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Android系统之闹钟模块浅析
关键词: JNI , HAL,Sqlite
在手机中,闹钟功能是一个最基本的功能,也是我们一个很常用的功能,现在来分析下android是怎么实现的,下面将采用自上而下的方式讲解。
1、APP层
进入桌面闹钟应用程序,选择设置新闹钟,会调到 Alarms.java 里面的 public static long setAlarm(Context context, Alarm alarm) { .... setNextAlert(context); .... } 接着也会调用到 public static void setNextAlert(final Context context) { if (!enableSnoozeAlert(context)) {
//通过查询数据库获取到一个离当前时间最近的alarm Alarm alarm = calculateNextAlert(context); if (alarm != null) { enableAlert(context, alarm, alarm.time); } else { disableAlert(context); } } } 然后继续调用到 private static void enableAlert(Context context, final Alarm alarm, final longatTimeInMillis) { .......
//下面参数RTC_WAKEUP, 就是保证即使系统睡眠了,都能唤醒,闹钟工作 am.set(AlarmManager.RTC_WAKEUP, atTimeInMillis, sender);..... }
/packages/apps/DeskClock/src/com/android/deskclock/Alarms.java
2、Framework层 然后就调用到了AlarmManager.java里面方法 public void set(int type, long triggerAtTime, PendingIntent operation) { try { mService.set(type, triggerAtTime, operation); } catch (RemoteException ex) { } } 然后就调用到了AlarmManagerService.java里面方法 public void set(int type, long triggerAtTime, PendingIntent operation) { setRepeating(type, triggerAtTime, 0, operation); } 然后继续调用 public void setRepeating(int type, long triggerAtTime, long interval, PendingIntent operation) { ..... synchronized (mLock) { Alarm alarm = new Alarm(); alarm.type = type; alarm.when = triggerAtTime; alarm.repeatInterval = interval; alarm.operation = operation; // Remove this alarm if already scheduled. removeLocked(operation); int index = addAlarmLocked(alarm); if (index == 0) { setLocked(alarm); } } } 然后就调用到 private void setLocked(Alarm alarm) { ......
//mDescriptor 这里的文件是 /dev/alarm set(mDescriptor, alarm.type, alarmSeconds, alarmNanoseconds); ..... }
AlarmManagerService程序在系统启动时被系统服务程序SystemServer启动并初始化闹铃设备(/dev/alarm)。
./frameworks/base/core/java/android/app/AlarmManager.java ./frameworks/base/services/java/com/android/server/AlarmManagerService.java
3、JNI的层
JNI : (Java Natative Interface ) 它允许JAVA代码和其他语言的代码进行交互,比如C/C++代码.
private nativevoid set(int fd, int type, long seconds, long nanoseconds); 这就调用到了com_android_server_AlarmManagerService.cpp里面 static JNINativeMethod sMethods[] = { /* name, signature, funcPtr */ {"init", "()I",(void*)android_server_AlarmManagerService_init}, {"close", "(I)V",(void*)android_server_AlarmManagerService_close}, {"set", "(IIJJ)V",(void*)android_server_AlarmManagerService_set}, {"waitForAlarm", "(I)I",(void*)android_server_AlarmManagerService_waitForAlarm}, {"setKernelTimezone", "(II)I",(void*)android_server_AlarmManagerService_setKernelTimezone}, }; set 对应的是android_server_AlarmManagerService_set,具体是 static void android_server_AlarmManagerService_set(JNIEnv* env, jobject obj,jint fd, jint type, jlong seconds, jlong nanoseconds) { #if HAVE_ANDROID_OS struct timespec ts; ts.tv_sec = seconds; ts.tv_nsec = nanoseconds; int result = ioctl(fd, ANDROID_ALARM_SET(type), &ts); if (result < 0) { LOGE("Unable to set alarm to %lld.%09lld: %s\n", seconds,nanoseconds, strerror(errno)); } #endif }
/frameworks/base/services/jni/com_android_server_AlarmManagerService.cpp
4.HAL层
AndroidHAL层,即硬件抽象层(Hardware abstract layer),是Google响应厂家“希望不公开源码”的要求推出的新概念。
上面的ioctl 就调用到了alarm-dev.c static long alarm_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { .... case ANDROID_ALARM_SET(0): if (copy_from_user(&new_alarm_time, (void __user *)arg, sizeof(new_alarm_time))) { rv = -EFAULT; goto err1; } from_old_alarm_set: spin_lock_irqsave(&alarm_slock, flags); pr_alarm(IO, "alarm %d set %ld.%09ld\n", alarm_type, new_alarm_time.tv_sec, new_alarm_time.tv_nsec); alarm_enabled |= alarm_type_mask; alarm_start_range(&alarms[alarm_type], timespec_to_ktime(new_alarm_time), timespec_to_ktime(new_alarm_time)); spin_unlock_irqrestore(&alarm_slock, flags); if (ANDROID_ALARM_BASE_CMD(cmd) != ANDROID_ALARM_SET_AND_WAIT(0) && cmd != ANDROID_ALARM_SET_AND_WAIT_OLD) break; /* fall though */ .... case ANDROID_ALARM_SET_RTC: if (copy_from_user(&new_rtc_time, (void __user *)arg, sizeof(new_rtc_time))) { rv = -EFAULT; goto err1; } rv = alarm_set_rtc(new_rtc_time); spin_lock_irqsave(&alarm_slock, flags); alarm_pending |= ANDROID_ALARM_TIME_CHANGE_MASK; wake_up(&alarm_wait_queue); spin_unlock_irqrestore(&alarm_slock, flags); if (rv < 0) goto err1; break; .... } 然后这边根据用户上层传过来的CMD就调用到了alarm_start_range设置闹钟,alarm_set_rtc 设置RTC时间,这些函数的具体实现在alarm.c文件中; /* set rtc while preserving elapsed realtime */ int alarm_set_rtc(const struct timespec ts); 下面看alarm.c里面实现: int alarm_set_rtc(struct timespec new_time) { .... ret = rtc_set_time(alarm_rtc_dev, &rtc_new_rtc_time); .... } 上面会调用到了interface.c intrtc_set_time(struct rtc_device *rtc, struct rtc_time *tm) { .... err =rtc->ops->set_time(rtc->dev.parent, tm); .... }
文件位置
kernel/drivers/rtc/alarm-dev.c kernel/drivers/rtc/alarm.c
4. Drive层 然后set_time 就看到具体的是那个RTC芯片,这边我们参考rtc-pcf8563.c static conststruct rtc_class_ops pcf8563_rtc_ops = { .read_time =pcf8563_rtc_read_time, .set_time =pcf8563_rtc_set_time, .read_alarm= pcf8563_rtc_read_alarm, .set_alarm =pcf8563_rtc_set_alarm, }; 然后就到了 static intpcf8563_rtc_set_time(struct device *dev, struct rtc_time *tm) { unsignedchar buf[TIME_NUM]; int ret; ret =data_calc(buf, tm, TIME_NUM); if (ret < 0) goto out; //这边就调用i2c统一接口,往pcf8563rtc芯片寄存器里面写出数据
ret= i2c_smbus_write_i2c_block_data(pcf8563_info->client,PCF8563_RTC_SEC, TIME_NUM, buf); out: return ret; } 文件位置
kernel/drivers/rtc/rtc-pcf8563.c
以上就是闹钟从应用层到驱动层的整个流程。
问题分析
问题一:设置闹钟后,系统如何在后台轮询的
AlarmManagerService 里面有个AlarmThread 会一直轮询/dev/alarm文件,如果打开失败就直接返回,成功就会做一些动作,比如查找时间最近的 alarm,比如睡眠被闹钟唤醒的时候,这边就发一个intent出去,然后在AlarmReceiver.java里面弹出里面会收到就会调用下面的 context.startActivity(alarmAlert); 然后弹出alarm 这个界面 Class c = AlarmAlert.class; 其中publicclass AlarmAlert extends AlarmAlertFullScreen 所以系统睡眠之后被alarm唤醒弹出的alarm就是这边start的 public class AlarmReceiver extends BroadcastReceiver { /** If the alarm is older than STALE_WINDOW, ignore. It is probably the result of a time or timezone change */ private final static int STALE_WINDOW = 30 * 60 * 1000; @Override public void onReceive(Context context, Intent intent) { ......... handleIntent(Context context, Intent intent) ........ }
问题二:数据库操作:添加和删除闹钟
当我们设置闹钟的时候,会进入到设置闹钟的窗口,当用户确认点击保存后,会来到 (SetAlarm.java)
private long saveAlarm() {
....
time = Alarms.setAlarm(this, alarm);
......
}
继续跟进会来到(Alarms)
public static long setAlarm(Context context, Alarm alarm){
.....
ContentValues values = createContentValues(alarm);
ContentResolver resolver = context.getContentResolver();
resolver.update(
ContentUris.withAppendedId(Alarm.Columns.CONTENT_URI, alarm.id),
values, null, null);
.....
}
到此就完成了闹钟添加到数据库的功能,想了解其中怎么实现的,可以去了解下
ContentResolver ,ContentProvider,SQLiteOpenHelper .从它们那里能找到你要的答案
问题三: 定时短信
对于这个功能实现的方式很多,我讲下我个人的思路,然后做了个小demo.
思路1:使用AlarmManager的set方法来实现该功能,当时间到时发送短信。
思路2:后台开启一个Server ,采用轮询的方式来实现该功能.
数据存储可以采用sqlite 或者 SharedPerferences 方式。
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