/*
 * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 总体分析
这段 Java 代码定义了一个名为DateTimePicker的自定义视图类，用于实现一个方便用户选择日期和时间的交互组件。它基于安卓的相关时间处理类以及视图组件（如NumberPicker）构建而成，支持 24 小时制和 12 小时制（含 AM/PM 标识）的时间显示与选择，并且可以方便地获取和设置年、月、日、时、分等具体时间信息，同时提供了相应的监听器接口，当时间相关的值发生改变时能触发回调通知外部代码，整体旨在为安卓应用中涉及时间选择的场景提供一个可定制且功能较全面的 UI 组件。
函数分析
构造函数相关
DateTimePicker(Context context)、DateTimePicker(Context context, long date)、DateTimePicker(Context context, long date, boolean is24HourView)：
功能概述：这几个是重载的构造函数，用于创建DateTimePicker实例。它们根据传入参数的不同来初始化组件的不同状态。最基础的构造函数会以当前系统时间作为初始时间进行初始化，而带有日期参数的构造函数则按照传入的指定日期来初始化，带有额外布尔值参数的构造函数还可以指定是否采用 24 小时制来初始化时间显示模式等。
具体细节：
在构造函数内部，首先获取一个Calendar实例用于表示日期时间，标记正在初始化（mInitialising设为true），根据当前小时数判断是上午还是下午（确定mIsAm的值），然后通过inflate方法加载对应的布局文件（R.layout.datetime_picker）来构建视图的外观。
接着获取布局中的各个NumberPicker组件（分别对应日期、小时、分钟、AM/PM），并为它们设置合适的最小值、最大值以及各自对应的OnValueChangeListener监听器，这些监听器会在对应NumberPicker的值发生改变时执行相应逻辑来更新整个时间状态以及触发对外的时间改变通知等。例如，mOnDateChangedListener用于处理日期选择改变时的逻辑，如更新日期、触发整体时间改变通知等。
之后调用一系列update开头的函数（如updateDateControl、updateHourControl、updateAmPmControl）来初始化各个时间相关组件的显示内容和状态，按照传入的参数设置是否为 24 小时制（set24HourView方法调用），设置初始时间（通过setCurrentDate相关方法），设置组件的启用状态（调用setEnabled方法），最后将mInitialising设为false表示初始化完成。
时间获取相关函数
getCurrentDateInTimeMillis()：
功能：返回当前通过DateTimePicker组件所表示的日期时间对应的毫秒数，通过获取内部Calendar实例（mDate）的时间毫秒值来实现，外部代码可以利用这个值来进一步存储或者传递该时间信息等。
getCurrentYear()、getCurrentMonth()、getCurrentDay()、getCurrentHourOfDay()、getCurrentMinute()：
功能：这些函数分别用于获取当前在DateTimePicker组件中所表示时间的年、月、日、24 小时制的小时数、分钟数，都是通过调用内部Calendar实例（mDate）的对应get方法（如Calendar.YEAR、Calendar.MONTH等）来获取相应的值，方便外部代码获取具体的时间字段信息。
时间设置相关函数
setCurrentDate(long date)、setCurrentDate(int year, int month, int dayOfMonth, int hourOfDay, int minute)：
功能：前者接收一个表示日期时间的毫秒数参数，后者接收年、月、日、小时、分钟的具体整数值参数，它们最终都是调用内部的一系列setCurrent开头的函数（如setCurrentYear、setCurrentMonth等）来分别设置对应的时间字段，在设置过程中会进行一些合理性判断（如判断是否正在初始化以及当前值与传入值是否相同等情况来决定是否执行更新操作），并且更新相关的时间显示组件以及触发时间改变的通知（通过onDateTimeChanged方法）。
setCurrentYear(int year)、setCurrentMonth(int month)、setCurrentDay(int dayOfMonth)、setCurrentHour(int hourOfDay)、setCurrentMinute(int minute)：
功能：这些函数分别用于单独设置时间中的年、月、日、小时、分钟字段的值，同样在设置时会进行一些前置判断（如是否正在初始化以及当前值与传入值对比等），然后通过mDate（Calendar实例）的对应set方法来更新内部时间状态，并且会更新相应的时间显示组件以及触发时间改变的通知，确保整个DateTimePicker组件的时间状态和显示能保持一致并且外部能得知时间的改变情况。
时间显示模式相关函数
is24HourView()：
功能：返回一个布尔值，用于表示当前DateTimePicker组件是否处于 24 小时制显示时间的模式，通过查看内部的mIs24HourView变量的值来确定，外部代码可以利用这个函数来知晓当前的时间显示格式情况。
set24HourView(boolean is24HourView)：
功能：用于设置DateTimePicker组件的时间显示模式，根据传入的布尔值参数来决定是否切换为 24 小时制或 12 小时制（含 AM/PM 显示）。在切换过程中，会调整AmPmSpinner组件的可见性，更新小时选择组件（HourSpinner）的取值范围，重新设置当前小时数并更新 AM/PM 显示控制等相关操作，以确保整个组件的显示与设置的时间显示模式相匹配。
 */

package net.micode.notes.ui;

import java.text.DateFormatSymbols;
import java.util.Calendar;

import net.micode.notes.R;


import android.content.Context;
import android.text.format.DateFormat;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.NumberPicker;

public class DateTimePicker extends FrameLayout {

    private static final boolean DEFAULT_ENABLE_STATE = true;

    private static final int HOURS_IN_HALF_DAY = 12;
    private static final int HOURS_IN_ALL_DAY = 24;
    private static final int DAYS_IN_ALL_WEEK = 7;
    private static final int DATE_SPINNER_MIN_VAL = 0;
    private static final int DATE_SPINNER_MAX_VAL = DAYS_IN_ALL_WEEK - 1;
    private static final int HOUR_SPINNER_MIN_VAL_24_HOUR_VIEW = 0;
    private static final int HOUR_SPINNER_MAX_VAL_24_HOUR_VIEW = 23;
    private static final int HOUR_SPINNER_MIN_VAL_12_HOUR_VIEW = 1;
    private static final int HOUR_SPINNER_MAX_VAL_12_HOUR_VIEW = 12;
    private static final int MINUT_SPINNER_MIN_VAL = 0;
    private static final int MINUT_SPINNER_MAX_VAL = 59;
    private static final int AMPM_SPINNER_MIN_VAL = 0;
    private static final int AMPM_SPINNER_MAX_VAL = 1;

    private final NumberPicker mDateSpinner;
    private final NumberPicker mHourSpinner;
    private final NumberPicker mMinuteSpinner;
    private final NumberPicker mAmPmSpinner;
    private Calendar mDate;

    private String[] mDateDisplayValues = new String[DAYS_IN_ALL_WEEK];

    private boolean mIsAm;

    private boolean mIs24HourView;

    private boolean mIsEnabled = DEFAULT_ENABLE_STATE;

    private boolean mInitialising;

    private OnDateTimeChangedListener mOnDateTimeChangedListener;

    private NumberPicker.OnValueChangeListener mOnDateChangedListener = new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            mDate.add(Calendar.DAY_OF_YEAR, newVal - oldVal);
            updateDateControl();
            onDateTimeChanged();
        }
    };

    private NumberPicker.OnValueChangeListener mOnHourChangedListener = new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            boolean isDateChanged = false;
            Calendar cal = Calendar.getInstance();
            if (!mIs24HourView) {
                if (!mIsAm && oldVal == HOURS_IN_HALF_DAY - 1 && newVal == HOURS_IN_HALF_DAY) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, 1);
                    isDateChanged = true;
                } else if (mIsAm && oldVal == HOURS_IN_HALF_DAY && newVal == HOURS_IN_HALF_DAY - 1) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, -1);
                    isDateChanged = true;
                }
                if (oldVal == HOURS_IN_HALF_DAY - 1 && newVal == HOURS_IN_HALF_DAY ||
                        oldVal == HOURS_IN_HALF_DAY && newVal == HOURS_IN_HALF_DAY - 1) {
                    mIsAm = !mIsAm;
                    updateAmPmControl();
                }
            } else {
                if (oldVal == HOURS_IN_ALL_DAY - 1 && newVal == 0) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, 1);
                    isDateChanged = true;
                } else if (oldVal == 0 && newVal == HOURS_IN_ALL_DAY - 1) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, -1);
                    isDateChanged = true;
                }
            }
            int newHour = mHourSpinner.getValue() % HOURS_IN_HALF_DAY + (mIsAm ? 0 : HOURS_IN_HALF_DAY);
            mDate.set(Calendar.HOUR_OF_DAY, newHour);
            onDateTimeChanged();
            if (isDateChanged) {
                setCurrentYear(cal.get(Calendar.YEAR));
                setCurrentMonth(cal.get(Calendar.MONTH));
                setCurrentDay(cal.get(Calendar.DAY_OF_MONTH));
            }
        }
    };

    private NumberPicker.OnValueChangeListener mOnMinuteChangedListener = new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            int minValue = mMinuteSpinner.getMinValue();
            int maxValue = mMinuteSpinner.getMaxValue();
            int offset = 0;
            if (oldVal == maxValue && newVal == minValue) {
                offset += 1;
            } else if (oldVal == minValue && newVal == maxValue) {
                offset -= 1;
            }
            if (offset != 0) {
                mDate.add(Calendar.HOUR_OF_DAY, offset);
                mHourSpinner.setValue(getCurrentHour());
                updateDateControl();
                int newHour = getCurrentHourOfDay();
                if (newHour >= HOURS_IN_HALF_DAY) {
                    mIsAm = false;
                    updateAmPmControl();
                } else {
                    mIsAm = true;
                    updateAmPmControl();
                }
            }
            mDate.set(Calendar.MINUTE, newVal);
            onDateTimeChanged();
        }
    };

    private NumberPicker.OnValueChangeListener mOnAmPmChangedListener = new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            mIsAm = !mIsAm;
            if (mIsAm) {
                mDate.add(Calendar.HOUR_OF_DAY, -HOURS_IN_HALF_DAY);
            } else {
                mDate.add(Calendar.HOUR_OF_DAY, HOURS_IN_HALF_DAY);
            }
            updateAmPmControl();
            onDateTimeChanged();
        }
    };

    public interface OnDateTimeChangedListener {
        void onDateTimeChanged(DateTimePicker view, int year, int month,
                int dayOfMonth, int hourOfDay, int minute);
    }

    public DateTimePicker(Context context) {
        this(context, System.currentTimeMillis());
    }

    public DateTimePicker(Context context, long date) {
        this(context, date, DateFormat.is24HourFormat(context));
    }

    public DateTimePicker(Context context, long date, boolean is24HourView) {
        super(context);
        mDate = Calendar.getInstance();
        mInitialising = true;
        mIsAm = getCurrentHourOfDay() >= HOURS_IN_HALF_DAY;
        inflate(context, R.layout.datetime_picker, this);

        mDateSpinner = (NumberPicker) findViewById(R.id.date);
        mDateSpinner.setMinValue(DATE_SPINNER_MIN_VAL);
        mDateSpinner.setMaxValue(DATE_SPINNER_MAX_VAL);
        mDateSpinner.setOnValueChangedListener(mOnDateChangedListener);

        mHourSpinner = (NumberPicker) findViewById(R.id.hour);
        mHourSpinner.setOnValueChangedListener(mOnHourChangedListener);
        mMinuteSpinner =  (NumberPicker) findViewById(R.id.minute);
        mMinuteSpinner.setMinValue(MINUT_SPINNER_MIN_VAL);
        mMinuteSpinner.setMaxValue(MINUT_SPINNER_MAX_VAL);
        mMinuteSpinner.setOnLongPressUpdateInterval(100);
        mMinuteSpinner.setOnValueChangedListener(mOnMinuteChangedListener);

        String[] stringsForAmPm = new DateFormatSymbols().getAmPmStrings();
        mAmPmSpinner = (NumberPicker) findViewById(R.id.amPm);
        mAmPmSpinner.setMinValue(AMPM_SPINNER_MIN_VAL);
        mAmPmSpinner.setMaxValue(AMPM_SPINNER_MAX_VAL);
        mAmPmSpinner.setDisplayedValues(stringsForAmPm);
        mAmPmSpinner.setOnValueChangedListener(mOnAmPmChangedListener);

        // update controls to initial state
        updateDateControl();
        updateHourControl();
        updateAmPmControl();

        set24HourView(is24HourView);

        // set to current time
        setCurrentDate(date);

        setEnabled(isEnabled());

        // set the content descriptions
        mInitialising = false;
    }

    @Override
    public void setEnabled(boolean enabled) {
        if (mIsEnabled == enabled) {
            return;
        }
        super.setEnabled(enabled);
        mDateSpinner.setEnabled(enabled);
        mMinuteSpinner.setEnabled(enabled);
        mHourSpinner.setEnabled(enabled);
        mAmPmSpinner.setEnabled(enabled);
        mIsEnabled = enabled;
    }

    @Override
    public boolean isEnabled() {
        return mIsEnabled;
    }

    /**
     * Get the current date in millis
     *
     * @return the current date in millis
     */
    public long getCurrentDateInTimeMillis() {
        return mDate.getTimeInMillis();
    }

    /**
     * Set the current date
     *
     * @param date The current date in millis
     */
    public void setCurrentDate(long date) {
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(date);
        setCurrentDate(cal.get(Calendar.YEAR), cal.get(Calendar.MONTH), cal.get(Calendar.DAY_OF_MONTH),
                cal.get(Calendar.HOUR_OF_DAY), cal.get(Calendar.MINUTE));
    }

    /**
     * Set the current date
     *
     * @param year The current year
     * @param month The current month
     * @param dayOfMonth The current dayOfMonth
     * @param hourOfDay The current hourOfDay
     * @param minute The current minute
     */
    public void setCurrentDate(int year, int month,
            int dayOfMonth, int hourOfDay, int minute) {
        setCurrentYear(year);
        setCurrentMonth(month);
        setCurrentDay(dayOfMonth);
        setCurrentHour(hourOfDay);
        setCurrentMinute(minute);
    }

    /**
     * Get current year
     *
     * @return The current year
     */
    public int getCurrentYear() {
        return mDate.get(Calendar.YEAR);
    }

    /**
     * Set current year
     *
     * @param year The current year
     */
    public void setCurrentYear(int year) {
        if (!mInitialising && year == getCurrentYear()) {
            return;
        }
        mDate.set(Calendar.YEAR, year);
        updateDateControl();
        onDateTimeChanged();
    }

    /**
     * Get current month in the year
     *
     * @return The current month in the year
     */
    public int getCurrentMonth() {
        return mDate.get(Calendar.MONTH);
    }

    /**
     * Set current month in the year
     *
     * @param month The month in the year
     */
    public void setCurrentMonth(int month) {
        if (!mInitialising && month == getCurrentMonth()) {
            return;
        }
        mDate.set(Calendar.MONTH, month);
        updateDateControl();
        onDateTimeChanged();
    }

    /**
     * Get current day of the month
     *
     * @return The day of the month
     */
    public int getCurrentDay() {
        return mDate.get(Calendar.DAY_OF_MONTH);
    }

    /**
     * Set current day of the month
     *
     * @param dayOfMonth The day of the month
     */
    public void setCurrentDay(int dayOfMonth) {
        if (!mInitialising && dayOfMonth == getCurrentDay()) {
            return;
        }
        mDate.set(Calendar.DAY_OF_MONTH, dayOfMonth);
        updateDateControl();
        onDateTimeChanged();
    }

    /**
     * Get current hour in 24 hour mode, in the range (0~23)
     * @return The current hour in 24 hour mode
     */
    public int getCurrentHourOfDay() {
        return mDate.get(Calendar.HOUR_OF_DAY);
    }

    private int getCurrentHour() {
        if (mIs24HourView){
            return getCurrentHourOfDay();
        } else {
            int hour = getCurrentHourOfDay();
            if (hour > HOURS_IN_HALF_DAY) {
                return hour - HOURS_IN_HALF_DAY;
            } else {
                return hour == 0 ? HOURS_IN_HALF_DAY : hour;
            }
        }
    }

    /**
     * Set current hour in 24 hour mode, in the range (0~23)
     *
     * @param hourOfDay
     */
    public void setCurrentHour(int hourOfDay) {
        if (!mInitialising && hourOfDay == getCurrentHourOfDay()) {
            return;
        }
        mDate.set(Calendar.HOUR_OF_DAY, hourOfDay);
        if (!mIs24HourView) {
            if (hourOfDay >= HOURS_IN_HALF_DAY) {
                mIsAm = false;
                if (hourOfDay > HOURS_IN_HALF_DAY) {
                    hourOfDay -= HOURS_IN_HALF_DAY;
                }
            } else {
                mIsAm = true;
                if (hourOfDay == 0) {
                    hourOfDay = HOURS_IN_HALF_DAY;
                }
            }
            updateAmPmControl();
        }
        mHourSpinner.setValue(hourOfDay);
        onDateTimeChanged();
    }

    /**
     * Get currentMinute
     *
     * @return The Current Minute
     */
    public int getCurrentMinute() {
        return mDate.get(Calendar.MINUTE);
    }

    /**
     * Set current minute
     */
    public void setCurrentMinute(int minute) {
        if (!mInitialising && minute == getCurrentMinute()) {
            return;
        }
        mMinuteSpinner.setValue(minute);
        mDate.set(Calendar.MINUTE, minute);
        onDateTimeChanged();
    }

    /**
     * @return true if this is in 24 hour view else false.
     */
    public boolean is24HourView () {
        return mIs24HourView;
    }

    /**
     * Set whether in 24 hour or AM/PM mode.
     *
     * @param is24HourView True for 24 hour mode. False for AM/PM mode.
     */
    public void set24HourView(boolean is24HourView) {
        if (mIs24HourView == is24HourView) {
            return;
        }
        mIs24HourView = is24HourView;
        mAmPmSpinner.setVisibility(is24HourView ? View.GONE : View.VISIBLE);
        int hour = getCurrentHourOfDay();
        updateHourControl();
        setCurrentHour(hour);
        updateAmPmControl();
    }

    private void updateDateControl() {
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(mDate.getTimeInMillis());
        cal.add(Calendar.DAY_OF_YEAR, -DAYS_IN_ALL_WEEK / 2 - 1);
        mDateSpinner.setDisplayedValues(null);
        for (int i = 0; i < DAYS_IN_ALL_WEEK; ++i) {
            cal.add(Calendar.DAY_OF_YEAR, 1);
            mDateDisplayValues[i] = (String) DateFormat.format("MM.dd EEEE", cal);
        }
        mDateSpinner.setDisplayedValues(mDateDisplayValues);
        mDateSpinner.setValue(DAYS_IN_ALL_WEEK / 2);
        mDateSpinner.invalidate();
    }

    private void updateAmPmControl() {
        if (mIs24HourView) {
            mAmPmSpinner.setVisibility(View.GONE);
        } else {
            int index = mIsAm ? Calendar.AM : Calendar.PM;
            mAmPmSpinner.setValue(index);
            mAmPmSpinner.setVisibility(View.VISIBLE);
        }
    }

    private void updateHourControl() {
        if (mIs24HourView) {
            mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_24_HOUR_VIEW);
            mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_24_HOUR_VIEW);
        } else {
            mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_12_HOUR_VIEW);
            mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_12_HOUR_VIEW);
        }
    }

    /**
     * Set the callback that indicates the 'Set' button has been pressed.
     * @param callback the callback, if null will do nothing
     */
    public void setOnDateTimeChangedListener(OnDateTimeChangedListener callback) {
        mOnDateTimeChangedListener = callback;
    }

    private void onDateTimeChanged() {
        if (mOnDateTimeChangedListener != null) {
            mOnDateTimeChangedListener.onDateTimeChanged(this, getCurrentYear(),
                    getCurrentMonth(), getCurrentDay(), getCurrentHourOfDay(), getCurrentMinute());
        }
    }
}