Android Settings.System的使用

在Android中，如果你要打开或关闭数据连接，WiFi，飞行模式，蓝牙，你需要对数据库中这些开关的值进行修改，这时，你会使用到Settings.System，在settings数据库中这些属性值以键值对的形式存储，通过其get和put方法可进行这些系统属性的修改。我们从如何添加一个属性开始，慢慢了解其使用方法。本例添加一个控制数据连接的属性：def_data_connection 。1、定义属于该属性的字段，可定义为integer，string，boolean等，这里设置为boolean型，并赋值为true。\frameworks\base\packages\SettingsProvider\res\values\defaults.xml

<bool name="def_data_connection">true</bool>

2、在settings中定义该属性名称：\frameworks\base\core\java\android\provider\Settings.java

public static final String DATA_CONNECTION = "data_connection";

在这个Settings.java里面同时写了获取Settings.System属性值的方法，如putInt()：

public static boolean putInt(ContentResolver cr, String name, int value) {return putIntForUser(cr, name, value, UserHandle.myUserId());}/** @hide */public static boolean putIntForUser(ContentResolver cr, String name, int value,int userHandle) {if (LOCATION_MODE.equals(name)) {// HACK ALERT: temporary hack to work around b/10491283.// TODO: once b/10491283 fixed, remove this hackreturn setLocationModeForUser(cr, value, userHandle);}return putStringForUser(cr, name, Integer.toString(value), userHandle);}

getInt()：

public static int getInt(ContentResolver cr, String name)throws SettingNotFoundException {return getIntForUser(cr, name, UserHandle.myUserId());}/** @hide */public static int getIntForUser(ContentResolver cr, String name, int userHandle)throws SettingNotFoundException {if (LOCATION_MODE.equals(name)) {// HACK ALERT: temporary hack to work around b/10491283.// TODO: once b/10491283 fixed, remove this hackreturn getLocationModeForUser(cr, userHandle);}String v = getStringForUser(cr, name, userHandle);try {return Integer.parseInt(v);} catch (NumberFormatException e) {throw new SettingNotFoundException(name);}}

当然还有getString，putString，getLong，putLong等等，不在一一列出。3、把该值插入到数据库中：\frameworks\base\packages\SettingsProvider\src\com\android\providers\settings\DatabaseHelper.java在loadSystemSettings方法中插入到数据库并赋予处置。

private void loadSystemSettings(SQLiteDatabase db) {SQLiteStatement stmt = null;try {stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"+ " VALUES(?,?);");........loadBooleanSetting(stmt, Settings.System.DATA_CONNECTION,R.bool.def_data_connection);//data connection.........} finally {if (stmt != null) stmt.close();}}    

其中loadBooleanSetting是赋值的方法：

    private void loadBooleanSetting(SQLiteStatement stmt, String key, int resid) {loadSetting(stmt, key,mContext.getResources().getBoolean(resid) ? "1" : "0");}

    private void loadSetting(SQLiteStatement stmt, String key, Object value) {stmt.bindString(1, key);stmt.bindString(2, value.toString());stmt.execute();}

此时第1步定义的def_data_connection被赋给了Settings.System.DATA_CONNECTION。4、使用Settings.System.DATA_CONNECTION此时我们工作已经基本结束了，接下来可以调用该属性进行操作了。取值：

boolean enable = Settings.System.getInt(getContentResolver(),Settings.System.DATA_CONNECTION, 1)==1;

赋值：

Settings.System.putInt(context.getContentResolver(),Settings.System.DATA_CONNECTION, 0);