android - 从日历中减去天数

Question

我的应用程序中有一个水平日历。所以我实现了以下库 https://github.com/Mulham-Raee/Horizontal-Calendar 我还实现了自己的后退和前进按钮。

从当前日期按后退一天，向前按一天。假设今天是 8 月 10 日，我水平滚动到 7 月 15 日，没有按下后退或前进按钮。现在，如果我按下后退按钮而不是转到 7 月 14 日，我将返回到 8 月 9 日。

以下是我的代码

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <com.myapplication.HorizontalCalendarView
        android:id="@+id/calendarView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:selectedDateBackground="@drawable/selected_date"
        />

    <Button
        android:id="@+id/back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginStart="8dp"
        android:text="Back"
        app:layout_constraintBottom_toTopOf="@+id/calendarView"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/forward"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="16dp"
        android:text="Forward"
        app:layout_constraintBottom_toTopOf="@+id/calendarView"
        app:layout_constraintEnd_toEndOf="parent" />

</android.support.constraint.ConstraintLayout>

Kotlin 代码:

    class MainActivity : AppCompatActivity() {

private var counter: Int = 0

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main_2)

    val format1 = SimpleDateFormat("yyyy-MM-dd", Locale.US)
    val currentDate = format1.format(Calendar.getInstance().time)

    Toast.makeText(this,currentDate.toString(),Toast.LENGTH_LONG).show()

    val startDate = Calendar.getInstance()
    startDate.add(Calendar.MONTH, -10)


    val endDate = Calendar.getInstance()
    endDate.add(Calendar.MONTH, 30)

    val horizontalCalendar = HorizontalCalendar.Builder(this, R.id.calendarView)
            .range(startDate, endDate)
            .datesNumberOnScreen(7)
            .build()


    horizontalCalendar.setCalendarListener(object : HorizontalCalendarListener() {
        override fun onDateSelected(date: Calendar, position: Int) {
            val selectedDate = format1.format(date.time)

            Toast.makeText(this@MainActivity,
                    "Pritish"+SimpleDateFormat("MMMM yyyy", Locale.US).format(date.time),
                    Toast.LENGTH_SHORT).show()

            if(format1.parse(selectedDate).before(format1.parse(currentDate))){
                Toast.makeText(this@MainActivity,"Cannot selecte previous date",Toast.LENGTH_LONG).show()
            } else {
                Toast.makeText(this@MainActivity,
                        selectedDate
                        ,Toast.LENGTH_LONG).show()
            }
        }

        override fun onCalendarScroll(calendarView: HorizontalCalendarView,
                                      dx: Int, dy: Int) {


            Log.i("Pritish",dx.toString()+dy.toString())


            counter += if(dx<0){
                -1
            } else {
                1
            }

        }

        override fun onDateLongClicked(date: Calendar, position: Int): Boolean {
            return true
        }
    })

    val cal = Calendar.getInstance()

    back.setOnClickListener {

        cal.add(Calendar.DAY_OF_MONTH,counter-1)
        counter = 0
        horizontalCalendar.selectDate(cal,false)
        horizontalCalendar.refresh()

    }

    forward.setOnClickListener {
        cal.add(Calendar.DAY_OF_MONTH,counter+1)
        counter = 0
        horizontalCalendar.selectDate(cal,false)
        horizontalCalendar.refresh()
    }
}
}

Answer 1

看起来 onDateSelected 可能会在滚动期间被触发，您可以使用它加上一个简单的 +1/-1，但您必须尝试一下看看它是否有效-- 很难仅基于查看库的代码来验证。