packages/apps/Settings/res/xml/display_settings.xml
<!-- Hide screen sleep
<ListPreference
android:key="screen_timeout"
android:title="@string/screen_timeout"
android:summary="@string/screen_timeout_summary"
android:persistent="false"
android:entries="@array/screen_timeout_entries"
android:entryValues="@array/screen_timeout_values" /> --> 

mScreenTimeoutPreference = (ListPreference) findPreference(KEY_SCREEN_TIMEOUT);
if (mScreenTimeoutPreference !=null ) {
final long currentTimeout = Settings.System.getLong(resolver, SCREEN_OFF_TIMEOUT,
FALLBACK_SCREEN_TIMEOUT_VALUE);
mScreenTimeoutPreference.setValue(String.valueOf(currentTimeout));
mScreenTimeoutPreference.setOnPreferenceChangeListener(this);
disableUnusableTimeouts(mScreenTimeoutPreference);
updateTimeoutPreferenceDescription(currentTimeout);
}

frameworks/base/packages/SettingsProvider/res/values/defaults.xml
<bool name="def_lockscreen_disabled">false</bool> 改为 true；即默认禁止锁屏
frameworks/base/core/res/res/values/config.xml
<integer name="config_multiuserMaximumUsers">1</integer> 不允许多用户；即最大用户数为1

frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
if (upgradeVersion == 54)// 版本为54才会设置timeout
......
private void upgradeScreenTimeoutFromNever(SQLiteDatabase db) {
// See if the timeout is -1 (for "Never").
Cursor c = db.query(TABLE_SYSTEM, new String[] { "_id", "value" }, "name=? AND value=?",
new String[] { Settings.System.SCREEN_OFF_TIMEOUT, "-1" },
null, null, null);
SQLiteStatement stmt = null;
if (c.getCount() > 0) {
c.close();
try {
stmt = db.compileStatement("INSERT OR REPLACE INTO system(name,value)"
+ " VALUES(?,?);");
// Set the timeout to 30 minutes in milliseconds
loadSetting(stmt, Settings.System.SCREEN_OFF_TIMEOUT,
Integer.toString(30 * 60 * 1000));
} finally {
if (stmt != null) stmt.close();
}
} else {
c.close();
}
}
......
if (SystemProperties.getBoolean("ro.lockscreen.disable.default", false) == true) {
loadSetting(stmt, Settings.System.LOCKSCREEN_DISABLED, "1");
} else {
loadBooleanSetting(stmt, Settings.System.LOCKSCREEN_DISABLED,
R.bool.def_lockscreen_disabled);
}

frameworks/base/packages/SettingsProvider/res/values/defaults.xml
<integer name="def_screen_off_timeout">60000</integer>
<bool name="def_lockscreen_disabled">false</bool>`