Question

如何将setOnDateChangeListener的值传递给DATABASE_NAME？

我像这样格式化了我的dbhelper

public static String getDateTime() {
        SimpleDateFormat dateFormat = new SimpleDateFormat(
                "yyyyMMdd", Locale.getDefault());
        Date date = new Date();
        return dateFormat.format(date);
    }

    // Database Name
    private static final String DATABASE_NAME = getDateTime();

虽然我将日历setOnDateChangeListener格式化，就像我格式化DATABASE_NAME一样。

以下是我的回购类，它从今天的日期获得总和（Fats）我想要的是从我点击日历的日期获得总和（Fats）。

public double totalFatB(){

        SQLiteDatabase db = dbHelper.getReadableDatabase();

        String query = "SELECT SUM(Fat) FROM " +breakfast.TABLE;

        Cursor c = db.rawQuery(query, null);

        c.moveToFirst();
        double i=c.getDouble(0);

        return i;

    }

这是我的onDateChangeListener

CalendarView calendarView=(CalendarView) findViewById(R.id.calendarView);
        calendarView.setOnDateChangeListener(new CalendarView.OnDateChangeListener() {

            @Override
            public void onSelectedDayChange(CalendarView view, int year, int month,
                                            int dayOfMonth) {
                month = month+1;
                if ((month == 1) || (month == 2)|| (month == 3)|| (month == 4)|| (month == 5)|| (month == 6)|| (month == 7)|| (month == 8)|| (month == 9) )
                {
                    String m= "0"+month;
                    if ((dayOfMonth == 1) || (dayOfMonth == 2)|| (dayOfMonth == 3)|| (dayOfMonth == 4)|| (dayOfMonth == 5)|| (dayOfMonth == 6)|| (dayOfMonth == 7)|| (dayOfMonth == 8)|| (dayOfMonth == 9) ) {
                        String d = "0" + dayOfMonth;
                         date= year +""+ m +""+ d;
                        Toast.makeText(getApplicationContext(),date, Toast.LENGTH_LONG).show();
                        /*Toast.makeText(getApplicationContext(), "" + year + m + d, Toast.LENGTH_LONG).show();*/
                    }
                        else
                        {
                             date= year +""+ m +""+ dayOfMonth;
                            Toast.makeText(getApplicationContext(),date, Toast.LENGTH_LONG).show();
                            /*Toast.makeText(getApplicationContext(), "" + year + m + dayOfMonth, Toast.LENGTH_LONG).show();*/
                        }
                }
                else if ((dayOfMonth == 1) || (dayOfMonth == 2)|| (dayOfMonth == 3)|| (dayOfMonth == 4)|| (dayOfMonth == 5)|| (dayOfMonth == 6)|| (dayOfMonth == 7)|| (dayOfMonth == 8)|| (dayOfMonth == 9) ) {
                    String d = "0" + dayOfMonth;
                     date= year +""+ month +""+ d;
                    Toast.makeText(getApplicationContext(),date, Toast.LENGTH_LONG).show();
                    /*Toast.makeText(getApplicationContext(), "" + year + month + d, Toast.LENGTH_LONG).show();*/
                }
                    else
                {
                    date= year +""+ month +""+ dayOfMonth;
                    Toast.makeText(getApplicationContext(),date, Toast.LENGTH_LONG).show();
                    /*Toast.makeText(getApplicationContext(), "" + year + month + dayOfMonth, Toast.LENGTH_LONG).show();*/
                }
            }
        });

Answer 1

如何将setOnDateChangeListener的值传递给DATABASE_NAME？

简单地说 - 你不应该这样做。如果这样做，那意味着每天有一个数据库文件，这会导致应用程序数据产生开销。

除此之外，SQLiteOpenHelper类只在构造时查看数据库名称字符串，因此如果您有多个名称，则为每个日期重新创建该对象，并且会耗尽设备的内存/电池。

从理论上讲，这是可能的......

@Override
public void onSelectedDayChange(CalendarView view, int year, int month,
                                        int dayOfMonth) {
    // Build a Calendar
    Calendar c = Calendar.getInstance();
    // c.set(); // TODO: Set year, month, dayOfMonth 
    ...
    SimpleDateFormat dateFormat = new SimpleDateFormat(
            "yyyyMMdd", Locale.getDefault());

    // Get a database by name
    String DATABASE_NAME = dateFormat.format(c.getTime());
    SQLiteDatabase db = SQLiteDatabase.openDatabase(DATABASE_NAME , null, SQLiteDatabase.OPEN_READONLY);

    // TODO: Query 'db'

但我不推荐它。

相反，您可以使用一个主数据库和store a date column (as a TEXT or INT) within your SQLlite table

然后，您可以直接执行public double totalFatB(Date date)或传递(year, month, day)并构建WHERE语句，以便从setOnDateChangeListener方法过滤特定日期。

另外，请在该方法中再次使用SimpleDateFormat来正确构建日期字符串，如图所示。如果陈述非常冗长。

将setOnDateChangeListener的值传递给DATABASE_NAME

1 个答案: