如何根據日期/時間過濾ArrayList並將其顯示在Android Studio的recyclerview中？

Question

我創建了一個允許用戶添加事件的事件列表，我想要做的只是顯示未通過當前日期和時間的事件。 我允許用戶選擇一個日期和時間，這些日期和時間以 dd/MM/yy (00/00/0000) 格式存儲為字符串，日期和 HH:mm (00:00) 格式存儲在單獨的字符串變量中。

我已經為此工作了近 3 天，但仍然無法弄清楚如何去做，這個概念就在我的腦海中，但似乎不想出去。 在嘗試了幾件事之后，我最終得到了類似的結果：

public void futureEvents() {
    ArrayList<Events> futureEvents = new ArrayList<>();
    long currentTime = new Date().getTime();
    Log.d("CurrentTime", String.valueOf(currentTime)); // This works fine, when I Log.d I get results like 1486243693904

    for(Events events : eventsList) {

        SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
        Date date = null;
        try { // I am forced to surround date = formatter.... code in try and catch
            date = formatter.parse(events.getEventDate());
        } catch (ParseException e) {

        }

        String eventTime = events.getEventTime();
        String []tokens = eventTime.split(":");
        long longEventTime = (long) ((Long.parseLong(tokens[0]) * 3.6e+6) + (Long.parseLong(tokens[1])* 1.66667e-5));
        long eventTimeAndDateInLong = Long.parseLong(String.valueOf(longEventTime + date.getTime()));

        if(currentTime < eventTimeAndDateInLong + 30*600000) {

            futureEvents.add(events); // throws a null object reference error
        }
    }

    adapter.filter(futureEvents); 
}

我不確定它是否有意義，但它肯定不起作用，而且我不想放棄，我厭倦了幾次嘗試后它不起作用，我對 Java 還很陌生，不現在還沒有我的方式。 如果有人可以提供幫助，我將不勝感激。

筆記。 我想要的只是過濾掉通過的事件並根據日期和時間顯示即將發生的事件。

更新 --- 堆棧跟蹤

02-05 11:33:47.282 19010-19010/com.example.myapp E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.myapp.SQLiteDB.EventsList_SQLDB.adapter.filter(java.util.ArrayList)' on a null object reference
                                                                          at layout.Events.upcomingEvents(Events.java:352)
                                                                          at layout.Events.onCreateView(Events.java:100)
                                                                          at android.support.v4.app.Fragment.performCreateView(Fragment.java:2184)
                                                                          at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1298)
                                                                          at android.support.v4.app.FragmentManagerImpl.moveFragmentsToInvisible(FragmentManager.java:2323)
                                                                          at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2136)
                                                                          at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2092)
                                                                          at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1969)
                                                                          at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:620)
                                                                          at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
                                                                          at android.support.v4.view.ViewPager.populate(ViewPager.java:1268)
                                                                          at android.support.v4.view.ViewPager.populate(ViewPager.java:1116)
                                                                          at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1642)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:714)
                                                                          at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90)
                                                                          at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1375)
                                                                          at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:784)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                          at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
                                                                          at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
                                                                          at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
                                                                          at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
                                                                          at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                          at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                          at com.android.internal.policy.DecorView.onMeasure(DecorView.java:689)
                                                                          at android.view.View.measure(View.java:19861)
                                                                          at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2275)
                                                                          at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1366)
                                                                          at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1619)
                                                                          at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254)
                                                                          at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6343)
                                                                          at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874)
                                                                          at android.view.Choreographer.doCallbacks(Choreographer.java:686)
                                                                          at android.view.Choreographer.doFrame(Choreographer.java:621)
                                                                          at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860)
                                                                          at android.os.Handler.handleCallback(Handler.java:751)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                          at android.os.Looper.loop(Looper.java:154)
02-05 11:33:47.282 19010-19010/com.example.myapp E/UncaughtException:     at android.app.ActivityThread.main(ActivityThread.java:6126)
                                                                          at java.lang.reflect.Method.invoke(Native Method)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

更新——什么是adapter.filter(FutureEvents) 這是一個簡單的過濾器，如果上面的代碼工作正常，它應該過濾掉以前的事件。 如果我將其他固定參數傳遞給它，它會起作用，例如 01/02/2017

public void setFilter(ArrayList<Events> filterEvents) {
        eventsLists = new ArrayList<>();
        eventsLists.addAll(filterevents);
        notifyDataSetChanged();
    }

Answer 1

Date類提供了測試日期是before()指定日期before()還是after()的方法。

您也可以獲取一個包含日期和時間信息的Date對象，然后將其與當前的 Date 對象進行比較。

使用所有這些，您可以像這樣大大簡化您的代碼：

public void futureEvents() {
    ArrayList<Events> futureEvents = new ArrayList<>();
    Date currentDate = new Date();

    for(Events events : eventsList) {    
        SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy HH:mm");
        Date date = null;
        try { 
            date = formatter.parse(events.getEventDate() + " " + events.getEventTime());
        } catch (ParseException e) {

        }

        if(currentDate.before(date)) {    
            futureEvents.add(events); 
        }
    }

    adapter.filter(futureEvents); 
}

編輯：以上仍然適用於您的代碼。 但是查看您的堆棧跟蹤，您會在adapter引用上收到NullPointerException 。 您的adapter對象引用為空。 確保在調用futureEvents()方法之前初始化adapter對象。

如果要在任一側設置閾值，可以修改當前日期對象，使其指向根據閾值設置的日期和時間。 例如，如果您想過濾接下來 30 分鍾內發生的事件，您可以執行以下操作：

public void futureEvents() {
    ArrayList<Events> futureEvents = new ArrayList<>();
    Date currentDate = new Date();

    for(Events events : eventsList) {    
        SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy HH:mm");
        Date date = null;
        try { 
            date = formatter.parse(events.getEventDate() + " " + events.getEventTime());
        } catch (ParseException e) {

        }

        Date thresholdDate = currentDate.clone(); //makes a copy of the currentDate object
        thresholdDate.setMinutes(thresholdDate .getMinutes() + 30);//Modify minutes to 30 minutes in future.

        if(currentDate.before(date) && date.before(thresholdDate)) {    
            futureEvents.add(events); 
        }
    }

    adapter.filter(futureEvents); 
}

同樣，您可以修改hours、days、months或years 。