我计划撰写一个免费版本和一个软件的完整版本。 我希望软件的自由版本所储存的信息也能从完整版本中获取(我不想使用内容提供者)。 我也希望确保软件更新时不会丢失这一数据。 我如何做到这一点?
你们需要以明智的方式提升你的助手。
您应始终拥有新的表格编制问题,并使用这一系统更新和转让任何现有数据。 注:上等值方法一度用于你的粉碎机助器,需要处理所有表格。
www。un。org/Depts/DGACM/index_spanish。htm 因此,建议升级:
if not exists (we are doing an upgrade, so the table might not exists yet, it will fail alter and drop)List<String> columns = DBUtils。GetColumns(db, TableName);ALTER table " + TableName + " RENAME TO temp_" + TableName)columns。retainAll(DBUtils。GetColumns(db, TableName));)String cols = StringUtils。join(columns, ",");
db。execSQL(String。format(
"INSERT INTO %s (%s) SELECT %s from temp_%s",
TableName, cols, cols, TableName));
)DROP table temp_" + TableName)(如果你重新命名一栏,本末处理下级表,你不会因为栏目名称不匹配而转移现有数据)。
。
public static List<String> GetColumns(SQLiteDatabase db, String tableName) {
List<String> ar = null;
Cursor c = null;
try {
c = db。rawQuery("select * from " + tableName + " limit 1", null);
if (c != null) {
ar = new ArrayList<String>(Arrays。asList(c。getColumnNames()));
}
} catch (Exception e) {
Log。v(tableName, e。getMessage(), e);
e。printStackTrace();
} finally {
if (c != null)
c。close();
}
return ar;
}
public static String join(List<String> list, String delim) {
StringBuilder buf = new StringBuilder();
int num = list。size();
for (int i = 0; i < num; i++) {
if (i != 0)
buf。append(delim);
buf。append((String) list。get(i));
}
return buf。toString();
}
I m relatively new to Android development. I m developing an app with a ListView. I ve followed the info in #1338475 and have my app recognizing the fling gesture, but after the gesture is complete, ...
I m converting my code from using Handler to AsyncTask. The latter is great at what it does - asynchronous updates and handling of results in the main UI thread. What s unclear to me is how to handle ...
I want to be able to download a file with a particular extension from the net, and have it passed to my application to deal with it, but I haven t been able to figure out the intent filter. The ...
I am quite impressed by the workflow I follow when developing Android applications: Define a layout in an xml file and then write all the code in a code-behind style. Is there an equivalent style for ...
To draw landscapes, backgrounds with patterns etc, we used TiledLayer in J2ME. Is there an android counterpart for that. Does android provide an option to set such tiled patterns in the layout XML?
When following the Android Open Source Project instructions on installing repo for use with Git, after running the repo init command, I run into this error: /c/Users/Andrew Rabon/bin/repo: line ...
I read in the Android documentation that by setting my Activity s launchMode property to singleTop OR by adding the FLAG_ACTIVITY_SINGLE_TOP flag to my Intent, that calling startActivity(intent) would ...
I have pretty good skills in PHP , Mysql and Javascript for a junior developer. If I wanted to try my hand as Android Development do you think I might find it tough ? Also what new languages would I ...