如何在UI線程中運行此類？

Question

我有類ScheduleTimer，它適用於日期數組。 這里是：

class ScheduleTimer {

    public TextView textView;

    private Timer dateTimer;

    private Timer remainderTimer;

    private Date formatDate = new Date();

    private Date nextDate;

    private boolean remainderTimerStarted;

    private static final long REMINDER_UPDATE_INTERVAL = 1000;

    private static String[] DATES;

    private int currentIndex;

    public ScheduleTimer(final TextView t) {
        textView = t;
        dateTimer = new Timer();
    }

    public void main(String[] dates) throws ParseException {
        checkDates(dates);
        run();
    }

    private void checkDates(String[] dates) throws ParseException {
        List<String> list = new ArrayList<>();
        DateFormat format = new SimpleDateFormat("dd.MM.yyyy HH:mm", Locale.ENGLISH);
        for(String date : dates) {
            long current = System.currentTimeMillis() + 1000;
            if(format.parse(date).getTime() - current > 0) {
                list.add(date);
            }
        }
        DATES = new String[list.size()];
        list.toArray(DATES);
    }

    private void run() {
        nextDate = parseDate(DATES[currentIndex]);
        schedule();
    }

    public void schedule() {
        runSecondsCounter();
        dateTimer.schedule(new TimerTask() {

            @Override
            public void run() {

                System.out.println("Current date is:" + new Date());
                currentIndex++;
                if (currentIndex < DATES.length) {
                    nextDate = parseDate(DATES[currentIndex]);
                    System.out.println("Next date is:" + nextDate);
                    schedule();
                } else {
                    remainderTimer.cancel();
                }
            }
        }, nextDate);

    }

    private Date parseDate(String nextDate) {
        Date date = null;
        DateFormat format = new SimpleDateFormat("dd.MM.yyyy HH:mm",
                Locale.ENGLISH);
        try {
            date = format.parse(nextDate);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }

    private void runSecondsCounter() {
        if (remainderTimerStarted) {
            remainderTimer.cancel();
        }

        remainderTimer = new Timer();
        remainderTimer.scheduleAtFixedRate(new TimerTask() {

            @Override
            public void run() {
                remainderTimerStarted = true;
                long remains = nextDate.getTime() - new Date().getTime();
                System.out.println("Remains: " + (remains / 1000) + " seconds");
                formatDate.setTime(remains);
                textView.setText(formatDate.toString());
            }
        }, REMINDER_UPDATE_INTERVAL, REMINDER_UPDATE_INTERVAL);
    }
}

如果我像Java應用程序一樣運行它，而不是android，它可以正常運行，並且它會在控制台中打印出每個計數秒。 但是當它在android環境中運行它時，它要么說不能從任何其他線程觸及UI線程，要么它在ScheduleTimer類的方法run()中給我NullPointerException 。

我正在使用它： new ScheduleTimer(textView).main(new String[] {"13.04.2015 13:59", "13.04.2015 14:14", "13.04.2015 14:15"});

我嘗試使用AsyncTask或Handler ，但可能，我做得不對。 無論如何，我需要找到使用這個類以某種方式更新我的TextView的方法。

有人可以幫我嗎？ 如何在我的onCreateView方法中正常運行它並正確傳遞所需的TextView ？

Answer 1

runOnUiThread()方法將發送您的Runnable執行到主線程。 在run() ，您可以操作UI控件：

@Override
public void run() {
     remainderTimerStarted = true;
     long remains = nextDate.getTime() - new Date().getTime();
     formatDate.setTime(remains);
     runOnUiThread(new Runnable() {    // <= here!
          @Override
          public void run() {
              textView.setText(formatDate.toString());
          }
     });
 }

檢查這個以獲得更多解釋。

Answer 2

AsyncTask的骨架將是：

public class ListLoader extends AsyncTask<Void, Void, String> {

        ProgressDialog Asycdialog = new ProgressDialog(CreateGroup.this);
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            System.out.println("Pre Execute");
            Asycdialog.setMessage("Working");
            Asycdialog.getWindow().setGravity(Gravity.CENTER_VERTICAL);
            Asycdialog.getWindow().setGravity(Gravity.CENTER_HORIZONTAL);
            Asycdialog.setCancelable(false);
            Asycdialog.show();
            super.onPreExecute();
        }

        protected void onPostExecute(String result) {
            Asycdialog.cancel();

            //Play with result here - Update UI
        }

        @Override
        protected String doInBackground(Context... params) {

            //Memory intense or long running operation here
            publishProgress(progress); //Publish your progress - update a textView

            return "result will be sent to onPostExecute()";

        }

        protected void onProgressUpdate(String... values) {

            super.onProgressUpdate(values);
            Asycdialog.setMessage("" + values[0]);
        }


    }

Answer 3

完整的答案是：你的片段：

public class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);

            TextView textView = (TextView) rootView.findViewById(R.id.tv);

            try {
                new ScheduleTimer(textView, getActivity())
                        .main(new String[] {"13.04.2015 13:59", "13.04.2015 14:14", "13.04.2015 14:15"});
            } catch (ParseException e) {
                e.printStackTrace();
            }

            return rootView;
        }
    }

您的ScheduleTimer類：

class ScheduleTimer {

    public TextView textView;

    private Timer dateTimer;

    private Timer remainderTimer;

    private Date formatDate = new Date();

    private Date nextDate;

    private boolean remainderTimerStarted;

    private static final long REMINDER_UPDATE_INTERVAL = 1000;

    private static String[] DATES;

    private int currentIndex;

    private Activity activity;

    public ScheduleTimer(final TextView t, Activity a) {
        textView = t;
        activity = a;
        dateTimer = new Timer();
    }

    public void main(String[] dates) throws ParseException {
        checkDates(dates);
        run();
    }

    private void checkDates(String[] dates) throws ParseException {
        List<String> list = new ArrayList<>();
        DateFormat format = new SimpleDateFormat("dd.MM.yyyy HH:mm", Locale.ENGLISH);
        for(String date : dates) {
            long current = System.currentTimeMillis() + 1000;
            if(format.parse(date).getTime() - current > 0) {
                list.add(date);
            }
        }
        DATES = new String[list.size()];
        list.toArray(DATES);
    }

    private void run() {
        nextDate = parseDate(DATES[currentIndex]);
        schedule();
    }

    public void schedule() {
        runSecondsCounter();
        dateTimer.schedule(new TimerTask() {

            @Override
            public void run() {

                System.out.println("Current date is:" + new Date());
                currentIndex++;
                if (currentIndex < DATES.length) {
                    nextDate = parseDate(DATES[currentIndex]);
                    System.out.println("Next date is:" + nextDate);
                    schedule();
                } else {
                    remainderTimer.cancel();
                }
            }
        }, nextDate);

    }

    private Date parseDate(String nextDate) {
        Date date = null;
        DateFormat format = new SimpleDateFormat("dd.MM.yyyy HH:mm",
                Locale.ENGLISH);
        try {
            date = format.parse(nextDate);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }

    private void runSecondsCounter() {
        if (remainderTimerStarted) {
            remainderTimer.cancel();
        }

        remainderTimer = new Timer();
        remainderTimer.scheduleAtFixedRate(new TimerTask() {

            @Override
            public void run() {
                remainderTimerStarted = true;
                long remains = nextDate.getTime() - new Date().getTime();
                System.out.println("Remains: " + (remains / 1000) + " seconds");
                formatDate.setTime(remains);

                activity.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        textView.setText(formatDate.toString());
                    }
                });

            }
        }, REMINDER_UPDATE_INTERVAL, REMINDER_UPDATE_INTERVAL);
    }
}