Android 如何使用辅助线程从数据库获取数据并填充GridView

我正在开发一个日历应用程序，它从数据库中检索事件并将它们填充到我的自定义日历中

public class GridAdapter extends ArrayAdapter {


private LayoutInflater mInflater;
private List<Date> monthlyDates;
private Calendar currentDate;
private List<Calendar> allEvents;
ShiftManager shiftManager;
Calendar theDay = null;
Context context;
Calendar dateCal;

public GridAdapter(Context context, List<Date> monthlyDates, Calendar currentDate, List<Calendar> allEvents) {
    super(context, com.example.trackmypay.R.layout.single_cell_layout);
    this.monthlyDates = monthlyDates;
    this.currentDate = currentDate;
    this.allEvents = allEvents;
    shiftManager = new ShiftManager((FragmentActivity)context);
    mInflater = LayoutInflater.from(context);
    this.context = context;


}


@NonNull
@Override
public View getView(int position, View convertView, final ViewGroup parent) {
    Date mDate = monthlyDates.get(position);
    dateCal = Calendar.getInstance();
    dateCal.setTime(mDate);

    dateCal.set(Calendar.HOUR_OF_DAY, 0);
    dateCal.set(Calendar.MINUTE, 0);
    dateCal.set(Calendar.SECOND, 0);
    dateCal.set(Calendar.MILLISECOND, 0);


    final int dayValue = dateCal.get(Calendar.DAY_OF_MONTH);
    final int displayMonth = dateCal.get(Calendar.MONTH) + 1;
    final int displayYear = dateCal.get(Calendar.YEAR);
    final int currentMonth = currentDate.get(Calendar.MONTH) + 1;
    final int currentYear = currentDate.get(Calendar.YEAR);

    View view = convertView;


    theDay = shiftManager.retrieveShiftsForCalendar(dateCal.getTimeInMillis());


    if(view == null){
        view = mInflater.inflate(com.example.trackmypay.R.layout.single_cell_layout, parent, false);

    }



    if(displayMonth != currentMonth || displayYear != currentYear){

        TextView dayNum = view.findViewById(R.id.calendar_date_id);
        dayNum.setTextColor(Color.parseColor("#b4b5bf"));

    }


    //Add day to calendar
    TextView cellNumber = view.findViewById(R.id.calendar_date_id);
    cellNumber.setText(String.valueOf(dayValue));
    Calendar tempC = Calendar.getInstance();
    if (dayValue == tempC.get(Calendar.DAY_OF_MONTH) && currentMonth == tempC.get(Calendar.MONTH) + 1  && currentYear == tempC.get(Calendar.YEAR))
    {
        cellNumber.setTextColor(Color.parseColor("#01579B"));
        cellNumber.setTypeface(Typeface.DEFAULT_BOLD);
    }


            ImageView eventIndicator = view.findViewById(R.id.event_id);


            if (theDay != null && dayValue == theDay.get(Calendar.DAY_OF_MONTH) && displayMonth == theDay.get(Calendar.MONTH) + 1 && displayYear == theDay.get(Calendar.YEAR)) {
                eventIndicator.setImageResource(R.drawable.ic_work);
            }


        //Add events to the calendar

    return view;
}

设置日历单元格

TextView cellNumber = view.findViewById(R.id.calendar_date_id);
cellNumber.setText(String.valueOf(dayValue));
Calendar tempC = Calendar.getInstance();
if (dayValue == tempC.get(Calendar.DAY_OF_MONTH) && currentMonth == tempC.get(Calendar.MONTH) + 1  && currentYear == tempC.get(Calendar.YEAR))
{
    cellNumber.setTextColor(Color.parseColor("#01579B"));
    cellNumber.setTypeface(Typeface.DEFAULT_BOLD);
}

如果此日期存在事件，则填充图标

        ImageView eventIndicator = view.findViewById(R.id.event_id);
if (theDay != null && dayValue == theDay.get(Calendar.DAY_OF_MONTH) && displayMonth == theDay.get(Calendar.MONTH) + 1 && displayYear == theDay.get(Calendar.YEAR)) {
            eventIndicator.setImageResource(R.drawable.ic_work);
        }

我本想使用AsyncTask来实现这一点，但Android 11中不推荐使用它

我对线程有点陌生，所以我想看看是否有人能帮我正确设置它，所以工作线程调用数据库，而UI线程设置日历单元格，然后一旦工作线程完成从数据库获取事件的工作，UI线程就会将其填充到日历单元格中

谢谢

看一看

• 遗嘱执行人：
• 处理程序：

执行者可以在后台轻松执行任务

Executors.newSingleThreadExecutor().execute(()->{

        //Background task

});

而处理程序使在主线程中执行代码变得容易

new Handler(Looper.getMainLooper()).post(() -> {
        // Main thread code
});

这些都是简单的代码片段，您可以保留对实际执行器实例或处理程序实例的引用，以避免大量代码重复

---

如果可能的话，您应该检查Android（Room、ViewModel、LiveData）中的架构组件（），它以更优雅的方式解决了这个问题，但它可能需要对您当前的代码库进行全面重构。

最终对我有效的解决方案：

    final Executor execDbCall = Executors.newCachedThreadPool();
    Runnable dbCall = new Runnable() {
        @Override
        public void run() {
            synchronized (execDbCall)
            {
                theDay = shiftManager.retrieveShiftsForCalendar(dateCal.getTimeInMillis());
                execDbCall.notify();

            }

        }
    };


    Runnable buildUI = new Runnable() {
        @Override
        public void run() {
            if(view[0] == null){
                view[0] = mInflater.inflate(com.example.trackmypay.R.layout.single_cell_layout, parent, false);

            }

            if(displayMonth != currentMonth || displayYear != currentYear){

                TextView dayNum = view[0].findViewById(R.id.calendar_date_id);
                dayNum.setTextColor(Color.parseColor("#b4b5bf"));

            }


            //Add day to calendar
            TextView cellNumber = view[0].findViewById(R.id.calendar_date_id);
            cellNumber.setText(String.valueOf(dayValue));
            Calendar tempC = Calendar.getInstance();
            if (dayValue == tempC.get(Calendar.DAY_OF_MONTH) && currentMonth == tempC.get(Calendar.MONTH) + 1  && currentYear == tempC.get(Calendar.YEAR))
            {
                cellNumber.setTextColor(Color.parseColor("#01579B"));
                cellNumber.setTypeface(Typeface.DEFAULT_BOLD);
            }



        }
    };

    Runnable setEvent = new Runnable() {
        @Override
        public void run() {
            ImageView eventIndicator = view[0].findViewById(R.id.event_id);

            if (theDay != null && dayValue == theDay.get(Calendar.DAY_OF_MONTH) && displayMonth == theDay.get(Calendar.MONTH) + 1 && displayYear == theDay.get(Calendar.YEAR)) {
                eventIndicator.setImageResource(R.drawable.ic_work);
            }

        }
    };


    ((FragmentActivity)context).runOnUiThread(buildUI);

    synchronized (execDbCall)
    {
        execDbCall.execute(dbCall);
        try {

            execDbCall.wait();

            ((FragmentActivity)context).runOnUiThread(setEvent);

        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

谢谢你djleop让我走上了解决方案的轨道

    final Executor execDbCall = Executors.newCachedThreadPool();
    Runnable dbCall = new Runnable() {
        @Override
        public void run() {
            synchronized (execDbCall)
            {
                theDay = shiftManager.retrieveShiftsForCalendar(dateCal.getTimeInMillis());
                execDbCall.notify();

            }

        }
    };


    Runnable buildUI = new Runnable() {
        @Override
        public void run() {
            if(view[0] == null){
                view[0] = mInflater.inflate(com.example.trackmypay.R.layout.single_cell_layout, parent, false);

            }

            if(displayMonth != currentMonth || displayYear != currentYear){

                TextView dayNum = view[0].findViewById(R.id.calendar_date_id);
                dayNum.setTextColor(Color.parseColor("#b4b5bf"));

            }


            //Add day to calendar
            TextView cellNumber = view[0].findViewById(R.id.calendar_date_id);
            cellNumber.setText(String.valueOf(dayValue));
            Calendar tempC = Calendar.getInstance();
            if (dayValue == tempC.get(Calendar.DAY_OF_MONTH) && currentMonth == tempC.get(Calendar.MONTH) + 1  && currentYear == tempC.get(Calendar.YEAR))
            {
                cellNumber.setTextColor(Color.parseColor("#01579B"));
                cellNumber.setTypeface(Typeface.DEFAULT_BOLD);
            }



        }
    };

    Runnable setEvent = new Runnable() {
        @Override
        public void run() {
            ImageView eventIndicator = view[0].findViewById(R.id.event_id);

            if (theDay != null && dayValue == theDay.get(Calendar.DAY_OF_MONTH) && displayMonth == theDay.get(Calendar.MONTH) + 1 && displayYear == theDay.get(Calendar.YEAR)) {
                eventIndicator.setImageResource(R.drawable.ic_work);
            }

        }
    };


    ((FragmentActivity)context).runOnUiThread(buildUI);

    synchronized (execDbCall)
    {
        execDbCall.execute(dbCall);
        try {

            execDbCall.wait();

            ((FragmentActivity)context).runOnUiThread(setEvent);

        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }