android 4.2 修改默锁屏为无

frameworks/base/core/java/com/android/internal/widget/LockSettingsService.java
   class DatabaseHelper extends SQLiteOpenHelper {
        private static final String TAG = "LockSettingsDB";
        private static final String DATABASE_NAME = "locksettings.db";
        private static final int DATABASE_VERSION = 1;
        public DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            setWriteAheadLoggingEnabled(true);
        }
        private void createTable(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE " + TABLE + " (" +
                    "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                    COLUMN_KEY + " TEXT," +
                    COLUMN_USERID + " INTEGER," +
                    COLUMN_VALUE + " TEXT" +
                    ");");
        }
        @Override
        public void onCreate(SQLiteDatabase db) {
            createTable(db);
            initializeDefaults(db);
        }
        private void initializeDefaults(SQLiteDatabase db) {
            // Get the lockscreen default from a system property, if available
            boolean lockScreenDisable = SystemProperties.getBoolean("ro.lockscreen.disable.default",
                    false);//在这里会去读默认值
            if (lockScreenDisable) {
                writeToDb(db, LockPatternUtils.DISABLE_LOCKSCREEN_KEY, "1", 0);
            }
        }
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int currentVersion) {
            // Nothing yet
        }
    }