MiCodeNotes/doc/DateTimePicker.txt

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 {
	//FrameLayout是布局模板之一
	//所有的子元素全部在屏幕的右上方
    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;
    //初始化控件
    private final NumberPicker mDateSpinner;
    private final NumberPicker mHourSpinner;
    private final NumberPicker mMinuteSpinner;
    private final NumberPicker mAmPmSpinner;
    //NumberPicker是数字选择器
    //这里定义的四个变量全部是在设置闹钟时需要选择的变量（如日期、时、分、上午或者下午）
    private Calendar mDate;
    //定义了Calendar类型的变量mDate，用于操作时间
    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();
        }
    };//OnValueChangeListener，这是时间改变监听器，这里主要是对日期的监听
    //将现在日期的值传递给mDate；updateDateControl是同步操作
 
    private NumberPicker.OnValueChangeListener mOnHourChangedListener = new NumberPicker.OnValueChangeListener() {
        //这里是对 小时（Hour） 的监听
    	@Override
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            boolean isDateChanged = false;
            Calendar cal = Calendar.getInstance();
            //声明一个Calendar的变量cal，便于后续的操作
            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;
                    //这里是对于12小时制时，晚上11点和12点交替时对日期的更改
                } 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;
                } 
                //这里是对于12小时制时，凌晨11点和12点交替时对日期的更改
                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();
                }//这里是对于12小时制时，中午11点和12点交替时对AM和PM的更改
            } else {
                if (oldVal == HOURS_IN_ALL_DAY - 1 && newVal == 0) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, 1);
                    isDateChanged = true;
                    //这里是对于24小时制时，晚上11点和12点交替时对日期的更改
                } else if (oldVal == 0 && newVal == HOURS_IN_ALL_DAY - 1) {
                    cal.setTimeInMillis(mDate.getTimeInMillis());
                    cal.add(Calendar.DAY_OF_YEAR, -1);
                    isDateChanged = true;
                }
            } //这里是对于12小时制时，凌晨11点和12点交替时对日期的更改
            int newHour = mHourSpinner.getValue() % HOURS_IN_HALF_DAY + (mIsAm ? 0 : HOURS_IN_HALF_DAY);
            //通过数字选择器对newHour的赋值
            mDate.set(Calendar.HOUR_OF_DAY, newHour);
            //通过set函数将新的Hour值传给mDate
            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
        //这里是对 分钟（Minute）改变的监听
        public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
            int minValue = mMinuteSpinner.getMinValue();
            int maxValue = mMinuteSpinner.getMaxValue();
            int offset = 0;
            //设置offset，作为小时改变的一个记录数据
            if (oldVal == maxValue && newVal == minValue) {
                offset += 1;
            } else if (oldVal == minValue && newVal == maxValue) {
                offset -= 1;
            }
            //如果原值为59，新值为0，则offset加1
            //如果原值为0，新值为59，则offset减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() {
        //对AM和PM的监听
    	@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());
    }//通过对数据库的访问，获取当前的系统时间
 
    public DateTimePicker(Context context, long date) {
        this(context, date, DateFormat.is24HourFormat(context));
    }//上面函数的得到的是一个天文数字（1970至今的秒数），需要DateFormat将其变得有意义
 
    public DateTimePicker(Context context, long date, boolean is24HourView) {
        super(context);
        //获取系统时间
        mDate = Calendar.getInstance();
        mInitialising = true;
        mIsAm = getCurrentHourOfDay() >= HOURS_IN_HALF_DAY;
        inflate(context, R.layout.datetime_picker, this);
        //如果当前Activity里用到别的layout，比如对话框layout
        //还要设置这个layout上的其他组件的内容，就必须用inflate()方法先将对话框的layout找出来
        //然后再用findViewById()找到它上面的其它组件
        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;
    }
    //存在疑问！！！！！！！！！！！！！setEnabled的作用
    //下面的代码通过原程序的注释已经比较清晰，另外可以通过函数名来判断
    //下面的各函数主要是对上面代码引用到的各函数功能的实现
    @Override
    public boolean isEnabled() {
        return mIsEnabled;
    }
 
    /**
     * Get the current date in millis
     *
     * @return the current date in millis
     */
    public long getCurrentDateInTimeMillis() {
        return mDate.getTimeInMillis();
    }//实现函数——得到当前的秒数
 
    /**
     * 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));
    }//实现函数功能——设置当前的时间，参数是date
 
    /**
     * 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);
    }//实现函数功能——设置当前的时间，参数是各详细的变量
 
    /**
     * Get current year
     *
     * @return The current year
     */
    //下面是得到year、month、day等值
    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();
    }// 对于星期几的算法
 
    private void updateAmPmControl() {
        if (mIs24HourView) {
            mAmPmSpinner.setVisibility(View.GONE);
        } else {
            int index = mIsAm ? Calendar.AM : Calendar.PM;
            mAmPmSpinner.setValue(index);
            mAmPmSpinner.setVisibility(View.VISIBLE);
        }// 对于上下午操作的算法
    }
 
    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);
        }// 对与小时的算法
    }
 
    /**
     * 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());
        }  
    }
}