Android系统SettingsPrivider分析与修改方法

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继上次分析Settings的文章Android 系统Settings概要之后，现要增加一些系统中没有的设置项，因上次只是猜测DatabaseHelper.java 在创建数据库时将defaults.xml中的配制存入了数据库中,因此现在来分析下SettingsPrivider源码（源码还是官方android-4.4_r1版本）.

第一，主要分析DatabaseHelper.java文件：

1. 数据库文件为 settings.db 定义的表有人个，里面system , secure ,global 是比主要的三个。

    private static final String TAG = "SettingsProvider";    private static final String DATABASE_NAME = "settings.db";    // Please, please please. If you update the database version, check to make sure the    // database gets upgraded properly. At a minimum, please confirm that 'upgradeVersion'    // is properly propagated through your change.  Not doing so will result in a loss of user    // settings.    private static final int DATABASE_VERSION = 98;    private Context mContext;    private int mUserHandle;    private static final HashSet<String> mValidTables = new HashSet<String>();    private static final String TABLE_SYSTEM = "system";    private static final String TABLE_SECURE = "secure";    private static final String TABLE_GLOBAL = "global";    static {        mValidTables.add(TABLE_SYSTEM);        mValidTables.add(TABLE_SECURE);        mValidTables.add(TABLE_GLOBAL);        mValidTables.add("bluetooth_devices");        mValidTables.add("bookmarks");        // These are old.        mValidTables.add("favorites");        mValidTables.add("gservices");        mValidTables.add("old_favorites");    }

2. 看onCreate（）方法，创建表和各表的索引，然后调用了loadBookmarks(db); loadVolumeLevels(db); loadSettings(db); 三个方法，loadBookmarks(db);是存系统几个常用的应用的intent ( 如，通讯录app，emailApp, 短信app,)，loadVolumeLevels(db); 初始化的是与声音相关的配制， loadSettings(db);方法就是从defaults.xml文件中读取默认值存入相应的表中，验证了之前的猜测。

    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("CREATE TABLE system (" +                    "_id INTEGER PRIMARY KEY AUTOINCREMENT," +                    "name TEXT UNIQUE ON CONFLICT REPLACE," +                    "value TEXT" +                    ");");        db.execSQL("CREATE INDEX systemIndex1 ON system (name);");        createSecureTable(db);        // Only create the global table for the singleton 'owner' user        if (mUserHandle == UserHandle.USER_OWNER) {            createGlobalTable(db);        }        db.execSQL("CREATE TABLE bluetooth_devices (" +                    "_id INTEGER PRIMARY KEY," +                    "name TEXT," +                    "addr TEXT," +                    "channel INTEGER," +                    "type INTEGER" +                    ");");        db.execSQL("CREATE TABLE bookmarks (" +                    "_id INTEGER PRIMARY KEY," +                    "title TEXT," +                    "folder TEXT," +                    "intent TEXT," +                    "shortcut INTEGER," +                    "ordering INTEGER" +                    ");");        db.execSQL("CREATE INDEX bookmarksIndex1 ON bookmarks (folder);");        db.execSQL("CREATE INDEX bookmarksIndex2 ON bookmarks (shortcut);");        // Populate bookmarks table with initial bookmarks        boolean onlyCore = false;        try {            onlyCore = IPackageManager.Stub.asInterface(ServiceManager.getService(                    "package")).isOnlyCoreApps();        } catch (RemoteException e) {        }        if (!onlyCore) {            loadBookmarks(db);        }        // Load initial volume levels into DB        loadVolumeLevels(db);        // Load inital settings values        loadSettings(db);    }

3 . loadSettings(db); 里面的三个方法者是从defaults.xml文件中读取默认值存入相应的表中，loadSystemSettings(db)是存入System表中，loadSecureSettings(db)是存入 secure表中。

private void loadSettings(SQLiteDatabase db) {        loadSystemSettings(db);        loadSecureSettings(db);        // The global table only exists for the 'owner' user        if (mUserHandle == UserHandle.USER_OWNER) {            loadGlobalSettings(db);        }    }

loadSetting（）方法中SQLiteStatement将值存入了数据库中：

 private void loadSystemSettings(SQLiteDatabase db) {        SQLiteStatement stmt = null;        try {            stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"                    + " VALUES(?,?);");            loadBooleanSetting(stmt, Settings.System.DIM_SCREEN,                    R.bool.def_dim_screen);            //..............省略..................            loadIntegerSetting(stmt, Settings.System.POINTER_SPEED,                    R.integer.def_pointer_speed);        } finally {            if (stmt != null) stmt.close();        }    }

第二，那如何来增加设置项（例如要在设置中增加一项账户信息）：

1. 在Settings 中增加界面相关的代码：

1.a. Settings/res/xml/settings_headers.xml文件中增加:

1.b. 增加字符串图标等，如 Settings/res/values/strings.xml文件中:
<string name="account_info_label" >"账号信息"</string>

         1.c 相关类与代码的编写：如创建Fragment:AccountInfoSettings 并写代码，里面的代码会Settings.System.put**的代码将操作SettingsProvider

     2. 修改SettingsPrivider

2. a defalult.xml

<bool name="def_acctount_islogin">false</bool>
<string name="def_acctount_name">请设置昵称</string>

2. b DatabaseHelper.java 在loadSecureSettings(SQLiteDatabase db) 方法中增加

loadBooleanSetting(stmt, Settings.Secure.ACCOUNT_ISLOGIN,
                    R.bool.def_account_islogin);
            loadStringSetting(stmt, Settings.Secure.ACCOUNT_NAME,
                    R.string.def_account_name);

3. 在/android-4.4_r1/frameworks/base/core/java/android/provider/Settings.java 文件中找到内部静态类：public static final class Secure extends NameValueTable {..........} 在Secure类中增加：

public static final String ACCOUNT_ISLOGIN = "def_account_islogin";
public static final String ACCOUNT_NAME = "def_account_name";

到此修改基本完成，可以编译，运行，测试了。实际开发中的步骤应该是3.2,1按倒着的顺序来做^-^.

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