/*
 * 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.
 */

//这段代码是一个BroadcastReceiver，在系统启动时被触发。它查询数据库中需要提醒的笔记，然后为每个笔记设置闹钟。
package net.micode.notes.ui;
 
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.ContentUris;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
 
import net.micode.notes.data.Notes;
import net.micode.notes.data.Notes.NoteColumns;
 
 
public class AlarmInitReceiver extends BroadcastReceiver {
 
    private static final String [] PROJECTION = new String [] {
        NoteColumns.ID,
        NoteColumns.ALERTED_DATE
    };
    //对数据库的操作，调用标签ID和闹钟时间;查询投影，定义了需要获取的列
    private static final int COLUMN_ID                = 0;
    private static final int COLUMN_ALERTED_DATE      = 1;
    // 列的索引
 
    @Override
    public void onReceive(Context context, Intent intent) {
        long currentDate = System.currentTimeMillis();
        //获取当前时间。System.currentTimeMillis()产生一个当前的毫秒
        //这个毫秒其实就是自1970年1月1日0时起的毫秒数
        Cursor c = context.getContentResolver().query(Notes.CONTENT_NOTE_URI,
                PROJECTION,
                NoteColumns.ALERTED_DATE + ">? AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE,
                new String[] { String.valueOf(currentDate) },
                //将long变量currentDate转化为字符串
                null);
        //Cursor在这里的作用是通过查找数据库中的标签内容，找到和当前系统时间相等的标签
 
        if (c != null) {
            if (c.moveToFirst()) {
                do {
                    long alertDate = c.getLong(COLUMN_ALERTED_DATE);
                    // 获取提醒时间和笔记ID
                    
                    Intent sender = new Intent(context, AlarmReceiver.class);
                    sender.setData(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, c.getLong(COLUMN_ID)));
                    // 创建用于触发闹钟的Intent

                    PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, sender, 0);
                    // 创建PendingIntent，用于启动AlarmReceiver

                    AlarmManager alermManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
                    // 获取AlarmManager

                    alermManager.set(AlarmManager.RTC_WAKEUP, alertDate, pendingIntent);
                    // 设置闹钟，在提醒时间触发
                } while (c.moveToNext());
            }
            c.close();
        }
        //然而通过网上查找资料发现，对于闹钟机制的启动，通常需要上面的几个步骤
        //如新建Intent、PendingIntent以及AlarmManager等
        //这里就是根据数据库里的闹钟时间创建一个闹钟机制
    }
}