修改步骤

Android系统默认是12小时制度的，现将它修改为24小时制。

一、修改默认配置文件

frameworks/base/packages/SettingsProvider/res/values/defaults.xml
添加配置

<string name="time_12_24">24</string> 

time_12_24字符串是在SettingsProvider目录下Settings.java中定义的。

二、数据库加载

frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
找到private void loadSystemSettings(SQLiteDatabase db) 方法，在该方法中添加

loadStringSetting(stmt, Settings.System.TIME_12_24, R.string.time_12_24);

三、测试

重新编译mm，将生成的SettingsProvider.apk安装到测试机
注意，只替换SettingsProvider模块，需要删除旧的数据库，否则数据库不会重新加载！

adb root
adb remount
adb push xxx/SettingsProvider.apk system/priv-app
adb shell
#rm -rf data/data/com.android.providers.settings/databases/
#reboot

测试代码：

String value = Settings.System.getString(context.getContentResolver(),
        Settings.System.TIME_12_24);

PS

android数据库中的load字段的方法是类型对应的，defaults.xml中定义的是<string name="time_12_24">24</string> ，这是一个string，就必须调用loadStringSetting，如果用loadIntSetting的话就加载不到了，显然24和"24"对java来说是一样可以强转的。其他类型也一样，需要一一对应

修改记录

diff --git a/packages/SettingsProvider/res/values/defaults.xml b/packages/SettingsProvider/res/values/defaults.xml
index 4de559e9..3b4185c5 100755
--- a/packages/SettingsProvider/res/values/defaults.xml
+++ b/packages/SettingsProvider/res/values/defaults.xml
@@ -17,6 +17,7 @@
  */
 -->
 <resources>
+    <string name="time_12_24">24</string>
     <bool name="def_dim_screen">true</bool>
     <integer name="def_screen_off_timeout">60000</integer>
     <integer name="def_button_light_off_timeout">1500</integer>
diff --git a/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java b/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
index 88fbce2f..28a294fe 100644
--- a/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
+++ b/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
@@ -1966,6 +1966,8 @@ public class DatabaseHelper extends SQLiteOpenHelper {
         try {
             stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"
                     + " VALUES(?,?);");
+            //set default time foramt--bianjb        
+            loadStringSetting(stmt, Settings.System.TIME_12_24, R.string.time_12_24);
 
             loadBooleanSetting(stmt, Settings.System.DIM_SCREEN,
                     R.bool.def_dim_screen);