我们知道Android系统的锁屏时间存放在Setting数据库中，字段为Settings.System.SCREEN_OFF_TIMEOUT。我们可以查看SettingsProvider源码，查看如下文件的源码如下：
～/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java 查看loadSystemSettings()函数的代码如下
private void loadSystemSettings(SQLiteDatabase db) { SQLiteStatement stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)" + " VALUES(?,?);"); Resources r = mContext.getResources(); loadBooleanSetting(stmt, Settings.System.DIM_SCREEN, R.bool.def_dim_screen); loadSetting(stmt, Settings.System.STAY_ON_WHILE_PLUGGED_IN, "1".equals(SystemProperties.get("ro.kernel.qemu")) ? 1 : 0); loadIntegerSetting(stmt, Settings.System.SCREEN_OFF_TIMEOUT, R.integer.def_screen_off_timeout); // Set default cdma emergency tone loadSetting(stmt, Settings.System.EMERGENCY_TONE, 0); // Set default cdma call auto retry loadSetting(stmt, Settings.System.CALL_AUTO_RETRY, 0); // Set default cdma DTMF type loadSetting(stmt, Settings.System.DTMF_TONE_TYPE_WHEN_DIALING, 0); // Set default hearing aid loadSetting(stmt, Settings.System.HEARING_AID, 0); // Set default tty mode loadSetting(stmt, Settings.System.TTY_MODE, 0); loadBooleanSetting(stmt, Settings.System.AIRPLANE_MODE_ON, R.bool.def_airplane_mode_on); loadStringSetting(stmt, Settings.System.AIRPLANE_MODE_RADIOS, R.string.def_airplane_mode_radios); loadStringSetting(stmt, Settings.System.AIRPLANE_MODE_TOGGLEABLE_RADIOS, R.string.airplane_mode_toggleable_radios); loadBooleanSetting(stmt, Settings.System.AUTO_TIME, R.bool.def_auto_time); // Sync time to NITZ loadIntegerSetting(stmt, Settings.System.SCREEN_BRIGHTNESS, R.integer.def_screen_brightness); loadBooleanSetting(stmt, Settings.System.SCREEN_BRIGHTNESS_MODE, R.bool.def_screen_brightness_automatic_mode); loadDefaultAnimationSettings(stmt); loadBooleanSetting(stmt, Settings.System.ACCELEROMETER_ROTATION, R.bool.def_accelerometer_rotation); loadDefaultHapticSettings(stmt); stmt.close(); }