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:
<header
android:id="@+id/account_info"
android:fragment="com.android.settings.accounts.AccountInfoSettings"
android:title="@string/account_info_label"
android:icon="@drawable/ic_menu_add_dark"/>
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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