown_Fragment();
        return (frag);
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {

        outState.putString("CurrentTimer", (String) tv.getText());
        Log.v("status", "saved fragment state" + tv.getText());
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        setRetainInstance(true);
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

            setRetainInstance(true);
            View result = inflater.inflate(R.layout.countdown_timer_layout,
                container, false);
        tv = (AutoResizeTextView) result.findViewById(R.id.timer_textview);
        tv.setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {
                new TimePickerDialog(getActivity(), t, 0, 0, true).show();
            }
        });
        if (savedInstanceState != null) {
            Log.v("status", "fragment is NOT empty");
            tv.setText(savedInstanceState.getString("CurrentTimer",
                    tv.toString()));
        } else {
            Log.v("status", "fragment is empty");
        //  tv.setText("00:00:00");

        }
        tv.resizeText();

        ThreetwooneGO = (AutoResizeTextView) result
                .findViewById(R.id.timer_countdown_text);

        HoursUp = (ImageButton) result.findViewById(R.id.hours_up);
        HoursDown = (ImageButton) result.findViewById(R.id.hours_down);
        MinutesUp = (ImageButton) result.findViewById(R.id.minutes_up);
        MinutesDown = (ImageButton) result.findViewById(R.id.minutes_down);
        SecondsUp = (ImageButton) result.findViewById(R.id.seconds_up);
        SecondsDown = (ImageButton) result.findViewById(R.id.seconds_down);
        Reset = (ImageButton) result.findViewById(R.id.reset);
        StartPausecount = (ImageButton) result
                .findViewById(R.id.startpausecount);
        Stopcount = (ImageButton) result.findViewById(R.id.stopcount);

        HoursUp.setOnClickListener(this);
        HoursDown.setOnClickListener(this);
        SecondsUp.setOnClickListener(this);
        SecondsDown.setOnClickListener(this);
        MinutesUp.setOnClickListener(this);
        MinutesDown.setOnClickListener(this);
        Reset.setOnClickListener(this);
        StartPausecount.setOnClickListener(this);
        Stopcount.setOnClickListener(this);

        return (result);
    }

    public void chooseTime(View v) {
        new TimePickerDialog(getActivity(), t, 0, 0, true).show();
    }

    TimePickerDialog.OnTimeSetListener t = new TimePickerDialog.OnTimeSetListener() {
        public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
            CountdownTime.set(Calendar.HOUR_OF_DAY, hourOfDay);
            CountdownTime.set(Calendar.MINUTE, minute);
            CountdownTime.set(Calendar.SECOND, 0);
            CountdownTime.set(Calendar.MILLISECOND, 0);

            updateLabel();
        }
    };

    private void updateLabel() {

        String entiretime;
        entiretime = String.format("%tT", CountdownTime);
        tv.setText(entiretime);
    }

这是我用于倒计时的计时器...

public class MyCountdownTimer {

private long millisInFuture;
private long countDownInterval;
Countdown_Fragment ctxt;
AutoResizeTextView Timer_edit;
private volatile boolean IsStopped = false;

public MyCountdownTimer(long pMillisInFuture, long pCountDownInterval,
        AutoResizeTextView Artv) {
    this.millisInFuture = pMillisInFuture;
    this.countDownInterval = pCountDownInterval;

    Timer_edit = Artv;

}

public void Start() {

    final Handler handler = new Handler();
    final Runnable counter = new Runnable() {

        public void run() {
            if (IsStopped == false) {
                if (millisInFuture <= 0) {
                    Countdown_Fragment.done_counting();
                } else {
                    long sec = millisInFuture / 1000;
                    Timer_edit.setText(String.format("%02d:%02d:%02d",
                            sec / 3600, (sec % 3600) / 60, (sec % 60)));
                    millisInFuture -= countDownInterval;
                    handler.postDelayed(this, countDownInterval);
                }
            }
        }
    };

    handler.postDelayed(counter, countDownInterval);
}

public void Cancel() {
    IsStopped = true;
    Timer_edit = null;
    Log.v("status", "Main Timer cancelled");
    // this.ctxt = null;

}
public long whatisourcount(){
    return(millisInFuture);
}
}
1个回答
4
事实证明，RetainInstance在ViewPager/Adapter/FragmentManager执行它们的任务时会与之发生冲突。移除它后，Pager可以正确重建Fragment，包括我之前所拥有的TextView。同时，在设置RetainInstance为True时，在OnCreateView中始终为空的Bundle也开始接收到了数据。
我不得不删除RetainInstance并利用OnSaveInstanceState和OnCreateView传递Fragment被销毁前的状态，并在OnCreateView中重新创建它以将Fragment重置为销毁前的状态。
我希望我使用的倒计时Runnable能够幸存下来或者我能够重新附加它，但我找不到方法。我必须保存当前计数（以毫秒为单位），并将其传回Fragment以继续从之前离开的地方开始。虽然这不是很大的问题，但我很好奇是否可以真正重新附加所有这些东西。Runnable在配置更改后仍然会继续运行，但它不再更新UI上的任何内容，因此当我在OnSaveInstanceState中时，我尝试取消回调并将其设为null。
我还在阅读一些只需要为具有AsyncTask或其他类似项附加RetainInstance的项使用它的内容...否则，只需在代码中重新构建即可。
嗨，我面临着类似的问题。是否有一种方法可以保持set retain instance为true并使其正常工作，否则我就必须重写我的整个逻辑。提前感谢您的帮助 :) - Nick
无法找到解决方法。 - Jeff DePiazza
https://dev59.com/zGw05IYBdhLWcg3w3lkl#29287415 - Morteza Rastgoo
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