AlarmInitReceiver 精读

src/net/micode/notes/ui/AlarmInitReceiver.java

@@ -28,38 +28,50 @@ import net.micode.notes.data.Notes;
 import net.micode.notes.data.Notes.NoteColumns;
 
 
+//AlarmInitReceiver 类继承自BroadcastReceiver， 广播接收者用于获取系统启动或其他特定事件的通知
 public class AlarmInitReceiver extends BroadcastReceiver {
 
+    //数据库查询的列名数组，只查询ID和提醒日期
     private static final String [] PROJECTION = new String [] {
-        NoteColumns.ID,
-        NoteColumns.ALERTED_DATE
+        NoteColumns.ID,             //便签的ID
+        NoteColumns.ALERTED_DATE    //便签的提醒日期
     };
 
+    //定义两个静态常量，代表数据表列索引ID和提醒日期
     private static final int COLUMN_ID                = 0;
     private static final int COLUMN_ALERTED_DATE      = 1;
 
+    //当广播被接收时执行此方法
     @Override
     public void onReceive(Context context, Intent intent) {
+        //获取系统的时间
         long currentDate = System.currentTimeMillis();
-        Cursor c = context.getContentResolver().query(Notes.CONTENT_NOTE_URI,
+        //通过内容解析器查询便签，寻找提醒时间大于当前时间且类型为TYPE_NOTE的便签
+        Cursor c = context.getContentResolver().query(Notes.CONTENT_NOTE_URI, // CONTENT_NOTE_URI是访问便签数据的URI
                 PROJECTION,
                 NoteColumns.ALERTED_DATE + ">? AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE,
                 new String[] { String.valueOf(currentDate) },
                 null);
 
+        //遍历查询出的结果
         if (c != null) {
-            if (c.moveToFirst()) {
+            if (c.moveToFirst()) { //移动游标到第一条记录
                 do {
+                    //读取提醒日期时间
                     long alertDate = c.getLong(COLUMN_ALERTED_DATE);
+                    //创建指向AlarmReceiver的Intent
                     Intent sender = new Intent(context, AlarmReceiver.class);
                     sender.setData(ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, c.getLong(COLUMN_ID)));
+                    //创建一个即将执行的PendingIntent
                     PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, sender, 0);
+                    //获取系统AlarmManager
                     AlarmManager alermManager = (AlarmManager) context
                             .getSystemService(Context.ALARM_SERVICE);
+                    //使用AlarmManager设置一个闹钟，当系统时间达到提醒日期时触发广播
                     alermManager.set(AlarmManager.RTC_WAKEUP, alertDate, pendingIntent);
-                } while (c.moveToNext());
+                } while (c.moveToNext()); //移动到下一条记录
             }
-            c.close();
+            c.close(); //关闭游标
         }
     }
 }