public class DatePreferenceController extends AbstractPreferenceController
        implements PreferenceControllerMixin, DatePickerDialog.OnDateSetListener {
    //省略部分代碼
    private final DatePreferenceHost mHost;
    
	@Override
    public boolean handlePreferenceTreeClick(Preference preference) {
        //點(diǎn)擊日期后處理
        if (!TextUtils.equals(preference.getKey(), KEY_DATE)) {
            return false;
        }
        //顯示日期選擇框
        mHost.showDatePicker();
        return true;
    }
    //省略部分代碼
}

@SearchIndexable
public class DateTimeSettings extends DashboardFragment implements
        TimePreferenceController.TimePreferenceHost, DatePreferenceController.DatePreferenceHost {
    //省略部分代碼
	@Override
    public void showDatePicker() {
        //顯示日期選擇對話框
        showDialog(DatePreferenceController.DIALOG_DATEPICKER);
    }
    //省略部分代碼
}

public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceFragment
        implements DialogCreatable, HelpResourceProvider, Indexable {    
	protected void showDialog(int dialogId) {
        if (mDialogFragment != null) {
            Log.e(TAG, "Old dialog fragment not null!");
        }
        //創(chuàng)建SettingsDialogFragment并進(jìn)行show
        mDialogFragment = SettingsDialogFragment.newInstance(this, dialogId);
        mDialogFragment.show(getChildFragmentManager(), Integer.toString(dialogId));
    }
}

    public static class SettingsDialogFragment extends InstrumentedDialogFragment {
        private static final String KEY_DIALOG_ID = "key_dialog_id";
        private static final String KEY_PARENT_FRAGMENT_ID = "key_parent_fragment_id";

        private Fragment mParentFragment;

        private DialogInterface.OnCancelListener mOnCancelListener;
        private DialogInterface.OnDismissListener mOnDismissListener;

        public static SettingsDialogFragment newInstance(DialogCreatable fragment, int dialogId) {
            if (!(fragment instanceof Fragment)) {
                throw new IllegalArgumentException("fragment argument must be an instance of "
                        + Fragment.class.getName());
            }

            final SettingsDialogFragment settingsDialogFragment = new SettingsDialogFragment();
            settingsDialogFragment.setParentFragment(fragment);
            settingsDialogFragment.setDialogId(dialogId);

            return settingsDialogFragment;
        }

        @Override
        public int getMetricsCategory() {
            if (mParentFragment == null) {
                return Instrumentable.METRICS_CATEGORY_UNKNOWN;
            }
            final int metricsCategory =
                    ((DialogCreatable) mParentFragment).getDialogMetricsCategory(mDialogId);
            if (metricsCategory <= 0) {
                throw new IllegalStateException("Dialog must provide a metrics category");
            }
            return metricsCategory;
        }

        @Override
        public void onSaveInstanceState(Bundle outState) {
            super.onSaveInstanceState(outState);
            if (mParentFragment != null) {
                outState.putInt(KEY_DIALOG_ID, mDialogId);
                outState.putInt(KEY_PARENT_FRAGMENT_ID, mParentFragment.getId());
            }
        }

        @Override
        public void onStart() {
            super.onStart();

            if (mParentFragment != null && mParentFragment instanceof SettingsPreferenceFragment) {
                ((SettingsPreferenceFragment) mParentFragment).onDialogShowing();
            }
        }

        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            if (savedInstanceState != null) {
                mDialogId = savedInstanceState.getInt(KEY_DIALOG_ID, 0);
                mParentFragment = getParentFragment();
                int mParentFragmentId = savedInstanceState.getInt(KEY_PARENT_FRAGMENT_ID, -1);
                if (mParentFragment == null) {
                    mParentFragment = getFragmentManager().findFragmentById(mParentFragmentId);
                }
                if (!(mParentFragment instanceof DialogCreatable)) {
                    throw new IllegalArgumentException(
                            (mParentFragment != null
                                    ? mParentFragment.getClass().getName()
                                    : mParentFragmentId)
                                    + " must implement "
                                    + DialogCreatable.class.getName());
                }
                // This dialog fragment could be created from non-SettingsPreferenceFragment
                if (mParentFragment instanceof SettingsPreferenceFragment) {
                    // restore mDialogFragment in mParentFragment
                    ((SettingsPreferenceFragment) mParentFragment).mDialogFragment = this;
                }
            }
            //通過DialogCreatable接口剝離了dialog的創(chuàng)建
            return ((DialogCreatable) mParentFragment).onCreateDialog(mDialogId);
        }

        @Override
        public void onCancel(DialogInterface dialog) {
            super.onCancel(dialog);
            if (mOnCancelListener != null) {
                mOnCancelListener.onCancel(dialog);
            }
        }

        @Override
        public void onDismiss(DialogInterface dialog) {
            super.onDismiss(dialog);
            if (mOnDismissListener != null) {
                mOnDismissListener.onDismiss(dialog);
            }
        }

        public int getDialogId() {
            return mDialogId;
        }

        @Override
        public void onDetach() {
            super.onDetach();

            // This dialog fragment could be created from non-SettingsPreferenceFragment
            if (mParentFragment instanceof SettingsPreferenceFragment) {
                // in case the dialog is not explicitly removed by removeDialog()
                if (((SettingsPreferenceFragment) mParentFragment).mDialogFragment == this) {
                    ((SettingsPreferenceFragment) mParentFragment).mDialogFragment = null;
                }
            }
        }

        private void setParentFragment(DialogCreatable fragment) {
            mParentFragment = (Fragment) fragment;
        }

        private void setDialogId(int dialogId) {
            mDialogId = dialogId;
        }
    }

@SearchIndexable
public class DateTimeSettings extends DashboardFragment implements
        TimePreferenceController.TimePreferenceHost, DatePreferenceController.DatePreferenceHost {
    //省略部分代碼
	@Override
    public Dialog onCreateDialog(int id) {
        //根據(jù)選項創(chuàng)建對應(yīng)的dialog
        switch (id) {
            case DatePreferenceController.DIALOG_DATEPICKER:
                return use(DatePreferenceController.class)
                        .buildDatePicker(getActivity());
            case TimePreferenceController.DIALOG_TIMEPICKER:
                return use(TimePreferenceController.class)
                        .buildTimePicker(getActivity());
            default:
                throw new IllegalArgumentException();
        }
    }
    //省略部分代碼
}

public class DatePreferenceController extends AbstractPreferenceController
        implements PreferenceControllerMixin, DatePickerDialog.OnDateSetListener {
    //省略部分代碼
	public DatePickerDialog buildDatePicker(Activity activity) {
        final Calendar calendar = Calendar.getInstance();
        //創(chuàng)建DatePickerDialog
        final DatePickerDialog d = new DatePickerDialog(
                activity,
                this,
                calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH));
        // The system clock can't represent dates outside this range.
        calendar.clear();
        calendar.set(2007, Calendar.JANUARY, 1);
        //設(shè)置最小時間為2007-01-01
        d.getDatePicker().setMinDate(calendar.getTimeInMillis());
        calendar.clear();
        calendar.set(2037, Calendar.DECEMBER, 31);
        //設(shè)置最大時間為2037-12-31
        d.getDatePicker().setMaxDate(calendar.getTimeInMillis());
        return d;
    }
    //省略部分代碼
}

public class DatePickerDialog extends AlertDialog implements OnClickListener,
        OnDateChangedListener {
    private static final String YEAR = "year";
    private static final String MONTH = "month";
    private static final String DAY = "day";

    @UnsupportedAppUsage
    private final DatePicker mDatePicker;

    private OnDateSetListener mDateSetListener;

    //省略部分代碼

    private DatePickerDialog(@NonNull Context context, @StyleRes int themeResId,
            @Nullable OnDateSetListener listener, @Nullable Calendar calendar, int year,
            int monthOfYear, int dayOfMonth) {
        super(context, resolveDialogTheme(context, themeResId));

        final Context themeContext = getContext();
        final LayoutInflater inflater = LayoutInflater.from(themeContext);
        //初始化Dialog的View
        final View view = inflater.inflate(R.layout.date_picker_dialog, null);
        setView(view);

        setButton(BUTTON_POSITIVE, themeContext.getString(R.string.ok), this);
        setButton(BUTTON_NEGATIVE, themeContext.getString(R.string.cancel), this);
        setButtonPanelLayoutHint(LAYOUT_HINT_SIDE);

        if (calendar != null) {
            year = calendar.get(Calendar.YEAR);
            monthOfYear = calendar.get(Calendar.MONTH);
            dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
        }

        mDatePicker = (DatePicker) view.findViewById(R.id.datePicker);
        mDatePicker.init(year, monthOfYear, dayOfMonth, this);
        mDatePicker.setValidationCallback(mValidationCallback);

        mDateSetListener = listener;
    }

    //省略部分代碼

    /**
     * Sets the listener to call when the user sets the date.
     *
     * @param listener the listener to call when the user sets the date
     */
    public void setOnDateSetListener(@Nullable OnDateSetListener listener) {
        mDateSetListener = listener;
    }

    @Override
    public void onClick(@NonNull DialogInterface dialog, int which) {
        switch (which) {
            case BUTTON_POSITIVE:
                if (mDateSetListener != null) {
                    // Clearing focus forces the dialog to commit any pending
                    // changes, e.g. typed text in a NumberPicker.
                    mDatePicker.clearFocus();
                    //設(shè)置完成回調(diào)
                    mDateSetListener.onDateSet(mDatePicker, mDatePicker.getYear(),
                            mDatePicker.getMonth(), mDatePicker.getDayOfMonth());
                }
                break;
            case BUTTON_NEGATIVE:
                cancel();
                break;
        }
    }

    //省略部分代碼

    /**
     * The listener used to indicate the user has finished selecting a date.
     */
    public interface OnDateSetListener {
        /**
         * @param view the picker associated with the dialog
         * @param year the selected year
         * @param month the selected month (0-11 for compatibility with
         *              {@link Calendar#MONTH})
         * @param dayOfMonth the selected day of the month (1-31, depending on
         *                   month)
         */
        void onDateSet(DatePicker view, int year, int month, int dayOfMonth);
    }
}

public class DatePreferenceController extends AbstractPreferenceController
        implements PreferenceControllerMixin, DatePickerDialog.OnDateSetListener {
	//省略部分代碼
    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) {
        //設(shè)置日期
        setDate(year, month, day);
        //更新UI
        mHost.updateTimeAndDateDisplay(mContext);
    }
    //省略部分代碼
    
    @VisibleForTesting
    void setDate(int year, int month, int day) {
        Calendar c = Calendar.getInstance();

        c.set(Calendar.YEAR, year);
        c.set(Calendar.MONTH, month);
        c.set(Calendar.DAY_OF_MONTH, day);
        //設(shè)置日期與定義的最小日期取最大值，也就意味著設(shè)置的日期不能小于定義的最小日期
        long when = Math.max(c.getTimeInMillis(), DatePreferenceHost.MIN_DATE);

        if (when / 1000 < Integer.MAX_VALUE) {
            //設(shè)置系統(tǒng)時間
            ((AlarmManager) mContext.getSystemService(Context.ALARM_SERVICE)).setTime(when);
        }
    }
}

public interface UpdateTimeAndDateCallback {
    // Minimum time is Nov 5, 2007, 0:00.
    long MIN_DATE = 1194220800000L;

    void updateTimeAndDateDisplay(Context context);
}

class AlarmManagerService extends SystemService {
    //省略部分代碼
	/**
     * Public-facing binder interface
     */
    private final IBinder mService = new IAlarmManager.Stub() {
        //省略部分代碼
		@Override
        public boolean setTime(long millis) {
            //先授權(quán)
            getContext().enforceCallingOrSelfPermission(
                    "android.permission.SET_TIME",
                    "setTime");
			//然后設(shè)置系統(tǒng)內(nèi)核時間
            return setTimeImpl(millis);
        }
        //省略部分代碼
    }
    
    //省略部分代碼
    
    boolean setTimeImpl(long millis) {
        if (!mInjector.isAlarmDriverPresent()) {
            Slog.w(TAG, "Not setting time since no alarm driver is available.");
            return false;
        }

        synchronized (mLock) {
            final long currentTimeMillis = mInjector.getCurrentTimeMillis();
            //設(shè)置系統(tǒng)內(nèi)核時間
            mInjector.setKernelTime(millis);
            final TimeZone timeZone = TimeZone.getDefault();
            final int currentTzOffset = timeZone.getOffset(currentTimeMillis);
            final int newTzOffset = timeZone.getOffset(millis);
            if (currentTzOffset != newTzOffset) {
                Slog.i(TAG, "Timezone offset has changed, updating kernel timezone");
                //設(shè)置系統(tǒng)內(nèi)核時區(qū)
                mInjector.setKernelTimezone(-(newTzOffset / 60000));
            }
            // The native implementation of setKernelTime can return -1 even when the kernel
            // time was set correctly, so assume setting kernel time was successful and always
            // return true.
            return true;
        }
    }
    
    //省略部分代碼
    
    @VisibleForTesting
    static class Injector {
    	//省略部分代碼
        void setKernelTime(long millis) {
            Log.d("jasonwan", "setKernelTime: "+millis);
            if (mNativeData != 0) {
                //在native層完成內(nèi)核時間的設(shè)置
                AlarmManagerService.setKernelTime(mNativeData, millis);
            }
        }
        //省略部分代碼
    }
    
    //native層完成
    private static native int setKernelTime(long nativeData, long millis);
    private static native int setKernelTimezone(long nativeData, int minuteswest);
    //省略部分代碼
}

class AlarmManagerService extends SystemService {
    //省略部分代碼
    
	@Override
    public void onStart() {
        mInjector.init();

        synchronized (mLock) {
            //省略部分代碼

            // We have to set current TimeZone info to kernel
            // because kernel doesn't keep this after reboot
            //設(shè)置時區(qū)，從SystemProperty中讀取
            setTimeZoneImpl(SystemProperties.get(TIMEZONE_PROPERTY));

            // Ensure that we're booting with a halfway sensible current time.  Use the
            // most recent of Build.TIME, the root file system's timestamp, and the
            // value of the ro.build.date.utc system property (which is in seconds).
            //設(shè)置時區(qū)
            //先讀取系統(tǒng)編譯時間
            long utc = 1000L * SystemProperties.getLong("ro.build.date.utc", -1L);
            //再讀取根目錄最近的修改的時間
            long lastModified = Environment.getRootDirectory().lastModified();
            //然后讀取系統(tǒng)構(gòu)建時間，三個時間取最大值
            final long systemBuildTime =  Long.max(
                    utc,
                    Long.max(lastModified, Build.TIME));
            //代碼1
            Log.d("jasonwan", "onStart: utc="+utc+", lastModified="+lastModified+", BuildTime="+Build.TIME+", currentTimeMillis="+mInjector.getCurrentTimeMillis());
            //設(shè)置的時間小于最大值，則將最大值設(shè)置為系統(tǒng)內(nèi)核的時間，注意，因為我們剛剛已經(jīng)設(shè)置了內(nèi)核時間，所以重啟后通過System.currentTimeMillis()得到的時間戳為我們設(shè)置的時間，此判斷意味著，系統(tǒng)編譯時間、根目錄最近修改時間、系統(tǒng)構(gòu)建時間、設(shè)置的時間，這四者當(dāng)中取最大值作為重啟后的內(nèi)核時間
            if (mInjector.getCurrentTimeMillis() < systemBuildTime) {
                //這里mInjector.getCurrentTimeMillis()其實就是System.currentTimeMillis()
                Slog.i(TAG, "Current time only " + mInjector.getCurrentTimeMillis()
                        + ", advancing to build time " + systemBuildTime);
                mInjector.setKernelTime(systemBuildTime);
            }
            //省略部分代碼

    }
    //省略部分代碼
        
    @VisibleForTesting
    static class Injector {
        //省略部分代碼
        void setKernelTimezone(int minutesWest) {
            AlarmManagerService.setKernelTimezone(mNativeData, minutesWest);
        }

        void setKernelTime(long millis) {
            //代碼2
            Log.d("jasonwan", "setKernelTime: "+millis);
            if (mNativeData != 0) {
                AlarmManagerService.setKernelTime(mNativeData, millis);
            }
        }

        //省略部分代碼
        long getElapsedRealtime() {
            return SystemClock.elapsedRealtime();
        }

        long getCurrentTimeMillis() {
            return System.currentTimeMillis();
        }
        //省略部分代碼
    }
}

/**
 * Information about the current build, extracted from system properties.
 */
public class Build {
    //省略部分代碼
	/** The time at which the build was produced, given in milliseconds since the UNIX epoch. */
    public static final long TIME = getLong("ro.build.date.utc") * 1000;
    //省略部分代碼
}